Altungulata
Clade of mammals / From Wikipedia, the free encyclopedia
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Altungulata or Pantomesaxonia (sensu Fischer 1986 and later authors) is an invalid clade (mirorder) of ungulate mammals comprising the perissodactyls, hyracoids, and tethytheres (sirenians, proboscideans, and related extinct taxa).[2]
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Top: Rock hyrax (Hyracoidea), Arsinoitherium zitteli (Embrithopoda); Middle: Asian elephant (Proboscidea), West Indian manatee (Sirenia); | |
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The name "Pantomesaxonia" was originally introduced by Franz 1924, a German zoologist and racial theorist. It was resurrected by Fischer 1986 by including sirenians and excluding South American ungulates, phenacodontids, and meniscotheriids from the original concept.[3]
The name "Altungulata", introduced by Prothero & Schoch 1989 and revised by McKenna & Bell 1997,[2] was erected as an alternative because the updated concept of "Pantomesaxonia" was regarded too deviant from the original concept.[3]
Both names are still in use, and, to add to the confusion, various authors assign different ranks to the involved taxa. For example, according to Thewissen & Domning 1992, Phenacodonta (Phenacodontidae and Meniscotheriidae) and Pantomesaxonia (Sirenia, Desmostylia, Proboscidea, Hyracoidea, and Perissodactyla) are sister groups together making up the superorder Paenungulata.[4]
Altungulata is not supported by molecular evidence unless perissodactyls are excluded (thus dividing Altungulata into Laurasiatheria and Afrotheria), and the validity of the following uniting synapomorphies remain disputed:[2]
- bilophodonty, two lophs or crests running transversally across the crown of the tooth
- large third molars
- molarization of posterior premolars
- elongated thoracic region with at least 19 vertebrae
- clavicle absent
- similar development of fetal membranes
Recent studies on Abdounodus showcase that dental synapomorphies between both groups arose independently, further discrediting the Altungulata hypothesis.[5]