page_title: Neochoristodera
section_title: Evolution
hierarchical_section_title: Neochoristodera / Evolution
caption_attribution_description: English: Holotype skeleton of Tchoiria klauseni at 'El Regreso de los Dinosaurios' Expo (Santiago de Chile).
context_page_description: 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, occurring in freshwater and coastal environments across the Cretaceous and early Cenozoic.
context_section_description: 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.
  Choristoderes reappear in the fossil record in the Campanian of North America and Europe (and possibly Timor) under the genus Champsosaurus. This genus survives the KT event unscathed and diversifies in the aftermath, being soon after joined by Simoedosaurus. Both taxa remain at high latitudes in North America and Europe until the Eocene, when they mysteriously disappear.
  Competition from crocodilians has been at times implicated in the extinction of neochoristoderes. There appears to be a niche partitioning between neochoristoderes and long-snouted crocodilians such as gharials, which are absent from freshwater sites in Laurasia until well after neochoristoderes disappear, but competition between both groups, if it even existed, is currently unaccounted for. Ultimately, both Champsosaurus and Simoedosaurus co-existed with a variety of broad-snouted species like alligatorids and Borealosuchus.
caption: Skeleton of Tchoiria
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