Craniomandibular osteology of Manidens condorensis (Ornithischia: Heterodontosauridae) from the upper Lower Jurassic of Argentina

ABSTRACT

Heterodontosauridae is a clade that appears early in the ornithischian fossil record, and includes small-bodied, highly specialized species characterized by an unusual heterodont dentition. Although known from relatively few taxa, the early representation of the clade and unsolved phylogenetic relationships within heterodontosaurids and among early ornithischians implies that novel information has a marked effect on broader phylogenetic hypotheses and our understanding of early diversification patterns within Ornithischia. This paper describes the cranial osteology of the heterodontosaurid Manidens condorensis based on computed micro-tomographic scans of MPEF-PV 3211 and MPEF-PV 3809. This enabled more detailed descriptions of previously recognized bones, corrections to the literature, and the identification of undescribed elements. We present a new skull reconstruction and propose an emended diagnosis in light of novel anatomical information. Areas of jaw muscle attachment were identified and compared with Heterodontosaurus and Lesothosaurus, and mandibular function among heterodontosaurids is discussed. Our results indicate that diverse skull morphologies and functions existed among Early Jurassic ornithischians, with Manidens being intermediate between the plesiomorphic cranial shape and function associated with a generalist diet in ornithischians such as Tianyulong and Lesothosaurus, and the more derived cranial construction specialized for herbivory identified in heterodontosaurids from South Africa such as Heterodontosaurus.

ACKNOWLEDGMENTS

This research represents part of the results of the doctoral thesis and postdoctoral studies of MGB, financed by CONICET (Consejo Nacional de Investigaciones Científicas y Tecnológicas, Argentina) doctoral and postdoctoral scholarships. Fieldwork was possible thanks to the authorities of the Secretaría de Cultura de la Provincia del Chubut. Fieldwork and research were supported by Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT, Argentina), under grants PICT 2017-1897 (to MGB), PICT 2019-03834, 2013-1288 and 2011-0808 (to DP), PICT 2020-01428 (to APC), and PICT 2016-2682 (to G. Rougier) Deutsche Forschungsgemeinschaft (DFG, Germany), under grant RA1012/9-1 (to OWMR); and National Science Foundation (NSF, U.S.A.), under grants DEB 0946430 and DEB 1068089 (to G. Rougier). The Deutscher Akademischer Austauschdienst (DAAD) provided funding for MGB to travel to Germany (ID 57130097). The Staatliche Naturwissenschaftliche Sammlungen Bayerns (Munich) and the staff of this institution, especially G. Rössner, is thanked for allowing the use of the micro-CT facilities. The kind help of Y. Herrera (Universidad Nacional de La Plata) is here thanked. SEM images were conducted thanks to ALUAR Aluminio Argentino SAIC facilities (Puerto Madryn, Chubut Province) and the help of J. Groizard and M. Luquet. The comments and corrections of P. M. Barrett, D. Madzia, an anonymous reviewer and the editors significantly enhanced this manuscript, and are also thanked.

LIST OF SUPPLEMENTARY FILES

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