Estamos trabajando para incorporar este artículo al repositorio
Consulte el artículo en la página del editor
Consulte la política de Acceso Abierto del editor


Background. Macelognathus vagans Marsh, 1884 from the Late Jurassic Morrison Fm. of Wyoming was originally described as a dinosaur by Marsh and in 1971 Ostrom suggested crocodilian affinities. In 2005, Göhlich and collaborators identified new material of this species from Colorado as a basal crocodylomorph. However, a partial skull found in association with mandibular and postcranial remains was not described. Methods. Due to the small size and delicate structures within the braincase, micro CT studies were performed on this specimen. The new anatomical information was incorporated in a phylogenetic dataset, expanding both character and taxon sampling. Results. This new material reinforces the non-crocodyliform crocodylomorph affinities of Macelognathus as it bears a large otic aperture, unfused frontals and lacks ornamentation on the dorsal cranial bones. The internal structures also support these affinities as this specimen bears traits (i.e., heavily pneumatized and expanded basisphenoid; the presence of additional pneumatic features on the braincase; and the otoccipitalquadrate contact) not present in most basal crocodylomorphs. Furthermore, the presence of a wide supraoccipital and a cranioquadrate passage are traits shared with Almadasuchus from the early Late Jurassic of Argentina. Macelognathus was recovered as one of the closest relatives of crocodyliforms, forming a clade (Hallopodidae) with two other Late Jurassic taxa (Almadasuchus and Hallopus). Discussion. The clade formed by Almadasuchus C Hallopus C Macelognathus, the Hallopodidae, is characterized by a higher degree of suturing of the braincase, posteriorly closed otic aperture (paralleled in mesoeucrocodylians) and cursorial adaptations. Also, the phylogenetic position of this lineage of derived crocodylomorphs as the sister group of Crocodyliformes implies a large amount of unsampled record (ghost lineage), at least 50 million years. © 2017 Leardi et al.


Documento: Artículo
Título:Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
Autor:Leardi, J.M.; Pol, D.; Clark, J.M.
Filiación:CONICET, Instituto de Estudios Andinos 'Don Pablo Groeber' (IDEAN), Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias Geológicas, Universidad de Buenos Aires, Buenos Aires, Argentina
CONICET, Museo Paleontológico Egidio Feruglio, Trelew, Chubut, Argentina
Department of Biological Sciences, George Washington University, Washington, D.C., United States
Palabras clave:Braincase; Crocodylomorpha; Late jurassic; Micro CT; Phylogeny; anatomy; archosaur; Argentina; bear; cladistics; dorsal region; human; human tissue; mandible; marsh; micro-computed tomography; nonhuman; parietal bone; relative; sampling; sister group; Upper Jurassic
Título revista:PeerJ
Título revista abreviado:PeerJ


  • Ague, J.J., Carpenter, K., Ostrom, J.H., Solution to the Hallopus enigma? (1995) American Journal of Science, 295, pp. 1-17
  • Alcober, O., Redescription of the skull of Saurosuchus galilei (Archosauria: Rauisuchidae) (2000) Journal of Vertebrate Paleontology, 20, pp. 302-316
  • Andrews, C.W., (1913) A descriptive catalogue of the marine reptiles of the Oxford clay, , Part II. London: British Museum (Natural History)
  • Bakker, R.T., Galton, P.M., Dinosaur monophyly and a new class of vertebrates (1974) Nature, 248, pp. 168-172
  • Baur, G., Remarks on the reptiles generally called Dinosauria (1891) American Naturalist, 25, pp. 434-454
  • Benton, M.J., Clark, J.M., Archosaur phylogeny and the relationships of the Crocodylia (1988) The phylogeny and classification of tetrapods, volume 1: amphibians, reptiles, birds, pp. 295-338. , MJ Benton, ed. Oxford: Clarendon Press
  • Bonaparte, J.F., Los tetrápodos del sector superior de la Formación Los Colorados, La Rioja, Argentina (Triásico Superior). 1 Parte (1972) Opera Lilloana, 22, pp. 1-183
  • Bonaparte, J.F., Pedeticosaurus leviseuri Van Hoepen, a probable protosuchian. Navorsinge van die Nasionale Museum (1972) Bloemfontein, 2, pp. 301-305
  • Brazeau, M.D., Problematic character coding methods in morphology and their effects (2011) Biological Journal of the Linnean Society, 104 (3), pp. 489-498
  • Brochu, C.A., (1992) Ontogeny of the postcranium in crocodylomorph archosaurs, , Ms. Thesis, University of Texas at Austin, Texas
  • Brusatte, S.L., Muir, A., Young, M.T., Walsh, S., Steel, L., Witmer, L.M., The braincase and neurosensory anatomy of an Early Jurassic marine crocodylomorph: implications for crocodilian sinus evolution and sensory transitions (2016) The Anatomical Record, 299, pp. 1511-1530
  • Busbey, A.B., III, Gow, C., A new protosuchian crocodile from the Upper Triassic Elliot Formation of South Africa (1984) Palaeontologia Africana, 25, pp. 127-149
  • Butler, R.J., Sullivan, C., Ezcurra, M.D., Liu, J., Lecuona, A., Sookias, R.B., New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and biogeography of the archosaur radiation (2014) BMC Evolutionary Biology, 14, p. 128
  • Carvalho, I.S., Campos, A.C.A., Nobre, P.H., Baurusuchus salgadoensis, a new crocodylomorpha from the Bauru Basin (Cretaceous), Brazil (2005) Gondwana Research, 8 (1), pp. 11-30
  • Clark, J.M., (1986) Phylogenetic relationships of the crocodylomorphs archosaurs, , D. Phill. Thesis, University of Chicago
  • Clark, J.M., Patterns of evolution in Mesozoic Crocodyliformes (1994) In the shadow of the dinosaurs, early mesozoic tetrapods, pp. 84-97. , Cambridge: Cambridge University Press
  • Clark, J.M., A new shartegosuchid crocodyliform from the Upper Jurassic Morrison Formation of western Colorado (2011) Zoological Journal of the Linnean Society, 163, pp. S152-S172
  • Clark, J.M., Sues, H.-D., Two new basal crocodylomorph archosaurs from the Lower Jurassic and the monophyly of the Sphenosuchia (2002) Zoological Journal of the Linnean Society, 136 (1), pp. 77-95
  • Clark, J.M., Sues, H.-D., Berman, D.S., A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs (2000) Journal of Vertebrate Paleontology, 20, pp. 683-704
  • Clark, J.M., Xu, X., Forster, C.A., Wang, Y., A Middle Jurassic "sphenosuchian" from China and the origin of the crocodilian skull (2004) Nature, 430, pp. 1021-1024
  • Colbert, E.H., Sebecus, representative of a peculiar suborder of fossil Crocodylia from Patagonia (1946) Bulletin of the American Museum of Natural History, 87, pp. 2017-2270
  • Colbert, E.H., A pseudosuchian reptile from Arizona (1952) Bulletin of the American Museum of Natural History, 99 (10), pp. 565-592
  • Cope, E.D., Synopsis of the extinct Batrachia, Reptilia, and Aves of North America (1869) Transactions of the American Philosophical Society, 14, pp. 1-252
  • Crush, P.J., A late Upper Triassic sphenosuchid crocodilian from Wales (1984) Palaeontol-ogy, 27, pp. 131-157
  • Drymala, S.A., Zanno, L.E., Osteology of Carnufex carolinensis (Archosauria: Pseudosuchia) from the Pekin Formation of North Carolina and its implications for Early Crocodylomorph Evolution (2016) PLOS ONE, 11 (6)
  • Ezcurra, M.D., Lecuona, A., Irmis, R.B., A review of the archosaur Trialestes romeri (Suchia, Crocodylomorpha) from the Upper Triassic Ischigualasto Formation of Argentina (2008) Libro de Resúmenes III Congreso Latinoamericano de Paleontología de Vertebrados, 88, p. 1
  • Foster, J.R., Paleoecological analyses of the vertebrate fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, USA (2003) New Mexico Museum of Natural History and Science Bulletin, 23, pp. 1-95
  • Galton, P.M., Prosauropod dinosaurs (Reptilia: Saurischia) of North America (1976) Postilla, 169, pp. 1-98
  • Gauthier, J.A., Saurischian monophyly and the origin of birds (1986) Memoirs of the California Academy of Science, 8, pp. 1-55
  • Göhlich, U.B., Chiappe, L.M., Clark, J.M., Sues, H.-D., The systematic position of the Late Jurassic alleged dinosaur Macelognathus (Crocodylomorpha: Sphenosuchia) (2005) Canadian Journal of Earth Sciences, 42, pp. 307-321
  • Goloboff, P.A., Farris, J.S., Nixon, K.C., TNT, a free program for phylogenetic analysis (2008) Cladistics, 24 (5), pp. 774-786
  • Goloboff, P.A., Farris, J.S., Nixon, K.C., (2008) TNT Tree analysis using new technologies, ,, (accessed on 2 April 2016)
  • Hay, O.P., (1930) Second bibliography and catalogue of fossil vertebrata of North America, 2. , 2 Washington, D.C.: Carnegie Institute of Washington
  • Holliday, C.M., Witmer, L.M., Cranial kinesis in dinosaurs: intracranial joints, protractor muscles, and their significance for cranial evolution and function in diapsids (2008) Journal of Vertebrate Paleontology, 28, pp. 1073-1088
  • Iordansky, N.N., The skull of Crocodylia (1973) Biology of reptili, 4, pp. 201-264. , Gans C, Parsons TS, eds. New York: Academic Press
  • Irmis, R.B., Nesbitt, S.J., Sues, H.-S., Early Crocodylomorpha (2013) Geological Society, London, Special Publications, 379, pp. 275-302
  • Jouve, S., The skull of Teleosaurus cadomensis (Crocodylomorpha; Thalattosuchia), and phylogenetic analysis of Thalattosuchia (2009) Journal of Vertebrate Paleontology, 29 (1), pp. 88-102
  • Kent, D.V., Malnis, P.S., Colombi, C.E., Alcober, O.A., Martínez, R.N., Age constrains on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina) (2014) Proceedings of the National Academy of Sciences of the United States of America, 111, pp. 7958-7963
  • Kley, N.J., Sertich, J.W., Turner, A.H., Krause, D.W., O'Connor, P.M., Georgi, J.A., Craniofacial morphology of Simosuchus clarki (Crocodyliformes: Notosuchia) from the Late Cretaceous of Madagascar (2010) Society of Vertebrate Paleontology Memoir, 10, pp. 13-98
  • Langston, W.J., The crocodylian skull in historical perspective (1973) The biology of the reptilia, 4, pp. 263-284. , London: Academic Press
  • Leardi, J.M., (2013) Evolución de la función locomotora durante la diversificación de Archosauria: patrones de cambio anatómico-funcional de la cintura escapular y el miembro anterior, , D. Phill. Thesis, Universidad de Buenos Aires
  • Lecuona, A., Desojo, J.B., Hind limb osteology of Gracilisuchus stipanicorum (Archosauria: Pseudosuchia) (2012) Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 102, pp. 105-128
  • Lecuona, A., Ezcurra, M.D., Irmis, R.B., Revision of the early crocodylomorph Tri-alestes romeri (Archosauria, Suchia) from the lower Upper Triassic of Ischigualasto Formation of Argentina: one of the oldest-known crocodylomorphs (2016) Papers in Palaeontology, 2 (4), pp. 585-622
  • Li, J., Wu, X.-C., Li, X., New material of Hsisosuchus chungkingensis from Sichuan, China (1994) Vertebrata Palasiatica, 32, pp. 107-126
  • Long, R.A., Murry, P.A., Late Triassic (Carnian and Norian) tetrapods from the southwestern United States (1995) New Mexico Museum of Natural History and Science, 4, pp. 1-254
  • Marsh, O.C., Principal characters of American Jurassic dinosaurs. Part V (1881) American Journal of Science, 21, pp. 417-423
  • Marsh, O.C., A new order of extinct Jurassic reptile (Macelognatha) (1884) American Journal of Science, 27 (3), p. 341
  • Mook, C.C., Notes on the postcranial skeleton in the Crocodylia (1921) Bulletin of the American Museum of Natural History, 44, pp. 69-100
  • Nascimento, P.M., Zaher, H., A new species of Baurusuchus (Crocodyliformes, Mesoeucrocodylia) from the Upper Cretaceous of Brazil, with the first complete postcranial skeleton described for the family Baurusuchidae (2010) Papéis Avulsos de Zoologia, 50, pp. 32-361
  • Nash, D.S., The morphology and relationships of a crocodilian, Orthosuchus stormbergi, from the Upper Triassic of Lesotho (1975) Annals of the South African Museum, 67, pp. 227-329
  • Nesbitt, S., The anatomy of Effigia okeeffea (Archosauria, Suchia), theropod-like convergence, and the distribution of related taxa (2007) Bulletin of the American Museum of Natural History, 302, pp. 1-84
  • Nesbitt, S.J., The early evolution of archosaurs: relationships and the origin of major clades (2011) Bulletin of the American Museum of Natural History, 352, pp. 1-292
  • Norell, M.A., Taxic origin and temporal diversity: the effect of phylogeny (1992) Extinction and phylogeny, pp. 89-118. , Novacek MJ, Wheeler QD, eds. New York: Columbia University Press
  • Norell, M.A., Storrs, G.W., Catalogue and review of the type fossil crocodilians in the yale peabody museum (1989) Postilla, 203, pp. 1-27
  • Ortega, F., Buscalioni, A.D., Gasparini, Z., Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia) (1996) Geobios, 29 (3), pp. 353-364
  • Osmólska, H., Hua, S., Buffetaut, E., Gobiosuchus kielanae (Protosuchia) from the Late Cretaceous of Mongolia: anatomy and relationships (1997) Acta Paleontologica Polonica, 4, pp. 257-289
  • Ostrom, J.H., On the systematic position of Macelognathus vagans (1971) Postilla, 153, pp. 1-10
  • Parrish, J.M., Phylogeny of the Crocodyotarsi, with reference to archosaurian and crurotarsan monophyly (1993) Journal of Vertebrate Paleontology, 13 (3), pp. 287-308
  • Peyer, K., Carter, J.G., Sues, H.-D., Novak, S.E., Olsen, P.E., A new suchian archosaur from the Upper Triassic of North Carolina (2008) Journal of Vertebrate Paleontology, 28 (2), pp. 363-381
  • Pierce, S., Benton, M.J., Pelagosaurus typus Bronn, 1841 (Mesoeucrocodylia: Thalattosuchia) from the Upper Lias (Toarcian, Lower Jurassic) of Somerset, England (2006) Jour-nal of Vertebrate Paleontology, 26 (3), pp. 621-635
  • Pierce, S.E., Williams, M., Benson, R.B.J., Virtual reconstruction of the brain and sinuses of the early Jurassic marine crocodylomorph Pelagosaurus typus (Thalattosuchia) (2016) PeerJ Preprints, 4
  • Pol, D., Gasparini, Z., Skull anatomy of Dakosaurus andiniensis (Thalattosuchia: Crocodylomorpha) and the phylogenetic position of Thalattosuchia (2009) Journal of Systematic Palaeontology, 7 (2), pp. 163-197
  • Pol, D., Nascimento, P.M., Carvalho, A.B., Riccomini, C., Pires-Domingues, R.A., Zaher, H., A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians (2014) PLOS ONE, 9
  • Pol, D., Norell, M.A., A new crocodyliform from Zos Canyon, Mongolia (2004) American Museum Novitates, 3445, pp. 1-36
  • Pol, D., Rauhut, O.W.M., Lecuona, A., Leardi, J.M., Xu, X., Clark, J.M., A new fossil from the Jurassic of Patagonia reveals the early basicranial evolution and the origins of Crocodyliformes (2013) Biological Reviews, 88, pp. 862-872
  • Reig, O.A., La presencia de dinosaurios saurisquios en los "estratos de Ischigualasto" (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina) (1963) Ameghiniana, 3, pp. 3-20
  • Schuchert, C., The geological horizon of the dinosaurs Hallopus and Nanosaurus agilis (1939) American Journal of Science, 237, pp. 19-26
  • Sereno, P.C., Wild, R., Procompsognathus: theropod, thecodont or both? (1992) Journal of Vertebrate Paleontology, 12 (4), pp. 435-458
  • Simpson, G.G., The fauna of quarry nine (1926) American Journal of Science, 12, pp. 1-11
  • Sues, H.-D., Olsen, P.E., Carter, J.G., Scott, D.M., A new crocodylomorph archosaur from the Upper Triassic of North Carolina (2003) Journal of Vertebrate Paleontology, 23 (2), pp. 329-343
  • Trotteyn, M.J., Desojo, J.B., Alcober, O.A., Nuevo material postcraneano de Sauro-suchus galilei Reig (Archosauria: Crurotarsi) del Triásico Superior del Centro-Oeste de Argentina (2011) Ameghiniana, 48, pp. 13-27
  • Von Huenne, F.R.F., (1956) Paläontologie und phylolgenie der nierderen tetrapoden, , Jena: Gustav Fischer Verlag
  • Walker, A.D., Triassic reptiles from the Elgin area: Stagonolepis, Dasygnathus and their allies (1961) Philosophical Transactions of the Royal Society of London B: Biological Sciences, 244, pp. 103-204
  • Walker, A.D., A revision of the Jurassic reptile Hallopus victor (Marsh) with remarks on the classification of the crocodiles (1970) Philosophical Transactions of the Royal Society of London, B, 257, pp. 323-372
  • Walker, A.D., A revision of Sphenosuchus acutus Haughton, a crocodylomorph reptile from the Elliot Formation (late Triassic or early Jurassic) of South Africa (1990) Philosophical Transactions of the Royal Society of London, B, 330, pp. 1-120
  • Weinbaum, J.C., (2002) Osteology and relationships of Postosuchus kirkpatricki (Archosauria: Crurotarsi), , Ms. Thesis, Texas Tech University
  • Weinbaum, J.C., The skull of Postosuchus kirkpatricki (Archosauria: Paracrocodyliformes) from the Upper Triassic of the United States (2011) PaleoBios, 30, pp. 18-44
  • Weinbaum, J.C., Hungerbühler, A., A revision of Poposaurus gracilis (Archosauria: Suchia) based on two new specimens from the Late Triassic of the southwestern USA (2007) Palaöntologische Zeitschrift, 81 (2), pp. 131-145
  • Wilberg, E.W., What's in an outgroup? The impact of outgroup choice on the phylogenetic position of Thalattosuchia (Crocodylomorpha) and the origin of Crocodyliformes (2015) Systematic Biology, , Epub ahead of print April 02 2015
  • Wu, X.-C., Chatterjee, S., Dibothrosuchus elaphros, a crocodylomorph from the Lower Jurassic of China and the phylogeny of the Sphenosuchia (1993) Journal of Vertebrate Paleontology, 13 (1), pp. 58-89
  • Wu, X.-C., Sues, H.-D., Dong, Z.-M., Sichuanosuchu shuhanensis, a new? Early Cretaceous Protosuchian (Archosauria: Crocodyliformes) from Sichuan (China), and the monophyly of Protosuchia (1997) Journal of Vertebrate Paleontology, 17, pp. 89-103
  • Zanno, L.E., Drymala, S., Nesbitt, S.J., Schneider, V.P., Early crocodylomorph increases top tier predator diversity during rise of dinosaurs (2015) Scientific Reports, 5


---------- APA ----------
Leardi, J.M., Pol, D. & Clark, J.M. (2017) . Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny. PeerJ, 2017(1).
---------- CHICAGO ----------
Leardi, J.M., Pol, D., Clark, J.M. "Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny" . PeerJ 2017, no. 1 (2017).
---------- MLA ----------
Leardi, J.M., Pol, D., Clark, J.M. "Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny" . PeerJ, vol. 2017, no. 1, 2017.
---------- VANCOUVER ----------
Leardi, J.M., Pol, D., Clark, J.M. Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny. PeerJ. 2017;2017(1).