Myogale subclavius

WHIDDEN, HOWARD P., 2000, Comparative Myology of Moles and the Phylogeny of the Talpidae (Mammalia, Lipotyphla), American Museum Novitates 3294, pp. 1-53 : 27-28

M. subclavius ( figs. 8 and 9 )

ORIGIN: As three poorly differentiated heads, one from the manubrium ventral to the ala, a second from the manubrium dorsal to the ala, and a third from the anterior surface of the first costal cartilage.

INSERTION: The head from the ventral manubrium broadly across the posterior surface of the clavicle, the head from the dorsal manubrium on the acromioclavicular ligament and the dorsal surface of the acromion process, and the head from the first costal cartilage via a narrow tendon on the posterior surface of the clavicle.

REMARKS: This muscle has the same general form in Parascalops , Scalopus , Scapanus , and Talpa . In Uropsilus , Desmana , and Galemys , it consists of a single undivided muscle mass extending from the manubrium and first rib to the clavicle. In Uropsilus , this muscle inserts only on the posterior surface of the clavicle, but in Desmana and Galemys , the dorsal portion inserts on the metacromion process. In Condylura , Neurotrichus , Scaptonyx , and Urotrichus , the muscle originates as three heads, as in Parascalops . The head from the dorsal manubrium inserts on the metacromion, the head from the ventral manubrium inserts broadly across the posterior surface of the clavicle, and the head from the first costal cartilage attaches to the posterior surface of the clavicle. This last head attaches fleshily to the clavicle in Neurotrichus , Scaptonyx , and Urotrichus , and via a flat tendon in Condylura .

The complex and variable form of this

muscle mass in talpids has led to confusion about its homology. Reed (1951) described the parts of this muscle mass as separate Mm. subclavius , costoscapularis ventralis, and costoscapularis dorsalis, and he presumed that these were three distinct muscles in the common ancestor of shrews and moles. This led him to erroneously conclude that the absence of M. costoscapularis in soricids is a secondary loss, and that previous workers on talpid myology either missed M. subclavius , failed to distinguish it from M. costoscapularis, or just forgot to describe one of the two muscles. Freeman’s (1886) and Campbell’s (1939) interpretations of this muscle are similar to mine.

M. pectoralis superficialis pars anticus ( fig. 8 )

ORIGIN: From the anterior end of the manubrium, and from a midventral raphe that extends anterior to the sternum.

INSERTION: On the medial side of the pectoral process of the humerus.

REMARKS: This muscle has the same general form in the 11 study taxa.

M. pectoralis superficialis pars posticus ( fig. 8 )

ORIGIN: From the lateral surface of the length of the sternum.

INSERTION: Along the lateral surface of the pectoral process of the humerus, adjacent to the lesser tuberosity.

REMARKS: This muscle has the same general form in the 11 study taxa.

Figures

Fig. 8. Ventral view of chest muscles of Parascalops; superficial muscles on left, deeper muscles on right.

Fig. 9. Dorsal view of pectoral limb muscles of Parascalops.