Systematics and phylogeny of Hipparion, Neohipparion, Nannippus, and Cormohipparion (Mammalia, Equidae) from the Miocene and Pliocene of the New World. Bulletin of the AMNH ; v. 179, article 1

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[New York] : American Museum of Natural History
"Hipparions are a polyphyletic assemblage of three-toed horses that lived during the Miocene and Pliocene in the Old and New worlds. Four hipparion genera are recognized from Central and North America, they are: Hipparion sensu stricto, Neohipparion, Nannippus, and Cormohipparion. Of the 41 previously named species of New World hipparions, 15 are referred to the existing genera and the remaining 26 species names are considered to be either junior synonyms, incertae sedis, nomina nuda, or nomina dubia. One new species, Hipparion shirleyi, is described from the late Barstovian of the Texas Gulf Coastal Plain. This paper presents the systematics of New World hipparions in a scheme that principally includes an integration of quantitative and qualitative dental and cranial characters such as the configuration of the dorsal preorbital fossa. Statistical analyses of crania and dentitions provide determinations of the amount of character variation for North American hipparions. The hipparion from Mt. Léberon in southern France, Hipparion prostylum de Christol, 1832, is the genotypic species of Hipparion sensu stricto. In the New World, Hipparion sensu stricto is represented by three species; H. shirleyi, new species, H. tehonense (Merriam), 1916a, and H. forcei Richey, 1948, collectively known from the late Barstovian to the early Hemphillian of North America. Six species comprise the genus Neohipparion: N. coloradense (Osborn), 1918, N. affine (Leidy), 1869, N. trampasense (Edwards), 1982, N. leptode Merriam, 1915a, N. eurystyle (Cope), 1893, and N. gidleyi Merriam, 1915a, collectively known from the Clarendonian through late Hemphillian of Central and North America. Four species comprise the genus Nannippus: N. minor (Sellards), 1916, N. ingenuus (Leidy), 1885, N. beckensis Dalquest and Donovan, 1973, and N. peninsulatus (Cope), 1885, collectively known from the Clarendonian through late Blancan of Central and North America. In the New World, the genus Cormohipparion consists of three species, C. goorisi MacFadden and Skinner, 1981, C. sphenodus (Cope), 1889, and C. occidentale (Leidy), 1856, collectively known from the early Barstovian through early Hemphillian of North America. Hipparions are closely related to, or arose from, at least two separate taxa within the merychippine horse complex. The earliest North American hipparion, C. goorisi, is known from the 15-million-year old early Barstovian Gulf Coastal Plain of Texas. The peak of hipparion diversity in North America occurred about 12 to 8 1/2 million years ago during the height of the Clarendonian chronofauna. Hipparion diversity dropped during the Hemphillian. Only the genus Nannippus is known from the Blancan. Some previous workers state that all Old World hipparions were monophyletically descended from the oldest Old World species H. primigenium. However, based on similar hipparion facial morphotypes represented in both the Old and New worlds, it is possible that there were at least two hipparion dispersal events across Beringia, resulting in a polyphyletic assemblage in the Old World"--P. 5.
195 p. : ill., map ; 26 cm.
Includes bibliographical references (p. 189-195).