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Condylarthra is an informal group – previously considered an order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates. It is now largely considered to be a wastebasket taxon, having serving as a dumping ground for ungulates not clearly established as part of either Perissodactyla or Cetartiodactyla, being composed thus of several unrelated lineages. == Taxonomic history == Condylarthra always was a problematic group. When Condylarthra was first described by , Phenacodontidae was the type and only family therein. , however, raised Condylarthra to an order and included a wide range of diverse placentals with generalized dentitions and postcranial skeletons. More recent researchers (i.e. post-WW2) have been more restrictive; either including only a limited number of taxa, or proposing that the term should be abandoned altogether. Due to their primitive characteristics condylarths have been considered ancestral to several ungulate orders, including the living Artiodactyla, Cetacea, Perissodactyla, Hyracoidea, Sirenia, and Proboscidea, as well as the extinct Desmostylia, Embrithopoda, Liptopterna, Notoungulata, and Astrapotheria. delimited condylarths as those having the following characters, but lacking the specializations present in more derived orders:〔 * superior ramus of stapedial artery shifted to petrosal or lost * mastoid foramen lost * bulla if present composed of ectotympanic * relatively bunodont teeth with low cusp relief * trigonids of lower molars shortened anteroposteriorly * large, posteriorly projecting hypoconulid on M3 (lower third molar) * head of astragalus is short and robust 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Condylarth」の詳細全文を読む スポンサード リンク
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