| Wannaganosuchus | |
|---|---|
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| Fossil ofWannaganosuchus brachymanus | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauria |
| Order: | Crocodilia |
| Family: | Alligatoridae |
| Subfamily: | Alligatorinae |
| Genus: | †Wannaganosuchus Erickson, 1982 |
| Type species | |
| †Wannaganosuchus brachymanus Erickson, 1982 | |
Wannaganosuchus (meaning "Wannagan crocodile", in reference to theWannagan Creek site where it was discovered) is anextinctgenus of smallalligatoridcrocodilian. It was found inLate Paleocene-age rocks ofBillings County, North Dakota, United States.
Wannaganosuchus isbased onSMM P76.28.247, a mostly complete skull andpostcranial skeleton missing somevertebrae,coracoids, part of the feet, ribs, and other pieces. A few smallbony scutes are also assigned to the genus, but not to the type specimen. SMM P76.28.247 was found semi-articulated in the lower part of theBullion Creek Formation, near the base of alignitic clay layer deposited in amarsh setting on a floodplain.Wannaganosuchus was named in 1982 byBruce R. Erickson. Thetype species isW. brachymanus; the specific name means "short forefoot".[2]
The skull of SMM P76.28.247 was low, without elevated rims over the eyes, and was 159 millimetres (6.3 in) long. The snout was short and pointed compared toCretaceous alligatorids. Itspremaxillae (the bones of the tip of the snout) had five teeth each, while themaxillae (main tooth-bearing bones of the upper jaw) had thirteen teeth each, with the fourth being the largest and the last three having broad flattened crowns. The lower jaws had twenty teeth on each side, and like the upper jaws, the last five had broad crushing crowns. The forelimbs were short (hence the specific name), and the hindlimbs were long in comparison. The scutes were extensive. Most of the scutes were keeled, but did not have spikes.[2]
Erickson regardedWannaganosuchus as a generalized early alligatorid closer to the line leading to modern alligatorids than other more specialized early alligatorids.[2] It may be the same asAllognathosuchus.[3]
Wannaganosuchus was found in a layer with abundant plant fossils suggesting the presence of a swamp forest in the area;taxodioid logs are common. The deposit was formed under 2 to 3 metres (6.6 to 9.8 ft) of water, and grades into a shoreline deposit about 20 metres (66 ft) away.Lilies andwater ferns grew along the shore and were shaded bycypress trees.[2]
SMM P76.28.247 was found in direct association with skeletons ofBorealosuchus formidabilis and the long-snoutedchampsosaurChampsosaurus. These three taxa probably occupied differentecological niches based on size andmorphology.Wannaganosuchus was a small alligatorid, only about 1.00 metre (3.28 ft) long as an adult, much smaller than its more abundant distant relative from the same quarry,Borealosuchus (roughly 4 metres (13 ft) long).Borealosuchus would have dominated the beach zone, whileChampsosaurus is interpreted as apiscivore that swam near the bottom.Wannaganosuchus is thought to have lived like the moderncaimanPaleosuchus, preferring seclusion. It may have floated among clumps of water plants. The structure of the arms, legs, and tail suggest that it was more aquatic than terrestrial. The mix of tooth shapes indicate it could eat a variety of foods.[2]
Recent studies have consistently resolvedWannaganosuchus as a member ofAlligatorinae, although its relative placement is disputed, as shown by thecladograms below.[4][5][6]
Cladogram from 2018 Bonaet al. study:[4]
| Alligatorinae |
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Cladogram from 2019 Massonneet al. study:[5]
| Alligatorinae |
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Cladogram from 2020 Cossette & Brochu study:[6]
| Alligatorinae |
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Extinctcrocodilians | |||||||||||||||||||||||||||||||||||||||||||
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