Pristichampsidae

Pristichampsidae Temporal range: Paleocene–Eocene PreЄ Є O S D C P T J K Pg N
Skull of Pristichampsus geiseltalensis
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Crocodilia
Family:	†Pristichampsidae Kuhn, 1968
Genera
†Pristichampsus

†Pristichampsus

Pristichampsidae is an extinct family of crocodilians that lived in Europe, Asia, and North America during the Paleogene. Two genera of pristichampsids are currently recognized, Pristichampsus and Planocrania. Pristichampsids were highly specialized crocodilians that were adapted to living on land. They have extensive body armor, long legs, and blunt claws resembling hooves, and are sometimes informally called "hoofed crocodiles". Most phylogenetic analyses (analyses of evolutionary relationships) place pristichampsids in a basal position within Crocodylia. Some of these analyses find that pristichampsids lie just outside Brevirostres, the group of crocodilians that includes alligators, caimans, and crocodiles but not gharials. Pristichampsids are inferred to have first appeared in the Late Cretaceous, several tens of millions of years before they actually occur in the fossil record. This is because the earliest members of Brevirostres appear in the Campanian stage of the Late Cretaceous, and Pristichampsidae, being an outgroup to Brevirostres, must have branched off before this time.

Pristichampsids were land-living (terrestrial) crocodilians with longer legs than living species of crocodilians. They grew to a maximum size of 2 to 3 metres (6.6 to 9.8 ft) in length. Nearly complete skeletons of Pristichampsus indicate that pristichampsids were more heavily armored than living crocodilians, with bony plates called osteoderms tightly interlocking along the back, completely encasing the tail, and extending down the legs. The claws are blunt and have been described as hoof-like in shape, suggesting that pristichampsids may have been unguligrade, walking on the tips of their toes like mammalian ungulates. The areas on the leg bones where muscles attach are in different positions in pristichampsids than they are in living crocodilians, possibly as an adaptation to walking on land. One study suggested that these anatomical modifications may have enabled pristichampsids to walk on their hind limbs for brief periods of time, making them possible facultative bipeds.