[N] 2006 First occurance of Glasbius in New Mexico
Williamson, T., Weil, A, & Becenti, L. (2006) First occurance of Glasbius (Mammalia, Metatheria) New Mexico and a Lancian age (Late Creatceous) for the Naashoibito Member, Kirtland Formation. JVP 26(3) Abstracts pp. 139
The definition of the Lancian Land-Mammal “Age” is problematic, largely because of difficulties in designating a first occurrence datum to mark its onset. However, three mammal taxa, Batodon, Glasbius, and Essonodon, that uniquely occur in the Lancian have been proposed as the best candidates for this. Here we report on the occurrence of one of these taxa, Glasbius from NMMNH locality 4005, in the Naashoibito Member, Kirtland Formation.
NMMNH L-4005 is located approximately 10 m above the base of the Naashoibito Member in Willow Wash, within the Bisti/De-na-zin Wilderness area of the San Juan Basin, New Mexico. It has yielded a diverse vertebrate microfauna including the teeth of lizards (e.g., Peneteius), dinosaurs (e.g., Titanosauridae indet., cf. Tyrannosaurus rex, Richardoestesia isosceles, Troodon sp.) and mammals. The mammals include several Multituberculata, including Essonodon, and at least one identifiable therian mammal. These are considered to be part of the Alamo Wash local fauna. Two specimens can be confidently referred to Glasbius. NMMNH P-46380 is a right m2 or m3. P-46381 is a right m4. It is possible that both specimens are from a single individual. Both teeth are larger than those of G. intricatus from the Lance Formation of Wyoming. They are approximately the size of G. twitchelli from the Hell Creek Formation of Montana, and are tentatively referred to that species. The m4 is much smaller than the m2 or 3. The m2 or 3 and m4 both have a labial cingulid with a cuspid anterolabial to the hypoconid.
The presence of Glasbius in the Naashoibito Member gives additional support for a Lancian age for the Alamo Wash local fauna.