Archibald, J. David Department of Biology, College of Sciences, San Diego State University, San Diego, California.
Last reviewed:October 2019
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The most diverse group of early Tertiary mammals are the archaic ungulates (condylarths). Although closely related, they are not a monophyletic group but, along with various extinct and extant mammals, form the taxon Ungulata (Fig. 1). They are ancestral to as many as 7 of 18 living orders of mammals: Artiodactyla, Cetacea, Hyracoidea, Perissodactyla, Proboscidea, Sirenia, and possibly Tubulidentata. Along with the Late Cretaceous zhelestids, best known from Asia, Ungulata forms the taxon Ungulatomorpha. Fossil (and molecular) evidence suggests that Ungulatomorpha separated from other placentals 85 million years ago.
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