T. E. Willamson¹ and T. D. Carr²

Pachycephalosaurs are a rare component in Late Cretaceous faunas of New Mexico. Previously, two pachycephalosaur partial skulls were recovered from the De-na-zin Member, Kirtland Formation, one pachycephalosaur frontoparietal, and a lower jaw and portions of lateral skull roofing bones were recovered from the Hunter Wash and Farmington Sandstone members of the Kirtland Formation, respectively. We report two new species from the De-na-zin Member that include frontoparietals.

NMMNH P-41020 is a partial frontoparietal from NMMNH locality L-5400. Breaks that border the fragment occurred prior to burial and show abrasion due to transport. The lateral surface includes portions of the sutural contacts for the left supraorbitals I and II. A portion of the dorsal surface of the frontoparietal exhibits the pitted texture that is characteristic of Pachycephalosauria.

NMMNH P-41135 is a partial frontoparietal from locality L-3921. It is weathered but largely complete. The frontoperietal is large (preserved length = 140 mm; preserved width = 116 mm) and high-domed (maximum preserved thickness = 95 mm). The ventral surface preserves portions of the ceilings of the adductor chambers. These are closely spaced medially and inclined as in Pachycephalosaurinae.

Both new pachycephalosaur specimens are too fragmentary to allow identification to genus and were found in close proximity (< 1 km) to the locality that yielded the holotype of Sphaerotholus goodwini (P-27403).

2005 New Mexico Geological Society Annual Spring Meeting April 15, 2005, Macey Center, New Mexico Tech campus, Socorro, NM Online ISSN: 2834-5800

Pages: 64