Pantodonta is an extinct suborder of eutherian mammals. These herbivorous mammals were one of the first groups of large mammals to evolve after the end of the Cretaceous. The last Pantodonts died out at the end of the Eocene. Pantodonta include some of the largest mammals of their time, but were a diversified group, with some primitive members weighing less than and the largest more than. The earliest and most primitive pantodonts, Bemalambda and Hypsilolambda, appear in the early PaleoceneShanghuan Formation in China. All more derived families are collectively classified as Eupantodonta. The pantodonts appear in North America in the middle Paleocene, where Coryphodon survived into the middle Eocene. Pantodont teeth have been found in South America and Antarctica, and footprints in a coal mine on Svalbard.
Description
The pantodonts varied considerably in size: the small Archaeolambda, of which there is a complete skeleton from the Late Palaeocene of China, was probably arboreal, while the North American, ground sloth-likeBarylambda was massive, slow-moving and probably browsed on high vegetation.
Dentition
The pantodonts have a primitive dental formula with little or no diastemata. Their most important synapomorphy are the P3–4 and upper molars. Most pantodonts lacked a hypocone and had small conules. The incisors are small but the canines large, occasionally sabertooth-like. On P3-M3 there is normally an ectoflexus. Asian families can typically be distinguished from the American because their paracone and metacone tend to be closer together. The cheek teeth in the lower jaw are also dilambdodont, with broad, high metalophids and tall metaconid with much lower paracristids and small paraconids.
Postcranial skeleton
Pantodonts have plesiomorphic and robust postcranial skeletons. Their five-toed feet are often hoofed with the tarsals similar to those of ungulates, which feature had led to previously suggested ties to arctocyonid "condylarths", but this similarity is now considered primitive.
Classification
The pantodonts were previously grouped with the ungulates as amblypods, paenungulates, or arctocyonids, but since they have been allied with the tillodonts and considered to be derived from the cimolestids. The interrelationship within Pantodonta is controversial, but, following, it contains about two dozen genera in ten families. Most of the families are known from the Paleocene of either Asia or North America. The pantolambdodontids and coryphodontids survived into the Eocene and the latter are known from across the northern hemisphere. Some dental features can possibly link the most primitve pantodonts to the palaeoryctids, a group of small and insectivorous mammals that evolved during the Cretaceous. Recently a close relationship with Periptychidae has been suggested. This would make pantodonts crown-group ungulateplacentals and not related to cimolestids at all. Genera from North America tended to be large and robust, starting with Pantolambda and Caenolambda in the MiddlePaleocene epoch, and later in the epoch started to get larger, with Barylambda as the largest Paleocene form of pantodont. However, Asian forms, such as Archaeolambda, tended to be thinner and less robust, around the size of a medium-sized dog. Only later in the Eocene, with Hypercoryphodon, did Asian pantodonts get large and robust.
