DOI: 10.15468/x8ews8
title: New insights into the fossil record of the turtle genus Chelus Duméril, 1806 including new specimens with information on cervicals and limb bones

description: This dataset contains the digitized treatments in Plazi based on the original journal article Cadena, Edwin-Alberto, Link, Andrés, Vanegas, Andrés, Avellaneda-Otero, Carlos A., Perdomo, César, Urueña-Carrillo, Diego A., Sánchez, Rodolfo, Vanegas, Rubén (2023): New insights into the fossil record of the turtle genus Chelus Duméril, 1806 including new specimens with information on cervicals and limb bones. Comptes Rendus Palevol 22 (34): 689-709, DOI: 10.5852/cr-palevol2023v22a34, URL: http://dx.doi.org/10.5852/cr-palevol2023v22a34ABSTRACTMatamata turtles (Chelus Duméril, 1806) are composed of two extant species, Chelus fimbriata Schneider, 1783 and Chelus orinocensis Vargas-Ramírez, Caballero, Morales-Betancourt, Lasso, Amaya, Martínez, Silva-Viana, Vogt, Farias, Hrbek, Campbell & Fritz, 2020, inhabitants of the main freshwater drainages of northern South America. The systematics and palaeobiogeography of Chelus is still unresolved. Here, we describe several new fossil specimens from the Late Miocene of Urumaco (Venezuela) and Tatacoa (Colombia). The fossils are mostly complete, articulated shells that allow reestablishing validity of two extinct taxa, Chelus colombiana Wood, 1976 and Chelus lewisi Wood, 1976. One of the specimens of C. lewisi from Urumaco represents the first record within the genus for which autopodial bones (a left manus) and additional limb bones are preserved together with ashell, demonstrating evolutionary conservatism in limb anatomy for the genus. The specimen comes from the Socorro Formation, representing the earliest so far known record of Chelus for the Urumaco sequence. Additionally, one specimen from Tatacoa is the first fossil for which cervical and pectoral girdle elements are preserved. Phylogenetic analysis supports the existence of two separate clades inside of Chelus, one formed by the extinct species and the other by the extant ones.KEY WORDSTestudines,South America,Chelidae,Matamata,Miocene fossils. RÉSUMÉDe nouvelles informations sur les archives fossiles du genre de tortue Chelus Duméril, 1806, y compris de nouveaux spécimens avec des informations sur les os cervicaux et les os des membres. Les tortues Matamata (Chelus Duméril, 1806) sont composées de deux espèces actuelles, Chelus fimbriata Schneider, 1783 et Chelus orinocensis Vargas-Ramírez, Caballero, Morales-Betancourt, Lasso, Amaya, Martínez, Silva-Viana, Vogt, Farias, Hrbek, Campbell, Fritz, 2020, habitants des principaux bassins versants d’eau douce du nord de l’Amérique du Sud. La systématique et la paléobiogéographie de Chelus ne sont toujours pas résolues. Nous décrivons ici plusieurs nouveaux spécimens fossiles du Miocène supérieur d’Urumaco (Venezuela) et de Tatacoa (Colombie). Les fossiles correspondent, pour la plupart, à des coquilles complètes et articulées, qui permettent de rétablir la validité de deux taxons éteints, Chelus colombiana Wood, 1976 et Chelus lewisi Wood, 1976. L’un des spécimens d’Urumaco représente la première occurrence au sein du genre pour lequel les os autopodiaux (manus gauche) et certains os des membres supplémentaires sont conservés avec une coquille, démontrant le conservatisme évolutif dans l’anatomie des membres du genre. Ce nouveau spécimen de Chelus lewisi provient de la formation de Socorro, représentant le plus ancien fossile connu de Chelus pour la séquence d’Urumaco. De plus, l’un des nouveaux spécimens de Tatacoa est le premier du genre pour lequel les éléments de la ceinture cervicale et pectorale sont conservés. L’analyse phylogénétique soutient l’existence de deux clades distincts à l’intérieur de Chelus, l’un formé par les espèces éteintes et l’autre par les espèces actuelles.MOTS CLÉS Testudines, Amérique du Sud, Chelidae, Matamata, fossiles du Miocène. INTRODUCTION With an extremely flat head and a highly decorated shell (dorsal ridges on the carapace) and limbs (integumentary fringes), the extant representatives of the genus Chelus Duméril, 1806, commonly known as matamata turtles, are iconic inhabitants of tropical South America. Besides its distinctive look, Chelus has been subject of debate in terms of whether the extant representatives constitute a monotypic taxon (a single species), or whether the morphological differences between the populations of the Amazon and the Orinoco basins represent two separate taxa (Sánchez-Villagra et al. 1995a, b; Pritchard 2008). Recently, a molecular study provided evidence for the existence of two genetically distinct lineages, Chelus fimbriata Schneider, 1783 (fimbriatus for some authors) and Chelus orinocensis Vargas-Ramírez, Caballero, Morales-Betancourt, Lasso, Amaya, Martínez, Silva-Viana, Vogt, Farias, Hrbek, Campbell & Fritz, 2020, which were estimated to have been geographically separated since at least the Late Miocene (c. 12.7 Ma) (Vargas-Ramírez et al. 2020). The two extinct taxa that were considered as valid by several authors for decades are Chelus colombiana Wood, 1976 (colombianus for some authors) and Chelus lewisi Wood, 1976 (Wood 1976; Bocquentin 1988; Sánchez-Villagra et al. 1995a; Cadena et al. 2008; Cadena & Jaramillo 2015a). Ferreira et al. (2016) more recently proposed that morphological differences between the two extinct taxa could be explained as intraspecific variation and, thus, synonymized both taxa as C. colombiana (Ferreira et al. 2016). Two decades of palaeontological expeditions to two of the most remarkable Miocene fossiliferous regions of northern South America, Urumaco, Falcón State, Venezuela and La Tatacoa, Huila Department, Colombia have yielded exceptionally rich remains of fossil vertebrates (Kay et al. 1997; Sánchez-Villagra et al. 2003; Carrillo et al. 2018; Carrillo-Briceño et al. 2018; Scheyer et al. 2013; Cadena et al. 2020 a, b, 2021; and references therein). Here we present several new articulated fossil shells (carapace and plastron) and other remains referrable to Chelus. This includes a specimen from the Middle Miocene Socorro Formation (Quiroz & Jaramillo 2010), which represents the oldest record of the genus in the Urumaco area and for the first time preserves limbs bones. The new material provides evidence for reestablishing two extinct taxa, as initially suggested by Wood (1976), instead of a single one (Ferreira et al. 2016). Finally, we performed a phylogenetic analysis to further explore the evolutionary history of matamata turtles.With an extremely flat head and a highly decorated shell (dorsal ridges on the carapace) and limbs (integumentary fringes), the extant representatives of the genus Chelus Duméril, 1806, commonly known as matamata turtles, are iconic inhabitants of tropical South America. Besides its distinctive look, Chelus has been subject of debate in terms of whether the extant representatives constitute a monotypic taxon (a single species), or whether the morphological differences between the populations of the Amazon and the Orinoco basins represent two separate taxa (Sánchez-Villagra et al. 1995a, b; Pritchard 2008). Recently, a molecular study provided evidence for the existence of two genetically distinct lineages, Chelus fimbriata Schneider, 1783 (fimbriatus for some authors) and Chelus orinocensis Vargas-Ramírez, Caballero, Morales-Betancourt, Lasso, Amaya, Martínez, Silva-Viana, Vogt, Farias, Hrbek, Campbell & Fritz, 2020, which were estimated to have been geographically separated since at least the Late Miocene (c. 12.7 Ma) (Vargas-Ramírez et al. 2020).The two extinct taxa that were considered as valid by several authors for decades are Chelus colombiana Wood, 1976 (colombianus for some authors) and Chelus lewisi Wood, 1976 (Wood 1976; Bocquentin 1988; Sánchez-Villagra et al. 1995a; Cadena et al. 2008; Cadena & Jaramillo 2015a). Ferreira et al. (2016) more recently proposed that morphological differences between the two extinct taxa could be explained as intraspecific variation and, thus, synonymized both taxa as C. colombiana (Ferreira et al. 2016).Two decades of palaeontological expeditions to two of the most remarkable Miocene fossiliferous regions of northern South America, Urumaco, Falcón State, Venezuela and La Tatacoa, Huila Department, Colombia have yielded exceptionally rich remains of fossil vertebrates (Kay et al. 1997; Sánchez-Villagra et al. 2003; Carrillo et al. 2018; Carrillo-Briceño et al. 2018; Scheyer et al. 2013; Cadena et al. 2020 a, b, 2021; and references therein). Here we present several new articulated fossil shells (carapace and plastron) and other remains referrable to Chelus. This includes a specimen from the Middle Miocene Socorro Formation (Quiroz & Jaramillo 2010), which represents the oldest record of the genus in the Urumaco area and for the first time preserves limbs bones. The new material provides evidence for reestablishing two extinct taxa, as initially suggested by Wood (1976), instead of a single one (Ferreira et al. 2016). Finally, we performed a phylogenetic analysis to further explore the evolutionary history of matamata turtles.