They had extensive body armor, long legs, and blunt claws resembling hooves, and are sometimes informally called "hoofed crocodiles".

Phylogenetic analyses based purely on morphological data have generally placed planocraniids in a basal position within the crocodilian crown group.

[2][5][6] However, molecular studies using DNA sequencing have found the group Brevirostres to be invalid upon finding that crocodiles and gavialids are more closely related than alligators.

[7][8][9][10][11] A 2018 tip dating study by Lee & Yates using both molecular, morphological and stratigraphic data instead recovered the planocraniids outside crown group Crocodylia.

The areas on the leg bones where muscles attach were in different positions in planocraniids than they are in living crocodilians, possibly as an adaptation to walking on land.