New Mexico Geological Society Annual Spring Meeting — Abstracts

Red-bed mudstones and lenticular, trough-crossbedded sandstones of the Hall Lake Member of the McRae Formation east of Elephant Butte Reservoir produce ceratopsian fossils from six new localities. These localities are in a 100-acre outcrop area and occur at five stratigraphic levels over a 25-m-thick interval of the middle? part of the Hall Lake Member. Previously reported ceratopsian fossils from the McRae Formation have been of generically indeterminate specimens referred to Triceratops without justification in the older literature. The newly collected fossils include a partial skull, vertebrae and ribs, a scapula-coracoid, ilium, femur and phalanges. The partial skull consists of the base of the paired parietals, a partial squamosal, the quadrate and the jugal. It can be identified as Torosaurus because of its fenestrated frill with relatively large parietal fenestrae, lack of epoccipitals and smooth lateral margin of the squamosal. This new record of Torosaurus is significant because: (1) it supports assigning a Lancian (late Maastrichtian) age to the Hall Lake Member; (2) it represents a rare association of cranial and postcranial material of Torosaurus; and (3) it suggests that previously reported large certatopsian fossils from the McRae Formation may all belong to Torosaurus.