Glyptodonts of North America

Abstract

All known North American glyptodonts belong in the genus <i>Glyptotherium</i> Osborn, 1903 (Family Glyptodontidae, Subfamily Glyptodontinae). Junior synonyms are <i>Brachyostracon</i> Brown, 1912; <i>Boreostracon</i> Simpson, 1929; <i>Xenoglyptodon</i> Meade, 1953; and all assignments of North American specimens to <i>Glyptodon</i> Owen, 1838. The ancestral species is <i>Glyptotherium texanum</i> from the Early Pleistocene Tusker (Arizona) and Blanco (Texas) local faunas of the Blancan Land Mammal Age; <i>G. texanum</i> is smaller and lacks many of the exaggerated features of the descendant species. The descendant species are <i>G. arizonae</i> (Blancan? and Irvingtonian); <i>G. floridanum</i> (Rancholabrean); and two species known from isolated localities in Mexico, <i>G. cylindricum</i> and <i>G. mexicanum</i>. The taxonomic validity of <i>G. mexicanum</i> is questionable. The geographic distribution and faunal associations of <i>Glyptotherium</i> clearly indicate tropical or subtropical habitats. North American glyptodonts exhibit extreme tendencies toward hypsodonty and homodonty in the dentition, and they lack both incisiform and caniniform teeth. They probably fed on soft vegetation near permanent bodies of water. Graviportal limb proportions and details of the gross osteology suggest slow and cumbersome locomotion, which probably precluded occupation of upland habitats. A substantial expansion in the number of specimens available for study has extensively improved our knowledge of the gross osteology of <i>Glyptotherium</i>, especially for <i>G. texanum</i> and <i>G. arizonae</i>.