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Perrichon G, Pochat-Cottilloux Y, Conedera D, Richardin P, Fernandez V, Hautier L, Martin JE. Neuroanatomy and pneumaticity of the extinct Malagasy "horned" crocodile Voay robustus and its implications for crocodylid phylogeny and palaeoecology. Anat Rec (Hoboken) 2024; 307:2749-2786. [PMID: 38116895 DOI: 10.1002/ar.25367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 10/05/2023] [Accepted: 11/29/2023] [Indexed: 12/21/2023]
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.
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Affiliation(s)
- Gwendal Perrichon
- CNRS UMR 5276, Université Claude Bernard Lyon 1, ENS de Lyon, Laboratoire de Géologie de Lyon-Terre, Planètes, Environnement, Villeurbanne, France
| | - Yohan Pochat-Cottilloux
- CNRS UMR 5276, Université Claude Bernard Lyon 1, ENS de Lyon, Laboratoire de Géologie de Lyon-Terre, Planètes, Environnement, Villeurbanne, France
| | - Davide Conedera
- CNRS UMR 5276, Université Claude Bernard Lyon 1, ENS de Lyon, Laboratoire de Géologie de Lyon-Terre, Planètes, Environnement, Villeurbanne, France
| | - Pascale Richardin
- Centre de Recherche et de Restauration des Musées de France (C2RMF), Palais du Louvre, Porte des Lions, Paris, France
- CNRS-UMR 8068, Technologie Ethnologie des Mondes Préhistoriques (TEMPS), Université Paris Nanterre, Nanterre Cedex, France
| | - Vincent Fernandez
- Imaging and Analysis Centre, The Natural History Museum, London, UK
- European Synchrotron Radiation Facility, Grenoble, France
| | - Lionel Hautier
- Institut des Sciences de l'Évolution, Université Montpellier, CNRS, IRD, EPHE, Montpellier, France
- Mammal Section, Life Sciences, Vertebrate Division, The Natural History Museum, London, UK
| | - Jeremy E Martin
- CNRS UMR 5276, Université Claude Bernard Lyon 1, ENS de Lyon, Laboratoire de Géologie de Lyon-Terre, Planètes, Environnement, Villeurbanne, France
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Gvoždík V, Dolinay M, Zassi-Boulou AG, Lemmon AR, Lemmon EM, Procházka M. Central African dwarf crocodiles found in syntopy are comparably divergent to South American dwarf caimans. Biol Lett 2024; 20:20230448. [PMID: 38716586 PMCID: PMC11135362 DOI: 10.1098/rsbl.2023.0448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 12/18/2023] [Accepted: 03/04/2024] [Indexed: 05/31/2024] Open
Abstract
Recent molecular taxonomic advancements have expanded our understanding of crocodylian diversity, revealing the existence of previously overlooked species, including the Congo dwarf crocodile (Osteolaemus osborni) in the central Congo Basin rainforests. This study explores the genomic divergence between O. osborni and its better-known relative, the true dwarf crocodile (Osteolaemus tetraspis), shedding light on their evolutionary history. Field research conducted in the northwestern Republic of the Congo uncovered a locality where both species coexist in sympatry/syntopy. Genomic analysis of sympatric individuals reveals a level of divergence comparable to that between ecologically similar South American dwarf caimans (Paleosuchus palpebrosus and Paleosuchus trigonatus), suggesting parallel speciation in the Afrotropics and Neotropics during the Middle to Late Miocene, 10-12 Ma. Comparison of the sympatric and allopatric dwarf crocodiles indicates no gene flow between the analysed sympatric individuals of O. osborni and O. tetraspis. However, a larger sample will be required to answer the question of whether or to what extent these species hybridize. This study emphasizes the need for further research on the biology and conservation status of the Congo dwarf crocodile, highlighting its significance in the unique biodiversity of the Congolian rainforests and thus its potential as a flagship species.
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Affiliation(s)
- Václav Gvoždík
- Institute of Vertebrate Biology of the Czech Academy of Sciences, Brno, Czech Republic
- Department of Zoology, National Museum of the Czech Republic, Prague, Czech Republic
| | - Matej Dolinay
- Institute of Vertebrate Biology of the Czech Academy of Sciences, Brno, Czech Republic
| | - Ange-Ghislain Zassi-Boulou
- Department of Biology, National Institute for Research in Exact and Natural Sciences (IRSEN), Brazzaville, Republic of the Congo
| | - Alan R. Lemmon
- Department of Scientific Computing, Dirac Science Library, Florida State University, Tallahassee, FL, USA
| | - Emily M. Lemmon
- Department of Biological Sciences, Florida State University, Tallahassee, FL, USA
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