A new caimanine alligatorid from the Middle Eocene of Southwest Texas and implications for spatial and temporal shifts in Paleogene crocodyliform diversity

Michelle R Stocker; Christopher A Brochu; E Christopher Kirk

doi:10.7717/peerj.10665

Back

A new caimanine alligatorid from the Middle Eocene of Southwest Texas and implications for spatial and temporal shifts in Paleogene crocodyliform diversity

Journal article

Open access

Peer reviewed

A new caimanine alligatorid from the Middle Eocene of Southwest Texas and implications for spatial and temporal shifts in Paleogene crocodyliform diversity

Michelle R Stocker, Christopher A Brochu and E Christopher Kirk

PeerJ (San Francisco, CA), Vol.9, pp.e10665-e10665

2021

DOI: 10.7717/peerj.10665

PMCID: PMC7812925

PMID: 33520458

Files and links (1)

url

https://doi.org/10.7717/peerj.10665View

Published (Version of record) Open Access

Abstract

Dramatic early Cenozoic climatic shifts resulted in faunal reorganization on a global scale. Among vertebrates, multiple groups of mammals (e.g., adapiform and omomyiform primates, mesonychids, taeniodonts, dichobunid artiodactyls) are well known from the Western Interior of North America in the warm, greenhouse conditions of the early Eocene, but a dramatic drop in the diversity of these groups, along with the introduction of more dry-tolerant taxa, occurred near the Eocene-Oligocene boundary. Crocodyliforms underwent a striking loss of diversity at this time as well. Pre-Uintan crocodyliform assemblages in the central Western Interior are characterized by multiple taxa, whereas Chadronian assemblages are depauperate with only previously known. Crocodyliform diversity through the intervening Uintan and Duchesnean is not well understood. The middle Eocene Devil's Graveyard Formation (DGF) of southwest Texas provides new data from southern latitudes during that crucial period. A new specimen from the middle member of the DGF (late Uintan-Duchesnean) is the most complete cranial material of an alligatorid known from Paleogene deposits outside the Western Interior. We identify this specimen as a caimanine based on notched descending laminae of the pterygoids posterior to the choanae and long descending processes of the exoccipitals that are in contact with the basioccipital tubera. Unlike , the anterior palatine process is rounded rather than quadrangular. The relationships and age of this new taxon support the hypothesis that the modern distribution of caimanines represents a contraction of a more expansive early Cenozoic distribution. We hypothesize that the range of caimanines tracked shifting warm, humid climatic conditions that contracted latitudinally toward the hothouse-icehouse transition later in the Eocene.

Climate change

Devil’s Graveyard Formation

Caimaninae

Diversity

Species distribution

Cenozoic

Fossils

Details

Title: Subtitle: A new caimanine alligatorid from the Middle Eocene of Southwest Texas and implications for spatial and temporal shifts in Paleogene crocodyliform diversity
Creators: Michelle R Stocker - The University of Texas at Austin
Christopher A Brochu - University of Iowa
E Christopher Kirk - The University of Texas at Austin
Resource Type: Journal article
Publication Details: PeerJ (San Francisco, CA), Vol.9, pp.e10665-e10665
DOI: 10.7717/peerj.10665
PMID: 33520458
PMCID: PMC7812925
NLM abbreviation: PeerJ
ISSN: 2167-8359
eISSN: 2167-8359
Grant note: name: The Jackson School of Geosciences, The University of Texas at Austin; name: UT College of Liberal Arts, the Society of Vertebrate Paleontology; name: Department of Geosciences at Virginia Tech
Language: English
Date published: 2021
Academic Unit: Earth and Environmental Sciences; University College Courses
Record Identifier: 9984229178202771

Metrics

29 Record Views

14 Times Cited - Web of Science