The walrus auditory region and the monophyly of pinnipeds. American Museum novitates ; no. 2871

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New York, N.Y. : American Museum of Natural History
"Within the customary tripartite division of pinnipeds a grouping of the Odobenidae (walruses) and Otariidae (sea lions) to the exclusion of the Phocidae (seals) has been almost universally recognized. An anatomical review of features, primarily of the auditory region, however, reveals that odobenids share a significant number of derived characters with phocids. The evidence supporting the traditional otariid/odobenid grouping is examined and is found to consist almost exclusively of primitive, and therefore phylogenetically uninformative, characters. A review of characters that have been proposed as supporting the widely accepted alliance of phocids and mustelids reveals that they fail to provide compelling evidence for pinniped diphyly; the arguments for diphyly are further weakened by acceptance of a phocid-walrus relationship. Some aspects of the cranial morphology of several putative early Miocene otarioids are reviewed, and it is suggested that Pinnarctidion and Allodesmus are actually better regarded as members of a group including phocids and odobenids. Thus, the major morphological gap between the highly derived phocids and their presumed sister group may largely be filled. A cladogram depicting a sister-group relationship between odobenids and phocids, the monophyly of pinnipeds, and the tentative relationships of these fossil taxa is presented"--P. [1].
31 p. : ill. ; 26 cm.
Includes bibliographical references (p. 27-29).