Xenungulata ("strange ungulates") is an order of extinct and primitive Meridiungulata that lived from the Late Paleocene to Early Eocene (Itaboraian to Casamayoran in the SALMA classification). Fossils of the order are known from deposits in Brazil, Argentina, Peru,
Description
Xenungulates are characterized by
bilophodonty M
1–2 and M
1–2, similar to
Pyrotheria, and complex lophate third molars, similar to
Uintatheriidae. Though other relationships, to
arctocyonidae for example, have been suggested, no proofs thereof have been found. The foot bones of xenungulates were short and robust and their digits terminated in broad, flat, and unfissured hoof-like
, quite unlike any other meridiungulates. The discovery of
Etayoa in Colombia
made it clear that xenungulates are distinct from other groups:
Etayoa lacks lophate molar talonid (in contrast to
Carodnia) and, since no distinct lophodonty is present in basal pyrotheres, there is reason to assume that bilophodonty evolved separately in xenungulates and pyrotheres. Xenungulates also show some dental similarity to primitive
Astrapotheriidae.
Taxonomy
grouped ''Carodnia'' with [[pyrotheres|Pyrotheria]] based on a similarity in [[astragalus|Talus bone]] morphology, but later concluded that this observation was incorrect.
Notoetayoa is most closely related to Etayoa.
Distribution
Xenungulata fossils have been found in:
[ Xenungulata at Fossilworks.org]
Bibliography
