A primitive paromomyid plesiadapiform primate, Edworthia lerbekmoi new genus and species, is described from a recently discovered locality in the Paskapoo Formation, exposed at a road cut in Edworthy Municipal Park, Bow River Valley, Calgary, Alberta, Canada. The new taxon, probably middle Torrejonian (To2) in age, is based on two dentary fragments containing well-preserved dentitions that bracket p2–4, m1–3. With the exception of the basal Paromomys, E. lerbekmoi differs from all other paromomyids in retaining p2, but p2 in the new paromomyid is single-rooted, not two-rooted as in Paromomys. E. lerbekmoi differs further from Paromomys in having an enlarged anterior alveolus for a tooth immediately anterior to p2, hypothesized to be i1. Unlike other paromomyids with an enlarged i1, however, this tooth in E. lerbekmoi was obliquely, not horizontally, oriented and its alveolus opens dorsally, in the alveolar row, not anteriorly, as in other paromomyids in which i1 is greatly enlarged. This suggests that E. lerbekmoi represents a previously unknown paromomyid lineage that evolved from an ancestor having obliquely oriented lower incisors as in the basal primate Purgatorius, not from an ancestor in which i1 was already subhorizontal in orientation, as in Paromomys. If this working hypothesis is correct or whether in the future some other evolutionary scenario will better account for the unique anterior dentition in E. lerbekmoi, the new paromomyid nonetheless demonstrates that crucial aspects of the earliest history of the important plesiadapiform family Paromomyidae remain to be discovered.
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Vol. 84 • No. 5