Cretaceous mammals of southern Utah. IV. Eutherian mammals from the Wahweap (Aquilan) and Kaiparowits (Judithian) Formations

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Abstract
Eutherian mammals are herein reported from the Wahweap and Kaiparowits formations, southern Utah, of probable Aquilan and Judithian age, respectively. Three species of the leptictid insectivoran Gypsonictops are tentatively recognized from the Kaiparowits Formation; none is identified, although the stratigraphically highest species bears some resemblance to G. clemensi from the lower Kirtland Shale of the San Juan Basin, New Mexico. Paranyctoides, the oldest undoubted North American eutherian and known elsewhere from faunas of Aquilan and Judithian age, is the stratigraphically lowest eutherian present in the local section and is represented in the Wahweap Formation by two unidentified species. Two other species of Paranyctoides, also unidentified and unnamed, are recognized from the overlying Kaiparowits Formation. Upper and lower premolars representing loci not previously known for Paranyctoides significantly augment knowledge of the genus. In known morphology, Paranyctoides contrasts with other known pre-Lancian eutherians and is structurally close to many Cenozoic placental groups, as has been previously suggested; a special relationship of the genus to nyctitheriid lipotyphlans is neither strongly supported nor contradicted by the new evidence. Avitotherium utahensis, of uncertain ordinal and familial affinities, is described as new from the Judithian Kaiparowits Formation. Although similar to Alostera and Paranyctoides in certain respects, Avitotherium lacks presumed autapomorphies seen in those genera, and in known morphology is suggestive of the latest Cretaceous and early Tertiary condylarth Protungulatum. Morphological diversity among known North American Cretaceous Eutheria suggests the possibility of considerable diversification on the continent prior to the Lancian.

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