DOCSLIB.ORG

A Reassessment of the Osteology of Mourasuchus Amazonensis Price, 1964 with Comments on the Taxonomy of the Species

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Reassessment of the Osteology of Mourasuchus Amazonensis Price, 1964 with Comments on the Taxonomy of the Species Palaeontologia Electronica palaeo-electronica.org A reassessment of the osteology of Mourasuchus amazonensis Price, 1964 with comments on the taxonomy of the species Giovanne M. Cidade, Douglas Riff, Jonas P. de Souza-Filho, and Annie Schmaltz Hsiou ABSTRACT This study is a thorough assessment on the morphology and taxonomy of Mourasuchus amazonensis, a fossil crocodylian of the Caimaninae clade from the late Miocene Solimões Formation of Brazil. A thorough redescription of the holotype of the species (DGM 562-R, a nearly complete skull with an associated incomplete left man- dible) is performed together with the redescription of the specimen UFAC-1424, a pos- terior portion of the skull with associated mandibular remains, and the description of the specimen LACM-160157, also a posterior portion of the cranium. As such, this paper brings the most comprehensive osteological study of M. amazonensis to be per- formed to date, enabling a thorough taxonomic reassessment of the species in ques- tion. This reassessment confirmed M. amazonensis as a valid species, with two autapomorphies and two other distinctive characters. UFAC-1424 and LACM-160157 are assigned as Mourasuchus cf. M. amazonensis, pending further studies on the tax- onomy of the species in order to clarify whether these specimens belong to the same species as DGM 526-R. Additionally, implications of the morphology observed in M. amazonensis for the taxonomic status of other Mourasuchus species are also dis- cussed, especially with respect to M. nativus, which is currently a junior synonym of M. arendsi. Giovanne M. Cidade. Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto-SP, 14040-901, Brazil; [email protected] Douglas Riff. Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia-MG, 38400-902, Brazil; [email protected] Jonas P. de Souza-Filho. Museu de Paleontologia, Universidade Federal do Acre, Rio Branco-AC, 69915- 900, Brazil; [email protected] Annie Schmaltz Hsiou. Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto-SP, 14040-901, Brazil; [email protected] Keywords: Mourasuchus amazonensis; Mourasuchus; Caimaninae; Crocodylia; Miocene; osteology Cidade, Giovanne M., Riff, Douglas, de Souza-Filho, Jonas P., and Schmaltz Hsiou, Annie. 2019. A reassessment of the osteology of Mourasuchus amazonensis Price, 1964 with comments on the taxonomy of the species. Palaeontologia Electronica 22.2.44A 1-23. https://doi.org/10.26879/893 palaeo-electronica.org/content/2019/2602-mourasuchus-amazonensis Copyright: July 2019 Society of Vertebrate Paleontology. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. creativecommons.org/licenses/by/4.0/creativecommons.org/licenses/by-nc-sa/4.0/ CIDADE ET AL.: MOURASUCHUS AMAZONENSIS Submission: 18 May 2018. Acceptance: 28 May 2019. INTRODUCTION Filho and Guilherme, 2011b; Scheyer & Delfino, 2016; Cidade et al., 2019b), and M. pattersoni from The fossil crocodyliform fauna of the Miocene the late Miocene of Venezuela (Cidade et al., of South America is well-known for its taxonomic 2017). Aside from these, there are several records diversity, morphological disparity, niche partition- of specimens assigned to “Mourasuchus sp.” from ing, and abundance of specimens (Rusconi, 1933; different deposits of the middle and of the late Mio- Patterson, 1936, 1943; Langston, 1965; Langston cene of South America (e.g., Salas-Gismondi et and Gasparini, 1997; Aguilera, 2004; Linares, al., 2007; Scheyer et al., 2013; Tineo et al., 2014; 2004; Paolillo and Linares, 2007; Salas-Gismondi Moreno-Bernal et al., 2016; Scheyer and Delfino, et al., 2007, 2015; Riff et al., 2010; Scheyer and 2016; Souza et al., 2016). Another species, Moreno-Bernal, 2010; Bona et al., 2013a; Bona Mourasuchus nativus, was erected by Gasparini and Barrios, 2015; Moreno-Bernal et al., 2016; (1985), but was later considered to be a junior syn- Scheyer and Delfino, 2016; Souza et al., 2016; onym of M. arendsi by Scheyer and Delfino (2016). Cidade et al., 2019a). The taxonomic diversity The current record of Mourasuchus amazon- includes sebecids, a clade of non-eusuchian croco- ensis is mainly restricted to the holotype DGM-526- dyliforms (Langston, 1965; Paolillo and Linares, R, an almost complete skull with an incomplete left 2007; Salas-Gismondi et al., 2007), and the eusu- hemimandible (see Price, 1964). An isolated left chian clades Gavialoidea (Gürich, 1912; Langston, jugal (UFAC-5269) has also been referred to the 1965; Bocquentin and Buffetaut, 1981; Brochu and taxon (Souza-Filho and Guilherme, 2011a). Both Rincón, 2004; Riff and Aguilera, 2008), Crocodyl- specimens are thought to be from the late Miocene oidea (Langston, 1965; Souza-Filho, 1993) and Solimões Formation of Brazil, with the holotype Alligatoroidea. This last group is represented coming from the Juruá River and the referred spec- mostly by taxa belonging to the clade Caimaninae, imen from the “Morro do Careca” locality, both in which also represents the most diverse crocodyli- the Acre state of Brazil. However, there has been form group of the Miocene of South America (Riff some doubt about the exact stratigraphic prove- et al., 2010; Bona et al., 2013a; Cidade et al., nance and age of the holotype, which will be 2019a). detailed below. One of the most distinctive representatives of The holotype of Mourasuchus amazonensis the caimanine fauna of the Miocene of South was only briefly described by Price (1964) and as America is Mourasuchus, which is characterized the species was the first of the genus to be mainly by its long, broad, dorsoventrally flattened described, the diagnosis offered in the original rostrum and long, slender mandibles with work was the same as of the genus. However, extremely short symphyses in which most of the diagnoses for Mourasuchus species described teeth are small in size (see Price, 1964; Langston, later were only minimally differentiated from M. 1965; Cidade et al., 2017). Whereas these cranial amazonensis (see Langston, 1966 and Bocquen- features, together with some vertebral characters tin-Villanueva, 1984). Recently, Cidade et al. (see Langston, 2008 and Tineo et al., 2014), have (2017) provided a more detailed comparison led some to consider Mourasuchus as a “straining” between the Mourasuchus species, from which it or “filter” feeder (Langston, 1965; Riff et al., 2010; could be shown that M. amazonensis is a valid Bona et al., 2013b), and others as a “gulp-feeder” species distinct from other Mourasuchus with (Cidade et al., 2017), a thorough assessment of respect to two autapomorphies, in addition to other the feeding habits of this taxon is still to be made distinguishing features (see Emended Diagnosis (Bona et al., 2013b; Cidade et al., 2017). below). A detailed reevaluation of the holotype, Mourasuchus includes the species M. ama- however, has never been performed. zonensis from the late Miocene of Brazil (Price, Therefore, the first objective of this paper is to 1964; Souza-Filho and Guilherme, 2011a), M. ato- provide a thorough redescription of the holotype of pus from the middle Miocene of Colombia and Mourasuchus amazonensis. The second objective Peru (Langston, 1965; Langston and Gasparini, is to provide a morphological assessment of two 1997; Salas-Gismondi et al., 2015), M. arendsi specimens from the late Miocene Solimões Forma- from the late Miocene of Venezuela, Brazil, and tion of Brazil that may be tentatively assigned Argentina (Bocquentin-Villanueva, 1984; Souza- 2 PALAEO-ELECTRONICA.ORG (Mourasuchus cf. amazonensis) to this species. and calcite as well as gypsum veins, lying in hori- One, UFAC-1424, is comprised of a posterior por- zontal to subhorizontal beds that can reach thick- tion of the skull and a fragment of the left dentary nesses of over 1000 m (Latrubesse et al., 2010). and was originally attributed to M. nativus upon its The depositional environment of the Solimões For- original, brief description by Bocquentin and mation is predominantly floodplain-lacustrine-palu- Souza-Filho (1990). The other, LACM-160157, has dal according to Latrubesse et al. (2010), with the not previously been described and comprises a Andes chain being considered the main source of posterior portion of the skull. The third objective the sediments (Latrubesse et al., 1997). Some addresses the bearing that our revised understand- workers assigned a late Miocene/Pliocene age to ing of M. amazonensis has on ongoing taxonomic the Solimões Formation as a whole (e.g., issues regarding Mourasuchus, especially regard- Latrubesse, 1992; Latrubesse et al., 1997), but ing the taxonomic status of M. nativus. recent geological, palynological, and sedimento- logical data suggests a late Miocene age for the MATERIALS AND METHODS formation (Cozzuol, 2006; Latrubesse et al., 2010), equivalent to the Huayquerian (∼9–6.8 Ma) South The three specimens examined in this paper American Land Mammal Age‒SALMA (Fortier et (the holotype of Mourasuchus amazonensis, DGM al., 2014). 526-R, and the specimens assigned as Mourasu- The holotype of Mourasuchus amazonensis chus cf. M. amazonensis LACM-160157 and (DGM-526-R) was collected from an outcrop in the UFAC-1424) are stored and available at their left bank of the Juruá River, located approximately respective institutions. The specimens were com- 4 km upstream from the mouth of the São João pared with other Mourasuchus specimens, in par- stream, which is a tributary stemming from the right ticular the holotypes of M. atopus (UCMP-38012), bank of the Juruá River, in the municipality of M. arendsi (CIAAP-1297) and M. pattersoni Marechal Thaumaturgo, Acre state, Brazil (Price, (MCNC-PAL-110-72V), as well as specimens 1964; Figure 1). This locality is identified as “Num- assigned to M. arendsi (MLP 73-IV-15-8, holotype ber 33” in the map of Simpson and Paula-Couto of M.
Load more

Recommended publications
  • For Peer Review
    Biological Journal of the Linnean Society Marine tethysuchian c rocodyliform from the ?Aptian -Albian (Early Cretaceous) of the Isle of Wight, England Journal:For Biological Peer Journal of theReview Linnean Society Manuscript ID: BJLS-3227.R1 Manuscript Type: Research Article Date Submitted by the Author: 05-May-2014 Complete List of Authors: Young, Mark; University of Edinburgh, Biological Sciences; University of Southampton, School of Ocean and Earth Science Steel, Lorna; Natural History Museum, Earth Sciences Foffa, Davide; University of Bristol, Department of Earth Sciences Price, Trevor; Dinosaur Isle Museum, Naish, Darren; University of Southampton, School of Ocean and Earth Science Tennant, Jon; Imperial College London, Department of Earth Science and Engineering Albian, Aptian, Cretaceous, Dyrosauridae, England, Ferruginous Sands Keywords: Formation, Isle of Wight, Pholidosauridae, Tethysuchia, Upper Greensand Formation Biological Journal of the Linnean Society Page 1 of 50 Biological Journal of the Linnean Society 1 2 3 Marine tethysuchian crocodyliform from the ?Aptian-Albian (Early Cretaceous) 4 5 6 of the Isle of Wight, England 7 8 9 10 by MARK T. YOUNG 1,2 *, LORNA STEEL 3, DAVIDE FOFFA 4, TREVOR PRICE 5 11 12 2 6 13 DARREN NAISH and JONATHAN P. TENNANT 14 15 16 1 17 Institute of Evolutionary Biology, School of Biological Sciences, The King’s Buildings, University 18 For Peer Review 19 of Edinburgh, Edinburgh, EH9 3JW, United Kingdom 20 21 2 School of Ocean and Earth Science, National Oceanography Centre, University of Southampton,
    [Show full text]
  • Crocodylomorpha, Neosuchia), and a Discussion on the Genus Theriosuchus
    bs_bs_banner Zoological Journal of the Linnean Society, 2015. With 5 figures The first definitive Middle Jurassic atoposaurid (Crocodylomorpha, Neosuchia), and a discussion on the genus Theriosuchus MARK T. YOUNG1,2, JONATHAN P. TENNANT3*, STEPHEN L. BRUSATTE1,4, THOMAS J. CHALLANDS1, NICHOLAS C. FRASER1,4, NEIL D. L. CLARK5 and DUGALD A. ROSS6 1School of GeoSciences, Grant Institute, The King’s Buildings, University of Edinburgh, James Hutton Road, Edinburgh EH9 3FE, UK 2School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, European Way, Southampton SO14 3ZH, UK 3Department of Earth Science and Engineering, Imperial College London, London SW6 2AZ, UK 4National Museums Scotland, Chambers Street, Edinburgh EH1 1JF, UK 5The Hunterian, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK 6Staffin Museum, 6 Ellishadder, Staffin, Isle of Skye IV51 9JE, UK Received 1 December 2014; revised 23 June 2015; accepted for publication 24 June 2015 Atoposaurids were a clade of semiaquatic crocodyliforms known from the Late Jurassic to the latest Cretaceous. Tentative remains from Europe, Morocco, and Madagascar may extend their range into the Middle Jurassic. Here we report the first unambiguous Middle Jurassic (late Bajocian–Bathonian) atoposaurid: an anterior dentary from the Isle of Skye, Scotland, UK. A comprehensive review of atoposaurid specimens demonstrates that this dentary can be referred to Theriosuchus based on several derived characters, and differs from the five previously recog- nized species within this genus. Despite several diagnostic features, we conservatively refer it to Theriosuchus sp., pending the discovery of more complete material. As the oldest known definitively diagnostic atoposaurid, this discovery indicates that the oldest members of this group were small-bodied, had heterodont dentition, and were most likely widespread components of European faunas.
    [Show full text]
  • 8. Archosaur Phylogeny and the Relationships of the Crocodylia
    8. Archosaur phylogeny and the relationships of the Crocodylia MICHAEL J. BENTON Department of Geology, The Queen's University of Belfast, Belfast, UK JAMES M. CLARK* Department of Anatomy, University of Chicago, Chicago, Illinois, USA Abstract The Archosauria include the living crocodilians and birds, as well as the fossil dinosaurs, pterosaurs, and basal 'thecodontians'. Cladograms of the basal archosaurs and of the crocodylomorphs are given in this paper. There are three primitive archosaur groups, the Proterosuchidae, the Erythrosuchidae, and the Proterochampsidae, which fall outside the crown-group (crocodilian line plus bird line), and these have been defined as plesions to a restricted Archosauria by Gauthier. The Early Triassic Euparkeria may also fall outside this crown-group, or it may lie on the bird line. The crown-group of archosaurs divides into the Ornithosuchia (the 'bird line': Orn- ithosuchidae, Lagosuchidae, Pterosauria, Dinosauria) and the Croco- dylotarsi nov. (the 'crocodilian line': Phytosauridae, Crocodylo- morpha, Stagonolepididae, Rauisuchidae, and Poposauridae). The latter three families may form a clade (Pseudosuchia s.str.), or the Poposauridae may pair off with Crocodylomorpha. The Crocodylomorpha includes all crocodilians, as well as crocodi- lian-like Triassic and Jurassic terrestrial forms. The Crocodyliformes include the traditional 'Protosuchia', 'Mesosuchia', and Eusuchia, and they are defined by a large number of synapomorphies, particularly of the braincase and occipital regions. The 'protosuchians' (mainly Early *Present address: Department of Zoology, Storer Hall, University of California, Davis, Cali- fornia, USA. The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds (ed. M.J. Benton), Systematics Association Special Volume 35A . pp. 295-338. Clarendon Press, Oxford, 1988.
    [Show full text]
  • A Teleosaurid (Crocodylia, Mesosuchia) from the Toarcian of Madagascar and Its Palaeobiogeographical Significance
    Pal~iont. Z. 55 I 3/4 313-319 Stuttgart, Dezember 1981 I A teleosaurid (Crocodylia, Mesosuchia) from the Toarcian of Madagascar and its palaeobiogeographical significance ERIC BUFFETAUT, GENEVIJ~VE TERMIER & HENRI TERM1ER, Paris* With 2 figures in the text Kurzfassung: Ein Oberkieferfragment eines Krokodiliers aus dem Toarcium von NW-Madagaskar wird als Stenosaurus sp. (Familie Teleosauridae) bestimmt. Es ist der ~ilteste aus Madagaskar bekannte Kro- kodilier und deutet aunistische B eziehungen mit Westeuropa und Siidamerika an. Die Verbreitung der ober- liassischen marinen Krokodilier, die derjenigen des Ammoniten Bouleiceras iihnelt, weist auf die Existenz einer epikontinentalen Seestraf~e vonder Tethys fiber die transerythr~iische Provinz bis zum siidlichen Tell Afrikas; diese Seestral~e bildete eine Verbindung zwischen Westeuropa und Siidamerika. A b s t r a c t : A fragment of the upper jaw of a crocodilian from the Toarcian of NW Madagascar is refer- red to Steneosaurus sp. (family Teleosauridae). It is the earliest known crocodilian from Madagascar. It indi- cates faunal relationships with western Europe and South America. The distribution of late Liassic marine crocodilians, similar to that of the ammonite Bouleiceras, suggests the existence of an epicontinental seaway from the Tethyan region to the southern part of Africa via the Transerythrean Province, which provided a marine connection between western Europe and South America. R ~ s u m ~ : Un fragment de mfichoire sup~rieure de Crocodilien du Toarcien du NW de Madagascar est rapport8 ~Steneosaurus sp. (famille Teleosauridae). C'est le plus ancien Crocodilien connu ~iMadagascar. I1 indique des relations fauniques avec l'Europe occidentale et l'Am&ique du Sud.
    [Show full text]
  • Hyaenodontidae (Creodonta, Mammalia) and the Position of Systematics in Evolutionary Biology
    Hyaenodontidae (Creodonta, Mammalia) and the Position of Systematics in Evolutionary Biology by Paul David Polly B.A. (University of Texas at Austin) 1987 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Paleontology in the GRADUATE DIVISION of the UNIVERSITY of CALIFORNIA at BERKELEY Committee in charge: Professor William A. Clemens, Chair Professor Kevin Padian Professor James L. Patton Professor F. Clark Howell 1993 Hyaenodontidae (Creodonta, Mammalia) and the Position of Systematics in Evolutionary Biology © 1993 by Paul David Polly To P. Reid Hamilton, in memory. iii TABLE OF CONTENTS Introduction ix Acknowledgments xi Chapter One--Revolution and Evolution in Taxonomy: Mammalian Classification Before and After Darwin 1 Introduction 2 The Beginning of Modern Taxonomy: Linnaeus and his Predecessors 5 Cuvier's Classification 10 Owen's Classification 18 Post-Darwinian Taxonomy: Revolution and Evolution in Classification 24 Kovalevskii's Classification 25 Huxley's Classification 28 Cope's Classification 33 Early 20th Century Taxonomy 42 Simpson and the Evolutionary Synthesis 46 A Box Model of Classification 48 The Content of Simpson's 1945 Classification 50 Conclusion 52 Acknowledgments 56 Bibliography 56 Figures 69 Chapter Two: Hyaenodontidae (Creodonta, Mammalia) from the Early Eocene Four Mile Fauna and Their Biostratigraphic Implications 78 Abstract 79 Introduction 79 Materials and Methods 80 iv Systematic Paleontology 80 The Four Mile Fauna and Wasatchian Biostratigraphic Zonation 84 Conclusion 86 Acknowledgments 86 Bibliography 86 Figures 87 Chapter Three: A New Genus Eurotherium (Creodonta, Mammalia) in Reference to Taxonomic Problems with Some Eocene Hyaenodontids from Eurasia (With B. Lange-Badré) 89 Résumé 90 Abstract 90 Version française abrégéé 90 Introduction 93 Acknowledgments 96 Bibliography 96 Table 3.1: Original and Current Usages of Genera and Species 99 Table 3.2: Species Currently Included in Genera Discussed in Text 101 Chapter Four: The skeleton of Gazinocyon vulpeculus n.
    [Show full text]
  • Marine Reptiles
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Institutional Research Information System University of Turin Geobios 39 (2006) 346–354 http://france.elsevier.com/direct/GEOBIO/ Marine reptiles (Thalattosuchia) from the Early Jurassic of Lombardy (northern Italy) Rettili marini (Thalattosuchia) del Giurassico inferiore della Lombardia (Italia settentrionale) Reptiles marins (Thalattosuchia) du Jurassique inférieur de la Lombardie (Italie du nord) Massimo Delfino a,*, Cristiano Dal Sasso b a Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, 50121 Firenze, Italy b Museo Civico di Storia Naturale, Corso Venezia 55, 20121 Milano, Italy Received 24 May 2004; accepted 3 January 2005 Available online 28 February 2006 Abstract The fossil remains of two small reptiles recently discovered in the Sogno Formation (Lower Toarcian) near Cesana Brianza (Lecco Province), represent the first mesoeucrocodylians reported for Lombardy and some of the few Jurassic reptiles from Italy. Due to the absence of diagnostic skeletal elements (the skulls are lacking), it is not possible to refer the new specimens at genus level with confidence. Although the well devel- oped dermal armour would characterise Toarcian thalattosuchians of the genera Steneosaurus (Teleosauridae) and Pelagosaurus (Metriorhynch- idae), the peculiar morphology of the osteoderms allow to tentatively refer the remains to the latter taxon (cf. Pelagosaurus sp.). The small size, along with the opening of the neurocentral vertebral sutures and, possibly, the non sutured caudal pleurapophyses, indicate that the specimens were morphologically immature at death. These “marine crocodiles” confirm the affinities between the fauna of the Calcare di Sogno Formation and coeval outcrops of central Europe that also share the presence of similar fishes and crustaceans.
    [Show full text]
  • Crown Clades in Vertebrate Nomenclature
    2008 POINTS OF VIEW 173 Wiens, J. J. 2001. Character analysis in morphological phylogenetics: Wilkins, A. S. 2002. The evolution of developmental pathways. Sinauer Problems and solutions. Syst. Biol. 50:689–699. Associates, Sunderland, Massachusetts. Wiens, J. J., and R. E. Etheridge. 2003. Phylogenetic relationships of Wright, S. 1934a. An analysis of variability in the number of digits in hoplocercid lizards: Coding and combining meristic, morphometric, an inbred strain of guinea pigs. Genetics 19:506–536. and polymorphic data using step matrices. Herpetologica 59:375– Wright, S. 1934b. The results of crosses between inbred strains 398. of guinea pigs differing in number of digits. Genetics 19:537– Wiens, J. J., and M. R. Servedio. 1997. Accuracy of phylogenetic analysis 551. including and excluding polymorphic characters. Syst. Biol. 46:332– 345. Wiens, J. J., and M. R. Servedio. 1998. Phylogenetic analysis and in- First submitted 28 June 2007; reviews returned 10 September 2007; traspecific variation: Performance of parsimony, likelihood, and dis- final acceptance 18 October 2007 tance methods. Syst. Biol. 47:228–253. Associate Editor: Norman MacLeod Syst. Biol. 57(1):173–181, 2008 Copyright c Society of Systematic Biologists ISSN: 1063-5157 print / 1076-836X online DOI: 10.1080/10635150801910469 Crown Clades in Vertebrate Nomenclature: Correcting the Definition of Crocodylia JEREMY E. MARTIN1 AND MICHAEL J. BENTON2 1UniversiteL´ yon 1, UMR 5125 PEPS CNRS, 2, rue Dubois 69622 Villeurbanne, France; E-mail: [email protected] 2Department of Earth Sciences, University of Bristol, Bristol, BS9 1RJ, UK; E-mail: [email protected] Downloaded By: [Martin, Jeremy E.] At: 19:32 25 February 2008 Acrown group is defined as the most recent common Dyke, 2002; Forey, 2002; Monsch, 2005; Rieppel, 2006) ancestor of at least two extant groups and all its descen- but rather expresses dissatisfaction with the increasingly dants (Gauthier, 1986).
    [Show full text]
  • New Study of Fossil Caimans in North America Determines Their Evolutionary History 31 August 2021
    New study of fossil caimans in North America determines their evolutionary history 31 August 2021 Márton Rabi. Avoiding snap extinction In their study, the researchers investigated the question of whether the caimans originally came from North or Central America. "Using other caiman fossils from Central America, we determined that these species actually represent extinct species more closely related to caimans living today. However, the caimans originally evolved in North America," says Jules Walter. He added that the caimans probably spread from there to South Skeleton and skull (enlargement) of one of the rare finds America in the Cretaceous period about 66 million of Tsoabichi greenriverensis, an early caiman crocodile, years ago—around the time of the mass extinction of from the approximately 52 million-year-old rocks of the Green River Formation in Wyoming, USA. Credit: Agnes the dinosaurs. Fatz, Tobias Massonne, Gustavo Darlim "Of all the dinosaur species, only the ancestors of today's birds survived. However, freshwater species such as crocodiles were not as strongly A new study of two approximately 52-million-year- affected by the great extinction," Walter explains. In old fossil finds from the Green River Formation in the Cretaceous, he says, North and South America Wyoming, U.S., has fit them into the evolutionary were connected only by a chain of islands, so history of crocodiles. Biogeologists Jules Walter, caimans had some difficulties to overcome. Dr. Márton Rabi of the University of Tübingen, "Nevertheless, it wasn't the only dispersal between working with some other colleagues, determined North to South America during evolution; there the extinct species Tsoabichi greenriverensis to be must have been further migrations between the two an early caiman crocodile.
    [Show full text]
  • New Transitional Fossil from Late Jurassic of Chile Sheds Light on the Origin of Modern Crocodiles Fernando E
    www.nature.com/scientificreports OPEN New transitional fossil from late Jurassic of Chile sheds light on the origin of modern crocodiles Fernando E. Novas1,2, Federico L. Agnolin1,2,3*, Gabriel L. Lio1, Sebastián Rozadilla1,2, Manuel Suárez4, Rita de la Cruz5, Ismar de Souza Carvalho6,8, David Rubilar‑Rogers7 & Marcelo P. Isasi1,2 We describe the basal mesoeucrocodylian Burkesuchus mallingrandensis nov. gen. et sp., from the Upper Jurassic (Tithonian) Toqui Formation of southern Chile. The new taxon constitutes one of the few records of non‑pelagic Jurassic crocodyliforms for the entire South American continent. Burkesuchus was found on the same levels that yielded titanosauriform and diplodocoid sauropods and the herbivore theropod Chilesaurus diegosuarezi, thus expanding the taxonomic composition of currently poorly known Jurassic reptilian faunas from Patagonia. Burkesuchus was a small‑sized crocodyliform (estimated length 70 cm), with a cranium that is dorsoventrally depressed and transversely wide posteriorly and distinguished by a posteroventrally fexed wing‑like squamosal. A well‑defned longitudinal groove runs along the lateral edge of the postorbital and squamosal, indicative of a anteroposteriorly extensive upper earlid. Phylogenetic analysis supports Burkesuchus as a basal member of Mesoeucrocodylia. This new discovery expands the meagre record of non‑pelagic representatives of this clade for the Jurassic Period, and together with Batrachomimus, from Upper Jurassic beds of Brazil, supports the idea that South America represented a cradle for the evolution of derived crocodyliforms during the Late Jurassic. In contrast to the Cretaceous Period and Cenozoic Era, crocodyliforms from the Jurassic Period are predomi- nantly known from marine forms (e.g., thalattosuchians)1.
    [Show full text]
  • A New Sebecid Mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of North-Western Argentina
    Zoological Journal of the Linnean Society, 2011, 163, S7–S36. With 17 figures A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina DIEGO POL1* and JAIME E. POWELL2 1CONICET, Museo Paleontológico Egidio Feruglio, Ave. Fontana 140, Trelew CP 9100, Chubut, Argentina 2CONICET, Instituto Miguel Lillo, Miguel Lillio 205, San Miguel de Tucumán CP 4000, Tucumán, Argentina Received 2 March 2010; revised 10 October 2010; accepted for publication 19 October 2010 A new basal mesoeucrocodylian, Lorosuchus nodosus gen. et sp. nov., from the Palaeocene of north-western Argentina is presented here. The new taxon is diagnosed by the presence of external nares facing dorsally, completely septated, and retracted posteriorly, elevated narial rim, sagittal crest on the anteromedial margins of both premaxillae, dorsal crests and protuberances on the anterior half of the rostrum, and anterior-most three maxillary teeth with emarginated alveolar margins. This taxon is most parsimoniously interpreted as a bizarre and highly autapomorphic basal member of Sebecidae, a position supported (amongst other characters) by the elongated bar-like pterygoid flanges, a laterally opened notch and fossa in the pterygoids located posterolaterally to the choanal opening (parachoanal fossa), base of postorbital process of jugal directed dorsally, and palatal parts of the premaxillae meeting posteriorly to the incisive foramen. Lorosuchus nodosus also shares with basal neosuchians a suite of derived characters that are interpreted as convergently acquired and possibly related to their semiaquatic lifestyle. The phylogenetic analysis used for testing the phylogenetic affinities of L. nodosus depicts Sebecidae as the sister group of Baurusuchidae, forming a monophyletic Sebecosuchia that is deeply nested within Notosuchia.
    [Show full text]
  • CROCODYLIFORMES, MESOEUCROCODYLIA) from the EARLY CRETACEOUS of NORTH-EAST BRAZIL by DANIEL C
    [Palaeontology, Vol. 52, Part 5, 2009, pp. 991–1007] A NEW NEOSUCHIAN CROCODYLOMORPH (CROCODYLIFORMES, MESOEUCROCODYLIA) FROM THE EARLY CRETACEOUS OF NORTH-EAST BRAZIL by DANIEL C. FORTIER and CESAR L. SCHULTZ Departamento de Paleontologia e Estratigrafia, UFRGS, Avenida Bento Gonc¸alves 9500, 91501-970 Porto Alegre, C.P. 15001 RS, Brazil; e-mails: [email protected]; [email protected] Typescript received 27 March 2008; accepted in revised form 3 November 2008 Abstract: A new neosuchian crocodylomorph, Susisuchus we recovered the family name Susisuchidae, but with a new jaguaribensis sp. nov., is described based on fragmentary but definition, being node-based group including the last com- diagnostic material. It was found in fluvial-braided sedi- mon ancestor of Susisuchus anatoceps and Susisuchus jagua- ments of the Lima Campos Basin, north-eastern Brazil, ribensis and all of its descendents. This new species 115 km from where Susisuchus anatoceps was found, in corroborates the idea that the origin of eusuchians was a rocks of the Crato Formation, Araripe Basin. S. jaguaribensis complex evolutionary event and that the fossil record is still and S. anatoceps share a squamosal–parietal contact in the very incomplete. posterior wall of the supratemporal fenestra. A phylogenetic analysis places the genus Susisuchus as the sister group to Key words: Crocodyliformes, Mesoeucrocodylia, Neosuchia, Eusuchia, confirming earlier studies. Because of its position, Susisuchus, new species, Early Cretaceous, north-east Brazil. B razilian crocodylomorphs form a very expressive Turonian–Maastrichtian of Bauru basin: Adamantinasu- record of Mesozoic vertebrates, with more than twenty chus navae (Nobre and Carvalho, 2006), Baurusuchus species described up to now.
    [Show full text]
  • Big-Headed Marine Crocodyliforms and Why We Must Be Cautious When Using Extant Species As Body Length Proxies for Long-Extinct Relatives
    Palaeontologia Electronica palaeo-electronica.org Big-headed marine crocodyliforms and why we must be cautious when using extant species as body length proxies for long-extinct relatives Mark T. Young, Márton Rabi, Mark A. Bell, Davide Foffa, Lorna Steel, Sven Sachs, and Karin Peyer ABSTRACT Body size is commonly used as a key variable for estimating ecomorphological trends at a macroevolutionary scale, making reliable body length estimates of fossil taxa critically important. Crocodylomorphs (extant crocodylians and their extinct rela- tives) evolved numerous 'aberrant' body-plans during their ~230 million-year history, ranging from ‘hooved’ terrestrial species to dolphin-like pelagic species. Such clades evolved distinct cranial and femoral scaling ratios (compared to total body length), thereby making extant taxa unsuitable proxies for estimating their body lengths. Here we illustrate that the fossil clade Teleosauridae also fits into this category. Teleosaurids were a predominately shallow marine clade that had a global distribution during the Jurassic. Known to have evolved a wide range of body lengths (2–5 m based on com- plete skeletons), there is currently no way of reliably estimating the size of incomplete specimens. This is surprising, as some teleosaurids have been considered very large (9–10 m in total length), thus making Teleosauridae the largest bodied clade during the first 100 million years of crocodylomorph evolution. Our examination and regression analyses of the best preserved teleosaurid skeletons demonstrates that: they were smaller than previously thought, with no known specimen exceeding 7.2 m in length; and that they had proportionally large skulls, and proportionally short femora, when compared to body length.
    [Show full text]