Genus: Aenigmadelphys CIFELLI & JOHANSON, 1994
Etymology: Latin, aenigma (Greek, ainigma), "obscure or inexplicable" and Greek , delphys, "womb," a common suffix for New World opossums and primitive marsupials in general. Allusion is to the enigmatic occurrence of this presumably primitive mammal in a Judithian horizon, and the difficulty in assessing its affinities on the basis of synapomorphy.

Species: archeri CIFELLI & JOHANSON, 1994
Etymology: In honor of Michael Archer, in recognition of his contributions to knowledge of marsupial evolution.

Holotype: OMNH 23328

Locality: OMNH localities V6, and V9, Kane County, Utah.

Horizon: Lower Kaiparowits Formation, Late Cretaceous.


Age: Judithian age, Late Campanian Stage, Senonian subepoch, Upper Gulf Epoch, Late Cretaceous.

Material: Left M3.


OMNH 22898, 262969: M1.

OMNH 20120, 20160: M2.

OMNH 23460: M3.

OMNH 23321, 23475: M4.

OMNH 20430: p2.

OMNH 23317: M2.

OMNH 20531: M3.

OMNH 20612: M4.