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Terrestrial locomotion in monotremes (Mammalia: Monotremata)
Author(s) -
Pridmore Peter A.
Publication year - 1985
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1985.tb05613.x
Subject(s) - biology , anatomy , humerus , femur , primate , pectoral girdle , theria , evolution of mammals , paleontology , biochemistry , structural basin , gene , phanerozoic , cenozoic
Cineradiographic analysis of the limb movements of Ornithorhynchus reveals that the proximal limb bones undergo horizontal retraction, long‐axis rotation and distal elevation (humerus) or depression (femur) during the propulsive phase of walking. Cinematographic records show that the locomotor movements of Ornithorhynchus differ in several respects from those of Tachyglossus and Zaglossus which are essentially similar. Comparison of the propulsive phase limb movements of Ornithorhynchus with those previously established radiographically for Tachyglossus reveals that the humerus is on average less laterally but more dorsally directed, and that the femur is on average more dorsally and slightly more laterally directed in Ornithorhynchus . Comparison of the limb orientations of monotremes with those empirically determined in therian mammals and lepidosaurian reptiles indicates that monotremes are most similar to therians. Consideration of several evidently derived features of the appendicular skeleton of monotremes leads to the conclusion that the limb orientations used by early mammals were probably similar to those used by locomotively generalized living therians, and that monotremes show modifications of this.