A new lower Turonian mosasaurid from the Western Interior Seaway and the antiquity of the unique basicranial circulation pattern in Plioplatecarpinae
Polcyn, Michael J.; Bardet, Nathalie; Albright III, L. Barry; Titus, Alan
(2023) Cretaceous Research, volume 151
(Article)
Abstract
We describe and name a new mosasaur taxon, Sarabosaurus dahli gen. et sp. nov., from the lower Turonian part of the Tropic Shale in Utah, USA. The holotype specimen preserves significant portions of the skull and axial postcranial skeleton. It was found in the upper part of the Watinoceras devonense
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Ammonite Zone, bounded by radioisotopic dates above and below, and is thus about 93.7 Ma, the oldest mosasaurid taxon known from the Western Interior Seaway. The new taxon possesses a vascular pattern of the basisphenoid heretofore only seen in late diverging plioplatecarpine mosasaurids. Reevaluation of the morphology of the basisphenoid of previously described Turonian mosasaurs using μCT techniques reveals the derived condition is also present in Yaguasaurus and the incipient condition in Tethysaurus and Russellosaurus. In these two taxa, the canals enter the basisphenoid, but do not pass into the basioccipital. Instead, they exit only high on the posterior wall of the sella turcica, in a position similar to the basilar artery of other lizards. This vascular pattern, both in its incipient and derived states, is unique among squamates and supports inclusion of the aforementioned taxa in a monophyletic Plioplatecarpinae, for which we provide an emended diagnosis. Phylogenetic analysis recovers Sarabosaurus dahli gen. et sp. nov. as the sister taxon to Yaguarasaurus and all other later diverging plioplatecarpines, with Russellosaurus and Tethysaurus as successive sister taxa. Tylosaurine mosasaurids retain the primitive condition of the basisphenoid vascularization pattern and implies a tylosaurine-plioplatecarpine divergence in the late Cenomanian or earliest Turonian.
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Keywords: Plioplatecarpinae, Tylosaurinae, Turonian, Mosasauridae, Tropic Shale
ISSN: 0195-6671
Publisher: Academic Press Inc.
Note: Funding Information: Many of the marine reptile specimens described from the Tropic Shale over the past several years were found by former Big Water residents D. Rankin and M. Graffam. We are pleased that they can now add mosasaurids to their list of discoveries. Our gratitude also extends to S. Richardson, who when given a request to find a mosasaur in the Tropic Shale by LBA under permit GLCA-2012-SCI-0006, went out and did just that – the type specimen, no less. J. Spence and S. Doyle at GLCA (and E. Clites formerly at GLCA) are thanked for their role in providing the permits required to collect fossils within Glen Canyon National Recreation Area and for their interest in our research; similar gratitude is extended to J. Kirkland and M. Hayden at the Utah Geological Survey for permission to search and collect on Utah state lands. T. Birthisel at UMNH (formerly at GSENM) helped in the field recovery and preparation of UMNH VP21800. For access to collections and assistance with specimens, we thank Jacques Gauthier, Dan Brinkman, and Marilyn Fox, Yale University; Anne Schulp and John Jagt, Natuurhistorisch Museum Maastricht; Dale Winkler, Shuler Museum of Paleontology at SMU; Annelise Folie, Royal Institute of Natural Sciences, Brussels,; Laura Wilson and Mike Everhart, Sternberg Museum of Natural History; Christopher Beard, University of Kansas; Mark Norell and Carl Mehling, American Museum of Natural History; Jun Ebersole, McWane Science Center, Birmingham AL; Adiel Klompmaker and Dana Ehret, Alabama Museum of Natural History. We thank Jason Anderson of the University of Calgary for access to the CT data, and Matt Colbert, Jessie Maisano HRCT lab at UTA and George D. Pylant III, for assistance with μCT scanning. We thank Louis Jacobs, Anne Schulp, Caitlin Keirnan and Bruno Augusta for comments on an earlier version of this manuscript. We thank Daniel Madzia and Joshua Lively for thorough and constructive reviews. The first author thanks ISEM at SMU (Southern Methodist University, Dallas, Texas, USA) for ongoing support of the Digital Earth Science Lab (Huffington Department of Earth Sciences, SMU)and financial support for μ CT scanning services. Funding Information: Many of the marine reptile specimens described from the Tropic Shale over the past several years were found by former Big Water residents D. Rankin and M. Graffam. We are pleased that they can now add mosasaurids to their list of discoveries. Our gratitude also extends to S. Richardson, who when given a request to find a mosasaur in the Tropic Shale by LBA under permit GLCA-2012-SCI-0006, went out and did just that – the type specimen, no less. J. Spence and S. Doyle at GLCA (and E. Clites formerly at GLCA) are thanked for their role in providing the permits required to collect fossils within Glen Canyon National Recreation Area and for their interest in our research; similar gratitude is extended to J. Kirkland and M. Hayden at the Utah Geological Survey for permission to search and collect on Utah state lands. T. Birthisel at UMNH (formerly at GSENM) helped in the field recovery and preparation of UMNH VP21800. For access to collections and assistance with specimens, we thank Jacques Gauthier, Dan Brinkman, and Marilyn Fox, Yale University; Anne Schulp and John Jagt, Natuurhistorisch Museum Maastricht; Dale Winkler, Shuler Museum of Paleontology at SMU; Annelise Folie, Royal Institute of Natural Sciences, Brussels,; Laura Wilson and Mike Everhart, Sternberg Museum of Natural History; Christopher Beard, University of Kansas; Mark Norell and Carl Mehling, American Museum of Natural History; Jun Ebersole, McWane Science Center, Birmingham AL; Adiel Klompmaker and Dana Ehret, Alabama Museum of Natural History. We thank Jason Anderson of the University of Calgary for access to the CT data, and Matt Colbert, Jessie Maisano HRCT lab at UTA and George D. Pylant III, for assistance with μCT scanning. We thank Louis Jacobs, Anne Schulp, Caitlin Keirnan and Bruno Augusta for comments on an earlier version of this manuscript. We thank Daniel Madzia and Joshua Lively for thorough and constructive reviews. The first author thanks ISEM at SMU (Southern Methodist University, Dallas, Texas, USA) for ongoing support of the Digital Earth Science Lab (Huffington Department of Earth Sciences, SMU)and financial support for μCT scanning services. Publisher Copyright: © 2023 The Author(s)
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