The middle Eocene Washakie Formation of Wyoming, USA, provides a rare window, within a single depositional basin, into the faunal transition that followed the early Eocene warming events. Based on extensive examination, we report a minimum of 27 species of carnivorous mammals from this formation, more than doubling the previous taxic count. Included in this revised list are a new species of carnivoraform, Neovulpavus mccarrolli, and up to ten other possibly new taxa. Our cladistic analysis of early Carnivoraformes incorporating new data clarified the array of middle Eocene taxa that are closely related to crown-group Carnivora. These anatomically relatively derived carnivoraforms collectively had an intercontinental distribution in North America and east Asia, exhibiting notable variations in body size and dental adaptation. This time period also saw parallel trends of increase in body-size and dental sectoriality in distantly-related lineages of carnivores spanning a wide range of body sizes. A new, model-based Bayesian analysis of diversity dynamics accounting for imperfect detection revealed a high probability of substantial loss of carnivore species between the late Bridgerian and early Uintan North American Land Mammal ‘Ages’, coinciding with the disappearance of formerly common mammals such as hyopsodontids and adapiform primates. Concomitant with this decline in carnivore diversity, the Washakie vertebrate fauna underwent significant disintegration as measured by patterns of coordinated detection of taxa at the locality level. These observations are consistent with a major biomic transition in the region in response to climatically-induced opening-up of forested habitats.

This dataset was compiled by the authors as described in the paper, and contains the following:

Supplemental Data 1 (SupData1_Rscripts_v2020_07_04 for Dryad.rtf). R scripts for: (1) Bayesian hierarchical multispecies occupancy-detection modeling; (2) model selection using reversible-jump Markov chain Monte Carlo method; and (3) analysis of vertebrate co-detection patterns.

Supplemental Data 2 (SupData2_character_matrix_and_trees.nex). NEXUS file containing morphological character matrix for cladistic analysis of early Carnivoraformes, most parsimonious trees obtained, and strict consensus tree.

Supplemental Data 3 (SupData3_vertebrate_occurrences_selectedlocs_v2019_11_10_forshare.csv). List of cataloged specimens of vertebrate fossils from the Washakie Formation, Wyoming, U.S.A., housed at the Field Museum of Natural History (FMNH; Chicago, U.S.A.) and included in analysis of vertebrate co-detection patterns.

Supplemental Data 4 (SupData4_localities_v2019_11_08.csv). List of FMNH localities and their attributes analyzed by occupancy-detection modeling.

Supplemental Data 5 (SupData5_carnivore_detections_by_locs_v2019_11_10.csv). Matrix of carnivore detections across FMNH localities analyzed by occupancy-detection modeling.