Eleven choristoderan genera are currently considered valid.
Here we review choristoderan distribution and diversity from the Jurassic to the Miocene, and offer a preliminary analysis of the possible ecological relationship between choristoderes and other aquatic taxa, notably crocodiles with which they are most often compared.
Fossil deposits in the Lower Cretaceous of Asia (Eastern Russia, Inner Mongolia, China, Japan) have yielded the greatest known choristodere diversity, with at least seven recorded genera representing all known choristoderan morphotypes (Fig.
The isolated choristoderan vertebra from the Gosau Group of Muthmannsdorf (Lower Austria) is about 15 mm in length.
Small incomplete choristoderan jaw elements have been reported from the Oldman and the Dinosaur Park formations of Alberta, Canada, in association with Champsosaurus and Leidyosuchus (Brinkman, 1990; Gao and Brinkman, 2005; Gao and Fox, 1998) The affinities of these specimens (e.g.
Climate and other physical conditions are likely to have played an important role in choristoderan distribution and possibly extinction (as they do for crocodiles, Markwick, 1998), and this needs to be analyzed more thoroughly than we have space to do here.
However, understanding these potential interactions requires a fuller knowledge of choristoderan diet and lifestyle, which ongoing studies of the gut contents, dentition and skull morphology should help to elaborate.
As yet, there is no record for that period and thus any discussion of early choristoderan evolution is speculative.
The apparent absence of aquatic neosuchian crocodiles in these continental localities/ecosystems may well have been crucial to this morphological diversification and almost certainly facilitated the evolution of the large gavial-like choristoderan ecomorphs.
(2005): A choristoderan reptile (Reptilia: Diapsida) from the Lower Miocene of Northwest Bohemia (Czech Republic).
(1999): A choristoderan reptile from the Lower Cretaceous of Japan.
(2007): Cranial morphology of an Early Cretaceous monjurosuchid (Reptilia: Diapsida) from Liaoning Province of China and evolution of the choristoderan palate.