Mammalian distal humerus fossils from eastern Montana, USA with implications for the Cretaceous-Paleogene mass extinction and the adaptive radiation of placentals

Postcrania of Cretaceous-Paleogene (K-Pg) mammals offer insights into richness, body size, and locomotor ecology that supplement patterns from well-sampled dental assemblages. Here, we describe and morphotype 50 distal humeri from Lancian-Puercan assemblages of eastern Montana. Using geometric morphometric analysis of a taxonomically broad sample of humeri from extant small-bodied therians of diverse locomotor modes, we constrain locomotor inferences of some morphotypes. We use this database to preliminarily assess body-size and locomotor diversity across the K-Pg boundary.