Neuroanatomy and pneumaticity of the extinct Malagasy “horned” crocodile Voay robustus and its implications for crocodylid phylogeny and palaeoecology

Neuroanatomie et pneumaticité du crocodile "cornu" éteint de Madagascar Voay robustus : implications pour la phylogénie et la paléoécologie des crocodylidés

Gwendal Perrichon (1) , Yohan Pochat‐cottilloux (1) , Davide Conedera (1) , Pascale Richardin (2, 3) , Vincent Fernandez (4, 5) , Lionel Hautier (6, 5) , Jeremy E Martin (1)

1 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
2 C2RMF - Centre de recherche et de restauration des musées de France
3 TEMPS - Technologie et Ethnologie des Mondes Préhistoriques
4 ESRF - European Synchrotron Radiation Facility [Grenoble]
5 NHM - The Natural History Museum [London]
6 UMR ISEM - Institut des Sciences de l'Evolution de Montpellier

Abstract Voay robustus , the extinct Malagasy “horned” crocodile, was originally considered to be the only crocodylian representative in Madagascar during most part of the Holocene. However, Malagasy crocodylian remains have had confused taxonomic attributions and recent studies have underlined that Crocodylus and Voay populations coexisted on the island for at least 7500 years. Here, we describe the inner braincase anatomy of Voay robustus using x‐ray computed tomography on four specimens, to provide new anatomical information that distinguishes Voay from Crocodylus , especially features of the brain endocast and the paratympanic sinuses. Geometric morphometric analyses are performed on 3D models of the internal organs to compare statistically Voay with a subset of extant Crocodylidae. Following these comparisons, we build an endocranial morphological matrix to discuss the proposed phylogenetic affinities of Voay with Osteolaeminae from an endocranial point of view. Additionally, we discuss the use of internal characters in systematic studies and find that they can have a major impact on morphological analyses. Finally, new radiocarbon data on Voay and subfossil Crocodylus specimens are recovered between 2010 and 2750 cal BP, which confirm the cohabitation of the two species in the same area for a long period of time. We thus assess several extinction scenarios, and propose a slightly different ecology of Voay compared to Crocodylus , which could have allowed habitat partitioning on the island. Our approach complements information obtained from previous molecular and morphological phylogenies, as well as previous radiocarbon dating, together revealing past diversity and faunal turnovers in Madagascar.

Keywords: endocranial characters; Malagasy crocodylians; morphometry; neuroanatomy; paratympanic sinus; Radiocarbon dating

Domains: Paleontology; Systematics, Phylogenetics and taxonomy

Gwendal Perrichon, Yohan Pochat‐cottilloux, Davide Conedera, Pascale Richardin, Vincent Fernandez, et al.. Neuroanatomy and pneumaticity of the extinct Malagasy “horned” crocodile Voay robustus and its implications for crocodylid phylogeny and palaeoecology. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 2023, ⟨10.1002/ar.25367⟩. ⟨hal-04357702⟩