Astercranidae

Astergnathidae is a family of Astergnathiformes distinguished by the presence of vertebrae in front of the pelvic ring, some of which are modified to form a skull. They typically have a membrane between their anal fingers which can be pulled back for mating, and their lateral arms are modified to be flipper-like.

All Astergnathid species have a pelvic ring and vertebrae. They swim with horizontal tail fins, like a Terran dolphin, and they have four sets of gills. All species have camera eyes of varying complexity. They are able to use their lateral mandibles for prey capture in conjunction with their "normal jaws", unlike their cousins the Astergnathids.