Background Saguinus leucopus is a Neotropical primate with an arboreal quadrupedal locomotion pattern, which requires wide movements of the shoulder and arm. This investigation studies the muscles of these regions in order to serve as a basis for clinical and surgical procedures and to compare with other primates. Methods Gross dissections of twenty thoracic limbs were performed. Results The muscles examined were the deltoid, supraspinatus, infraspinatus, subscapularis, teres major, teres minor, coracobrachialis longus, coracobrachialis brevis, biceps brachii, brachialis, triceps brachii, tensor fasciae antebrachii, and anconeus epitrochlearis. The anconeus was absent. The following variants were found: an accessory head of the biceps brachii, the unilateral absence of the short head of the biceps brachii, an accessory head of the coracobrachialis longus, and one infraspinatus muscle innervated by the axillary nerve. Conclusions These muscles are adapted to quadrupedal locomotion and can have inter‐ and intraspecific variations in their attachments and innervation.

The white‐footed tamarin (Saguinus leucopus) is an endangered endemic primate of Colombia, mainly due to the deforestation of its habitat and illegal trade, which generates a high incidence of these animals in wildlife care centres. Musculoskeletal system disorders in S. leucopus are one of the most common diseases and therefore the aim of this study was to contribute to the morphologic studies with a morphometric, anatomic and radiographic description of the scapula in this species to provide a basis for medical interventions, surgical approaches, radiologic diagnoses and comparative functions of this bone. Gross dissections of each scapular region were made in eight specimens without a diagnosis of osteomuscular disease. These specimens died from natural cases in the wildlife care centres of the Corporación Autónoma Regional de Caldas (CORPORCALDAS); after necropsy their carcasses were fixed with 10% formaldehyde, 5% mineral oil and 1% phenic acid in these centres over the course of at least 1 week. X‐rays of the scapula were taken in the small animal clinic of the Universidad del Tolima, and morphometric data of the scapulae were obtained with a digital calliper. The scapula of the white‐footed tamarin was a flat triangular bone with a deep scapular notch in its cranial margin, where there was a cranial transverse scapular ligament that was absent in two specimens. The coracoid process was highly developed, medially covering the humeral joint. The dorsal margin was covered by the scapular cartilage, which was highly developed in the caudal angle. In the dorsal fourth of the caudal margin, there was a surface from which the m. teres major originated. The lateral surface had a scapular spine with a long hamatus process of the acromion until the lateral part of the humeral joint. The infraspinatus fossa was wider than the supraspinous fossa. On the costal surface, the subscapular fossa was formed by three subscapular lines and one subscapular ridge, the latter helping to form the surface for the m. teres major. In the two radiographic views, caudocranial to the scapula and dorsoventral to the thorax, the scapular spine, acromion, coracoid process, scapular incisura, supraglenoid tubercle, caudal margin, subscapular ridge, and the joints with the clavicle and the humerus could be observed. The scapula of the white‐footed tamarin presented bony reliefs that share characteristics with other primates but also with domestic mammals due to its quadrupedal locomotion, which allowed us to correlate its morphologic adaptation with its quadrupedal arboreal displacement.

The crab-eating raccoon Procyon cancrivorus (Cuvier, 1798) is a species of the order Carnivora and family Procyonidae with a geographical distribution in Central and South America. Although crab-eating raccoons use scansorial locomotion, they also have aquatic habits, displaying greatly developed skills when handling their food. This species can frequently be found in wildlife care centers due to injuries caused by domestic dogs, humans, and car collisions. Having knowledge of the species’ gross anatomy and anatomical bases is imperative to perform the most appropriate medical and surgical procedures. Thus, the objective of this investigation was to analyze the interspecific and intraspecific differences of the craniolateral forearm muscles of Procyon cancrivorus. Gross dissections were performed in four specimens describing the origin, insertion, shape, innervation, and arterial supply of the craniolateral forearm muscles. There is a constant and well development of brachioradialis muscle comparatively to that described in strictly cursorial species; the extensor carpi radialis muscle has two bellies that are fused proximally; the extensor digitorum communis muscle can also extend the tendon to the digit I as an anatomical variant, and the extensor digiti I and II muscle also extends the tendon to digit III. All are innervated by the deep branch of the radial nerve, and their arterial supply is mainly by the radial collateral, cubital transverse, and cranial interosseous arteries. The anatomical characteristics observed in this study complement the previous descriptions for Procyon cancrivorus, and the anatomical variants found in this species can also be in other carnivorans. Thus, the intraspecific anatomical variations of the digital extensor muscles in P. cancrivorus are phylogenetic traits that can occur as a common pattern or as anatomical variants in other species of the order Carnivora.

Sapajus apella is a Neotropical primate, commonly known as robust brown capuchin monkey. It belongs to the family Cebidae, which has two genera, such as Sapajus and Cebus. 1 The former comprises the most robust capuchins, and the latter consists of smaller-sized capuchins. 2 S. apella is distributed in South America, with the majority of the population in Brazil. It has a coat that varies between yellow and brown color. 3,4 The S. apella is considered a small primate, weighing between five and six kilogrames, 3,5 a characteristic that makes it easy-to-handle for laboratory work. In addition, it has the capacity to adapt to closed spaces and reproduce relatively easy in captivity. 5 Its diet is based on fruits, seeds, flowers, and insects, 3 for which it has developed an arboreal locomotion with terrestrial capacities.It is thought to spend 40% of its time in quadrupedal locomotion, and the remaining 60%, in arboreal habitats, mainly with climbing movements in trees and jumping between branches. 6 This species is one of the platyrrhine primates with the most remarkable cognitive abilities, 7 as it can handle tools due to, even with intermittent bipedalism. 8 Despite these locomotor skills, the anatomy involved in its different types of locomotion has not been described, particularly the extrinsic thoracic limb and brachial muscles. There is only a study about the intrinsic scapular muscles, 3 but the other muscles were not described. Other anatomical studies related to the