Genus: Pachycostasaurus CRUICKSHANK, MARTILL & NOE, 1996
Etymology: Greek, pachus, “thick”, Latin, costa, “rib” and Greek, sauros, “lizard”: Thick rib lizard.

Species: dawni CRUICKSHANK, MARTILL & NOE, 1996
Etymology: In honor of Alan Dawn, discoverer of the genus.

Holotype: PETMG R338

Locality: The King’s Dyke Clay Pit at Whitlesey, near Peterborough, Cambridgeshire County, England, Southern United Kingdom.

Horizon: Bed 10/11, Peterborough Member of the Oxford Clay Formation.

Biostratigraphy: Jason Zone, Jason Subzone, (Monster beds of Martill, 1985).

Age: Callovian Stage, Upper Dogger Epoch, Middle Jurassic.

Material: Fragmentary specimen.