Teleosaurids were thalattosuchians closely related to the fully aquatic metriorhynchoids, but were less adapted to an open-ocean, pelagic lifestyle. The family was originally coined to include all the semi-aquatic (i.e.
Teleosaurids were thalattosuchian reptiles that shared affinities with fully aquatic metriorhynchoids; however, they were less adapted for life in the open ocean. This group was initially defined as a family to comprise all semi-aquatic species.