# Hand Musculature of the Common Marmoset (Callithrix jacchus): An Anatomical Study with Reference to the Rhesus Monkey (Macaca mulatta)

## TL;DR

This study provides a detailed anatomical description of the hand muscles in common marmosets, comparing them to rhesus monkeys to aid in medical care.

## Contribution

The study offers a modern, detailed anatomical analysis of the marmoset hand musculature with color photographs and comparisons to rhesus monkeys.

## Key findings

- The hand musculature of the common marmoset is highly similar to that of the rhesus monkey.
- Dorsal and palmar views of the marmoset's hand musculature were described in detail with color photographs.
- Notable differences in hand musculature between the two species were identified and discussed.

## Abstract

The common marmoset (Callithrix jacchus) is often used as a primate model in scientific research. The hand of this animal is sometimes wounded during conflicts with conspecifics. Tending the wounds requires insight into the anatomy of the hand, especially the muscles and tendons. Therefore, these structures were examined in detail during the dissections of several cadavers. Color photographs were taken, and the observed muscles and tendons were described. The findings were compared with the scarce literature about the anatomy of the marmoset. Unfortunately, the literature showed outdated terms, provided only line drawings, or did not include the anatomy of the hand. The hand musculature of the common marmoset resembles that of the rhesus monkey (Macaca mulatta). A few dissimilarities have been observed and are discussed. This work can be used for veterinarians responsible for the medical care of wounded marmosets.

The common marmoset (Callithrix jacchus) is a New World Monkey that frequently serves as a model in biomedical research. Our knowledge of its anatomy is the fundament of the provision of the correct environment, housing, and care together with provision of accurate medical care in the case it gets wounded. In this anatomical research article, the focus is on the hand musculature, as it plays a pivotal role in the interaction with the environment and conspecifics. Surprisingly, anatomical works on the common marmoset are scarce. The available books and atlases are either outdated in terms of illustrations, providing only simplified line drawings, and/or fail to recapitulate the anatomy of the hand using contemporary anatomical nomenclature. The present work describes the myology of the hand, based on dissections of common marmoset cadavers. Color photographs taken during the subsequent steps of the examinations lead the reader through the textual descriptions. Dorsal and palmar views of the antebrachial muscles with influence on the wrist and hand as well as the intrinsic hand musculature are scrutinized. The findings are finally discussed in view of potential contradictions with the available literature. In addition, comparison is made with the rhesus monkey (Macaca mulatta) whose hand musculature was recently revisited. It is concluded that the hand musculature of both species is highly similar, although remarkable differences are present. This work could serve as an anatomical foundation for medical interventions of the injured hand.