Morphometric, anatomic and radiographic study of the scapula in the white‐footed tamarin (Saguinus leucopus): report of scapular cartilage and one variation in cranial (superior) transverse scapular ligament

Abstract

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.

Anatomical and radiographic study of the scapula in juveniles and adults of Tamandua mexicana (Xenarthra: Myrmecophagidae)

“…For human and domestic mammals, there is no specific term for this surface (Federative International Committee on Anatomical Terminology, ; ICVGAN, ), but it can be seen a surface for the origin of the m. teres major in the graphic representations of the scapula in the domestic dog (Evans & de Lahunta, ) and the human (Standring, ). Even in non‐human primates, this surface has already been previously described (Mivart, ), and current studies have indicated its presence such as in Lemur catta (Makungu, Groenewald, Plessis, Barrows, & Koeppel, ), cercopithecids (Dunham, Kane, & McGraw, ) and Saguinus leucopus (Vélez‐García, Monroy‐Cendales, & Castañeda‐Herrera, ). However, these are different to Tamandua, because this surface is not so great as to give origin to the m. subscapular, similar to what occurs in armadillos, where it is observed that this surface is wide but only at the level of the caudal angle (Acuña, Sidorkewicj, Popp, & Casanave, ; Miles, ; Olson, Womble, Thomas, Glenn, & Butcher, ; Taylor, ), which is considered by Monteiro and Abe () as an expansion of the infraspinous fossa in armadillos and developed due to the greater retraction required by the thoracic limb in order to dig—where a major part of the force is contributed by the m. teres major for their fossorial habits (Olson et al, ).…”

“…This differs to our findings in T. mexicana where there is a scapular cartilage, similar to that of domestic carnivores, which extends the insertion surface of the rhomboideus muscles (Budras et al, ; Dyce et al, ; Evans & de Lahunta, ; Liebich et al, ), where these are extrinsic muscles and, together with the cartilage, should act as a shock absorber during quadrupedal locomotion (Liebich et al, ). This cartilage has been reported in a primate such as S. leucopus , which has arboreal quadrupedal locomotion (Vélez‐García et al, ), and thus, the development of this cartilage in T. mexicana allows us to suggest that it is an adaptation for movement in trees and on the ground. This cartilage can ossify with the passing of the age in T. mexicana similar to equines (Dyce et al, ; Liebich et al, ).…”

“…The ligament in the cranial margin at the level of the incisura scapular in T. mexicana, which by Silva and Cuenca (2012) in T. tetradactyla is reported as complete, by comparative anatomy must correspond to the superior transverse scapular ligament of the human (FICAT, 1998) and the cranial transverse scapular ligament of S. leucopus , since in these species develop one space for the passage of the suprascapular nerve (Netter, 2017;Standring, 2016;Vélez-García et al, 2019) and sometimes as an anatomical variant it is ossified, developing one foramen in the human (Agrawal et al, 2015;Bayramoğlu et al, 2003;Büyükmumcu et al, 2013;Kannan, Kannan, Anbalagan, & Rao, 2014;Polguj et al, 2014;Standring, 2016), which is normal in other primates (Ackermann, 2003;Ankel-Simons, 2007;Mivart, 1866;Osman-Hill, 1959;Youlatos, 2000). This foramen is not found in Cyclopes because the coracoid has been reduced (McDonald et al, 2008), but it can be found in other xenarthrans as sloths (Flower, 1882;Montilla-Rodríguez et al, 2016;Toledo et al, 2013).…”

Gross anatomy of the shoulder and arm intrinsic muscles in the white‐footed tamarin (Saguinus leucopus – Günther, 1876): Inter‐ and intraspecific anatomical variations

“…Another female with mid‐radial amputation was also included. Ten of them were previously used for a morphometric, anatomic, and radiographic study of the scapula …”

“…The white‐footed tamarin ( Saguinus leucopus ) is an endemic primate of Colombia that is illegally trafficked as a pet, and as such, it is continuously present in wildlife care centers with injuries to its musculoskeletal system, in which the shoulder and arm may be affected. Thus, it is of great importance to provide specific anatomical knowledge of its muscles so that adequate clinical and surgical approaches to the scapula and humerus may be performed.…”