 All known "Umoonasaurus" come from the Bulldog Shale, a member of the Marree Subgroup located in the Eromanga Basin of South Australia.Some horizons of the Bulldog Shale, including those around Coober Pedy, contain rich opal deposits.Fossilized macroinvertebrates and pollen have been used to recover an early Aptian to early Albian age for this formation.