The first two names come from the fact their tails easily break or snap off.

They first appeared in Europe during the early Eocene, approximately 48.6 million years ago, originating from North American ancestors that crossed over from Greenland via the Thule Land Bridge and spread toward Asia sometime after the drying of the Turgai Strait at the beginning of the Oligocene, and then across the Bering Land Bridge to North America during the Miocene.

[1] Very vestigial hindlegs are present in Hyalosaurus and Pseudopus, but are entirely absent in the other genera.

[2] The largest living species, the Sheltopusik (Pseudopus apodus),[3] can reach lengths of 120 centimetres (47 in).

Relationships after Lavin & Girman, 2019:[1]Hyalosaurus Anguis Pseudopus Ophisaurus Dopasia