Evolutionary derivation inferences of the intrinsic shoulder and brachial muscles in crab-eating raccoon (Procyon cancrivorus, Caniformia, Carnivora) based on the topology, innervation, and anatomical variants

Evolutionary derivation inferences of the intrinsic shoulder and brachial muscles in crab-eating raccoon (Procyon cancrivorus, Caniformia, Carnivora) based on the topology, innervation, and anatomical variants | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Evolutionary derivation inferences of the intrinsic shoulder and brachial muscles in crab-eating raccoon (Procyon cancrivorus, Caniformia, Carnivora) based on the topology, innervation, and anatomical variants Juan Fernando Vélez García, Diego Alejandro Carrión Blanco, Gabriela Moreno Gómez, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4644708/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Sep, 2024 Read the published version in Zoomorphology → Version 1 posted 10 You are reading this latest preprint version Abstract The crab-eating raccoon ( Procyon cancrivorus ) is a carnivoran of the family Procyonidae geographically distributed in Center and South America. It is a scansorial species with more terrestrial than arboreal abilities. Previous studies have described the intrinsic shoulder and brachial muscles in this species; however, all have different descriptions. Besides, these studies did not take into account the innervation to infer the evolutionary derivation of the muscles, and neither did the arterial supply. Therefore, the present study aimed to analyze the anatomical arrangement of the intrinsic shoulder and brachial muscles in six Procyon cancrivorus specimens fixed with 10% formaldehyde. The shape, origin, insertion, arterial supply, and variations were described. Furthermore, the innervation previously reported was reviewed again in detail to infer the evolutionary derivation of these muscles. Differences were found with that reported formerly in the same species and other procyonids. Some intraspecific anatomical variants were discovered, such as an accessory head in the biceps brachii muscle bilaterally; a biceps brachii muscle joined to the brachialis muscle unilaterally; and a fusion of the lateral and accessory heads of the triceps brachii muscle bilaterally. Tensor fasciae antebrachii muscle is divided into two parts in most cases, and both are innervated by the radial nerve. The anconeus medialis muscle is independent to the triceps brachii muscle and is innervated by the ulnar nerve. In conclusion, based on the topology, anatomical variations, and innervation of these muscles in P. cancrivorus , they potentially conserve the evolutionary derivation of the last common ancestor of mammals. Anatomy Insertion Myology Origin Procyonidae Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Crab-eating raccoon ( Procyon cancrivorus ) is a species belonging to the family Procyonidae, suborder Caniformia, and order Carnivora (Nyakatura and Bininda-Emonds 2012 ; Hassanin et al. 2021 ). P. cancrivorus is geographically distributed from Mexico to Brazil (Reid et al. 2016 ). It belongs to the genus Procyon , which is characterized by having long thoracic limbs with manus adapted to a semidigitigrade support (McClearn 1992 ). These limbs are mainly used for cursorial locomotion, but also to swim, manipulate food, and climb trees when is vitally necessary, such as escape from predators (Nowak 2005 ; Whiteside 2009 ; Santos et al. 2015 ). To these functions in this species, the antebrachial muscles perform several movements, such as rotation, flexion, and extension of the manus and digits (Perdomo-Cárdenas et al. 2021 ; Vélez-García et al. 2022 ; Tarquini et al. 2023 ). However, the proximal thoracic limb muscles must act to move and fix the shoulder and elbow joints, giving support in the thoracic limb to allow more precise movements of the manus (Ercoli et al. 2015 ; Vélez-García et al. 2023 ). The intrinsic muscles of the scapular, shoulder, and brachial regions have been studied in several caniforms to review interspecific gross anatomical differences (Fisher et al. 2009 ; Ercoli et al. 2015 ; Pereira et al. 2016 ; Souza-Junior et al. 2018 ; Vélez et al. 2018 ; Vélez-García et al. 2018b , 2023 ; Smith et al. 2020 ). Specifically on P. cancrivorus , there are only four anatomical studies where the shoulder and brachial muscles are involved (Windle 1888 ; Pereira et al. 2010 ; Santos et al. 2010b ; Tarquini et al. 2023 ). Among them, the more recent study performed a detailed anatomical description of Nasua nasua , where only the differences with P. cancrivorus were included (Tarquini et al. 2023 ). There are several differences among these studies regarding some muscles. Among them, the m. triceps brachii has been reported with three (Windle 1888 ), four (Pereira et al. 2010 ; Santos et al. 2010b ), and five heads (Tarquini et al. 2023 ). The m. biceps brachii was reported inserted onto the radial and ulnar tuberosities (Pereira 2010 ; Santos et al. 2010b ), and only onto the radial tuberosity (Windle 1888 ; Tarquini et al. 2023 ). The m. brachialis was also reported with insertions onto radial and ulnar tuberosities (Santos et al. 2010b ), only onto radial tuberosity (Pereira et al. 2010 ) or proximomedial aspect of the ulnar shaft (Tarquini et al. 2023 ). These insertions to both muscles could be intraspecific anatomical variations in P. cancrivorus , since the brachialis and biceps brachii muscles in most species of the infraorder Arctoidea only insert onto the ulna and radius, respectively (Windle and Parsons 1897 ; Davis 1964 ; Böhmer et al. 2020 ; Vélez-García et al. 2023 ). The other insertion onto the ulna by the m. biceps brachii is normally only present in species of the family Canidae (Windle and Parsons 1897 ; Pereira et al. 2016 ; Souza-Junior et al. 2018 ; Vélez et al. 2018 ; Böhmer et al. 2020 ; Hermanson 2020 ). Therefore, one of the characteristics to review in the present study is the anatomical arrangement of the biceps brachii and brachialis muscles in P. cancrivorus . Caudal to the m. tensor fasciae antebrachii was found as an accessory belly with origin from the m. cutaneus trunci, which the authors inferred that said muscle is a part of the latter muscle, and not from the m. tensor fasciae antebrachii (Tarquini et al. 2023 ). However, these authors did not take into account the innervation, which should be included together with the topology to infer the evolutionary muscle derivation (Diogo and Abdala 2010 ), such as has been performed in other muscular groups in carnivorans (Diogo et al. 2012 ; Vélez-García and Miglino 2023 ; Vélez-García et al. 2023 ). For this belly to be considered part of the cutaneous trunci muscle, it would have been innervated by the lateral thoracic nerve. Specifically, in the procyonid P. flavus , the cranial belly to the m. tensor fasciae antebrachii was considered part of this muscle since it is innervated by the radial nerve (Vélez-García et al. 2023 ). Therefore, one of the hypotheses of the present study is that the accessory belly is part of the m. tensor fasciae antebrachii, and not of the m. cutaneus trunci in P. cancrivorus . Another muscle that is not taken into account in several studies is the m. anconeus medialis (m. anconeus epitrochlearis) (Windle 1888 ; Pereira et al. 2010 ; Santos et al. 2010b ). In a recent study, the muscle was considered as a head of the m. triceps brachii (Tarquini et al. 2023 ). This may have occurred because the name of this muscle is not present at the Nomina Anatomica Veterinaria (International Committee on Veterinary Gross Anatomical Nomenclature 2017 ), and its evolutionary derivation was not considered as proposed in vertebrates (Diogo et al. 2018 ). In a former study and a recent study performed through a literature review and direct gross dissections in non-ursid arctoids was established that the m. anconeus medialis is the most constant muscle in these species and is innervated by the ulnar nerve (Windle and Parsons 1897 ; Vélez-García et al. 2023 ). In Felis catus , there is one author who agrees with the name m. anconeus medialis because it is independent of the m. triceps brachii and is located collateral to the m. anconeus, which thus is named m. anconeus lateralis (Barone 2020b ). Thereby, in the procyonid P. flavus , the m. anconeus medialis was not considered as a head of the m. triceps brachii since its origin and insertion were independent, and it was innervated by the ulnar nerve (Vélez-García et al. 2023 ). This agrees with the evolutionary derivation of the m. anconeus medialis with the m. flexor carpi ulnaris, such as has been found in vertebrates from amphibians (Diogo and Abdala 2010 ; Diogo et al. 2018 ). Therefore, another hypothesis is that the m. anconeus medialis in P. cancrivorus is not a head of the m. triceps brachii, and conserves the evolutionary origin of most mammals. The present study aimed to review the topology and anatomical variants of the intrinsic scapular, shoulder, and brachial muscles in P. cancrivorus compared with those reported in previous studies (Windle 1888 ; Pereira et al. 2010 ; Santos et al. 2010b ; Tarquini et al. 2023 ). The arterial supply to these muscles is also described to complement the study. Besides, to discuss the evolutionary derivation, the innervation reported previously was retaken in more detail (Vélez García et al. 2023 ). All these characteristics will contribute to the knowledge of evolutionary adaptations, muscle reconstructions in fossils, and veterinary procedures (Tarquini et al. 2019 ; Dunn et al. 2022 ; Vélez-García et al. 2022 ). 2. Materials and Methods Six cadavers of P. cancrivorus fixed in 10% formaldehyde (two females and four males) were used (Table 1 ). Five of them were previously dissected for the brachial plexus study (Vélez García et al. 2023 ). However, the characteristics of the muscles were not reported in that study. Gross anatomical dissections from superficial to deep on the intrinsic scapular and brachial muscles of all specimens were performed. The terminology was mainly based on the Nomina Anatomica Veterinaria (International Committee on Veterinary Gross Anatomical Nomenclature 2017 ), and other muscle terms were used, such as m. anconeus lateralis, m. anconeus medialis, pars caudalis and pars cranialis of the m. tensor fasciae antebrachii (Barone 2020a ; Vélez García et al. 2023 ). The arterial supply was only studied in three specimens (PcS1, PcS5, and PcS6), which had vascular repletion with natural latex tinctured with red vinyl. Photographs of the dissections were taken with a Canon T5i camera associated with a macro lens of 60 mm, and an EOS 6D camera associated with a macro lens of 100 mm. The use of these specimens was approved by the environmental entities of Colombia (CORTOLIMA and CORPOCALDAS) and Brazil (SISBIO Number 37072-2). This research was approved by the bioethics committees of the Universidad del Tolima (agreement number 2.3–059), Universidade de São Paulo (CEUAx agreement number 3928240820), and Universidade de Catalão (CEUA-UFCAT agreement number 01/22). Table 1 Identification of the thoracic limbs dissected in Procyon cancrivorus Species Sex Age ID Limb Procyon cancrivorus F J PcS1 RTL LTL F J PcS2 RTL LTL M A PcS3 RTL LTL M A PcS4 RTL LTL M A PcS5 RTL LTL M A PcS6 RTL A, adult; F, female; ID, specimen identification; J, juvenile; L, left thoracic limb; M, male; RTL, right thoracic limb 3. Results 3.1 Lateral scapular and shoulder muscles M. deltoideus The m. deltoideus has two parts, pars acromialis and pars scapularis (Figure 1). The pars acromialis is fusiform, originates via tendinous and fleshy fibers from the ventral margin of the acromion (hamatus and suprahamatus processes). The origin is tendinous superficially and fleshy deeply. It is also fleshy at the caudal extreme of the suprahamatus process. Distally its fleshy fibers join to the pars scapularis tendon and also insert directly onto the deltoid tuberosity. It also receives fibers from the m. cleidobrachialis. The pars scapularis is triangular and fusiform, originates via an aponeurosis from the fascia over the m. infraspinatus and the distal half of the scapular spine. It originates via fleshy fibers from the caudal aspect of the suprahamatus process. It forms a wide tendon, which is also formed by a few tendinous fibers of the pars acromialis, and it receives fleshy fibers from this latter to insert onto the distal half of the lateral surface to the crest of greater tubercle and deltoid tuberosity. In one specimen unilaterally (PcS1), the pars scapularis also originated from the middle third of the caudal margin of the scapula via a common aponeurosis with the m. teres minor (Figure 2). Both parts are supplied by the caudal circumflex artery, and the pars scapularis also by the subscapular artery (Figure 2). M. supraspinatus The m. supraspinatus is bipennate, originates via fleshy fibers from the supraspinous fossa, cranial aspect of the scapular spine (Figure 1), and intermuscular septum with the m. subscapularis (Supplementary figure 1). It inserts onto the proximal extreme of the greater tubercle of the humerus via a strong tendon (Figure 2a). In one specimen (PcS5-LTL), an accessory belly originated from the distal margin of the acromion and was inserted caudally to the supraspinatus tendon. At the same specimen unilaterally (PcS5-LTL), an accessory belly was present cranially, which separated from the main belly for the pass of the brachiocephalic nerve (Figure 1b). The muscle is supplied by the lateral and medial branches of the suprascapular and caudal circumflex humeral arteries. M. infraspinatus The m. infraspinatus is pyramidal and bipennate, originates in a fleshy manner from the infraspinous fossa, the caudal aspect of the scapular spine, medial aspect of the suprahamatus process, and origin aponeurosis of the m. teres minor. It inserts via a tendon onto the caudoproximal extreme of the greater tubercle ( facies m. infraspinatus ), and there is a synovial bursa deep to the infraspinatus tendon ( Bursa subtendinea m. infraspinati ). It is supplied by the subscapular, caudal circumflex humeral, and circumflex scapular arteries (Figures 1 and 2a). M. teres minor The m. teres minor is fusiform, originates via an aponeurosis from the ventral third of the scapular caudal margin, and inserts onto the teres minor tuberosity, distally to the insertion of the supraspinatus tendon. It originated from the ventral half of the scapular caudal margin in PcS6, and the two ventral thirds in PcS5. In one specimen unilaterally (PcS1-RTL), it originated via a common aponeurosis with the m. deltoideus pars scapularis. It is supplied by the caudal circumflex humeral artery. In two specimens (PcS1, PcS6), it also was supplied by a branch of the subscapular artery, which perforated the origin tendon of the caput longum of m. triceps brachii (Figures 1 and 2). 3.2 Medial scapular and shoulder muscles M. teres major The m. teres major is fusiform, originates from the lateral and caudal surfaces of the caudal angle of the scapula, adjacent fascia over the m. infraspinatus close to the caudal angle, dorsal third of the caudal margin of the scapula, and dorsal third of the intermuscular septum with the m. subscapularis (Supplementary figure 1). It joins to the m. latissimus dorsi at the proximal extreme of the brachium and both form a common tendon to insert onto teres major tuberosity. It is supplied by the thoracodorsal, subscapular, and caudal circumflex humeral arteries (Figures 3 and 4). M. subscapularis The m. subscapularis is multipennate with between five and seven bipennate bellies, which originate from the subscapular fossa, cranial margin of the scapula, middle third of the caudal margin of scapula (between the origins of the teres major and triceps brachiii caput longum muscles), and dorsal thirds of the intermuscular septa with the supraspinatus and teres major muscles (Supplementary figure 1). It inserts via a thick tendon onto the lesser tubercle of the humerus. In PcS6, it was also inserted onto the joint capsule and via fleshy fibers onto the caudal extreme of lesser tubercle. It is supplied by the subscapular, suprascapular, and deep cervical arteries. This later artery supplied it after passing through the m. serratus ventralis cervicis (Figures 3 and 4). M. coracobrachialis The m. coracobrachialis is fusiform, originates from the coracoid process via a tendon that passes medial to the subscapular tendon protected by a synovial sheath, which is adhered to the subscapular tendon. It inserts via fleshy and tendinous fibers onto the caudal surface of the crest of lesser tubercle, just medial to the origin of the caput accessorium of m. triceps brachii (Figures 3 and 4). It is supplied by the cranial circumflex humeral artery. 3.3 Cranial group of the brachium M. biceps brachii The m. biceps brachii is bipennate, originates from the supraglenoid tubercle via a tendon, which passes deeply to the shoulder joint capsule and intertubercular groove protected by the transverse humeral retinaculum. It inserts via a flat tendon onto the caudolateral surface of the radial tuberosity. The tendon is protected by a synovial bursa in the medial surface of the radial tuberosity (Figures 3 and 4). In PcS1 bilaterally, the muscle had an accessory head (humeral head) that originated from the intertubercular groove, proximal to the insertion of the common tendon of the teres major and latissimus dorsi muscles (Figure 2a). In PcS5 unilaterally (RTL), the belly was shorter and distally divided into two gross fibrous fascicles, where one extended to the radial tuberosity and the other one joined to the m. brachialis. The more lateral fleshy fibers of the belly were directed toward the lateral fascicle. The medial antebrachial cutaneus nerve and the cubital transverse artery passed to the antebrachium between both fibrous fascicles (Supplementary Figure 2). The m. biceps brachii is supplied proximally by the cranial circumflex humeral artery, at the medium by two bicipital arteries (both originate directly from the brachial artery), and distally by the transverse cubital and superficial brachial arteries. M. brachialis The m. brachialis is bipennate, originates mainly via fleshy fibers and also some superficial tendinous fibers from a wide region of the humerus, reaching the caudal and lateral surfaces of the humerus. It originates from the lateral aspect of the humeral neck, caudal aspect of the deltoid tuberosity, lateral aspect of the humeral crest (adjacent to the insertion of the cleidobrachialis tendon), and three proximal thirds of the medial aspect of the lateral supracondylar crest (Figure 5). It inserts via a flat tendon onto the distal surface to the medial coronoid process of the ulna. It is supplied by the axillary, transverse cubital, and radial collateral arteries (Figures 2, 3 and 4). 3.4 Caudal group of the brachium M. triceps brachii The m. triceps brachii is multipennate with four heads, such as caput longum, caput laterale, caput mediale and caput accessorium. The caput longum originates via a strong flat tendon from the medial aspect of the ventral third of caudal scapular margin, and a stronger tendon from the infraglenoid tubercle (Figure 3c). Both tendons internally have fleshy fibers that also originate directly from the scapula. The formation of two tendons is performed for the pass of a branch of the subscapular artery toward the teres minor muscle (Figure 2b). The caput longum is supplied by the caudal humeral circumflex, deep brachial, collateral radial, and subscapular arteries. The caput laterale originates via an aponeurosis from the brachial fascia, tricipital line and lateral half of the humeral neck. It sends fleshy fibers to the longum and accessorium heads at the middle of the brachium, and to the caput mediale at the distal third. It is supplied by the axillary, radial collateral, and caudal humeral circumflex arteries. It also was supplied by the deep brachial artery in PcS1. The caput accessorium originates mainly via fleshy fibers, extending from the medial half of the humeral neck to a short distance of the humeral shaft where begin the origin of the caput mediale. Tendinous fibers are observed medially in its origin. In PcS6, proximal fleshy fibers also originated from the shoulder joint capsule. It is supplied by the caudal humeral circumflex, deep brachial, and radial collateral arteries. In PcS5, the laterale and accessorium heads were fused bilaterally. The caput mediale originates via an aponeurosis from the proximal quarter of the medial aspect of humeral shaft and sends fibers to the caput accessorium at the distal third of the brachium. It is supplied by the deep brachial and ulnar collateral arteries. The laterale, accessorium and mediale heads insert through a tendon onto the cranial aspect of the olecranon tuberosity. The laterale and longum heads insert onto the caudal aspect of the olecranon tuberosity. The tendon of the caput laterale also inserts onto the lateral margin of the olecranon parallel to the insertion of the m. anconeus lateralis. The caput mediale also inserts via fleshy fibers at the medial aspect of the olecranon tuberosity, just proximal to the insertion of the m. anconeus medialis. There two tricipital synovial bursas between the tendons and the olecranon tuberosity. One is located laterally between the common tendon formed by the longum and laterale heads. Another one is located medially between the common tendon formed by the laterale, mediale and accessorium heads, and the m. anconeus lateralis (Figure 5). M. tensor fasciae antebrachii The m. tensor fasciae antebrachii is divided into two flattened bellies, cranial and caudal parts (pars cranialis and pars caudalis). The cranial part is totally located at the medial aspect of the brachium, parallel and cranial to the caudal part. It originates via an aponeurosis from a common tendon of several extrinsic thoracic limb muscles (medial belly of the m. latissimus dorsi, caudal part of the m. pectoralis profundus, pectoralis abdominalis and cutaneus trunci muscles). The caudal part is located at the caudal and medial aspects of the caput longum of m. triceps brachii, being always observed from the lateral view of the dissections of the brachium. It originates via fleshy fibers from the main belly of the m. latissimus dorsi, and in some cases via fibrous fibers from the m. teres major (PcS3-RTL, PcS4, PcS5, PcS6). In PcS6, it was extended more cranially and was partially covered by the cranial part in both limbs. Both parts only join at the distal brachium in a common wide aponeurosis that fuses with the caudal and medial aspect of the caput longum triceps brachii tendon. It also inserts independently onto the medial margin of the olecranon and antebrachial fascia (Figure 6). The cranial part was absented in three limbs (PcS2 bilaterally, and PcS3-RTL) and had a vestigial shape in one limb (PcS3-LTL -Supplementary figure 2-). Both parts are supplied by the deep brachial artery, and the caudal part is also by the ulnar collateral artery. M. anconeus lateralis ( M. anconeus ) The m. anconeus lateralis is pyramidal and originates via fleshy fibers from the distal third of the humeral shaft, caudal aspect of the lateral supracondylar crest, and lateral epicondyle of the humerus. It inserts via fleshy and tendinous fibers onto the lateral surface of the olecranon and caudolateral margin of the olecranon (Figures 2b, 3, and 5). The muscle always was deeply fused to the joint capsule of the elbow. It is supplied by the collateral ulnar and collateral radial arteries. M. anconeus medialis The m. anconeus medialis is triangular, originates via fleshy fibers from along the proximomedial margin of the supracondylar foramen, and medial epicondyle of the humerus. It inserts onto the medial surface of the olecranon, proximally via tendinous fibers, and distal- and deeply via fleshy fibers. It is supplied by the ulnar collateral artery (Figures 2c, 3, 4, and 5). 4. Discussion 4.1 Comparative anatomy of the intrinsic scapular and shoulder muscles in procyonids The m. deltoideus of P. cancrivorus had a similar arrangement to that described formerly in the same species (Santos et al. 2010b; Tarquini et al. 2023), and other procyonids, such as Procyon lotor (Allen 1882; Feeney 1999), Nasua nasua (Mackintosh 1875; Santos et al. 2010a; Böhmer et al. 2020; Tarquini et al. 2023), Nasua narica (Mackintosh 1875), Bassaricyon alleni (Beddard 1900), and P. flavus (Beswick-Perrin 1871; Windle and Parsons 1897; Böhmer et al. 2020). However, the pars scapularis always originated from the fascia of the m. infraspinatus, in contrast with the findings of Tarquini et al. (2023) who only found that origin in N. nasua . On the other side, the variant origin of the pars scapularis from a common aponeurosis with the m. teres minor was not reported in any procyonid. The extended origin cranially to the cranial margin of scapula of the supraspinatus and subscapularis muscles forming an intermuscular septum had been described similarly in the same species (Santos et al. 2010b)and N. nasua (Santos et al. 2010a). The origin between both muscles was not reported in other studies in the same species (Windle 1888; Tarquini et al. 2023), and neither in P. lotor (Allen 1882; Windle and Parsons 1897)and P. flavus (Beswick-Perrin 1871; Windle and Parsons 1897; Böhmer et al. 2020; Vélez-García et al. 2023). In one specimen of N. nasua , a strong fascia was between both muscles, and in another specimen both muscles shared fibers (Tarquini et al. 2023). The variant presence of two bellies in the m. supraspinatus also was reported in this species (Tarquini et al. 2023), but in that case, the accessory belly was superficial but not located cranially, such as occurred in one P. cancrivorus specimen of the present study and one P. lotor (Allen 1882). The insertion onto the humeral transverse retinaculum was found in none, while Tarquini et al. (2023) found it in their three specimens. The m. teres minor was completely independent to the m. infraspinatus in P. cancrivorus , such as was formerly described in the same species (Windle 1888; Pereira et al. 2010; Santos et al. 2010b; Tarquini et al. 2023) and other procyonids (Davis 1949; Böhmer et al. 2020; Tarquini et al. 2023; Vélez-García et al. 2023). In some specimensof P. lotor and P. flavus , the muscle may be fused to the m. infraspinatus (Beswick-Perrin 1871; Allen 1882; Julitz 1909). The origin of the m. teres minor from the infraglenoid tubercle as was reported in P. cancrivorus and N. nasua (Santos et al. 2010a, b) was not found since the tubercle was occupied by the origin tendon of the m. triceps brachii caput longum, such as was recently reported (Tarquini et al. 2023). The origin of the m. infraspinatus from the origin aponeurosis of the m. teres minor has only been described in P. flavus (Vélez-García et al. 2023). Based on the most authors, the m. subscapularis does not have important differences among procyonid species (Beswick-Perrin 1871; Mackintosh 1875; Windle and Parsons 1897; Julitz 1909; Santos et al. 2010a, b; Böhmer et al. 2020). However, it is divided into two portions in Bassariscus (Davis 1949), P. lotor (Davis 1949) , N. narica (Davis 1949), and N. nasua (Tarquini et al. 2023). Besides, the muscle does not only originate from the subscapular fossa but from the cranial and caudal margins of the scapula in P. cancrivorus (Tarquini et al., 2023; present study)and N. nasua (Tarquini et al. 2023). The origin of the m. teres major from the infraspinatus and subscapularis muscles contrasts with other studies that did not find a connection with these muscles in the same species (Santos et al. 2010b; Tarquini et al. 2023). While in P. lotor (Allen 1882; Davis 1949), B. astutus , N. narica (Davis 1949) and N. nasua (Tarquini et al. 2023), the origin is very similar to that found in our P. cancrivorus specimens . The origin from the infraspinatus muscle is not found in P. flavus (Windle and Parsons 1897; Julitz 1909; Vélez-García et al. 2023), and in some specimens of N. nasua (Santos et al. 2010a). Other authors did not report none origin to this muscle in P. cancrivorus (Windle 1888) and Nasua (Mackintosh 1875). On the other side, the insertion onto the humerus was not found separated from the m. latissimus dorsi as was reported by other authors (Tarquini et al. 2023). The m. coracobrachialis of P. cancrivorus presented a small shape, such as was reported formerly in the same species (Windle 1888; Tarquini et al. 2023), and other procyonids (Mackintosh 1875; Allen 1882; Beddard 1900; Santos et al. 2010a; Tarquini et al. 2023). P. flavus has another m. coracobrachialis named m. coracobrachialis longus (Beswick-Perrin 1871; Windle and Parsons 1897; Julitz 1909; Vélez-García et al. 2023), which is absent in P. cancrivorus and other procyonids. However, it can also be absent in some P. flavus specimens (Vélez-García et al. 2023). 4.2 Comparative anatomy of the brachial muscles in procyonids The m. biceps brachii had one head in most specimens of P. cancrivorus , being similar to that formerly described (Mackintosh 1875; Windle 1888; Pereira et al. 2010; Santos et al. 2010a, b; Tarquini et al. 2023). The other insertion onto the ulnar tuberosity described by some authors (Pereira et al. 2010; Santos et al. 2010a, b) was not found by us and other studies (Windle 1888; Tarquini et al. 2023). In P. flavus , the presence of a well-developed second head (caput breve) originating from the coracoid process of scapula is normal (Beswick-Perrin 1871; Windle and Parsons 1897; Julitz 1909; Böhmer et al. 2020; Vélez-García et al. 2023). In P. lotor , that same head may be present in a feeble shape as anatomical variant (Windle and Parsons 1897). However, that head (caput breve) is not the same accessory head found in one P. cancrivorus specimen, since it originated from the humerus. Similarly, a small humeral head was found in one case of P. flavus (Vélez-García et al. 2023). The m. brachialis originated from along caudolateral surface of the humerus including the medial aspect of the lateral supracondylar crest in P. cancrivorus , which is similar to that reported previously (Tarquini et al. 2023). In contrast, other studies reported the origin only from the proximal part of the humerus in the same species (Pereira et al. 2010; Santos et al. 2010b) and N. nasua (Santos et al. 2010a; Böhmer et al. 2020). The origin from the whole lateral surface of the humerus was described in N. nasua (Mackintosh 1875), N. narica (Mackintosh 1875), P. lotor (Allen 1882), and P. flavus (Julitz 1909; Vélez-García et al. 2023). However, the origin has been described from the proximal half of the humerus in the latter species (Beswick-Perrin 1871). The insertion only onto the ulna agrees with that described by most authors in procyonids (Beswick-Perrin 1871; Mackintosh 1875; Allen 1882; Windle 1888; Beddard 1900; Julitz 1909; Böhmer et al. 2020; Tarquini et al. 2023), while the insertion onto the radius described by some authors in P. cancrivorus and N. nasua was not found (Pereira et al. 2010; Santos et al. 2010a, b). The four heads of the m. triceps brachii in P. cancrivorus were found as was previously reported by other authors (Pereira et al. 2010; Santos et al. 2010b), and similar to B. alleni (Beddard 1900), P. lotor (Allen 1882; Feeney 1999), N. nasua (Santos et al. 2010a), and P. flavus (Julitz 1909; Vélez-García et al. 2023) . Several studies did not describe the caput accessorium of the m. triceps brachii or a homologous portion in procyonids (Beswick-Perrin 1871; Mackintosh 1875; Windle 1888; Böhmer et al. 2020). Former studies only reported three heads in P. cancrivorus (Windle 1888), N. nasua (Mackintosh 1875), and P. flavus (Beswick-Perrin 1871). A more recent study named four heads in N. nasua and P. flavus (Böhmer et al. 2020), although the caput mediale accessorium is actually the m. anconeus medialis (Vélez-García et al. 2023). In another more recent study was described that the muscle has five heads in P. cancrivorus and N. nasua (Tarquini et al. 2023), although, the caput mediale accessorium is actually the m. anconeus medialis. P. lotor and P. flavus may have five heads due to the presence of a second caput laterale (Windle and Parsons 1897; Vélez-García et al. 2023). N. narica may have four heads due to the presence of a second caput longum from the edge of the glenoid cavity (Mackintosh 1875), which could be similar to that found in P. cancrivorus where the caput longum had two origins. In our study, several differences were found concerning that reported by Tarquini et al. (2023). Among them, fleshy fibers were not found at the origin of the caput laterale; the caput laterale sent fleshy fibers to all other heads; two tricipital bursas; and the division of the caput longum tendon by a perforating branch of the subscapular artery. The formation of two parts (cranial and caudal parts) in the m. tensor fasciae antebrachii in P. cancrivorus has only been described in P. lotor (Feeney 1999) , P. flavus (Vélez-García et al. 2023) and B. alleni (Beddard 1900). The origin from the m. teres major was only found in N. narica (Mackintosh 1875) and P. flavus (Vélez-García et al. 2023). The insertion onto the olecranon and antebrachial fascia was reported in P. flavus (Beswick-Perrin 1871; Julitz 1909; Vélez-García et al. 2023) and one study in P. cancrivorus (Pereira et al. 2010). While the unique insertion onto the olecranon was described in most procyonids (Mackintosh 1875; Allen 1882; Santos et al. 2010a; Böhmer et al. 2020; Tarquini et al. 2023). The tendinous fusion with the caput longum tendon of m. triceps brachii was not reported in any other study. The m. anconeus medialis in P. cancrivorus had a similar arrangement to that described in a homologous part (with another term or portion of the m. triceps brachii) in the same species ("caput mediale accessorium" Tarquini et al., 2023), N. nasua ("m. triceps brachii caput mediale" Böhmer et al., 2020; Mackintosh, 1875), P. lotor ("m. anconeus epitrochlearis" Allen, 1882; Windle & Parsons, 1897), and P. flavus (Beswick-Perrin 1871; Windle and Parsons 1897; Vélez-García et al. 2023). We found origin also from the medial epicondyle of the humerus in all P. cancrivorus specimens similar to that found in P. flavus (Vélez-García et al. 2023). In contrast, it differs from that reported in the same species and N. nasua where the origin only was from the supracondylar foramen (Tarquini et al. 2023). This muscle or a homologous portion was not described by other authors (Windle 1888; Pereira et al. 2010; Santos et al. 2010b), however, in one of those studies, it was pointed as accessory head of the m. triceps brachii in the figure 3 (Santos et al. 2010b). This corroborates that the muscle several times is missed by the authors, which may be because it is not present at the NAV (ICVGAN 2017). In the case of N. narica , both anconei muscles are reported united to the biceps (Mackintosh 1875). However, this union could be a mistake of the author and could have referred to the m. triceps brachii since the anatomical relationship is closer with this muscle than the m. biceps brachii. The origin of the m. anconeus lateralis ( m. anconeus ) extended proximally reaching part of the humeral shaft in our specimens of P. cancrivorus , which differed from other studies where the muscle only originates from the lateral supracondylar crest (Mackintosh 1875; Pereira et al. 2010; Santos et al. 2010b; Böhmer et al. 2020; Tarquini et al. 2023). P. lotor (Allen 1882) and P. flavus (Vélez-García et al. 2023) are the only two procyonid species where the muscle reaches the humeral shaft, even being more proximally extended than P. cancrivorus . The muscle was not reported in a former study of P. cancrivorus (Windle 1888). In some specimens of P. flavus , the m. anconeus lateralis may be fused to the caput mediale of the m. triceps brachii (Beswick-Perrin 1871; Julitz 1909). 4.3 Anatomical variants of P. cancrivorus present in other carnivorans Some anatomical variants found in P. cancrivorus may be present in other species within the order Carnivora. The presence of two bellies in the m. supraspinatus has been reported in the canid Cerdocyon thous (Vélez-García et al. 2018b), the felid Panthera leo (Barone 1963), and the viverrid Civettictis civetta (Macalister 1873b). While in the mustelid Galictis cuja, it has three bellies (Ercoli et al. 2015). The origin of the m. infraspinatus from the aponeurosis of the m. teres minor has been described in the ailurid Ailurus fulgens (Fisher et al. 2009). The m. tensor fasciae antebrachii has only been reported with more than one part in a few species. In two species, it has been reported with two portions with similar origins to those of P. cancrivorus , such as the mustelids Eira barbara (Macalister 1873), Martes caurina, Martes martes (Yousefi et al. 2018) , Pekania penanti (Feeney 1999), and the ursid Ailuropoda melanoleuca (Davis 1964). In the ursid Ursus americanus , it was reported with three portions and inserted onto the medial epicondyle and olecranon (Shepherd 1883). The insertion onto the triceps brachii tendon by the m. tensor fasciae antebrachii has been reported in the canid Canis lupus familiaris (Hermanson 2020), the mustelid M. martes (Yousefi et al. 2018) and the felid Leopardus pardalis (Julik et al. 2012). The origin from the m. teres major by the m. tensor fascia antebrachii has been reported in U. americanus (Shepherd 1883), M. martes (Yousefi et al. 2018) and the felid Puma concolor (Concha et al. 2004). From our knowledge, two anatomical variants found in P. cancrivorus have not been reported in other carnivorans, such as the common origin aponeurosis of the teres minor and deltoideus pars scapularis muscles; the two variations of the m. biceps brachii; and the fusion of the laterale and accessorium heads of the m. triceps brachii. 4.4 Comparative functional and evolutionary analysis of the intrinsic shoulder and brachial muscles in Procyon cancrivorus based on the topology and innervation The functional analysis has been excellently developed in the study of Tarquini et al. (2023) since they compared the muscle volume among muscular groups and other species. However, below, we include other functional and evolutionary inferences that were not analyzed in P. cancrivorus . The m. deltoideus in procyonidsis mainly divided into two parts, however, based on the topology of the m. cleidobrachialis and the distribution of the axillary nerve (Enciso-García and Vélez-García 2022; Vélez García et al. 2023), this latter muscle is the third part of the m. deltoideus named pars clavicularis (Vélez-García and Miglino 2023). Evolutionarily, it was a part joined to the pars acromialis from the reptiles to the last common ancestor of mammals ("deltoideus acromialis et clavicularis" Diogo et al., 2016). In carnivorans, both parts should have been separated due to the involution of the clavicle and its functional antagonism. This is because the acromialis and scapularis parts act together to flex the shoulder, and the pars clavicularis act to extend the shoulder together the m. cleidocephalicus (Diogo et al. 2012; Hermanson 2020; Vélez-García and Miglino 2023; Vélez‐García et al. 2023). The origin in common with the m. deltoideus pars scapularis and m. teres minor in one limb of P. cancrivorus could be associated with the evolutionary derivation of the m. teres minor from the m. deltoideus in tetrapods (Diogo et al. 2018, 2019). This can be supported within carnivorans since the m. teres minor has been found fused to the m. infraspinatus in mustelids of the superfamily Lutrinae (Otters) (Macalister 1870; Howard 1973; Ramírez Arango et al. 2024). Recently, it was corroborated due to the caudal aspect of the m. infraspinatus was being innervated by the n. axillaris in Lontra longicaudis (Ramírez Arango et al. 2024). Therefore, the presentation of a common origin of the deltoideus pars scapularis and teres minor muscles is a phylogenetic trade associated with the muscular derivation of the shoulder flexor muscles in mammals (Table 2). The shoulder joint is extended and stabilized by the supraspinatus and infraspinatus muscles. Besides, the presence of an intermuscular septum between the supraspinatus and subscapularis muscles in carnivorans has been related to a more force to extend and stabilize the shoulder since the bands of both muscles are disposed cranially to the scapula. This arrangement has been associated in species with locomotion mainly cursorial as canids (Vélez-García et al. 2018b) and as occurs in P. cancrivorus . The m. biceps brachii is another muscle that supports cranially the shoulder joint and extends it since its tendon of origin crosses internally the joint capsule of the shoulder. The teres major, teres minor, and subscapularis are shoulder flexors, and they are powered by the caudal portion of the m. tensor fasciae antebrachii due to its caudal arrangement together with the caput longum of the m. triceps brachii in P. cancrivorus . The same muscle support should occur in other carnivorans where the m. tensor fasciae antebrachii has a caudal arrangement, such as other procyonids (Beswick-Perrin 1871; Julitz 1909; Böhmer et al. 2020; Vélez-García et al. 2023), most mustelids (Macalister 1873; Cohen and Hart 1968; Howard 1973; Leach 1977; Ercoli et al. 2015; Böhmer et al. 2018, 2020; Yousefi et al. 2018; Ramírez Arango et al. 2024), ursids (Shepherd 1883; Davis 1964), and some felids (Concha et al. 2004; Vargas et al. 2017). The m. coracobrachialis is adductor and extensor of the shoulder(Hermanson et al. 2020) . The presence of only one m. coracobrachialis could be associated with species with more cursorial abilities that do not need major adduction force (Vélez-García et al. 2023), such as occurs in P. cancrivorus . The presence of two coracobrachialis muscles is a feature only present in some species of the suborders Caniformia and Feliformia. Among caniforms, this character is present in the procyonid P. flavus (Beswick-Perrin 1871; Julitz 1909; Vélez-García et al. 2023), mustelids of the genera Martes , Pekania and Eira (Macalister 1873; Mackintosh 1875; Leach 1977; Yousefi et al. 2018), the ailurid Ailurus fulgens (Carlsson 1925; Fisher et al. 2009), and ursids (Shepherd 1883; Kelley 1888; Windle and Parsons 1897; Davis 1964; Annie et al. 2019). Among feliforms, it is present in the euplerid Cryptoprocta ferox (Carlsson 1925; Böhmer et al. 2020)and viverrids of the genus Genetta (Taylor 1982)(Figure 7). The presence of two coracobrachialis muscles is phylogenetically related from the amphibians (Diogo et al. 2018), which is an arrangement that persists in reptiles, monotremes, some marsupials, and some eutherians (Gambaryan et al. 2015; Diogo et al. 2018; Richards et al. 2023). However, from an analysis of the functional and phylogenetic point of view within the family Carnivora, most of these species with two coracobrachialis muscles could be associated with a common ancestor with high arboreal abilities (Figure 7). This is supported due to the m. coracobrachialis has been lost together with m. teres minor in mustelids that do not have any arboreal ability, such as occurs in otters (Lutrinae) who are more specialized for natatorial locomotion (Haughton 1864; Windle and Parsons 1897; Cohen and Hart 1968; Howard 1973; Ramírez Arango et al. 2024). The elbow flexion is performed mainly by the biceps brachii and brachialis muscles, besides during flexion, they are supported by the brachioradialis and extensor carpi radialis muscles (Hermanson 2020; Vélez-García et al. 2022). Therefore, the presence of a second head in the m. biceps brachii should potentiate the elbow flexion intraspecifically in P. cancrivorus due to an origin more distal since it originated from the humerus. In other carnivorans with caput breve, the elbow flexion should increase the flexion velocity of the elbow since it has a more proximal origin (scapula), such as occurs in P. flavus (Böhmer et al. 2020; Vélez-García et al. 2023), A. fulgens (Fisher et al. 2009), and some ursids (Shepherd 1883; Kelley 1888; Davis 1964). The presence of a vestigial caput breve of m. biceps brachii in a P. lotor (Windle and Parsons 1897) could support the hypothesis that the common ancestor of procyonids potentially had it and conserved it from the common ancestor of arctoids. The caput breve could have disappeared within the family Procyonidae when the non- Potos genera diverged from the genus Potos (Table 2) (Fig. 7). Previously, the presence of several bicipital arteries had been associated with a higher activity of the m. biceps brachii in P. flavus (Vélez-García et al. 2023). However, after reviewing the arterial supply to the m. biceps brachii in P. cancrivorus , the presence of several bicipital arteries could be a characteristic within procyonids, which differs from canids (Vélez et al. 2018; Hermanson et al. 2020) and Felis catus (ICVGAN 2017), which only have one bicipital artery. The elbow extension in P. cancrivorus is powered by a m. triceps brachii with four heads, two anconeal muscles, and the two parts of the m. tensor fasciae antebrachii. Tarquini et al. (2023) for P. cancrivorus reported the cranial part of the m. tensor fascia antebrachii as a “caudal belly” to this, which originated from the m. cutaneous trunci and was also considered as part of this latter. However, these authors did not take into account the innervation and the direction of the muscle fibers to this belly, which should be reviewed to infer muscle derivation in vertebrates (Diogo and Abdala 2010). Therefore, based on the radial nerve distribution where the branch to the caudal part branched also to the cranial part, and the direction of the fibers is parallel, said belly is actually a part of the m. tensor fasciae antebrachii (Figure 4). Furthermore, the insertion aponeurosis is also fused to the tendon of the m. triceps brachii caput longum (Figure 6b), which is not reported in other studies of the same species and other procyonids. Thus, the synapomorphy of several origins in arctoids for the m. tensor fasciae antebrachii is also retained in P. cancrivorus . Previous studies in caniforms have determined that canids only conserve the cranial part of the m. tensor fasciae antebrachii while arctoids the caudal part (Feeney 1999; Vélez-García et al. 2023). In contrast, based on the origin of the m. tensor fasciae antebrachii only from the m. latissimus dorsi in canids (Feeney 1999; Pereira et al. 2016; Souza-Junior et al. 2018; Vélez et al. 2018; Böhmer et al. 2020; Smith et al. 2020), actually the part more conserved in caniforms is the caudal part while the presentation of the cranial part is variable in arctoids. What happens is that the m. tensor fasciae antebrachii is so developed in arctoids that it extends caudally to the caput longum of the triceps brachii, and is observed in the lateral views of the figures of several studies (Hall 1926; Davis 1964; Fisher et al. 2009; Moore et al. 2013; Ercoli et al. 2015; Böhmer et al. 2020; Tarquini et al. 2023; Vélez-García et al. 2023; Ramírez Arango et al. 2024). Besides, based on its topology and innervation, we could infer that this muscle is derived from the caput longum of the m. triceps brachii in carnivorans, which agrees with the evolutionary derivation from the last common ancestor of mammals (Diogo et al. 2018). The presence of a caput accessorium in the m. triceps brachii has been found in monotremes, and it has been inferred that it is a division of the caput mediale caused by the pass of the radial nerve (Gambaryan et al. 2015), which also occurs in carnivorans. On the other hand, the fusion presented by the laterale and accessorium heads in one P. cancrivorus specimen, and the distribution of the radial nerve to these heads, allow us to suggest that the caput accessorium could also be evolutionarily derived from the caput laterale in procyonids (Table 2). The extensor elbow muscles are supplied by the caudal circumflex, deep brachial, radial, and ulnar collateral arteries in P. cancrivorus , similar to that described in P. flavus (Vélez-García et al. 2023), A. melanoleuca (Davis 1964), C. thous (Vélez et al. 2018) and C. lupus familiaris (Hermanson et al. 2020). In PcS6, the deep brachial artery originated from the thoracodorsal artery differing from other specimens., Similarly in A. melanoleuca , that branch was described as a descending branch of the thoracodorsal artery that anastomoses with the deep brachial artery (Davis 1964). This differs from that presented in one specimen of P. cancrivorus since there was no formation of a homologous branch from the brachial artery. Unilaterally in PcS1, the deep brachial artery was formed by two branches of the brachial artery, which is not reported in any species. Based on the former dissections performed by Windle and Parsons (1897) in several carnivorans, the m. anconeus medialis is the most constant and is supplied by the ulnar nerve. This has been corroborated more recently in procyonids (Enciso-García and Vélez-García 2022; Vélez García et al. 2023), the mustelid Lontra longicaudis (Ramírez Arango et al. 2024), and felids (Barone 2020a; Barreto‐Mejía et al. 2022). In contrast, this muscle normally is not present in canids (Pereira et al. 2016; Souza-Junior et al. 2018; Vélez et al. 2018; Hermanson 2020; Smith et al. 2020) and ursids (Shepherd 1883; Davis 1964). If it is present in those species, it has a vestigial shape (Kelley 1888; Vélez-García et al. 2018a; Böhmer et al. 2020) or is fused to the caput mediale of the m. triceps brachii as was reported in the ursid Ailuropoda melanoleuca (Davis 1964). Therefore, the m. anconeus medialis lost functionality in the families Canidae and Ursidae. Several myological studies have named this muscle as another head of the m. triceps brachii in species of the order Carnivora, such as those studies performed in caniforms (Shepherd 1883; Leach 1977; Fisher et al. 2009; Ercoli et al. 2015; Böhmer et al. 2020) and feliforms (Julik et al. 2012; Viranta et al. 2016; Böhmer et al. 2020; Smith et al. 2021; Dunn et al. 2022). However, due to its topology and innervation by the ulnar nerve, the m. anconeus medialis in the order Carnivora retains its evolutionary derivation together the m. flexor carpi ulnaris in the caudolateral muscular complex of the antebrachium (Table 2) (Figure 7). This is due to the muscle is present in chordates from the amphibians, and it is not derivate from the m. triceps brachii (Diogo and Abdala 2010; Diogo et al. 2018; Molnar and Diogo 2021). The m. anconeus medialis should also act as a medial stabilizer of the elbow joint when the thoracic limb is fixed on the substrate. The presence of this muscle in procyonids could be related to a more developed medial epicondyle of the humerus (Tarquini et al. 2019; Vélez-García et al. 2023), which also gives origin to the caudomedial antebrachial musculature (McClearn 1985; Perdomo-Cárdenas et al. 2021). Therefore, high handling abilities in P. cancrivorus may also require more medial stabilization of the elbow while the caudomedial antebrachial musculature is acting. In conclusion, the most intrinsic shoulder and brachial musclesof P. cancrivorus potentially conserve the evolutionary derivation of the last common ancestor of mammals based on the topology, innervation, and anatomical variants. However, the division of the m. tensor fasciae antebrachii into two parts is a characteristic that appears within the infraorder Arctoidea and remains in most cases in P. cancrivorus . Statements and Declarations Funding This research was supported by grants from the Central Research Office of the University of Tolima to Juan Fernando Vélez García (Project Number 390116). Competing interests The authors declare no competing interests. Availability of Data and Materials Data are available in article supporting information. Acknowledgments Thanks to Universidad del Tolima, Universidade de São Paulo, Universidade Federal de Catalão, and CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Bolsa No. 88887.685526/2022-00) for support this research, and special thanks for CORTOLIMA and CORPOCALDAS for donating the cadavers. Conflict of Interest Statement The authors declare no competing interests. Author contributions JFVG and MAM performed the conception and design of the study. JFVG, DACB, GMG, and RACB acquired the data. JFVG, DACB, GMG, and MAM interpreted the data. JFVG, DACB, and GMG made the first version of the manuscript. 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AL, m. anconeus lateralis; AM, m. anconeus medialis; BTL, bursa tricipitalis lateralis; BTM, bursa tricipitalis medialis; Sb; m. subscapularis; SS, supraspinatus; TB, m. triceps brachii; TBa, caput accessorium; TBLa, caput laterale; TBLo, caput longum; TBm, caput mediale; TMaj, m. teres major. Supplementaryfigure2.jpg Supplementary figure 2 (a) cranial view of a m. biceps brachii joined to the m. brachialis in a right brachium; (b) medial view of a vestigial TFACr in a right brachium. AM, m. anconeus medialis; B, m. brachialis; BB, m. biceps brachii; CAMn, cutaneus antebrachii medialis nerve; TFACr, m. tensor fasciae antebrachii pars cranialis; TFACd, m. tensor fasciae antebrachii pars caudalis. , BB tendon joined to B *, medial independent tendon of BB. White bars: 10 mm. Cite Share Download PDF Status: Published Journal Publication published 23 Sep, 2024 Read the published version in Zoomorphology → Version 1 posted Editorial decision: Revision requested 05 Aug, 2024 Reviews received at journal 17 Jul, 2024 Reviews received at journal 08 Jul, 2024 Reviewers agreed at journal 05 Jul, 2024 Reviewers agreed at journal 01 Jul, 2024 Reviewers agreed at journal 01 Jul, 2024 Reviewers invited by journal 30 Jun, 2024 Editor assigned by journal 28 Jun, 2024 Submission checks completed at journal 28 Jun, 2024 First submitted to journal 26 Jun, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4644708","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":329495195,"identity":"8c7994d8-c61a-4c4a-9927-4a47e3471cc3","order_by":0,"name":"Juan Fernando Vélez García","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1klEQVRIiWNgGAWjYBACxuYDDAwPgAx+MJeNGC1tCQwMQMQg2cBMpBYGNqgWgwPEamFu4zF8kFBRZ7f5Rv4Bhg9lhxn42xsIOYzH2CDhDFvythvJDIwzzh1mkDhzgICW+W1pEoltPMlmQC3MvG2HGQwkEgjZwpb+I/GfRLLxDKCWv8RpYT7GkNhgYGcgAdTCSKSWwxIJxxISJM48NjjYcy6dh6BfDNsYGz98qKmz529PfPjgR5m1HMEQM4TKJ4JokPE8+NUDgTyUtieochSMglEwCkYuAADA/UEG7MsBUgAAAABJRU5ErkJggg==","orcid":"","institution":"Universidad del Tolima","correspondingAuthor":true,"prefix":"","firstName":"Juan","middleName":"Fernando Vélez","lastName":"García","suffix":""},{"id":329495198,"identity":"ec979644-78d6-4929-9bf3-640b3c95d57d","order_by":1,"name":"Diego Alejandro Carrión Blanco","email":"","orcid":"","institution":"Universidad del Tolima","correspondingAuthor":false,"prefix":"","firstName":"Diego","middleName":"Alejandro Carrión","lastName":"Blanco","suffix":""},{"id":329495200,"identity":"f5d75074-b048-49ac-8712-5dc8ac5d58f9","order_by":2,"name":"Gabriela Moreno Gómez","email":"","orcid":"","institution":"Universidad del Tolima","correspondingAuthor":false,"prefix":"","firstName":"Gabriela","middleName":"Moreno","lastName":"Gómez","suffix":""},{"id":329495203,"identity":"06e4fef1-52bd-4aef-80c5-c15eb5760987","order_by":3,"name":"Roseãmely Angelica Carvalho Barros","email":"","orcid":"","institution":"Universidade Federal de Catalão","correspondingAuthor":false,"prefix":"","firstName":"Roseãmely","middleName":"Angelica Carvalho","lastName":"Barros","suffix":""},{"id":329495205,"identity":"9bb8d4a1-a542-411a-bc88-78e71fc85df7","order_by":4,"name":"Maria Angelica Miglino","email":"","orcid":"","institution":"Universidade de Marília (UNIMAR)","correspondingAuthor":false,"prefix":"","firstName":"Maria","middleName":"Angelica","lastName":"Miglino","suffix":""}],"badges":[],"createdAt":"2024-06-26 20:02:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4644708/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4644708/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00435-024-00684-1","type":"published","date":"2024-09-23T15:57:36+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":60810682,"identity":"8bf85189-cbbd-42b4-a676-d280c5987e18","added_by":"auto","created_at":"2024-07-22 10:49:37","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":405360,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eLateral views of the intrinsic shoulder and brachial muscles in \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eProcyon cancrivorus\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e. Superficial (a) and deep views (b) of left thoracic limbs. \u003c/strong\u003eCHCdA, circumflexa humeri caudalis artery; B, m. brachialis; BcN, Brachiocephalic nerve; ClB, m. cleidobrachialis; Da, m. deltoideus pars acromialis; Ds, m. deltoideus pars scapularis; IS, m. infraspinatus; LD, m. latissimus dorsi; SbA, subscapularis artery; SS, m. supraspinatus; TB, m. triceps brachii; TBLa, caput laterale; TBLo, caput longum; TFACd, m. tensor fasciae antebrachii pars caudalis; TMaj, m. teres major; TMin, m. teres minor. White bars: 10 mm.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/5ccd62aa407198266148fa24.jpg"},{"id":60810683,"identity":"5525a826-c345-4bb1-a488-00764b45ba30","added_by":"auto","created_at":"2024-07-22 10:49:37","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":416904,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDeep views of the intrinsic shoulder and brachial muscles in \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eProcyon cancrivorus\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e. \u003c/strong\u003e(a) Lateral view of a right scapular region after to retract the supraspinatus and infraspinatus muscles; (b) Deep lateral view of the brachial region after to retract the caput laterale of the m. triceps brachii; (c) Medial view of a right m. biceps brachii with two heads. AL, m. anconeus lateralis; AM, m. anconeus medialis; Ax, axillaris nerve; B, m. brachialis; BB, m. biceps brachii; BBa, accessory head of BB; CHCdA, circumflexa humeri caudalis artery; ClB, m. cleidobrachialis; Da, m. deltoideus pars acromialis; Ds, m. deltoideus pars scapularis; Ds+TMin, common origin tendon of both muscles; IS, m. infraspinatus; PBA, profunda brachii artery; R, radialis nerve; RCA, radialis collateralis artery; Sb, m. subscapularis; SbpA, perforating branch of the subscapularis artery; SS, m. supraspinatus; SSc, suprascapularis nerve; TB, m. triceps brachii; TB, caput accessorium; TBLa, caput laterale; TBLo, caput longum; TMaj, m. teres major; TMin, m. teres minor. White bars: 10 mm.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/bb51d7bc93042793e8f23abf.jpg"},{"id":60811631,"identity":"cc08fbd8-2398-471b-9cfb-b61be69c3427","added_by":"auto","created_at":"2024-07-22 10:57:37","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":611655,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMedial photographic views of the intrinsic shoulder and brachial muscles of the right thoracic limb of a \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eProcyon cancrivorus\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e. \u003c/strong\u003e(a) TFACr was displaced caudally; (b) TFACr and TFACd were displaced caudally, and the BB cranially; (c) TFACr, TFACd , LD, CB, and Sb were removed. AM, m. anconeus medialis; B, m. brachialis; BB, m. biceps brachii; CB, m. coracobrachialis; LD, m. latissimus dorsi; Sb, m. subscapularis; SS, m. supraspinatus; TB, m. triceps brachii; TBa, caput accessorium; TBLa, caput laterale; TBLo, caput longum; TBm, caput mediale. TFACr, m. tensor fasciae antebrachii pars cranialis; TFACd, m. tensor fasciae antebrachii pars caudalis, TMaj, m. teres major, TMaj+LDi, insertion common area of both muscles, TMaj+LDT, common insertion tendon of both muscles. White bars: 10 mm.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/8a6c3b0b9857b17099084a4e.jpg"},{"id":60811633,"identity":"83fef74b-4f37-4091-afac-bbca660d4bfb","added_by":"auto","created_at":"2024-07-22 10:57:37","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":457629,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMedial photographic views of the arterial and nerve supply to the intrinsic shoulder and brachial muscles in a right thoracic limb of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eProcyon cancrivorus\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e. \u003c/strong\u003e(a) TFACr and TFACd were displaced caudally, and the BB cranially; (b) the arteries were removed. AA, axillary artery; AM, m. anconeus medialis; B, m. brachialis; BB, m. biceps brachii; BA, brachialis artery; BSA, brachialis superficialis artery; CB, m. coracobrachialis; CSA, cervicalis superficialis artery; CUA, collateralis ulnaris artery; LD, m. latissimus dorsi; Mc, musculocutaneus nerve; R, Radialis nerve; R’, branches to the TFA and TBLo; Sb, m. subscapularis; SbA, subscapularis artery; SS, m. supraspinatus; TB, m. triceps brachii; TBa, caput accessorium; TBLa, caput laterale; TBLo, caput longum; TBm, caput mediale. TCA, transversa cubiti artery; TD, thoracodorsalis nerve; TFACr, m. tensor fasciae antebrachii pars cranialis; TFACd, m. tensor fasciae antebrachii pars caudalis, TLA, thoracica lateralis artery; TMaj, m. teres major; U, ulnaris nerve. Black wide arrows: profunda brachii artery; White arrows, thoracodorsalis artery; *, bicipital arteries. White bars: 10 mm.\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/7b3c706d73e495a0c702787b.jpg"},{"id":60810690,"identity":"65ce3297-a184-41f3-ad8a-86e0f0687365","added_by":"auto","created_at":"2024-07-22 10:49:37","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":655920,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSuperficial photographic views of the tensor fasciae antebrachii muscle in \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eProcyon cancrivorus\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e. \u003c/strong\u003e(a) Medial view of a left brachium, (b) caudal view; (c) medial view of a right brachium. BB, m. biceps brachii; CT, m. cutaneus trunci; LD, m. latissimus dorsi; PS, mm. pectorales superficiales; PPCd, m. pectoralis profundus pars caudalis; TB, m. triceps brachii; TBLa, caput laterale; TBLo, caput longum; TFACr, m. tensor fasciae antebrachii pars cranialis; TFACd, m. tensor fasciae antebrachii pars caudalis, TMaj, m. teres major. Black wide arrows: profunda brachii artery; White arrows, thoracodorsalis artery; *, bicipital arteries. White bars: 10 mm.\u003c/p\u003e","description":"","filename":"Figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/9811e45c6fd3cf5ff08ec864.jpg"},{"id":60812398,"identity":"139cfb50-a34a-4cf6-be00-539bc2a412e6","added_by":"auto","created_at":"2024-07-22 11:05:37","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":390882,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDeep photographic views of the brachial muscles of the right thoracic limb of a \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eProcyon cancrivorus\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e. \u003c/strong\u003e(a) lateral view where the caput laterale was disposed caudally; (b) caudal view after to disposed laterally the TBLa and TBLo; (c) proximal view of the triciptal bursas; (d) caudal view after remove all triceps barchii haeds. AL, m. anconeus lateralis; AM, m. anconeus medialis; B, m. brachialis; BB, m. biceps brachii; BTL, bursa tricipitalis lateralis; BTM, bursa tricipitalis medialis; Sb; m. subscapularis; TB, m. triceps brachii; TBa, caput accessorium; TBLa, caput laterale; TBLo, caput longum; TBm, caput mediale. TFACr, m. tensor fasciae antebrachii pars cranialis; TFACd, m. tensor fasciae antebrachii pars caudalis. White bars: 10 mm.\u003c/p\u003e","description":"","filename":"Figure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/d7dd4cd34f32000ddb195f24.jpg"},{"id":60812399,"identity":"5549d44e-18eb-4b58-9fa4-4153d8276ad2","added_by":"auto","created_at":"2024-07-22 11:05:37","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":223290,"visible":true,"origin":"","legend":"\u003cp\u003eSome of the major features of the intrinsic shoulder and brachial muscles from the order Carnivora to family Procyonidae based on literature review and the present study. The phylogenetic three was based on Nyakatura et al. (2012).\u003c/p\u003e","description":"","filename":"Figure7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/80e011ff14a7a956b089d35d.jpg"},{"id":65627219,"identity":"76acd810-cc50-4abd-b95d-a52314e015bc","added_by":"auto","created_at":"2024-09-30 16:13:29","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4107241,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/854e994a-0387-4687-b41c-4d01078b9bce.pdf"},{"id":60810687,"identity":"31ced867-3b7d-47e1-861d-6f2689c4dd26","added_by":"auto","created_at":"2024-07-22 10:49:37","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":602725,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSupplementary figure 1\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(a) Cranial view of the intermuscular septum between the SS and Sb muscles in a right brachium; (b) Medial view of the intermuscular septum between the Sb and TMaj muscles in a left scapular region; (c) proximal view of the tricipital bursas of a right brachium. AL, m. anconeus lateralis; AM, m. anconeus medialis; BTL, bursa tricipitalis lateralis; BTM, bursa tricipitalis medialis; Sb; m. subscapularis; SS, supraspinatus; TB, m. triceps brachii; TBa, caput accessorium; TBLa, caput laterale; TBLo, caput longum; TBm, caput mediale; TMaj, m. teres major.\u003c/p\u003e","description":"","filename":"Supplementaryfigure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/0d13e8abdf67a9448e674dbd.jpg"},{"id":60810684,"identity":"4afda79e-ed10-4d47-844c-0169049b7609","added_by":"auto","created_at":"2024-07-22 10:49:37","extension":"jpg","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":501249,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSupplementary figure 2\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(a) cranial view of a m. biceps brachii joined to the m. brachialis in a right brachium; (b) medial view of a vestigial TFACr in a right brachium. AM, m. anconeus medialis; B, m. brachialis; BB, m. biceps brachii; CAMn, cutaneus antebrachii medialis nerve; TFACr, m. tensor fasciae antebrachii pars cranialis; TFACd, m. tensor fasciae antebrachii pars caudalis. *, BB tendon joined to B**, medial independent tendon of BB. White bars: 10 mm.\u003c/p\u003e","description":"","filename":"Supplementaryfigure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4644708/v1/f5df17c9fda0be71e8328722.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evolutionary derivation inferences of the intrinsic shoulder and brachial muscles in crab-eating raccoon (Procyon cancrivorus, Caniformia, Carnivora) based on the topology, innervation, and anatomical variants","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCrab-eating raccoon (\u003cem\u003eProcyon cancrivorus\u003c/em\u003e) is a species belonging to the family Procyonidae, suborder Caniformia, and order Carnivora (Nyakatura and Bininda-Emonds \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Hassanin et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). \u003cem\u003eP. cancrivorus\u003c/em\u003e is geographically distributed from Mexico to Brazil (Reid et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). It belongs to the genus \u003cem\u003eProcyon\u003c/em\u003e, which is characterized by having long thoracic limbs with manus adapted to a semidigitigrade support (McClearn \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). These limbs are mainly used for cursorial locomotion, but also to swim, manipulate food, and climb trees when is vitally necessary, such as escape from predators (Nowak \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Whiteside \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). To these functions in this species, the antebrachial muscles perform several movements, such as rotation, flexion, and extension of the manus and digits (Perdomo-C\u0026aacute;rdenas et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, the proximal thoracic limb muscles must act to move and fix the shoulder and elbow joints, giving support in the thoracic limb to allow more precise movements of the manus (Ercoli et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe intrinsic muscles of the scapular, shoulder, and brachial regions have been studied in several caniforms to review interspecific gross anatomical differences (Fisher et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Ercoli et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Pereira et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Souza-Junior et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; V\u0026eacute;lez et al. \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2018b\u003c/span\u003e, \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Smith et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Specifically on \u003cem\u003eP. cancrivorus\u003c/em\u003e, there are only four anatomical studies where the shoulder and brachial muscles are involved (Windle \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e1888\u003c/span\u003e; Pereira et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2010b\u003c/span\u003e; Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Among them, the more recent study performed a detailed anatomical description of \u003cem\u003eNasua nasua\u003c/em\u003e, where only the differences with \u003cem\u003eP. cancrivorus\u003c/em\u003e were included (Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). There are several differences among these studies regarding some muscles. Among them, the m. triceps brachii has been reported with three (Windle \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e1888\u003c/span\u003e), four (Pereira et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2010b\u003c/span\u003e), and five heads (Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The m. biceps brachii was reported inserted onto the radial and ulnar tuberosities (Pereira \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2010b\u003c/span\u003e), and only onto the radial tuberosity (Windle \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e1888\u003c/span\u003e; Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The m. brachialis was also reported with insertions onto radial and ulnar tuberosities (Santos et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2010b\u003c/span\u003e), only onto radial tuberosity (Pereira et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) or proximomedial aspect of the ulnar shaft (Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). These insertions to both muscles could be intraspecific anatomical variations in \u003cem\u003eP. cancrivorus\u003c/em\u003e, since the brachialis and biceps brachii muscles in most species of the infraorder Arctoidea only insert onto the ulna and radius, respectively (Windle and Parsons \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e1897\u003c/span\u003e; Davis \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1964\u003c/span\u003e; B\u0026ouml;hmer et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The other insertion onto the ulna by the m. biceps brachii is normally only present in species of the family \u003cem\u003eCanidae\u003c/em\u003e (Windle and Parsons \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e1897\u003c/span\u003e; Pereira et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Souza-Junior et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; V\u0026eacute;lez et al. \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; B\u0026ouml;hmer et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Hermanson \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Therefore, one of the characteristics to review in the present study is the anatomical arrangement of the biceps brachii and brachialis muscles in \u003cem\u003eP. cancrivorus\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eCaudal to the m. tensor fasciae antebrachii was found as an accessory belly with origin from the m. cutaneus trunci, which the authors inferred that said muscle is a part of the latter muscle, and not from the m. tensor fasciae antebrachii (Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, these authors did not take into account the innervation, which should be included together with the topology to infer the evolutionary muscle derivation (Diogo and Abdala \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), such as has been performed in other muscular groups in carnivorans (Diogo et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a and Miglino \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). For this belly to be considered part of the cutaneous trunci muscle, it would have been innervated by the lateral thoracic nerve. Specifically, in the procyonid \u003cem\u003eP. flavus\u003c/em\u003e, the cranial belly to the m. tensor fasciae antebrachii was considered part of this muscle since it is innervated by the radial nerve (V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Therefore, one of the hypotheses of the present study is that the accessory belly is part of the m. tensor fasciae antebrachii, and not of the m. cutaneus trunci in \u003cem\u003eP. cancrivorus\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eAnother muscle that is not taken into account in several studies is the m. anconeus medialis (m. anconeus epitrochlearis) (Windle \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e1888\u003c/span\u003e; Pereira et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2010b\u003c/span\u003e). In a recent study, the muscle was considered as a head of the m. triceps brachii (Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). This may have occurred because the name of this muscle is not present at the \u003cem\u003eNomina Anatomica Veterinaria\u003c/em\u003e (International Committee on Veterinary Gross Anatomical Nomenclature \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and its evolutionary derivation was not considered as proposed in vertebrates (Diogo et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In a former study and a recent study performed through a literature review and direct gross dissections in non-ursid arctoids was established that the m. anconeus medialis is the most constant muscle in these species and is innervated by the ulnar nerve (Windle and Parsons \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e1897\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In \u003cem\u003eFelis catus\u003c/em\u003e, there is one author who agrees with the name m. anconeus medialis because it is independent of the m. triceps brachii and is located collateral to the m. anconeus, which thus is named m. anconeus lateralis (Barone \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020b\u003c/span\u003e). Thereby, in the procyonid \u003cem\u003eP. flavus\u003c/em\u003e, the m. anconeus medialis was not considered as a head of the m. triceps brachii since its origin and insertion were independent, and it was innervated by the ulnar nerve (V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). This agrees with the evolutionary derivation of the m. anconeus medialis with the m. flexor carpi ulnaris, such as has been found in vertebrates from amphibians (Diogo and Abdala \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Diogo et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Therefore, another hypothesis is that the m. anconeus medialis in \u003cem\u003eP. cancrivorus\u003c/em\u003e is not a head of the m. triceps brachii, and conserves the evolutionary origin of most mammals.\u003c/p\u003e \u003cp\u003eThe present study aimed to review the topology and anatomical variants of the intrinsic scapular, shoulder, and brachial muscles in \u003cem\u003eP. cancrivorus\u003c/em\u003e compared with those reported in previous studies (Windle \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e1888\u003c/span\u003e; Pereira et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2010b\u003c/span\u003e; Tarquini et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The arterial supply to these muscles is also described to complement the study. Besides, to discuss the evolutionary derivation, the innervation reported previously was retaken in more detail (V\u0026eacute;lez Garc\u0026iacute;a et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). All these characteristics will contribute to the knowledge of evolutionary adaptations, muscle reconstructions in fossils, and veterinary procedures (Tarquini et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Dunn et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; V\u0026eacute;lez-Garc\u0026iacute;a et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eSix cadavers of \u003cem\u003eP. cancrivorus\u003c/em\u003e fixed in 10% formaldehyde (two females and four males) were used (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Five of them were previously dissected for the brachial plexus study (V\u0026eacute;lez Garc\u0026iacute;a et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, the characteristics of the muscles were not reported in that study. Gross anatomical dissections from superficial to deep on the intrinsic scapular and brachial muscles of all specimens were performed. The terminology was mainly based on the \u003cem\u003eNomina Anatomica Veterinaria\u003c/em\u003e (International Committee on Veterinary Gross Anatomical Nomenclature \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and other muscle terms were used, such as m. anconeus lateralis, m. anconeus medialis, pars caudalis and pars cranialis of the m. tensor fasciae antebrachii (Barone \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020a\u003c/span\u003e; V\u0026eacute;lez Garc\u0026iacute;a et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The arterial supply was only studied in three specimens (PcS1, PcS5, and PcS6), which had vascular repletion with natural latex tinctured with red vinyl. Photographs of the dissections were taken with a Canon T5i camera associated with a macro lens of 60 mm, and an EOS 6D camera associated with a macro lens of 100 mm. The use of these specimens was approved by the environmental entities of Colombia (CORTOLIMA and CORPOCALDAS) and Brazil (SISBIO Number 37072-2). This research was approved by the bioethics committees of the Universidad del Tolima (agreement number 2.3\u0026ndash;059), Universidade de S\u0026atilde;o Paulo (CEUAx agreement number 3928240820), and Universidade de Catal\u0026atilde;o (CEUA-UFCAT agreement number 01/22).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIdentification of the thoracic limbs dissected in \u003cem\u003eProcyon cancrivorus\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecies\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eID\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLimb\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"9\" rowspan=\"10\"\u003e \u003cp\u003e\u003cem\u003eProcyon cancrivorus\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePcS1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePcS2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePcS3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePcS4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePcS5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePcS6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRTL\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eA, adult; F, female; ID, specimen identification; J, juvenile; L, left thoracic limb; M, male; RTL, right thoracic limb\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"3. Results","content":"\u003cp\u003e\u003cstrong\u003e3.1\u0026nbsp;\u0026nbsp;Lateral scapular and shoulder muscles\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. deltoideus\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. deltoideus has two parts, pars acromialis and pars scapularis (Figure 1). The pars acromialis is fusiform, originates via tendinous and fleshy fibers from the ventral margin of the acromion (hamatus and suprahamatus processes). The origin is tendinous superficially and fleshy deeply. It is also fleshy at the caudal extreme of the suprahamatus process. Distally its fleshy fibers join to the pars scapularis tendon and also insert directly onto the deltoid tuberosity. It also receives fibers from the m. cleidobrachialis. The pars scapularis is triangular and fusiform, originates via an aponeurosis from the fascia over the m. infraspinatus and the distal half of the scapular spine. It originates via fleshy fibers from the caudal aspect of the suprahamatus process. It forms a wide tendon, which is also formed by a few tendinous fibers of the pars acromialis, and it receives fleshy fibers from this latter to insert onto the distal half of the lateral surface to the crest of greater tubercle and deltoid tuberosity. In one specimen unilaterally (PcS1), the pars scapularis also originated from the middle third of the caudal margin of the scapula via a common aponeurosis with the m. teres minor (Figure 2). Both parts are supplied by the caudal circumflex artery, and the pars scapularis also by the subscapular artery (Figure 2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. supraspinatus\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. supraspinatus is bipennate, originates via fleshy fibers from the supraspinous fossa, cranial aspect of the scapular spine (Figure 1), and intermuscular septum with the m. subscapularis\u0026nbsp;(Supplementary figure 1). It inserts onto the proximal extreme of the greater tubercle of the humerus via a strong tendon (Figure 2a). In one specimen (PcS5-LTL), an accessory belly originated from the distal margin of the acromion and was inserted caudally to the supraspinatus tendon. At the same specimen unilaterally (PcS5-LTL), an accessory belly was present cranially, which separated from the main belly for the pass of the brachiocephalic nerve (Figure 1b). The muscle is supplied by the lateral and medial branches of the suprascapular and caudal circumflex humeral arteries.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. infraspinatus\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. infraspinatus is pyramidal and bipennate, originates in a fleshy manner from the infraspinous fossa, the caudal aspect of the scapular spine, medial aspect of the suprahamatus process, and origin aponeurosis of the m. teres minor. It inserts via a tendon onto the caudoproximal extreme of the greater tubercle\u0026nbsp;(\u003cem\u003efacies m. infraspinatus\u003c/em\u003e), and there is a synovial bursa deep to the infraspinatus tendon (\u003cem\u003eBursa subtendinea m. infraspinati\u003c/em\u003e). It is supplied by the subscapular, caudal circumflex humeral, and circumflex scapular arteries (Figures 1 and 2a).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. teres minor\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. teres minor is fusiform, originates via an aponeurosis from the ventral third of the scapular caudal margin, and inserts onto the teres minor tuberosity, distally to the insertion of the supraspinatus tendon. It originated from the ventral half of the scapular caudal margin in PcS6, and the two ventral thirds in PcS5. In one specimen unilaterally (PcS1-RTL), it originated via a common aponeurosis with the m. deltoideus pars scapularis. It is supplied by the caudal circumflex humeral artery. In two specimens (PcS1, PcS6), it also was supplied by a branch of the subscapular artery, which perforated the origin tendon of the caput longum of m. triceps brachii (Figures 1 and 2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2\u0026nbsp;\u0026nbsp;Medial scapular and shoulder muscles\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. teres major\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. teres major is fusiform, originates from the lateral and caudal surfaces of the caudal angle of the scapula, adjacent fascia over the m. infraspinatus close to the caudal angle, dorsal third of the caudal margin of the scapula, and dorsal third of the intermuscular septum with the m. subscapularis\u0026nbsp;(Supplementary figure 1). It joins to the m. latissimus dorsi at the proximal extreme of the brachium and both form a common tendon to insert onto teres major tuberosity. It is supplied by the thoracodorsal, subscapular, and caudal circumflex humeral arteries (Figures 3 and 4).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. subscapularis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. subscapularis is multipennate with between five and seven bipennate bellies, which originate from the subscapular fossa, cranial margin of the scapula, middle third of the caudal margin of scapula (between the origins of the teres major and triceps brachiii caput longum muscles), and dorsal thirds of the intermuscular septa with the supraspinatus and teres major muscles (Supplementary figure 1). It inserts via a thick tendon onto the lesser tubercle of the humerus. In PcS6, it was also inserted onto the joint capsule and via fleshy fibers onto the caudal extreme of lesser tubercle. It is supplied by the subscapular, suprascapular, and deep cervical arteries. This later artery supplied it after passing through the m. serratus ventralis cervicis (Figures 3 and 4).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. coracobrachialis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. coracobrachialis is fusiform, originates from the coracoid process via a tendon that passes medial to the subscapular tendon protected by a synovial sheath, which is adhered to the subscapular tendon. It inserts via fleshy and tendinous fibers onto the caudal surface of the crest of lesser tubercle, just medial to the origin of the caput accessorium of m. triceps brachii (Figures 3 and 4). It is supplied by the cranial circumflex humeral artery.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3\u0026nbsp;\u0026nbsp;Cranial group of the brachium\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. biceps brachii\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. biceps brachii is bipennate, originates from the supraglenoid tubercle via a tendon, which passes deeply to the shoulder joint capsule and intertubercular groove protected by the transverse humeral retinaculum. \u0026nbsp;It inserts via a flat tendon onto the caudolateral surface of the radial tuberosity. The tendon is protected by a synovial bursa in the medial surface of the radial tuberosity (Figures 3 and 4). In PcS1 bilaterally, the muscle had an accessory head (humeral head) that originated from the intertubercular groove, proximal to the insertion of the common tendon of the teres major and latissimus dorsi muscles (Figure 2a).\u0026nbsp;In PcS5 unilaterally (RTL), the belly was shorter and distally divided into two gross fibrous fascicles, where one extended to the radial tuberosity and the other one joined to the m. brachialis. The more lateral fleshy fibers of the belly were directed toward the lateral fascicle. The medial antebrachial cutaneus nerve and the cubital transverse artery passed to the antebrachium between both fibrous fascicles (Supplementary Figure 2). The m. biceps brachii is supplied proximally by the cranial circumflex humeral artery, at the medium by two bicipital arteries (both originate directly from the brachial artery), and distally by the transverse cubital and superficial brachial arteries.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. brachialis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. brachialis is bipennate, originates mainly via fleshy fibers and also some superficial tendinous fibers from a wide region of the humerus, reaching the caudal and lateral surfaces of the humerus. It originates from the lateral aspect of the humeral neck, caudal aspect of the deltoid tuberosity, lateral aspect of the humeral crest (adjacent to the insertion of the cleidobrachialis tendon), and three proximal thirds of the medial aspect of the lateral supracondylar crest (Figure 5). It inserts via a flat tendon onto the distal surface to the medial coronoid process of the ulna. It is supplied by the axillary, transverse cubital, and radial collateral arteries (Figures 2, 3 and 4).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4\u0026nbsp;\u0026nbsp;Caudal group of the brachium\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. triceps brachii\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. triceps brachii is multipennate with four heads, such as caput longum, caput laterale, caput mediale and caput accessorium.\u0026nbsp;The caput longum originates via a strong flat tendon from the medial aspect of the ventral third of caudal scapular margin, and a stronger tendon from the infraglenoid tubercle (Figure 3c). Both tendons internally have fleshy fibers that also originate directly from the scapula. The formation of two tendons is performed for the pass of a branch of the subscapular artery toward the teres minor muscle (Figure 2b). The caput longum is supplied by the caudal humeral circumflex, deep brachial, collateral radial, and subscapular arteries.\u003c/p\u003e\n\u003cp\u003eThe caput laterale originates via an aponeurosis from the brachial fascia, tricipital line and lateral half of the humeral neck. It sends fleshy fibers to the longum and accessorium heads at the middle of the brachium, and to the caput mediale at the distal third. It is supplied by the axillary, radial collateral, and caudal humeral circumflex arteries. It also was supplied by the deep brachial artery in PcS1.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe caput accessorium originates mainly via fleshy fibers, extending from the medial half of the humeral neck to a short distance of the humeral shaft where begin the origin of the caput mediale. Tendinous fibers are observed medially in its origin. In PcS6, proximal fleshy fibers also originated from the shoulder joint capsule. It is supplied by the caudal humeral circumflex, deep brachial, and radial collateral arteries. In PcS5, the laterale and accessorium heads were fused bilaterally.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe caput mediale originates via an aponeurosis from the proximal quarter of the medial aspect of humeral shaft and sends fibers to the caput accessorium at the distal third of the brachium. It is supplied by the deep brachial and ulnar collateral arteries.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe laterale, accessorium and mediale heads insert through a tendon onto the cranial aspect of the olecranon tuberosity. The laterale and longum heads insert onto the caudal aspect of the olecranon tuberosity. The tendon of the caput laterale also inserts onto the lateral margin of the olecranon parallel to the insertion of the m. anconeus lateralis. The caput mediale also inserts via fleshy fibers at the medial aspect of the olecranon tuberosity, just proximal to the insertion of the m. anconeus medialis. There two tricipital synovial bursas between the tendons and the olecranon tuberosity. One is located laterally between the common tendon formed by the longum and laterale heads. Another one is located medially between the common tendon formed by the laterale, mediale and accessorium heads, and the m. anconeus lateralis (Figure 5).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. tensor fasciae antebrachii\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. tensor fasciae antebrachii is divided into two flattened bellies, cranial and caudal parts (pars cranialis and pars caudalis). The cranial part is totally located at the medial aspect of the brachium, parallel and cranial to the caudal part. It originates via an aponeurosis from a common tendon of several extrinsic thoracic limb muscles (medial belly of the m. latissimus dorsi, caudal part of the m. pectoralis profundus, pectoralis abdominalis and cutaneus trunci muscles). The caudal part is located at the caudal and medial aspects of the caput longum of m. triceps brachii, being always observed from the lateral view of the dissections of the brachium. \u0026nbsp;It originates via fleshy fibers from the main belly of the m. latissimus dorsi, and in some cases via fibrous fibers from the m. teres major (PcS3-RTL, PcS4, PcS5, PcS6). In PcS6, it was extended more cranially and was partially covered by the cranial part in both limbs. Both parts only join at the distal brachium in a common wide aponeurosis that fuses with the caudal and medial aspect of the caput longum triceps brachii tendon. It also inserts independently onto the medial margin of the olecranon and antebrachial fascia (Figure 6). The cranial part was absented in three limbs (PcS2 bilaterally, and PcS3-RTL) and had a vestigial shape in one limb (PcS3-LTL -Supplementary figure 2-). Both parts are supplied by the deep brachial artery, and the caudal part is also by the ulnar collateral artery.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. anconeus\u0026nbsp;lateralis (\u003cem\u003eM. anconeus\u003c/em\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. anconeus lateralis is pyramidal and originates via fleshy fibers from the distal third of the humeral shaft, caudal aspect of the lateral supracondylar crest, and lateral epicondyle of the humerus. It inserts via fleshy and tendinous fibers onto the lateral surface of the olecranon and caudolateral margin of the olecranon (Figures 2b, 3, and 5). The muscle always was deeply fused to the joint capsule of the elbow. It is supplied by the collateral ulnar and collateral radial arteries.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM. anconeus medialis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. anconeus medialis is triangular, originates via fleshy fibers from along the proximomedial margin of the supracondylar foramen, and medial epicondyle of the humerus. It inserts onto the medial surface of the olecranon, proximally via tendinous fibers, and distal- and deeply via fleshy fibers. It is supplied by the ulnar collateral artery (Figures 2c, 3, 4, and 5).\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003e\u003cstrong\u003e4.1\u0026nbsp;\u0026nbsp;Comparative anatomy of the intrinsic scapular and shoulder muscles in procyonids\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. deltoideus of \u003cem\u003eP. cancrivorus\u003c/em\u003e had a similar arrangement to that described formerly in the same species\u0026nbsp;(Santos et al. 2010b; Tarquini et al. 2023), and other procyonids, such as \u003cem\u003eProcyon lotor\u003c/em\u003e (Allen 1882; Feeney 1999), \u003cem\u003eNasua nasua\u003c/em\u003e (Mackintosh 1875; Santos et al. 2010a; Böhmer et al. 2020; Tarquini et al. 2023),\u0026nbsp;\u003cem\u003eNasua narica\u0026nbsp;\u003c/em\u003e(Mackintosh 1875),\u003cem\u003e\u0026nbsp;Bassaricyon alleni\u003c/em\u003e (Beddard 1900), and\u0026nbsp;\u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Beswick-Perrin 1871; Windle and Parsons 1897; Böhmer et al. 2020). However, the pars scapularis always originated from the fascia of the m. infraspinatus, in contrast with the findings of Tarquini et al. (2023) who only found that origin in\u0026nbsp;\u003cem\u003eN. nasua\u003c/em\u003e. On the other side, the variant origin of the pars scapularis from a common aponeurosis with the m. teres minor was not reported in any procyonid.\u003c/p\u003e\n\u003cp\u003eThe extended origin cranially to the cranial margin of scapula of the supraspinatus and subscapularis muscles forming an intermuscular septum had been described similarly in the same species\u0026nbsp;(Santos et al. 2010b)and \u003cem\u003eN. nasua\u0026nbsp;\u003c/em\u003e(Santos et al. 2010a).\u0026nbsp;The origin between both muscles was not reported in other studies in the same species\u0026nbsp;(Windle 1888; Tarquini et al. 2023), and neither in \u003cem\u003eP. lotor\u0026nbsp;\u003c/em\u003e(Allen 1882; Windle and Parsons 1897)and \u003cem\u003eP. flavus\u003c/em\u003e (Beswick-Perrin 1871; Windle and Parsons 1897; Böhmer et al. 2020; Vélez-García et al. 2023). In one specimen of\u0026nbsp;\u003cem\u003eN. nasua\u003c/em\u003e, a strong fascia was between both muscles, and in another specimen both muscles shared fibers\u0026nbsp;(Tarquini et al. 2023). The\u0026nbsp;variant presence of two bellies in the m. supraspinatus also was reported in this species\u0026nbsp;(Tarquini et al. 2023), but in that case, the accessory belly was superficial but not located cranially, such as occurred in one \u003cem\u003eP. cancrivorus\u003c/em\u003e specimen of the present study and one \u003cem\u003eP. lotor\u003c/em\u003e(Allen 1882). The insertion onto the humeral transverse retinaculum was found in none, while Tarquini et al. (2023) found it in their three specimens.\u003c/p\u003e\n\u003cp\u003eThe m. teres minor was completely independent to the m. infraspinatus in \u003cem\u003eP. cancrivorus\u003c/em\u003e, such as was formerly described in the same species\u0026nbsp;(Windle 1888; Pereira et al. 2010; Santos et al. 2010b; Tarquini et al. 2023)\u0026nbsp;and other procyonids\u0026nbsp;(Davis 1949; Böhmer et al. 2020; Tarquini et al. 2023; Vélez-García et al. 2023).\u0026nbsp;In some specimensof \u003cem\u003eP. lotor\u0026nbsp;\u003c/em\u003eand \u003cem\u003eP. flavus\u003c/em\u003e, the muscle may be fused to the m. infraspinatus\u0026nbsp;(Beswick-Perrin 1871; Allen 1882; Julitz 1909). The origin of the m. teres minor from the infraglenoid tubercle as was reported in \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003eand \u003cem\u003eN. nasua\u003c/em\u003e (Santos et al. 2010a, b)\u0026nbsp;was not found since the tubercle was occupied by the origin tendon of the m. triceps brachii caput longum, such as was recently reported\u0026nbsp;(Tarquini et al. 2023). The origin of the m. infraspinatus from the origin aponeurosis of the m. teres minor has only been described in \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Vélez-García et al. 2023).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBased on the most authors, the m. subscapularis does not have important differences among procyonid species\u0026nbsp;(Beswick-Perrin 1871; Mackintosh 1875; Windle and Parsons 1897; Julitz 1909; Santos et al. 2010a, b; Böhmer et al. 2020). However, it is divided into two portions in \u003cem\u003eBassariscus\u003c/em\u003e (Davis 1949), \u003cem\u003eP. lotor\u0026nbsp;\u003c/em\u003e(Davis 1949)\u003cem\u003e, N. narica\u003c/em\u003e (Davis 1949), and\u003cem\u003e\u0026nbsp;N. nasua\u003c/em\u003e (Tarquini et al. 2023). Besides, the muscle does not only originate from the subscapular fossa but from the cranial and caudal margins of the scapula in \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003e(Tarquini et al., 2023; present study)and \u003cem\u003eN. nasua\u0026nbsp;\u003c/em\u003e(Tarquini et al. 2023).\u003c/p\u003e\n\u003cp\u003eThe origin of the m. teres major from the infraspinatus and subscapularis muscles contrasts with other studies that did not find a connection with these muscles in the same species\u0026nbsp;(Santos et al. 2010b; Tarquini et al. 2023). While in \u003cem\u003eP. lotor\u0026nbsp;\u003c/em\u003e(Allen 1882; Davis 1949), \u003cem\u003eB. astutus\u003c/em\u003e, \u003cem\u003eN. narica\u0026nbsp;\u003c/em\u003e(Davis 1949)\u0026nbsp;and \u003cem\u003eN. nasua\u0026nbsp;\u003c/em\u003e(Tarquini et al. 2023), the origin is very similar to that found in our \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003especimens\u003cem\u003e.\u0026nbsp;\u003c/em\u003eThe origin from the infraspinatus muscle is not found in \u003cem\u003eP. flavus\u003c/em\u003e (Windle and Parsons 1897; Julitz 1909; Vélez-García et al. 2023), and in some specimens of \u003cem\u003eN. nasua\u003c/em\u003e (Santos et al. 2010a). Other authors did not report none origin to this muscle in \u003cem\u003eP. cancrivorus\u003c/em\u003e (Windle 1888)\u0026nbsp;and \u003cem\u003eNasua\u0026nbsp;\u003c/em\u003e(Mackintosh 1875). On the other side, the insertion onto the humerus was not found separated from the m. latissimus dorsi as was reported by other authors\u0026nbsp;(Tarquini et al. 2023).\u003c/p\u003e\n\u003cp\u003eThe m. coracobrachialis of \u003cem\u003eP. cancrivorus\u003c/em\u003e presented a small shape, such as was reported formerly in the same species\u0026nbsp;(Windle 1888; Tarquini et al. 2023), and other procyonids\u0026nbsp;(Mackintosh 1875; Allen 1882; Beddard 1900; Santos et al. 2010a; Tarquini et al. 2023). \u003cem\u003eP. flavus\u003c/em\u003e has another m. coracobrachialis named m. coracobrachialis longus\u0026nbsp;(Beswick-Perrin 1871; Windle and Parsons 1897; Julitz 1909; Vélez-García et al. 2023), which is absent in \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003eand other procyonids. However, it can also be absent in some \u003cem\u003eP. flavus\u003c/em\u003e specimens\u0026nbsp;(Vélez-García et al. 2023).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.2\u0026nbsp;\u0026nbsp;Comparative anatomy of the brachial muscles in procyonids\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe m. biceps brachii had one head in most specimens of \u003cem\u003eP. cancrivorus\u003c/em\u003e, being similar to that formerly described\u0026nbsp;(Mackintosh 1875; Windle 1888; Pereira et al. 2010; Santos et al. 2010a, b; Tarquini et al. 2023).\u0026nbsp;The other insertion onto the ulnar tuberosity described by some authors\u0026nbsp;(Pereira et al. 2010; Santos et al. 2010a, b)\u0026nbsp;was not found by us and other studies\u0026nbsp;(Windle 1888; Tarquini et al. 2023). In \u003cem\u003eP. flavus\u003c/em\u003e, the presence of a well-developed second head (caput breve) originating from the coracoid process of scapula is normal\u0026nbsp;(Beswick-Perrin 1871; Windle and Parsons 1897; Julitz 1909; Böhmer et al. 2020; Vélez-García et al. 2023). \u0026nbsp;In \u003cem\u003eP. lotor\u003c/em\u003e, that same head may be present in a feeble shape as anatomical variant\u0026nbsp;(Windle and Parsons 1897). However, that head (caput breve) is not the same accessory head found in one\u0026nbsp;\u003cem\u003eP. cancrivorus\u003c/em\u003e specimen, since it originated from the humerus. Similarly, a small humeral head was found in one case of\u0026nbsp;\u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Vélez-García et al. 2023).\u003c/p\u003e\n\u003cp\u003eThe m. brachialis originated from along caudolateral surface of the humerus including the medial aspect of the lateral supracondylar crest in \u003cem\u003eP. cancrivorus\u003c/em\u003e, which is similar to that reported previously\u0026nbsp;(Tarquini et al. 2023). In contrast, other studies reported the origin only from the proximal part of the humerus in the same species\u0026nbsp;(Pereira et al. 2010; Santos et al. 2010b)\u0026nbsp;and \u003cem\u003eN. nasua\u003c/em\u003e (Santos et al. 2010a; Böhmer et al. 2020). The origin from the whole lateral surface of the humerus was described in \u003cem\u003eN. nasua\u0026nbsp;\u003c/em\u003e(Mackintosh 1875), \u003cem\u003eN. narica\u003c/em\u003e (Mackintosh 1875), \u003cem\u003eP. lotor\u003c/em\u003e (Allen 1882), and \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Julitz 1909; Vélez-García et al. 2023). However, the origin has been described from the proximal half of the humerus in the latter species\u0026nbsp;(Beswick-Perrin 1871). The insertion only onto the ulna agrees with that described by most authors in procyonids\u0026nbsp;(Beswick-Perrin 1871; Mackintosh 1875; Allen 1882; Windle 1888; Beddard 1900; Julitz 1909; Böhmer et al. 2020; Tarquini et al. 2023), while the insertion onto the radius described by some authors in \u003cem\u003eP. cancrivorus\u003c/em\u003e and \u003cem\u003eN. nasua\u003c/em\u003e was not found\u0026nbsp;(Pereira et al. 2010; Santos et al. 2010a, b).\u003c/p\u003e\n\u003cp\u003eThe four heads of the m. triceps brachii in \u003cem\u003eP. cancrivorus\u003c/em\u003e were found as was previously reported by other authors\u0026nbsp;(Pereira et al. 2010; Santos et al. 2010b), and similar to \u003cem\u003eB. alleni\u003c/em\u003e (Beddard 1900), \u003cem\u003eP. lotor\u0026nbsp;\u003c/em\u003e(Allen 1882; Feeney 1999), \u003cem\u003eN. nasua\u0026nbsp;\u003c/em\u003e(Santos et al. 2010a), and \u003cem\u003eP. flavus\u003c/em\u003e (Julitz 1909; Vélez-García et al. 2023)\u003cem\u003e.\u0026nbsp;\u003c/em\u003eSeveral studies did not describe the caput accessorium of the m. triceps brachii or a homologous portion in procyonids\u0026nbsp;(Beswick-Perrin 1871; Mackintosh 1875; Windle 1888; Böhmer et al. 2020). Former studies only reported three heads in \u003cem\u003eP. cancrivorus\u003c/em\u003e (Windle 1888), \u003cem\u003eN. nasua\u0026nbsp;\u003c/em\u003e(Mackintosh 1875), and \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Beswick-Perrin 1871). A more recent study named four heads in \u003cem\u003eN. nasua\u003c/em\u003e and \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Böhmer et al. 2020), although the caput mediale accessorium is actually the m. anconeus medialis\u0026nbsp;(Vélez-García et al. 2023). In another more recent study was described that the muscle has five heads in \u003cem\u003eP. cancrivorus\u003c/em\u003e and \u003cem\u003eN. nasua\u003c/em\u003e (Tarquini et al. 2023), although, the caput mediale accessorium is actually the m. anconeus medialis. \u003cem\u003eP. lotor\u003c/em\u003e and \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003emay have five heads due to the presence of a second caput laterale\u0026nbsp;(Windle and Parsons 1897; Vélez-García et al. 2023). \u003cem\u003eN. narica\u003c/em\u003e may have four heads due to the presence of a second caput longum from the edge of the glenoid cavity\u0026nbsp;(Mackintosh 1875), which could be similar to that found in \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003ewhere the caput longum had two origins. In our study, several differences were found concerning that reported by Tarquini et al. (2023). Among them, fleshy fibers were not found at the origin of the caput laterale; the caput laterale sent fleshy fibers to all other heads; two tricipital bursas; and the division of the caput longum tendon by a perforating branch of the subscapular artery.\u003c/p\u003e\n\u003cp\u003eThe formation of two parts (cranial and caudal parts) in the m. tensor fasciae antebrachii in \u003cem\u003eP. cancrivorus\u003c/em\u003e has only been described in \u003cem\u003eP. lotor\u0026nbsp;\u003c/em\u003e(Feeney 1999)\u003cem\u003e, P. flavus\u003c/em\u003e (Vélez-García et al. 2023)\u0026nbsp;and \u003cem\u003eB. alleni\u0026nbsp;\u003c/em\u003e(Beddard 1900). The origin from the m. teres major was only found in \u003cem\u003eN. narica\u0026nbsp;\u003c/em\u003e(Mackintosh 1875)\u0026nbsp;and \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Vélez-García et al. 2023). The insertion onto the olecranon and antebrachial fascia was reported in\u003cem\u003e\u0026nbsp;P. flavus\u003c/em\u003e (Beswick-Perrin 1871; Julitz 1909; Vélez-García et al. 2023)\u0026nbsp;and one study in \u003cem\u003eP. cancrivorus\u003c/em\u003e (Pereira et al. 2010). While the unique insertion onto the olecranon was described in most procyonids\u0026nbsp;(Mackintosh 1875; Allen 1882; Santos et al. 2010a; Böhmer et al. 2020; Tarquini et al. 2023).\u0026nbsp;The tendinous fusion with the caput longum tendon of m. triceps brachii was not reported in any other study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe m. anconeus medialis in \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003ehad a similar arrangement to that described in a homologous part (with another term or portion of the m. triceps brachii) in the same species\u0026nbsp;(\"caput mediale accessorium\" Tarquini et al., 2023), \u003cem\u003eN. nasua\u0026nbsp;\u003c/em\u003e(\"m. triceps brachii caput mediale\" Böhmer et al., 2020; Mackintosh, 1875), \u003cem\u003eP. lotor\u003c/em\u003e (\"m. anconeus epitrochlearis\" Allen, 1882; Windle \u0026amp; Parsons, 1897), and \u003cem\u003eP. flavus\u003c/em\u003e (Beswick-Perrin 1871; Windle and Parsons 1897; Vélez-García et al. 2023). We found origin also from the medial epicondyle of the humerus in all \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003especimens similar to that found in \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Vélez-García et al. 2023). In contrast, it differs from that reported in the same species and \u003cem\u003eN. nasua\u003c/em\u003e where the origin only was from the supracondylar foramen\u0026nbsp;(Tarquini et al. 2023). This muscle or a homologous portion was not described by other authors\u0026nbsp;(Windle 1888; Pereira et al. 2010; Santos et al. 2010b), however, in one of those studies, it was pointed as accessory head of the m. triceps brachii in the figure 3\u0026nbsp;(Santos et al. 2010b). This corroborates that the muscle several times is missed by the authors, which may be because it is not present at the NAV\u0026nbsp;(ICVGAN 2017). In the case of \u003cem\u003eN. narica\u003c/em\u003e, both anconei muscles are reported united to the biceps\u0026nbsp;(Mackintosh 1875). However, this union could be a mistake of the author and could have referred to the m. triceps brachii since the anatomical relationship is closer with this muscle than the m. biceps brachii.\u003c/p\u003e\n\u003cp\u003eThe origin of the m. anconeus lateralis (\u003cem\u003em. anconeus\u003c/em\u003e) extended proximally reaching part of the humeral shaft in our specimens of \u003cem\u003eP. cancrivorus\u003c/em\u003e, which differed from other studies where the muscle only originates from the lateral supracondylar crest\u0026nbsp;(Mackintosh 1875; Pereira et al. 2010; Santos et al. 2010b; Böhmer et al. 2020; Tarquini et al. 2023).\u0026nbsp;\u003cem\u003eP. lotor\u003c/em\u003e (Allen 1882)\u0026nbsp;and \u003cem\u003eP. flavus\u003c/em\u003e (Vélez-García et al. 2023)\u0026nbsp;are the only two procyonid species where the muscle reaches the humeral shaft, even being more proximally extended than \u003cem\u003eP. cancrivorus\u003c/em\u003e. The muscle was not reported in a former study of \u003cem\u003eP. cancrivorus\u003c/em\u003e (Windle 1888). In some specimens of \u003cem\u003eP. flavus\u003c/em\u003e, the m. anconeus lateralis may be fused to the caput mediale of the m. triceps brachii\u0026nbsp;(Beswick-Perrin 1871; Julitz 1909).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.3 Anatomical variants of \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003epresent in other carnivorans\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSome anatomical variants found in \u003cem\u003eP. cancrivorus\u003c/em\u003e may be present in other species within the order Carnivora. The presence of two bellies in the m. supraspinatus has been reported in the canid \u003cem\u003eCerdocyon thous\u0026nbsp;\u003c/em\u003e(Vélez-García et al. 2018b), the felid \u003cem\u003ePanthera leo\u003c/em\u003e (Barone 1963), and the viverrid \u003cem\u003eCivettictis civetta\u003c/em\u003e (Macalister 1873b). While in the mustelid \u003cem\u003eGalictis cuja,\u003c/em\u003e it has three bellies\u0026nbsp;(Ercoli et al. 2015). The origin of the m. infraspinatus from the aponeurosis of the m. teres minor has been described in the ailurid\u0026nbsp;\u003cem\u003eAilurus fulgens\u003c/em\u003e (Fisher et al. 2009).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe m. tensor fasciae antebrachii has only been reported with more than one part in a few species. In two species, it has been reported with two portions with similar origins to those of \u003cem\u003eP. cancrivorus\u003c/em\u003e, such as the mustelids \u003cem\u003eEira barbara\u003c/em\u003e (Macalister 1873), \u003cem\u003eMartes caurina, Martes martes\u0026nbsp;\u003c/em\u003e(Yousefi et al. 2018)\u003cem\u003e, Pekania penanti\u003c/em\u003e (Feeney 1999), and the ursid \u003cem\u003eAiluropoda melanoleuca\u003c/em\u003e (Davis 1964). In the ursid \u003cem\u003eUrsus americanus\u003c/em\u003e, it was reported with three portions and inserted onto the medial epicondyle and olecranon\u0026nbsp;(Shepherd 1883). The insertion onto the triceps brachii tendon by the m. tensor fasciae antebrachii has been reported in the canid \u003cem\u003eCanis lupus familiaris\u003c/em\u003e (Hermanson 2020), the\u0026nbsp;mustelid \u003cem\u003eM. martes\u003c/em\u003e (Yousefi et al. 2018)\u0026nbsp;and the\u0026nbsp;felid\u0026nbsp;\u003cem\u003eLeopardus pardalis\u003c/em\u003e (Julik et al. 2012). The origin from the m. teres major\u0026nbsp;by the m. tensor fascia antebrachii\u0026nbsp;has been reported in \u003cem\u003eU. americanus\u003c/em\u003e (Shepherd 1883), \u003cem\u003eM. martes\u003c/em\u003e (Yousefi et al. 2018)\u0026nbsp;and the felid \u003cem\u003ePuma concolor\u003c/em\u003e (Concha et al. 2004).\u003c/p\u003e\n\u003cp\u003eFrom our knowledge, two anatomical variants found in \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003ehave not been reported in other carnivorans, such as the common origin aponeurosis of the teres minor and deltoideus pars scapularis muscles; the two variations of the m. biceps brachii; and the fusion of the laterale and accessorium heads of the m. triceps brachii.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.4 Comparative functional and evolutionary analysis of the intrinsic shoulder and brachial muscles in \u003cem\u003eProcyon cancrivorus\u0026nbsp;\u003c/em\u003ebased on the topology and innervation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe functional analysis has been excellently developed in the study of Tarquini et al. (2023) since they compared the muscle volume among muscular groups and other species. However, below, we include other functional and evolutionary inferences that were not analyzed in \u003cem\u003eP. cancrivorus\u003c/em\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe m. deltoideus in procyonidsis mainly divided into two parts, however, based on the topology of the m. cleidobrachialis and the distribution of the axillary nerve\u0026nbsp;(Enciso-García and Vélez-García 2022; Vélez García et al. 2023), this latter muscle is the third part of the m. deltoideus named pars clavicularis\u0026nbsp;(Vélez-García and Miglino 2023). Evolutionarily, it was a part joined to the pars acromialis from the reptiles to the last common ancestor of mammals\u0026nbsp;(\"deltoideus acromialis et clavicularis\" Diogo et al., 2016). In carnivorans, both parts should have been separated due to the involution of the clavicle and its functional antagonism. This is because the acromialis and scapularis parts act together to flex the shoulder, and the pars clavicularis act to extend the shoulder together the m. cleidocephalicus\u0026nbsp;(Diogo et al. 2012; Hermanson 2020; Vélez-García and Miglino 2023; Vélez‐García et al. 2023).\u0026nbsp;The origin in common with the m. deltoideus pars scapularis and m. teres minor in one limb of \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003ecould be associated with the evolutionary derivation of the m. teres minor from the m. deltoideus in tetrapods\u0026nbsp;(Diogo et al. 2018, 2019). This can be supported within carnivorans since the m. teres minor has been found fused to the m. infraspinatus in mustelids of the superfamily Lutrinae (Otters)\u0026nbsp;(Macalister 1870; Howard 1973; Ramírez Arango et al. 2024). Recently, it was corroborated due to the caudal aspect of the m. infraspinatus was being innervated by the n. axillaris in \u003cem\u003eLontra longicaudis\u003c/em\u003e (Ramírez Arango et al. 2024). Therefore, the presentation of a common origin of the deltoideus pars scapularis and teres minor muscles is a phylogenetic trade associated with the muscular derivation of the shoulder flexor muscles in mammals (Table 2).\u003c/p\u003e\n\u003cp\u003eThe shoulder joint is extended and stabilized by the supraspinatus and infraspinatus muscles. Besides, the presence of an intermuscular septum between the supraspinatus and subscapularis muscles in carnivorans has been related to a more force to extend and stabilize the shoulder since the bands of both muscles are disposed cranially to the scapula. This arrangement has been associated in species with locomotion mainly cursorial as canids\u0026nbsp;(Vélez-García et al. 2018b)\u0026nbsp;and as occurs in \u003cem\u003eP. cancrivorus\u003c/em\u003e. The m. biceps brachii is another muscle that supports cranially the shoulder joint and extends it since its tendon of origin crosses internally the joint capsule of the shoulder.\u003c/p\u003e\n\u003cp\u003eThe teres major, teres minor, and subscapularis are shoulder flexors, and they are\u0026nbsp;powered by the caudal portion of the m. tensor fasciae antebrachii due to its caudal arrangement together with the caput longum of the m. triceps brachii in \u003cem\u003eP. cancrivorus\u003c/em\u003e. The same muscle support should occur in other carnivorans where the m. tensor fasciae antebrachii has a caudal arrangement, such as other procyonids\u0026nbsp;(Beswick-Perrin 1871; Julitz 1909; Böhmer et al. 2020; Vélez-García et al. 2023), most mustelids\u0026nbsp;(Macalister 1873; Cohen and Hart 1968; Howard 1973; Leach 1977; Ercoli et al. 2015; Böhmer et al. 2018, 2020; Yousefi et al. 2018; Ramírez Arango et al. 2024), ursids\u0026nbsp;(Shepherd 1883; Davis 1964), and some felids\u0026nbsp;(Concha et al. 2004; Vargas et al. 2017).\u003c/p\u003e\n\u003cp\u003eThe m. coracobrachialis is adductor and extensor of the shoulder(Hermanson et al. 2020)\u003cem\u003e.\u0026nbsp;\u003c/em\u003eThe presence of only one m. coracobrachialis could be associated with species with more cursorial abilities that do not need major adduction force\u0026nbsp;(Vélez-García et al. 2023), such as occurs in\u0026nbsp;\u003cem\u003eP. cancrivorus\u003c/em\u003e. The presence of two coracobrachialis muscles is a feature only present in some species of the suborders Caniformia and Feliformia. Among caniforms, this character is present in the procyonid\u0026nbsp;\u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Beswick-Perrin 1871; Julitz 1909; Vélez-García et al. 2023), mustelids of the genera\u0026nbsp;\u003cem\u003eMartes\u003c/em\u003e,\u0026nbsp;\u003cem\u003ePekania\u003c/em\u003e and\u0026nbsp;\u003cem\u003eEira\u0026nbsp;\u003c/em\u003e(Macalister 1873; Mackintosh 1875; Leach 1977; Yousefi et al. 2018), the ailurid\u0026nbsp;\u003cem\u003eAilurus fulgens\u0026nbsp;\u003c/em\u003e(Carlsson 1925; Fisher et al. 2009), and ursids\u0026nbsp;(Shepherd 1883; Kelley 1888; Windle and Parsons 1897; Davis 1964; Annie et al. 2019). Among feliforms, it is present in the euplerid\u0026nbsp;\u003cem\u003eCryptoprocta ferox\u0026nbsp;\u003c/em\u003e(Carlsson 1925; Böhmer et al. 2020)and viverrids of the genus\u0026nbsp;\u003cem\u003eGenetta\u0026nbsp;\u003c/em\u003e(Taylor 1982)(Figure 7). The presence of two coracobrachialis muscles is phylogenetically related from the amphibians\u0026nbsp;(Diogo et al. 2018), which is an arrangement that persists in reptiles, monotremes, some marsupials, and some eutherians\u0026nbsp;(Gambaryan et al. 2015; Diogo et al. 2018; Richards et al. 2023). However, from an analysis of the functional and phylogenetic point of view within the family Carnivora, most of these species with two coracobrachialis muscles could be associated with a common ancestor with high arboreal abilities (Figure 7). This is supported due to the m. coracobrachialis has been lost together with m. teres minor in mustelids that do not have any arboreal ability, such as occurs in otters (Lutrinae) who are more specialized for natatorial locomotion\u0026nbsp;(Haughton 1864; Windle and Parsons 1897; Cohen and Hart 1968; Howard 1973; Ramírez Arango et al. 2024).\u003c/p\u003e\n\u003cp\u003eThe elbow flexion is performed mainly by the biceps brachii and brachialis muscles, besides during flexion, they are supported by the brachioradialis and extensor carpi radialis muscles\u0026nbsp;(Hermanson 2020; Vélez-García et al. 2022). Therefore, the presence of a second head in the m. biceps brachii should potentiate the elbow flexion intraspecifically in \u003cem\u003eP. cancrivorus\u003c/em\u003e due to an origin more distal since it originated from the humerus. In other carnivorans with caput breve, the elbow flexion should increase the flexion velocity of the elbow since it has a more proximal origin (scapula), such as occurs in \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Böhmer et al. 2020; Vélez-García et al. 2023), \u003cem\u003eA. fulgens\u003c/em\u003e (Fisher et al. 2009), and some ursids\u0026nbsp;(Shepherd 1883; Kelley 1888; Davis 1964). The presence of a vestigial caput breve of m. biceps brachii\u0026nbsp;in a \u003cem\u003eP. lotor\u003c/em\u003e (Windle and Parsons 1897)\u0026nbsp;could support the hypothesis that the common ancestor of procyonids potentially had it and conserved it from the common ancestor of arctoids. The caput breve could have disappeared within the family Procyonidae when the non-\u003cem\u003ePotos\u003c/em\u003e genera diverged from the genus \u003cem\u003ePotos\u0026nbsp;\u003c/em\u003e(Table 2) (Fig. 7). Previously, the presence of several bicipital arteries had been associated with a higher activity of the m. biceps brachii in\u0026nbsp;\u003cem\u003eP. flavus\u003c/em\u003e (Vélez-García et al. 2023). However, after reviewing the arterial supply to the m. biceps brachii in\u0026nbsp;\u003cem\u003eP. cancrivorus\u003c/em\u003e, the presence of several bicipital arteries could be a characteristic within procyonids, which differs from canids\u0026nbsp;(Vélez et al. 2018; Hermanson et al. 2020)\u0026nbsp;and\u0026nbsp;\u003cem\u003eFelis catus\u003c/em\u003e (ICVGAN 2017), which only have one bicipital artery.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe elbow\u0026nbsp;extension in \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003eis powered by a m. triceps brachii with four heads, two anconeal muscles, and the two parts of the m. tensor fasciae antebrachii. Tarquini et al. (2023) for \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003ereported the cranial part of the m. tensor fascia antebrachii as a “caudal belly” to this, which originated from the m. cutaneous trunci and was also considered as part of this latter. However, these authors did not take into account the innervation and the direction of the muscle fibers to this belly, which should be reviewed to infer muscle derivation in vertebrates\u0026nbsp;(Diogo and Abdala 2010). Therefore, based on the radial nerve distribution where the branch to the caudal part branched also to the cranial part, and the direction of the fibers is parallel, said belly is actually a part of the m. tensor fasciae antebrachii (Figure 4). Furthermore, the insertion aponeurosis is also fused to the tendon of the m. triceps brachii caput longum (Figure 6b), which is not reported in other studies of the same species and other procyonids. Thus, the synapomorphy of several origins in arctoids for the m. tensor fasciae antebrachii is also retained in \u003cem\u003eP. cancrivorus\u003c/em\u003e. Previous studies in caniforms have determined that canids only conserve the cranial part of the m. tensor fasciae antebrachii while arctoids the caudal part\u0026nbsp;(Feeney 1999; Vélez-García et al. 2023). In contrast, based on the origin of the m. tensor fasciae antebrachii only from the m. latissimus dorsi in canids\u0026nbsp;(Feeney 1999; Pereira et al. 2016; Souza-Junior et al. 2018; Vélez et al. 2018; Böhmer et al. 2020; Smith et al. 2020), actually the part more conserved in caniforms is the caudal part while the presentation of the cranial part is variable in arctoids. What happens is that the m. tensor fasciae antebrachii is so developed in arctoids that it extends caudally to the caput longum of the triceps brachii, and is observed in the lateral views of the figures of several studies\u0026nbsp;(Hall 1926; Davis 1964; Fisher et al. 2009; Moore et al. 2013; Ercoli et al. 2015; Böhmer et al. 2020; Tarquini et al. 2023; Vélez-García et al. 2023; Ramírez Arango et al. 2024).\u0026nbsp;Besides, based on its topology and innervation, we could infer that this muscle is derived from the caput longum of the m. triceps brachii in carnivorans, which agrees with the evolutionary derivation from the last common ancestor of mammals\u0026nbsp;(Diogo et al. 2018). The presence of a caput accessorium in the m. triceps brachii has been found in monotremes, and it has been inferred that it is a division of the caput mediale caused by the pass of the radial nerve\u0026nbsp;(Gambaryan et al. 2015), which also occurs in carnivorans. On the other hand, the fusion presented by the laterale and accessorium heads in one \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003especimen, and the distribution of the radial nerve to these heads, allow us to suggest that the caput accessorium could also be evolutionarily derived from the caput laterale in procyonids (Table 2).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe extensor elbow muscles are supplied by the caudal circumflex, deep brachial, radial, and ulnar collateral arteries in \u003cem\u003eP. cancrivorus\u003c/em\u003e, similar to that described in \u003cem\u003eP. flavus\u0026nbsp;\u003c/em\u003e(Vélez-García et al. 2023), \u003cem\u003eA. melanoleuca\u003c/em\u003e (Davis 1964), \u003cem\u003eC. thous\u003c/em\u003e (Vélez et al. 2018)\u0026nbsp;and \u003cem\u003eC. lupus familiaris\u0026nbsp;\u003c/em\u003e(Hermanson et al. 2020). In PcS6, the deep brachial artery originated from the thoracodorsal artery differing from other specimens., Similarly in \u003cem\u003eA. melanoleuca\u003c/em\u003e, that branch was described as a\u0026nbsp;descending branch of the thoracodorsal artery that anastomoses with the deep brachial artery\u0026nbsp;(Davis 1964). This differs from that presented in one specimen of \u003cem\u003eP. cancrivorus\u003c/em\u003e since there was no formation of a homologous branch from the brachial artery. Unilaterally in PcS1, the deep brachial artery was formed by two branches of the brachial artery, which is not reported in any species.\u003c/p\u003e\n\u003cp\u003eBased on the former dissections performed by Windle and Parsons\u0026nbsp;(1897)\u0026nbsp;in several carnivorans, the m. anconeus medialis is the most constant and is supplied by the ulnar nerve. This has been corroborated more recently in procyonids\u0026nbsp;(Enciso-García and Vélez-García 2022; Vélez García et al. 2023), the mustelid \u003cem\u003eLontra longicaudis\u0026nbsp;\u003c/em\u003e(Ramírez Arango et al. 2024), and felids\u0026nbsp;(Barone 2020a; Barreto‐Mejía et al. 2022). In contrast,\u0026nbsp;this muscle normally is not present in canids\u0026nbsp;(Pereira et al. 2016; Souza-Junior et al. 2018; Vélez et al. 2018; Hermanson 2020; Smith et al. 2020)\u0026nbsp;and ursids\u0026nbsp;(Shepherd 1883; Davis 1964). If it is present in those species, it has a vestigial shape\u0026nbsp;(Kelley 1888; Vélez-García et al. 2018a; Böhmer et al. 2020)\u0026nbsp;or is fused to the caput mediale of the m. triceps brachii as\u0026nbsp;was reported in the ursid \u003cem\u003eAiluropoda melanoleuca\u0026nbsp;\u003c/em\u003e(Davis 1964). Therefore, the m. anconeus medialis lost functionality in the families Canidae and Ursidae. Several myological studies have named this muscle as another head of the m. triceps brachii in species of the order Carnivora, such as those studies performed in caniforms\u0026nbsp;(Shepherd 1883; Leach 1977; Fisher et al. 2009; Ercoli et al. 2015; Böhmer et al. 2020)\u0026nbsp;and feliforms\u0026nbsp;(Julik et al. 2012; Viranta et al. 2016; Böhmer et al. 2020; Smith et al. 2021; Dunn et al. 2022).\u0026nbsp;However, due to its topology and innervation by the ulnar nerve, the m. anconeus medialis in the order Carnivora retains its evolutionary derivation together the m. flexor carpi ulnaris in the caudolateral muscular complex of the antebrachium (Table 2) (Figure 7). This is due to the muscle is present in chordates from the amphibians, and it is not derivate from the m. triceps brachii\u0026nbsp;(Diogo and Abdala 2010; Diogo et al. 2018; Molnar and Diogo 2021).\u0026nbsp;The m. anconeus medialis should also act as a medial stabilizer of the elbow joint when the thoracic limb is fixed on the substrate. The presence of this muscle in procyonids could be related to a more developed medial epicondyle of the humerus\u0026nbsp;(Tarquini et al. 2019; Vélez-García et al. 2023), which also gives origin to the caudomedial antebrachial musculature\u0026nbsp;(McClearn 1985; Perdomo-Cárdenas et al. 2021). Therefore, high handling abilities in \u003cem\u003eP. cancrivorus\u003c/em\u003e may also require more medial stabilization of the elbow while the caudomedial antebrachial musculature is acting.\u003c/p\u003e\n\u003cp\u003eIn conclusion, the most intrinsic shoulder and brachial musclesof \u003cem\u003eP. cancrivorus\u0026nbsp;\u003c/em\u003epotentially conserve the evolutionary derivation of the last common ancestor of mammals based on the topology, innervation, and anatomical variants. However, the division of the m. tensor fasciae antebrachii into two parts is a characteristic that appears within the infraorder Arctoidea and remains in most cases in \u003cem\u003eP. cancrivorus\u003c/em\u003e.\u003c/p\u003e"},{"header":"Statements and Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eThis research was supported by grants from the Central Research Office of the University of Tolima to Juan Fernando V\u0026eacute;lez Garc\u0026iacute;a (Project Number 390116).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData are available in article supporting information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThanks to Universidad del Tolima, Universidade de S\u0026atilde;o Paulo, Universidade Federal de Catal\u0026atilde;o, and CAPES (Coordena\u0026ccedil;\u0026atilde;o de Aperfei\u0026ccedil;oamento de Pessoal de N\u0026iacute;vel Superior, Bolsa No. 88887.685526/2022-00) for support this research, and special thanks for CORTOLIMA and CORPOCALDAS for donating the cadavers.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJFVG and MAM performed the conception and design of the study. JFVG, DACB, GMG, and RACB acquired the data. JFVG, DACB, GMG, and MAM interpreted the data. JFVG, DACB, and GMG made the first version of the manuscript. All authors approved the last version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAllen H (1882) The Muscles of the Limbs of the Raccoon (Procyon lotor). Proc Acad Nat Sci Philadelphia 34:115\u0026ndash;144\u003c/li\u003e\n\u003cli\u003eAnnie VR., Jamuna KV., Arun AS., et al (2019) Architecture of arm muscles of sloth bear (Melursus ursinus). J Entomol Zool Stud 7:1511\u0026ndash;1515\u003c/li\u003e\n\u003cli\u003eBarone R (2020a) Anatomie compar\u0026eacute;e des mammif\u0026egrave;res Domestiques. Tome 2: Arthrologie et Myologie., 4th edn. Association Centrale D\u0026rsquo;Entraide V\u0026eacute;t\u0026eacute;rinaire, Paris\u003c/li\u003e\n\u003cli\u003eBarone R (1967) La Myologie du lion (Panthera leo). Mammalia 31:459\u0026ndash;514. https://doi.org/10.1515/mamm.1967.31.3.459\u003c/li\u003e\n\u003cli\u003eBarone R (2020b) Anatomie compar\u0026eacute;e des mammif\u0026egrave;res Domestiques. Tome 2: Arthrologie et Myologie., 4th edn. Association Centrale D\u0026rsquo;Entraide V\u0026eacute;t\u0026eacute;rinaire, Paris\u003c/li\u003e\n\u003cli\u003eBarreto‐Mej\u0026iacute;a R, Ceballos CP, Tamayo‐Arango LJ (2022) Anatomical description of the origin and distribution of the brachial plexus to the antebrachium in one puma ( Puma concolor ) (Linnaeus, 1771). Anat Histol Embryol 51:153\u0026ndash;159. https://doi.org/10.1111/ahe.12761\u003c/li\u003e\n\u003cli\u003eBeddard FE (1900) On the Anatomy of Bassaricyon alleni. Proc Zool Soc London 69:661\u0026ndash;675. https://doi.org/10.1111/j.1096-3642.1890.tb01730.x\u003c/li\u003e\n\u003cli\u003eBeswick-Perrin J (1871) On the myology of the limbs of the Kinkajou (Cercoleptes caudivolvulus). Proc Zool Soc London 1871:547\u0026ndash;559\u003c/li\u003e\n\u003cli\u003eB\u0026ouml;hmer C, Fabre AC, Herbin M, et al (2018) Anatomical Basis of Differences in Locomotor Behavior in Martens: A Comparison of the Forelimb Musculature Between Two Sympatric Species of Martes. Anat Rec 301:449\u0026ndash;472. https://doi.org/10.1002/ar.23742\u003c/li\u003e\n\u003cli\u003eB\u0026ouml;hmer C, Theil J-C, Fabre A-C, Herrel A (2020) Atlas of Terrestrial Mammal Limbs. CRC press Taylor \u0026amp; FRancis Groups, Boca Raton\u003c/li\u003e\n\u003cli\u003eCarlsson A (1925) \u0026Uuml;ber Ailurus fulgens. Acta Zool 6:269\u0026ndash;305. https://doi.org/10.1111/j.1463-6395.1925.tb00268.x\u003c/li\u003e\n\u003cli\u003eCohen A, Hart JT (1968) On the anatomy of intonation. Lingua 19:177\u0026ndash;192. https://doi.org/10.1016/0024-3841(69)90118-1\u003c/li\u003e\n\u003cli\u003eConcha I, Adaro L, Borroni C, Altamirano C (2004) Consideraciones anat\u0026oacute;micas sobre la musculatura intrinseca del miembo tor\u0026aacute;cico del puma (Puma concolor). Int J Morphol 22:. https://doi.org/10.4067/S0717-95022004000200004\u003c/li\u003e\n\u003cli\u003eDavis DD (1964) The giant panda: a morphological study of evolutionary mechanisms. Fieldiana 3:1\u0026ndash;339\u003c/li\u003e\n\u003cli\u003eDavis DD (1949) The shoulder architecture of bears and other carnivores. Chicago Nat Hist Museum 31:285\u0026ndash;305. https://doi.org/10.5962/bhl.title.1291\u003c/li\u003e\n\u003cli\u003eDiogo R, Abdala V (2010) Muscles of vertebrates: Comparative anatomy, evolution, homologies and development, 1st edn. CRC press, Enfield\u003c/li\u003e\n\u003cli\u003eDiogo R, Bello‐Hellegouarch G, Kohlsdorf T, et al (2016) Comparative Myology and Evolution of Marsupials and Other Vertebrates, With Notes on Complexity, Bauplan, and \u0026ldquo;Scala Naturae.\u0026rdquo; Anat Rec 299:1224\u0026ndash;1255. https://doi.org/10.1002/ar.23390\u003c/li\u003e\n\u003cli\u003eDiogo R, Pastor F, De Paz F, et al (2012) The Head and Neck Muscles of the Serval and Tiger: Homologies, Evolution, and Proposal of a Mammalian and a Veterinary Muscle Ontology. Anat Rec Adv Integr Anat Evol Biol 295:2157\u0026ndash;2178. https://doi.org/10.1002/ar.22589\u003c/li\u003e\n\u003cli\u003eDiogo R, Siomava N, Gitton Y (2019) Development of human limb muscles based on whole-mount immunostaining and the links between ontogeny and evolution. Development 146:. https://doi.org/10.1242/dev.180349\u003c/li\u003e\n\u003cli\u003eDiogo R, Ziermann J, Molnar J, et al (2018) Chordate Muscles: Development, Homologies and Evolution. Taylor \u0026amp; Francis, Oxford, UK.\u003c/li\u003e\n\u003cli\u003eDunn RH, Beresheim A, Gubatina A, et al (2022) Muscular anatomy of the forelimb of tiger ( Panthera tigris ). J Anat. https://doi.org/10.1111/joa.13636\u003c/li\u003e\n\u003cli\u003eEnciso-Garc\u0026iacute;a LM, V\u0026eacute;lez-Garc\u0026iacute;a JF (2022) Origin and distribution of the brachial plexus in kinkajou ( Potos flavus \u0026ndash; Schreber, 1774). Anat Histol Embryol 51:221\u0026ndash;235. https://doi.org/10.1111/ahe.12781\u003c/li\u003e\n\u003cli\u003eErcoli MD, \u0026Aacute;lvarez A, Stefanini MI, et al (2015) Muscular anatomy of the forelimbs of the lesser grison (Galictis cuja), and a functional and phylogenetic overview of Mustelidae and other Caniformia. 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Rev FZVA 17:262\u0026ndash;275\u003c/li\u003e\n\u003cli\u003eSantos CMD., Santos SMD., Pizzutto CS., Cust\u0026oacute;dio AEI (2015) Enriquecimento Ambiental para Guaxinim, Procyon cancrivorus (Cuvier, 1798). Biosci j 31:275\u0026ndash;282\u003c/li\u003e\n\u003cli\u003eShepherd F (1883) Short notes on the myology of the american black bear (Ursus americanus). J Anat Physiol 18:103\u0026ndash;117. https://doi.org/10.1007/bf00203353\u003c/li\u003e\n\u003cli\u003eSmith HF, Adrian B, Koshy R, et al (2020) Adaptations to cursoriality and digit reduction in the forelimb of the African wild dog (Lycaon pictus). PeerJ 8:1\u0026ndash;34. https://doi.org/10.7717/peerj.9866\u003c/li\u003e\n\u003cli\u003eSmith HF, Townsend KEB, Adrian B, et al (2021) Functional Adaptations in the Forelimb of the Snow Leopard (Panthera uncia). Integr Comp Biol 61:1852\u0026ndash;1866. https://doi.org/10.1093/icb/icab018\u003c/li\u003e\n\u003cli\u003eSouza-Junior P, Santos LMRP dos, Viotto-Souza W, et al (2018) Functional myology of the thoracic limb in Pampas fox (Lycalopex gymnocercus): a descriptive and comparative analysis. J Anat 233:783\u0026ndash;806. https://doi.org/10.1111/joa.12892\u003c/li\u003e\n\u003cli\u003eTarquini J, Morgan CC, Toledo N, Soibelzon LH (2019) Comparative osteology and functional morphology of the forelimb of Cyonasua (Mammalia, Procyonidae), the first South American carnivoran. J Morphol 280:446\u0026ndash;470. https://doi.org/10.1002/jmor.20956\u003c/li\u003e\n\u003cli\u003eTarquini J, Mosto MC, Ercoli MD (2023) Functional and phylogenetic interpretation of the forelimb myology of two South American carnivorans, the ring‐tailed coati (Nasua nasua) and crab‐eating raccoon (Procyon cancrivorus). 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J Anat Physiol 23:81\u0026ndash;89\u003c/li\u003e\n\u003cli\u003eWindle B, Parsons F (1897) Myology of the terrestrial carnivora. Part I. Muscles of the head, neck, and fore-limb. Proc Zool Soc London 65:370\u0026ndash;409\u003c/li\u003e\n\u003cli\u003eYousefi MH, Rasouli B, Ghodrati S, et al (2018) Anatomical study of extrinsic and some intrinsic muscles of the thoracic limb in Iranian pine marten (Martes martes): A case report. Iran J Vet Med 12:273\u0026ndash;282. https://doi.org/10.22059/ijvm.2018.252150.1004876\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"zoomorphology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"zomo","sideBox":"Learn more about [Zoomorphology](http://link.springer.com/journal/435)","snPcode":"435","submissionUrl":"https://submission.nature.com/new-submission/435/3","title":"Zoomorphology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Anatomy, Insertion, Myology, Origin, Procyonidae","lastPublishedDoi":"10.21203/rs.3.rs-4644708/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4644708/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe crab-eating raccoon (\u003cem\u003eProcyon cancrivorus\u003c/em\u003e) is a carnivoran of the family Procyonidae geographically distributed in Center and South America. It is a scansorial species with more terrestrial than arboreal abilities. Previous studies have described the intrinsic shoulder and brachial muscles in this species; however, all have different descriptions. Besides, these studies did not take into account the innervation to infer the evolutionary derivation of the muscles, and neither did the arterial supply. Therefore, the present study aimed to analyze the anatomical arrangement of the intrinsic shoulder and brachial muscles in six \u003cem\u003eProcyon cancrivorus\u003c/em\u003e specimens fixed with 10% formaldehyde. The shape, origin, insertion, arterial supply, and variations were described. Furthermore, the innervation previously reported was reviewed again in detail to infer the evolutionary derivation of these muscles. Differences were found with that reported formerly in the same species and other procyonids. Some intraspecific anatomical variants were discovered, such as an accessory head in the biceps brachii muscle bilaterally; a biceps brachii muscle joined to the brachialis muscle unilaterally; and a fusion of the lateral and accessory heads of the triceps brachii muscle bilaterally. Tensor fasciae antebrachii muscle is divided into two parts in most cases, and both are innervated by the radial nerve. The anconeus medialis muscle is independent to the triceps brachii muscle and is innervated by the ulnar nerve. In conclusion, based on the topology, anatomical variations, and innervation of these muscles in \u003cem\u003eP. cancrivorus\u003c/em\u003e, they potentially conserve the evolutionary derivation of the last common ancestor of mammals.\u003c/p\u003e","manuscriptTitle":"Evolutionary derivation inferences of the intrinsic shoulder and brachial muscles in crab-eating raccoon (Procyon cancrivorus, Caniformia, Carnivora) based on the topology, innervation, and anatomical variants","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-22 10:49:32","doi":"10.21203/rs.3.rs-4644708/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-08-05T12:06:55+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-17T17:50:08+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-08T15:43:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"126732266629213974496334145143649188995","date":"2024-07-05T18:49:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"227621988406442896469052497310383020809","date":"2024-07-01T12:32:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"229791047203529025876874897738810339047","date":"2024-07-01T12:17:17+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-30T09:31:55+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-06-28T07:41:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-06-28T07:40:24+00:00","index":"","fulltext":""},{"type":"submitted","content":"Zoomorphology","date":"2024-06-26T20:00:22+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"zoomorphology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"zomo","sideBox":"Learn more about [Zoomorphology](http://link.springer.com/journal/435)","snPcode":"435","submissionUrl":"https://submission.nature.com/new-submission/435/3","title":"Zoomorphology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"b270a904-60c2-41e9-9817-89f526fd7814","owner":[],"postedDate":"July 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-09-30T16:03:18+00:00","versionOfRecord":{"articleIdentity":"rs-4644708","link":"https://doi.org/10.1007/s00435-024-00684-1","journal":{"identity":"zoomorphology","isVorOnly":false,"title":"Zoomorphology"},"publishedOn":"2024-09-23 15:57:36","publishedOnDateReadable":"September 23rd, 2024"},"versionCreatedAt":"2024-07-22 10:49:32","video":"","vorDoi":"10.1007/s00435-024-00684-1","vorDoiUrl":"https://doi.org/10.1007/s00435-024-00684-1","workflowStages":[]},"version":"v1","identity":"rs-4644708","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4644708","identity":"rs-4644708","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}