Askeptosaurids are distinguished from other thalattosaurs by their long necks and narrow skulls.

[4] Later that year a new study placed Endennasaurus outside Askeptosauridae as a basal member of Askeptosauroidea.

Below is a cladogram modified from Wu et al. (2009) showing the phylogenetic relationships of askeptosaurids:[5] Endennasaurus acutirostris Anshunsaurus huangguoshuensis Anshunsaurus wushaensis Askeptosaurus italicus Miodentosaurus brevis It was assigned to Thalattosauria by Kuhn (1966)[6] and Carroll (1988);[7] and to Askeptosauroidea by Wu et al.

[4] When the two major thalattosaur assemblages split, the Edennasaurus and Askeptosaurids still kept some similar appendages to each other, such as a relatively well-ossified carpus and tarsus.

These bone structures show that these animals still made trips onto the land around them.