Pantodonta
| Pantodonta Temporal range: Paleocene - Eocene, 63–34Ma | |
|---|---|
 | |
| Barylambda | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Vertebrata |
| Class: | Mammalia |
| Infraclass: | Eutheria |
| Order: | †Cimolesta |
| Suborder: | †Pantodonta Cope 1873 |
| Subgroups | |
| |
Pantodonta is an extinct suborder (or, according to some, an order) of early eutherian mammals. They were herbivorous, placental mammals, and among the first groups of placentals to evolve after the end of the Cretaceous.
Pantodonta include some of the largest mammals of their time, but were a diversified group, with some primitive members weighting less than 10 kg (22 lb) and the largest more than 500 kg (1,100 lb).[1]
The earliest and most primitive pantodonts, Bemalambda (with a 20 cm (7.9 in) 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,[2] and footprints in a coal mine on Svalbard.[3]
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, graviportal and probably browsed on high vegetation.[2]
Dentition
The pantodonts have a primitive dental formula (3.1.4.33.1.4.3) 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.[1]
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.[1]
Postcranium
Pantodonts have plesiomorphic (unaltered) and robust postcrania. Their feet are pentadactyl and often hoofed with the tarsals similar to those of ungulates, which had led to previous ties to arctocyonids "condylarths", but this similarity is now considered primitive.[1]
Classification
The pantodonts were previously grouped with the ungulates as amblypods, paenungulates, or arctocyonids, but since McKenna & Bell 1997 they have been allied with the tillodonts and considered derived from the cimolestids. The interrelationship within Pantodonta is controversial,[2] but, following McKenna & Bell 1997, contain 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.[1] 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.[2]
Timeline of genera
References
- Cope, E. D. (1873). "On the short footed Ungulata of the Eocene of Wyoming". Proceedings of the American Philosophical Society 13: 38–74. Retrieved July 2013.
- Kemp, Tom S. (2005). The Origin and Evolution of Mammals. Oxford University Press. ISBN 0198507615. OCLC 56652579.
- McKenna, Malcolm C.; Bell, Susan K. (1997). Classification of Mammals Above the Species Level. New York: Columbia University Press. ISBN 0231110138. OCLC 37345734.
- Rose, Kenneth David (2006). The beginning of the age of mammals. Baltimore: JHU Press. ISBN 0801884721.
- "†PANTODONTA - pantodonts". After McKenna & Bell (1997), and Alroy (2002). Retrieved 3 November 2013.