Carnivorous mammals from the middle Eocene Washakie Formation, Wyoming, USA, and their diversity trajectory in a post-warming world

Susumu Tomiya,John J Flynn,Shawn P Zack,Michelle Spaulding

doi:10.1017/jpa.2020.74

Abstract

AbstractThe 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 mccarrollin. sp., 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.UUID:http://zoobank.org/9162f1a6-a12c-4d55-ba1d-dc66e8cda261

Highlights

Discoveries of middle Eocene mammalian carnivores in North America stimulated development of ideas about the processes of carnivore evolution, and were essential components of the new evolutionary synthesis in the middle of the twentieth century (Simpson, 1944)
A classic collection of Washakie fossil vertebrates curated at the American Museum of Natural History (AMNH) paved the way for the early works of Granger (1909) and Matthew (1909), which established the basic biostratigraphic framework for the formation
Analysis of carnivore diversity dynamics using occupancydetection modeling.—We investigated the trajectory of mammalian carnivore diversity from the late Bridgerian to early Uintan NALMAs within the Washakie Basin

Summary

Introduction

Discoveries of middle Eocene mammalian carnivores in North America stimulated development of ideas about the processes of carnivore evolution, and were essential components of the new evolutionary synthesis in the middle of the twentieth century (Simpson, 1944). The middle Eocene Washakie Formation of south central Wyoming and northwestern Colorado have produced a wealth of vertebrate fossils since the late nineteenth century (Black and Dawson, 1966; Roehler, 1973; Turnbull, 1978, 2002). A classic collection of Washakie fossil vertebrates curated at the American Museum of Natural History (AMNH) paved the way for the early works of Granger (1909) and Matthew (1909), which established the basic biostratigraphic framework for the formation. Turnbull of the Field Museum of Natural History (FMNH), building on earlier work by Rainer Zangerl, and Downloaded from https://www.cambridge.org/core.

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