Wikipedia
Altungulata or Pantomesaxonia ( sensu and later authors) is an invalid clade ( mirorder) of ungulate mammals comprising the perissodactyls, hyracoids, and tethytheres ( sirenians, proboscideans, and related extinct taxa.)
The name "Pantomesaxonia" was originally introduced by , a German zoologist and racial theorist . It was resurrected by by including sirenians and excluding South American ungulates, phenacodontids, and meniscotheriids from the original concept.
The name "Altungulata", introduced by and revised by , was erected as an alternative because the updated concept of "Pantomesaxonia" was regarded too deviant from the original concept.
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 , Phenacodonta (Phenacodontidae and Meniscotheriidae) and Pantomesaxonia (Sirenia, Desmostylia, Proboscidea, Hyracoidea, and Perissodactyla) are sister groups together making up the superorder Paenungulata.
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:
- 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.