A new look at Crocodylopodus meijidei: implications for crocodylomorph locomotion

ABSTRACT

A review of the type material of the crocodylomorph ichnotaxon Crocodylopodus meijidei Fuentes Vidarte and Meijide Calvo, 2001 from the Berriasian of Spain is carried out. The review allows a better characterization of this type ichnotaxon and provides interesting new data on the candidate trackmakers and especially on their locomotion. Three different size classes possibly related to different ontogenetic states or sexual dimorphism of the same small- to medium-sized crocodylomorph trackmaker are distinguished. Morphological differences within the sample such as digital impression lengths might be a consequence of differences in allometric growth, assuming similarities with extant crocodylians. Other differences are a consequence of variation in the morphological quality and mode of preservation across the sample. Some trackway features (intermediate-gauge trackways with high pace angulation, absence of tail, belly or drag marks) indicate the trackmakers, presumed neosuchian crocodylomorphs, were walking in a ‘high-walk’ mode with a semi-erect posture at a moderate speed. The trackmaker may have walked with more erect limb posture and with the center of mass located more anteriorly than occurs in extant species, albeit not as erect as quadrupedal animals such as mammals or other extinct archosaurs including trackmakers of other crocodylomorph ichnotaxa (e.g., Batrachopus).

ACKNOWLEDGMENTS

DC was funded by the Alexander von Humboldt Foundation and by the Beatriu de Pinós postdoctoral programme (BP2017-00195) of the Government of Catalonia’s Secretariat for Universities and Research of the Ministry of Economy and Knowledge. EPP is supported by postdoctoral grants and projects funded by the Fundação para a Ciência e a Tecnologia, Portugal (SFRH/BPD/116759/2016 and Geobiotec UIDB/04035/2020). EPP is also beneficiary of a contract/grant “ayudas para la recualificación del sistema universitario español, para 2021-2023. Modalidad María Zambrano” This study was subsidized in part by Project CGL2017-85038-P of the Spanish Ministerio de Economía y Competitividad-ERDF, as well as by the Aragón Regional Government (“grupo de Referencia Aragosaurus: reconstrucciones paleoambientales y recursos geológicos”). M.A. Arlegui Sánchez, B. Martínez, M. L. Revilla Andía, J. L. García and D. Diez Corral (Museo Numantino de Soria) are gratefully acknowledged for their help with the collections housed in the Museo Numantino de Soria. L. Piñuela (MUJA) provided valuable information on the Late Jurassic Asturian fossils; M. Belvedere (Università degli studi di Firenze) provided significant help with the use of the CloudCompare software and I. Díaz-Martínez provided valuable discussion on ichnotaxonomy. R. Glasgow (Zaragoza, Spain) revised the English grammar of a previous version of the manuscript. The comments of the reviewers, J.O. Farlow and T. Kubo, and the editor S.W. Salisbury have helped to improve the manuscript and are greatly appreciated.