Genus: Umoonasaurus KEAR, SCHROEDER & LEE, 2006
Etymology: Antakirinja, indigenous name for the Coober Pedy area, 'Umoona', and Greek, sauros, "lizard."

Species: demoscyllus KEAR, SCHROEDER & LEE, 2006
Etymology: Greek, demos, "of the people" and Greek, Scyll, a sea monster of classical mythology; referring to the type locality and purchase of the holotype specimen by public donations.

Holotype: AM F99374

Locality: Zorba Extension Opal Field, west of Coober Pedy, South Australia State, Australia.

Horizon: Bulldog Shale, Marree Subgroup.

Biostratigraphy: Correlates to the Cyclosporites hughesii, Crybelosporites stratus zones/Odontochitina operculata, Diconodinium davidii, and Muderongia tetracantha zones.

Age: Late Aptian-Early Albian Stage, Early Gallic Subepoch, Late Early Cretaceous Epoch, Late Early Cretaceous.

Material: Skull and skeleton.

Note: Two sections of gastric mass (sample 1, sample 2), total of 60 gastroliths, and associated 17 osteichthyan vertebrae.

Note: Opalized.