19-10 An Early Campanian Mammal Fauna from Texas: The Southernmost Record in Laramidia

Session: The Campanian Crucible: A synthesis of vertebrate paleobiogeography and ecosystem dynamics in Laramidia

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Abstract:

The Abajo Shale Member of the Aguja Formation in the Big Bend region of Texas is one of very few early Campanian terrestrial units in Laramidia. The diverse microvertebrate assemblage from Texas, the Lowerverse Local Fauna, includes chondrichthyan and osteichthyan fishes, amphibians, lizards, dinosaurs, birds, and mammals. Mammals are represented by more than 325 teeth and tooth fragments forming a diverse assemblage, including several spalacotheriid “symmetrodonts”, and at least ten species of multituberculates including ?Janumys, Paracimexomys, Cedaromys, Dakotamys, Cimolodon, and Meniscoessus. Seven species of marsupials are also present, including new species of Eoalphadon and Turgidodon, as well as representatives of Albertatherium, Varalphadon, and the pediomyid Aquiladelphis. Eutherians are represented by Paranyctoides and a new species of Gallolestes. A single unusual Ferugiotheriidae tooth fragment is also present. This taxon has not previously been reported in North America. While unique, endemic aspects of the Lowerverse mammalian assemblage may reflect its southern paleolatitude, it also includes some cosmopolitan taxa.

Although North American late Santonian (Aquilan) and middle Campanian (Judithian) mammalian faunas are well known, only two localities have thus far yielded probable early Campanian mammals: the lower Wahweap Formation of Utah, and the Menefee Formation of New Mexico. The Lowerverse fauna from Texas represents a third assemblage from this intermediate time frame, as well as representing the paleolatitudinally southernmost assemblage of this age in Laramidia.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4, 2026

doi: 10.1130/abs/2026RM-14872

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