Pantodonta

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Pantodonta
Temporal range: Paleocene - Eocene, 63–34Ma
Barylambda BW.jpg
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 eutherian mammals. These herbivorous mammals were one of 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[edit]

Undescribed specimen
Restoration of Titanoides primaevus

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.[2]

Dentition[edit]

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]

Postcranial skeleton[edit]

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.[1]

Classification[edit]

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[edit]

Paleogene Oligocene Eocene Paleocene Hypercoryphodon Coryphodon Titanoides Barylambda Pantolambda Paleogene Oligocene Eocene Paleocene

References[edit]

Footnotes[edit]

  1. ^ a b c d e Rose 2006, p. 114
  2. ^ a b c d Kemp 2005, pp. 238–40
  3. ^ "Fossil Arctic animal tracks point to climate risks". Reuters. April 25, 2007. Retrieved July 2013. 

External links[edit]