Asiatic Mesonychidae (Mammalia, Condylarthra). Bulletin of the AMNH ; v. 132, article 2

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New York : [American Museum of Natural History]
"The subfamily Mesonychinae is rediagnosed. Two new genera and species are described: Mongolonyx dolichognathus from the 'Irdin Manha' beds and Mongolestes hadrodens from the 'Ulan Gochu' Formation of Inner Mongolia. Harpagolestes was probably represented in Asia. ?Harpagolestes orientalis, new species, is described, and the published literature and most of the known specimens of this probably holarctic genus are re-evaluated. This is not, however, a substitute for a systematic revision of Harpagolestes. 'Mesonyx obtusidens,' reported by Gromova (1952), from the Naran Bulak beds of Mongolia, is a species of Pachyaena. Olsenia, a mesonychid described by Matthew and Granger (1925a) based solely on astragali, is not comparable to most of the known genera because of the scarcity of associations between mesonychid teeth and foot bones. The name 'Olsenia' is suggested to be a nomen dubium. A new subfamily, the Hapalodectinae, is erected and is based on Hapalodectes. 'Hapalodectes auctus,' described by Matthew and Granger (1925b), is not a mesonychid but a didymaconid. A new subfamily, the Andrewsarchinae, is diagnosed and is based on Andrewsarchus. Several unallocated Asiatic mesonychids are described. Studying the feeding mechanism of mesonychids led to a re-examination of the previous ideas of Boule, Matthew, and others, who maintained that the Mesonychidae had a very weak jaw musculature and that therefore these mammals could not fill a carnivore or scavenger niche. On the basis of the present studies, it seems very probable that mesonychids had a powerful mandibular musculature. The variation of the length/width ratio of homologous lower check teeth of various species of mesonychids might serve as an index to feeding habit. A relatively long lower cheek tooth suggests a carnivorous habit, while a relatively transverse, blunt lower tooth may indicate an omnivorous or scavenging habit. The Mesonychoidea, in agreement with the action of Van Valen (1966), are transferred from the Carnivora to the Condylarthra. No sound phylogenetic conclusions can be offered for the evolution within the Mesonychidae. The known diversity of mesonychids in the late Eocene and early Oligocene of Asia, and our ignorance of the Asiatic Paleocene and early and middle Eocene faunas would badly mar any proposed phylogeny. As a heuristic alternative, the arrangement of the known mesonychid genera to form several adaptive levels may partially clarify mesonychid diversity. In this paper the following five adaptive levels are suggested without implying any phyletic relationship between the various levels: carnivore level, advanced carnivore level, omnivore-carnivore level, omnivore level, bone-crushing level. This study of Asiatic mesonychids revealed a previously unsuspected diversity of genera among the Asiatic forms in comparison to European and North American taxa. The presence of at least 10 genera is ascertained from the poorly known Asiatic strata in comparison to the seven known genera of mesonychids from the relatively well-known early Tertiary of North America and Europe. For a summary of the known worldwide temporal and geographic distribution of the Mesonychidae, see tables 10 and 11"--P. 171.
p. 129-173, [13] p. of plates : ill., map ; 27 cm.
Includes bibliographical references (p. 171-173).