| Crocodylomorphs | |
|---|---|
 | |
| Skeleton ofTerrestrisuchus, an early saltoposuchid crocodylomorph | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauria |
| Clade: | Pseudosuchia |
| Clade: | Paracrocodylomorpha |
| Clade: | Loricata |
| Clade: | Crocodylomorpha Hay, 1930 |
| Subgroups | |
Crocodylomorpha is a group ofpseudosuchianarchosaurs that includes thecrocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive theend-Triassic extinction. Extinct crocodylomorphs were considerably more ecologically diverse than modern crocodillians. The earliest and most primitive crocodylomorphs are represented by "sphenosuchians", aparaphyletic assemblage containing small-bodied, slender forms with elongated limbs that walked upright, which represents the ancestral morphology of Crocodylomorpha. These forms persisted until the end of the Jurassic.[5] During the Jurassic, crocodylomorphs morphologically diversified into numerous niches, with the subgroupsNeosuchia (which includes modern crocodilians) and the extinctThalattosuchia adapting to aquatic life, while some terrestrial groups adopted herbivorous and omnivorous lifestyles. Terrestrial crocodylomorphs would continue to co-exist alongside aquatic forms until becoming extinct during theMiocene.
The earliest lineages of Crocodylomorpha are placed into the paraphyletic "Sphenosuchia", which are characterized by slender bodies with elongate legs. The oldest known crocodylomorph isTrialestes, known from the Late Triassic (Carnian-Norian) of Argentina, around 231–225 million years ago,[6] the last groups of "sphenosuchians" persisted until the end of the Jurassic.[5] During the Jurassic, crocodylomorphs diversified, including the emergence of herbivorous and omnivorous forms,[7] as well as the aquatically adaptedNeosuchia andThalattosuchia, with Thalattosuchia and several groups of neosuchians becoming adapted to a marine lifestyle over the Jurassic and Cretaceous[8] During the Cretaceous, theNotosuchia were a diverse group across the Southern Hemisphere occupying many diverse ecologies.[9] Moderncrocodilians, a subgroup of Neosuchia, emerged during the Late Cretaceous.[8] Crocodylomorph diversity was severely reduced by theend-Cretaceous extinction event.[9] The last group of terrestrially adapted crocodylomorphs was theSebecidae, a group of large predatory notosuchians which persisted in South America until the middleMiocene around 12 million years ago.[10][8]
Historically, all known living and extinct crocodiles were indiscriminately lumped into theorder Crocodilia. However, beginning in the late 1980s, many scientists began restricting the order Crocodilia to the living species and close extinct relatives such asMekosuchus. The various other groups that had previously been known as Crocodilia were moved to Crocodylomorpha and the slightly more restrictiveCrocodyliformes.[11] Crocodylomorpha has been given the rank ofsuperorder in some 20th and 21st century studies.[12]
The old Crocodilia was subdivided into the suborders:
Mesosuchia is aparaphyletic group as it does not include eusuchians (which nest within Mesosuchia).Mesoeucrocodylia was the name given to the clade that contains mesosuchians and eusuchians (Whetstone and Whybrow, 1983).
The previous definitions of Crocodilia and Eusuchia did not accurately convey evolutionary relationships within the group. The only order-level taxon that is currently considered valid is Crocodilia in its present definition. Prehistoric crocodiles are represented by many taxa, but since few major groups of the ancient forms are distinguishable, a conclusion on how to define new order-level clades is not yet possible. (Benson & Clark, 1988). Crocodylomorpha in the modern sense, as defined byPaul Sereno in 2005, is phylogenetically defined as the most inclusive clade containingCrocodylus niloticus (the Nile crocodile), but notRauisuchus tiradentes,Poposaurus gracilis,Gracilisuchus stipanicicorum,Prestosuchus chiniquensis, orAetosaurus ferratus.[13]
Below is acladogram of most known crocodylomorphs from Stephan F. Speikeman in 2023.[14] The modern consensus is that "sphenosuchians" form a paraphyletic assemblage leading towards the more derivedCrocodyliformes. The basal crocodylomorph Saltoposuchidae was defined by Speikman, 2023 as the most inclusive clade containingSaltoposuchus connectens, but notSphenosuchus acutus,Carnufex carolinensis, andTrialestes romeri. The clade Solidocrania was established by Alexander A. Ruebenstahl and colleagues in 2022 to unite crocodyliforms with their closest "sphenosuchian" relatives who both share similarly reinforced skulls. This clade was defined as the least inclusive clade includingJunggarsuchus sloani,Almadasuchus figarii, andMacelognathus vagans.[4]
| Crocodylomorpha | |
The Crocodylomorpha comprise a variety of forms, shapes, and sizes, which occupied a range of habitats. As with mostamniotes, Crocodylomorphs were and areoviparous, laying eggs in a nest or mound, known from strata as old as the Late Jurassic.[15]Adult size varies widely, from about 55 cm long inKnoetschkesuchus to much larger dimensions, as inSarcosuchus. Most crocodylomorphs werecarnivores, but many lineages evolved to be obligatepiscivores, such as the extant gharials.
In some forms, likeHesperosuchus andTerrestrisuchus,metatarsal V still had one or twophalanges,[16] but in Crocodyliformes all metatarsal V phalanges have been lost.[14]
