[2][3] Lagerpetid fossils are known from the Triassic of San Juan (Argentina), Arizona, New Mexico, and Texas (United States), Rio Grande do Sul (Brazil), and Madagascar.

[4][5][6][7][2] They were generally small animals; the largerst lagerpetids include Dromomeron gigas and a specimen from the Santa Rosa Formation attributed to D. sp.

However, it also extends further forwards than in most dinosauromorphs, snaking along the length of the pubic peduncle (the area of the ilium which connects to the pubis).

[6] The hip in general was wide, had a closed acetabulum (i.e. one with a bony inner wall), and had two sacral vertebrae, lacking many specializations of later dinosauromorphs, like dinosaurs.

Like pterosaurs and dinosaurs (but unlike Marasuchus and most other archosaurs), the facet on the calcaneum which receives the fibula is concave and there is no evidence of a pronounced rearward bump known as a calcaneal tuber.

The family was originally named Lagerpetonidae by Arcucci in 1986,[4] though it was later renamed Lagerpetidae in a phylogenetic study by S. J. Nesbitt and colleagues in 2009.

A clade of lagerpetids was also recovered in the large phylogenetic analyses of early dinosaurs and other dinosauromorphs that were produced by Baron, Norman & Barrett (2017).