Pantodonta is an extinct order (or, according to some, an suborder) of eutherian mammals. These herbivorous mammals were one of the first groups of large mammals to evolve (around 66 million years ago) after the end of the Cretaceous. The last pantodonts died out at the end of the Eocene (around 34 million years ago).
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 (with a skull probably the size of a dog) and Hypsilolambda, appear in the early Paleocene Shanghuan 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 (Alcidedorbignya) 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-like Barylambda was massive, slow-moving ("graviportal") 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 zalambdodont (V-shaped ectoloph opening towards lip) P3–4 and (except in the most primitive families) dilambdodont (W-shaped ectoloph) upper molars. Most pantodonts lacked a hypocone (fourth cusp) and had small conules (additional small cusps). The incisors are small but the canines large, occasionally sabertooth-like. On P3-M3 there is normally an ectoflexus (indentation on the outer side). Asian families can typically be distinguished from the American because their paracone and metacone (bottom of W on side of tongue) tend to be closer together.
The cheek teeth in the lower jaw are also dilambdodont, with broad, high metalophids (posterior crest) and tall metaconid (posterior-interior cusp) with much lower paracristids and small paraconids.
Postcranial skeleton Pantodonts have plesiomorphic (unaltered) 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 primitive 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 ungulate placentals and not related to cimolestids at all.
Genera from North America tended to be large and robust, starting with Pantolambda and Caenolambda in the Middle Paleocene 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.
The following taxa are recognized in Pantodonta:
Order/Suborder Pantodonta Cope, 1873 Family Alcidedorbignyidae de Muizon & Marshall, 1987 Genus Alcidedorbignya de Muizon & Marshall, 1987 Family Barylambdidae Patterson, 1939 Genus Barylambda Patterson, 1937 Genus Haplolambda Patterson, 1939 Genus ?Ignatiolambda Simons, 1960 Genus ?Leptolambda Patterson & Simons, 1958 Family Bemalambdidae Chow et al., 1973 Genus Bemalambda Chow et al., 1973 Genus Hypsilolambda Wang, 1975 Family Coryphodontidae Marsh, 1876 Genus Asiocoryphodon Xu, 1976 Genus Coryphodon Owen, 1845 Genus Eudinoceras Osborn, 1924 Genus Heterocoryphodon Lucas & Tong, 1987 Genus Hypercoryphodon Osborn & Granger, 1932 Genus Wutucoryphodon Tong & Wang, 2006 Family Harpyodidae Wang, 1979 Genus Harpyodus Qiu & Li, 1977 (= Wanglia Van Valen, 1988) Family Pantolambdidae Cope, 1883 Genus Caenolambda Gazin, 1956 Genus Nanxiongilambda Quan & Wang, 2024 Genus Pantolambda Cope, 1882 Family Pantolambdodontidae Granger & Gregory, 1934 Genus Archaeolambda Flerov, 1952 Genus Celaenolambda Tong and Wang 2006 Genus Dilambda Tong, 1978 Genus Guichilambda Huang & Chen, 1997 Genus Nanlingilambda Tong, 1979 Genus Oroklambda Dashzeveg, 1980 Genus Pantolambdodon Granger & Gregory, 1934 Family Pastoralodontidae Chow & Qi, 1978 Genus Altilambda Chow & Wang, 1978 Genus Convallisodon Chow & Qi, 1978 Genus Pastoralodon Chow & Qi 1978 Genus ?Huananius Huang & Zheng, 1999 Family Titanoideidae Patterson, 1934 Genus Titanoides Gidley, 1917 Ichnogenus Thulitheripus Lüthje et al., 2010 (tracks attributed to Titanoides) Family ?Cyriacotheriidae Rose & Krause, 1982 Genus ?Cyriacotherium Rose and Krause, 1982 Genus ?Presbytherium Scott, 2010 Genus ?Crustulus Clemens, 2017
Timeline of genera
References
Footnotes
External links Paleocene-Mammals