Data from: Mammals across the K/Pg boundary in northeastern Montana, U.S.A.: dental morphology and body-size patterns reveal extinction selectivity and immigrant-fueled ecospace filling

The Cretaceous/Tertiary (K/Pg) mass extinction has long been viewed as a
pivotal event in mammalian evolutionary history, in which the extinction
of non-avian dinosaurs allowed mammals to rapidly expand from
small-bodied, generalized insectivores to a wide array of body sizes and
ecological specializations. Many studies have used global- or
continental-scale taxonomic databases to analyze this event on coarse
temporal scales, but few studies have documented morphological diversity
of mammalian paleocommunities on fine spatiotemporal scales in order to
examine ecomorphological selectivity and ecospace filling across this
critical transition. Focusing on well-sampled and temporally
well-constrained mammalian faunas across the K/Pg boundary in northeastern
Montana, I quantified dental-shape disparity and morphospace occupancy via
landmark- and semilandmark-based geometric morphometrics and mean body
size, body-size disparity, and body-size structure via body-mass
estimates. My results reveal several key findings: (1) latest Cretaceous
mammals, particularly metatherians and multituberculates, had a greater
ecomorphological diversity than is generally appreciated, occupying
regions of the morphospace that are interpreted as strict carnivory,
plant-dominated omnivory, and herbivory; (2) the decline in dental-shape
disparity and body-size disparity across the K/Pg boundary shows a pattern
of constructive extinction selectivity against larger-bodied dietary
specialists, particularly strict carnivores and taxa with plant-based
diets, that suggests the kill mechanism was related to depressed primary
productivity rather than a globally instantaneous event; (3) the
ecomorphological recovery in the earliest Paleocene was fueled by
immigrants, namely three multituberculate families (taeniolabidids,
microcosmodontids, eucosmodontids) and to a lesser extent archaic
ungulates; and (4) despite immediate increases in the taxonomic richness
of eutherians, their much-celebrated post-K/Pg ecomorphological expansion
had a slower start than is generally perceived and most likely only began
400,000 to 1 million years after the extinction event.