any animal of the extinct order Pantotheria that lived during the late Mesozoic Era, believed to be the ancestor of the marsupial and placental mammals.

Origin of pantothere

< New Latin Pantotheria name of order, equivalent to panto- panto- + -theria, plural of -therium -there Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019