Robert Reisz

University of Toronto, Biology, Faculty Member

Jilin University, College of Earth Sciences, Faculty Member

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Professor in Biology and Paleontology. Main interest in the evolution of terrestrial vertebrates of the Paleozoic , with focus on the origin and early diversification of amniotes. Published mainly on Late Carboniferous and Permian tetrapods, but also delved into lungfish dental and cranial evolution, and dinosaur evolution and development. Current interest also includes dental development and evolution

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Jose Ruben Guzman-Gutierrez

Universidad Humanista de las Americas

James Kirkland

Utah Geological Survey

Thomas Holtz

University of Maryland

Andrew Heckert

Appalachian State University

Christine Janis

Brown University

Manuel Hernández Fernández

Universidad Complutense de Madrid

Paúl M Velazco

American Museum of Natural History

Richard Cloutier

Université du Québec à Rimouski

Jeffrey Schwartz

University of Pittsburgh

Jana Javornik

University of East London

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Papers by Robert Reisz

Computed tomography of the hapsidopareiid 'microsaur' Llistrofus (project)

MorphoBank datasets, 2019

A redescription of the late Carboniferous trematopid Actiobates peabodyi from Garnett, Kansas

Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, Feb 10, 2020

Dissorophoids are a diverse clade of predominantly Permo‐Carboniferous temnospondyls with a wide ... more Dissorophoids are a diverse clade of predominantly Permo‐Carboniferous temnospondyls with a wide geographic distribution and broad ecological diversity. Each of the various dissorophoid clades first appears in the late Carboniferous, but their records are relatively sparse and fragmentary compared to those of the early Permian when dissorophoids reach their peak diversity and distribution, particularly in terrestrial environments where they are by far the most taxonomically diverse clade of non‐amniote tetrapods. This provides an impetus for further study of the late Carboniferous terrestrial dissorophoids in order to contextualize the early stages in the clade's radiation into terrestrial ecosystems. Here we present a redescription of the late Carboniferous trematopid Actiobates peabodyi from Kansas, USA, which is represented by a nearly complete skeleton and which represents the earliest occurrence of trematopids in North America. Only the skull was previously described, and the taxon has been largely overlooked in the context of early terrestrial dissorophoid evolution. Here, we provide an updated cranial description, the first postcranial description, and a discussion of the position of A. peabodyi in the context of olsoniform evolution. Our most significant finding is the characterization of postcranial anatomy that is highly similar to that of later trematopid taxa. This high degree of conservatism indicates that the earliest trematopids were already well adapted for terrestrial environments, and post‐Carboniferous radiations of olsoniforms may be attributed to an expansion of the dryland terrestrial environments in which these taxa already thrived, rather than to novel acquisition of adaptive features later in the clade's evolution.

A new varanopid synapsid from the early Permian of Oklahoma and the evolutionary stasis in this clade

Royal Society Open Science, Oct 1, 2019

Varanopids are a basal clade of small-to medium-sized nontherapsid synapsids, whose range extends... more Varanopids are a basal clade of small-to medium-sized nontherapsid synapsids, whose range extends from the late Pennsylvanian to the late middle Permian, and are found in North America, Russia, Europe and South Africa. The greatest varanopid diversity is observed at the fossiliferous cave deposits near Richards Spur, Oklahoma, well known for the preservation of a complex early Permian upland community. Two previously described varanopids, Mycterosaurus and Varanops, are known only from fragmentary disarticulated material at Richards Spur. A third putative varanopid, Basicranodon fortsillensis, represented by a partial parasphenoid, has been synonymized with Mycterosaurus longiceps. This study reports on a new varanopid taxon, represented by substantially more complete material, including three nearly complete skulls. Such comprehensive cranial material allows for a detailed study of the taxon and its relationship to other varanopids. This new varanopid bears great morphological similarity to Mesenosaurus romeri from the middle Permian Mezen River Basin of northern Russia. Phylogenetic analysis recovers a sister relationship between this taxon and Me. romeri. This relationship, in conjunction with a detailed morphological comparison, supports the placement of this taxon within Mesenosaurus, as a new species, Me. efremovi. These results reveal an unexpected extension of the geographical and temporal range of Mesenosaurus, contributing to our understanding of varanopid dispersal. The extended persistence of this basal clade of predatory synapsids, underscored by the apparent evolutionary stasis of this genus, is unusual among Palaeozoic tetrapods.

Robert Reisz

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