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
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]
^Gheerbrant, Emmanuel; Filippo, Andrea; Schmitt, Arnaud (2016). "Convergence of Afrotherian and Laurasiatherian Ungulate-Like Mammals: First Morphological Evidence from the Paleocene of Morocco". PLOS ONE. 11 (7): e0157556. doi:10.1371/journal.pone.0157556.
^Fang-Yuan Mao, Yuan-Qing Wang, Qian Li & Xun Jin (2015): New records of archaic ungulates from the Lower Eocene of Sanshui Basin, Guangdong, China, Historical Biology: An International Journal of Paleobiology, DOI: 10.1080/08912963.2015.1034120
References
Fischer, Martin S. (1986). Die Stellung der Schliefer (Hyracoidea) im phylogenetischen System der Eutheria. Courier Forschungsinstitut Senckenberg (in German). Vol. 84. pp. 1–132. ISBN9783924500214. OCLC15682192.
Franz, Victor (1924). Die Geschichte der Organismen. Jena: Verlag G. Fischer.
McKenna, Malcolm C.; Bell, Susan K. (1997). Classification of Mammals Above the Species Level. New York: Columbia University Press. ISBN0231110138. OCLC37345734.
Thewissen, J.G.M.; Domning, Daryl Paul (1992). "The role of phenacodontids in the origin of the modern orders of ungulate mammals". Journal of Vertebrate Paleontology. 12 (4): 494–504. doi:10.1080/02724634.1992.10011476. OCLC4649662166.