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ABSTRACT
Palacrodon, a near-crown stem reptile, is known from several Triassic sites across the globe, and is easily recognized by its dentition characterized by labiolingually expanded molariform teeth coupled with acrodont tooth implantation. Here we explore the nature of tooth implantation and attachment in specimens of Palacrodon from South Africa and Arizona, U.S.A. using µCT. We note the presence of unusual ridges located underneath the tooth crowns in Palacrodon browni. Such ridges are not present in specimens from Arizona, which warrants the naming of a new species P. parkeri. We conducted a broad survey of internal tooth morphology across extant and extinct pan-reptiles (n = 212), and we conclude that homologous ridges like those we observe in P. browni are not present in any other species of reptile. As such, our ability to determine the function of the ridges is limited, though we hypothesize it is related to tooth attachment via unmineralized soft tissues.
ACKNOWLEDGMENTS
We thank the many field crews that assisted in collection at Driefontein, and D. Luus for access to land and logistical support. For museum and CT assistance in South Africa we thank B. Rubidge, B. Zipfel, S. Jirah, and K. Jakata (University of the Witwatersrand). For access to and assistance with material from Arizona, we thank A. Marsh (Petrified Forest National Park), J. Gillette (Museum of Northern Arizona), and B. Kligman (Smithsonian Institution), and for CT assistance in Texas we thank J. Maisano (UTCT). Further assistance with comparative material was provided by A. Resetar and C. Browning. We appreciate the helpful reviews from B. Kligman and X. Jenkins which improved the final manuscript. Funding was provided by Sam Houston State University Department of Biological Sciences, Sigma Xi Grants-in-Aid of Research, and the Geology Foundation of the Jackson School of Geosciences.
DISCLOSURE STATEMENT
No potential conflict of interest was reported by the author(s).
AUTHOR CONTRIBUTIONS
KMJ and PJL designed the project. KMJ and PJH gathered data. KMJ drafted the manuscript. All authors edited the manuscript.
DATA AVAILABILITY STATEMENT
CT scans utilized for this work are available for download on Morphosource.org: https://www.morphosource.org/concern/media/000607799?locale=en and https://www.morphosource.org/concern/media/000607796?locale=en
SUPPLEMENTARY FILE
Supplementary File 1.docx: List of species and sources surveyed (see Methods).