Simoedosauridae
| Neohoristodera Temporal range: Early Cretaceous - Eocene, 130–40 Ma |
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| Life restoration of Simoedosaurus. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Choristodera |
| Suborder: |
†Neochoristodera Cope, 1884 |
| Families | |
Neochoristodera is a lineage of specialised crocodile-like fully aquatic choristodere reptiles. Noted for their long jaws and large size, these animals were predominant across the northern hemisphere (and possibly Australasia), occurring in freshwater and coastal environments across the Cretaceous and early Cenozoic.
Long-jawed choristoderes form a monophyletic group. They are generally divided into two main families: Champsosauridae, which includes Champsosaurus and Eotomistoma, and Simoedosauridae which includes Simoedosaurus, Liaoxisaurus, Ikechosaurus and Tchoiria. Various taxa of uncertain affinities within this group are known, including a specimen from the Cedar Mountain Formation and from the Kuwajima Formation.
Neochoristoderes first appear in the Early Cretaceous of Asia, where they co-exist with other choristodere groups like monjurosuchids and hyphalosaurids. Here, a regional absence of aquatic crocodilians, possibly due to colder temperatures, seems to have opened the ecological niche for these choristoderes to occupy a similar ecological niche.
Other than a possible specimen from the Cedar Mountain Formation, a large gap occurs between these Early Cretaceous faunas and the Late Cretaceous ones. There are no fossils of neochoristoderes in the Asian Late Cretaceous, but the subsequent distribution of Simoedosaurus in the Paleocene and Eocene implies that there were Asian taxa around this time, seeing as Simoedosauridae is predominantly Asian and Simoedosaurus only propagated widely after the KT event.
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