The Deltoid Musculature of the Marsupialia

Abstract

The musculature of the thirteen different genera of the Marsupials is described on a comparative basis. Homologies and functional adaptations have been discussed and phylogenetic possibilities suggested. The relationship of the M.trapezius and the M.deltoideus is emphasized as a characteristic of the group. Notoryctes is shown to possess a typical marsupial musculature. So far very little work has been done on the musculature of the Marsupialia. Even such interesting animals as Notoryctes have not been touched at all. The present paper deals with the musculature of the Marsupialia on a comparative basis. While all the muscles of the shoulder region were studied, stress has been laid on the musculature a muscle complex responsible for the very important movements of abduction and adduction of the anterior limb. An attempt has been made for the first time to trace and suggest the phylogenetic lines on the basis of the musculature as well as to consider the functional significance of the various adaptive modifications. Homologies have been discussed to understand the correct nature of the muscles concerned. The following dissections (total number in parenthesis) were made at the Laboratory of Comparative Anatomy, Museum of Natural History, Paris. 1-Didelphis virginiana (6) 9-Dactylopsila sp. (2) 2-Didelphis sp. (4) 10-Pseudocheirus cooki (2) 3-Dasyurus viverrinus (2) 11-Petaurus breviceps (2) 4-Sarcophilus satanicus (2) 1 2-Petauroides volans (2) 5-Notoryctes typhlops (2) 13-Macropus giganteus (4) 6-Perameles nasuta (2) 14-M.ruflicollis benetti (2) 7-Phalanger sp. (2) 15-Dendrolagus sp. (2) 8-Trichosurus vulpecula (2) These dissections form the basis of the descriptive part of this paper. All diagrams have been drawn from the actual dissections of the muscles and bones. The author is greatly indebted to Professors J. Millot, J. Anthony and C. Devillers of Paris under whose guidance the work was carried out. He is equally thankful to Professor D. S. Srivastava of Saugar University who encouraged him to publish the work. DESCRIPTION Myological work on the Marsupialia may be said to have started with the publication of myological plates of Didelphis, Phalangista and Macropus by Cuvier and Laurillard (1849). The plates are still 305 This content downloaded from 207.46.13.66 on Mon, 02 Jan 2017 19:03:07 UTC All use subject to http://about.jstor.org/terms 306 THE AMERICAN MIDLAND NATURALIST 67(2) interesting and instructive. Owen (1852) worked on the anatomy of the tree-kangaroo. Macalister (1870) makes a reference to the muscle as undivided in the Giant Kangaroo, in Macro pus benetti and the Virginia Opossum. Coues (1872) described the osteology and myology of Didelphis. Cunningham (1882) dealt with the general musculature of the genera Thylacinus, Phalangista and Phascogale, while MacCormack (1886) studied the limb musculature of Dasyurus. Parsons (1896) compared the anatomy of Petrogale with that of other kangaroos and found that the deltoid has the three constituent parts fused as in man. Windle and Parsons (1898) further studied Macro pus rufus and gave a short account of the general musculature of the body. All the above authors are essentially quite brief on the shoulder musculature. Gregory (1910) discussed the relationships of the different orders of mammals from various aspects. Osgood (1921) produced a monographic study of the marsupial Coenolestes. Sonntag (1922) made a more detailed description of the shoulder musculature of the wombat, koala and phalanger. According to him, the is unbroken in Phascolomys and Phascolarctos. In Phalanger and Pseudocheirus the has distinct clavicular and scapular parts. In Phascolomys, he indicates a powerful cephalohumeralis, a slip of the scapular to the fore-arm and the fusion of the clavicular with the superficial part of the pectoralis major. Recently Cze-Ching Cheng (1955) has studied the development of the shoulder musculature of Didelphis. Scapulum Clavicle Hume@ru5 te5 i no' claviculbo spkmt1 deJtioid eitoloi 41n$Ui&I*l!trpeZius 7+rsn 5pitI t('aPe2IuF spiv)I deLtoid | , clavicuf{ 2 ta re1 cv eor bvit.ufhp ly \9 /~~~~~~~~~~~~~~~~~~~~~~~dlOC