In 1911, Paul Miller discovered the remains of various dissorophid bones in
New Mexico that were attributed to a new species,
Aspidosaurus novomexicanus. The skull closely resembled that of a specimen of
Cacops aspidephorus found in
Texas but the arrangement of ridges in the otic region was different. The teeth found were slender and conical and all of an approximately equal size. The vertebral column, pelvis and limb bones were also similar but the new specimen was distinguished from
Cacops by the armour, the single row of vertical plates that were originally attached to the neural spines of the
vertebrae. The genus
Alegeinosaurus Case, 1911 was synonymized with
Aspidosaurus by Gee (2018) based on a redescription of the holotype. ==Phylogeny==