An early diverging crocodylid from the Middle Miocene of Thailand highlights the role of SE Asia for the radiation of the Crocodyloidea

ABSTRACT

The Neogene period witnessed the radiation of modern crocodylian genera, as evidenced from their fossil record in intertropical zones. Despite its recognition as a modern biodiversity hotspot, South East Asia remains undersampled for that age bin. Here, we describe a new crocodylian from northern Thailand, Antecrocodylus chiangmuanensis n. gen. n. sp. from the Middle Miocene lignite seams of Chiang Muan and refer to it other specimens from the nearby lignite seams of Mae Moh. The holotype specimen preserves the posterior half of the skull and mandible. Anatomical observations are aided by medical computed tomography. A phylogenetic analysis places the new taxon in a basal position relative to Crocodylidae. This discovery highlights the underrated fossil record of Neogene crocodyloids in Asia compared to Africa or Australia and allows us to reconsider palaeobiogeographic relationships between supposed endemic clades.

KEYWORDS:

• Crocodylia
• Crocodylidae
• Miocene
• Asia

Acknowledgments

We are grateful to Palaeontological Research and Education Centre, Mahasarakham University, Mae Moh Mine, and Office of Mineral Resources, Region 1, Department of Mineral Resources for supporting our fieldwork in northern Thailand and for allowing us to prepare specimens. We extend our deep gratitude to the authorities of the Chiang Muan Mine for permitting this study and Sra Subdistrict Administrative Organization for encouragement. We express our appreciation to Nikorn Wongchai for providing assistance and sharing informative data during our work. Our thanks go to Assistant Governor – Mae Moh Mine, Varavudh Suteethorn for his support, Suravech Suteethorn for CT scan and sending specimen back, Wattana Wongsab, Siripa Pongsaengthong, Yupa Thasod, and Rattanaphorn Hanta for their help, as well as to all colleagues who participated in the fieldwork. JEM was supported by Agence Nationale de la Recherche (SEBEK project N° ANR-19-CE31-0006-01). The final version of this manuscript benefited from the comments of Jorgo Ristevski and Michela M. Johnson.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2023.2278152