A NEW CAENAGNATHID OJORAPTORSAURUS BOEREI, N. GEN., N. SP. (DINOSAURIA, OVIRAPTOROSAURIA), FROM THE UPPER CRETACEOUS OJO ALAMO FORMATION (NAASHOIBITO MEMBER), SAN JUAN BASIN, NEW MEXICO

A nearly complete pair of pubes is identified as a new caenagnathid oviraptorosaur, Ojoraptorsaurus boerei, n. gen., n. sp., based on having a "spoon-shaped" depression on the anterior dorsal surface of the pubic boot, an elongated anterior process of the pubic boot, a recessed enclosed pubic fossa, the distal end of the pubic shaft convex anteriorly, and a sub-trapezoidal pubic peduncle articulation surface. Ojoraptorsaurus boerei is most similar to ROM 43250 (previously assigned to Chirostenotes pergracilis Gilmore) from the Horseshoe Canyon Formation (upper Campanian-lower Maastrichtian) of Alberta, Canada, but differs from it in having a pubic fossa that is lower on the shaft, a trapezoidal-shaped articulation surface of the pubes, a shorter shaft length and in being more robust. ROM 43250 is placed in a new genus and species, Epichirostenotes curriei, that is much younger than Chirostenotes pergracilis (sensu stricto), which may include the holotype of Macrophalangia canadensis (CMN 8538) and a referred specimen TMP 79.20.1, all of which are from the Dinosaur Park Formation and predate E. curriei by nearly 3 million years. The holotype specimen of Epichirostenotes curriei (ROM 43250) differs morphologically from Chirostenotes pergracilis (sensu stricto), based on TMP 79.20.1, in features of the ischium. We note minor differences in the morphology of the left manus of the holotype of Chirostenotes pergracilis (CMN 2367) compared to TMP 79.20.1, suggesting that these two may not be conspecific. Ojoraptorsaurus boerei is from the Naashoibito Member of the Ojo Alamo Formation, San Juan Basin, New Mexico, and is part of the Alamo Wash local fauna. This fauna is considered to be 69 Ma and thus is early Maastrichtian in age. Ojoraptorsaurus boerei represents the southern-most occurrence of a caenagnathid in North America. It is the first and only known caenagnathid from New Mexico and from the lower Maastrichtian of North America.