Muscular Anatomy of the Forelimbs of the Lesser Grison (Galictis cuja), and a Functional and Phylogenetic Overview of Mustelidae and Other Caniformia

Abstract

The extrinsic and intrinsic forelimb musculature of the lesser grison (Galictis cuja), a short-legged mustelid of southern South America, is studied for the first time. We present descriptions, muscular maps, and weight data. Muscular anatomy description of the lesser grison provides the framework for discussing the myological diversity of mustelids and other caniforms, for addressing nomenclatural problems (such as synonymy and homonymy), and for highlighting some functional and phylogenetically informative traits. We recognize in the lesser grison features shared by all mustelid species, and some other caniforms, especially mephitids, such as the presence of rhomboideus profundus, an angular head of triceps brachii, and, apparently, the absence of a flexor digitorum brevis manus. An unexpected record of articularis humeri, a proximal origin of the brachioradialis, and the absence of the tensor fascia antebrachii are recorded for this species. As other ictonychines and mustelines, Galictis cuja possesses stronger and subdivided protractors and sagittal rotators of the forelimbs, as well as shoulder and elbow extensors. These features allow for resistance in landing during bounds and increase the stride length during epigean and subterranean crouched locomotion. Powerful neck musculature assists during hunting and carrying of prey. Weakness of some retractors and intrinsic flexors is related to a relatively minor importance of the forelimbs as propellers during bounding and the lack of other specializations. The configuration of the rhomboideus and the absence of coracobrachialis seem to be informative at the subfamiliar level within Mustelidae. The comprehensive and comparative review of available information leads us to propose possible solutions to old nomenclatural problems and of identification. This allows us to reassess of some myological features as diagnostic of caniform clades.

Occurrence and morphometrics of the brachioradialis muscle in wild carnivorans (Carnivora: Caniformia, Feliformia)

“…A muscle attached close to a fulcrum is less powerful than a comparable muscle inserted at a greater distance, although the former produces its effects faster. This reflects a conflict between the requirements of speed and power (DYCE et al 2010).…”

“…1) (BUDRAS et al 2012, HERMANSON 2013. It is positioned between the superficial and deep layers of antebrachial fascia and adheres to the surface of the deep fascia's leaflet (MILLS 2003, DYCE et al 2010, HERMANSON 2013, together with the cephalic vein and the superficial branch of the radial nerve (SAINT CLAIR 1986, SEBASTIANI & FISHBECK 2005, therefore being the most cranial and superficial muscle of the craniolateral group of the forearm (BOHENSKY 2002, SEBASTIANI & FISHBECK 2005.…”

“…It ends in the periosteum of the radius at the level of the third or fourth distal parts, by a thin aponeurosis (BOHENSKY 2002, MILLS 2003, BUDRAS et al 2012, HERMANSON 2013. Some authors describe its insertion into the styloid process of the radius (LEACH 1976, SEBASTIAN & FISHBECK 2005, LIEBICH et al 2011, MOORE et al 2013, ERCOLI et al 2014.…”

“…There are no reports in the literature, as far as we know, about the occurrence of the brachioradialis muscle in wild carnivorans, although there are studies with variable contexts containing references to the presence of the muscle in Carnivora (DAVIS 1964, ARLAMOWSKA-PALIDER 1970, JULIK et al 2012, SÁNCHEZ et al 2013, ERCOLI et al 2014.…”

“…Despite this diversity, the accumulated knowledge of myological variation within the order is still incomplete (MACALISTER 1873a, MACKINTOSH 1875, WINDLE & PARSONS 1897, HALL 1926, 1927, HOWARD 1973, LEACH 1976, FISCHER et al 2009, MOORE et al 2013, ERCOLI et al 2014. Hence, these animals provide a good model for this study, as they represent one of the most successful cases of repeated and independent evolution of similar morphologies in a great range of ecologies (ANDERSSON 2004a, b, 2005, NOWAK 2005, SATO et al 2009, SLATER et al 2012, FABRE et al 2013a, SAMUELS et al 2013, MARTÍN-SERRA et al 2014.…”