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Diversity patterns of nonmammalian cynodonts (Synapsida, Therapsida) and the impact of taxonomic practice and research history on diversity estimates

Published online by Cambridge University Press:  05 December 2018

Marcus Lukic-Walther ,
Neil Brocklehurst ,
Christian F. Kammerer  and
Jörg Fröbisch
Marcus Lukic-Walther
Affiliation:
Erst-Reuter-Gesellschaft, Freie Universität Berlin, Kaiserswerther Strasse 16–18, 14195 Berlin, Germany. E-mail: mawa01@zedat.fu-berlin.de
Neil Brocklehurst
Affiliation:
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, D-10115 Berlin, Germany.
Christian F. Kammerer
Affiliation:
North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, North Carolina 27601-1029, U.S.A. E-mail: christian.kammerer@naturalsciences.org
Jörg Fröbisch
Affiliation:
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, and Institut für Biologie, Humboldt Universität zu Berlin, Invalidenstraße 42, D-10115 Berlin, Germany. E-mail: Joerg.froebisch@mfn-berlin.de
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Abstract

Nonmammalian cynodonts represent a speciose and ecologically diverse group with a fossil record stretching from the late Permian until the Cretaceous. Because of their role as major components of Triassic terrestrial ecosystems and as the direct ancestors of mammals, cynodonts are an important group for understanding Mesozoic tetrapod diversity. We examine patterns of nonmammalian cynodont species richness and the quality of their fossil record. A supertree of cynodonts is constructed from recently published trees and time calibrated using a Bayesian approach. While this approach pushes the root of Cynodontia back to the earliest Guadalupian, the origins of Cynognathia and Probainognathia are close to their first appearance in the fossil record. Taxic, subsampled, and phylogenetic diversity estimates support a major cynodont radiation following the end-Permian mass extinction, but conflicting signals are observed at the end of the Triassic. The taxic diversity estimate shows high diversity in the Rhaetian and a drop across the Triassic/Jurassic boundary, while the phylogenetic diversity indicates an earlier extinction between the Norian and Rhaetian. The difference is attributed to the prevalence of taxa based solely on teeth in the Rhaetian, which are not included in the phylogenetic diversity estimate. Examining the completeness of cynodont specimens through geological time does not support a decrease in preservation potential; although the median completeness score decreases in the Late Triassic, the range of values remains consistent. Instead, the poor completeness scores are attributed to a shift in sampling and taxonomic practices: an increased prevalence in microvertebrate sampling and the naming of fragmentary material.

Type
Articles
Information
Paleobiology , Volume 45 , Issue 1 , February 2019 , pp. 56 - 69
Copyright
Copyright © 2018 The Paleontological Society. All rights reserved 

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Footnotes

*

Present address: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, UK, OX1 3AN. E-mail: neil.brockehurst@earth.ox.ac.uk

Data available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.6jk8416

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