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The late Miocene caimanine fauna (Crocodylia: Alligatoroidea) of the Urumaco Formation, Venezuela

Torsten M. Scheyer and Massimo Delfino

Plain Language Abstract

The late Miocene Urumaco Formation of Venezuela presents one of the most important lagerstaetten of extinct vertebrates in the Neotropics. One of the outstanding components of the fauna is the crocodylians, which are very numerous and show a high species diversity related to diet. In our manuscript we present novel osteological descriptions and anatomical details of the fossils that could be identified as belonging to Caimaninae, the most common crocodylians in the fauna, from all major palaeontological collections that house material from the Urumaco Formation. This will enable a closer comparison of specimens with those of other Neogene faunas from South America that gained much attention lately, to get a better understanding of crocodylian systematics and biogeographic patterns.

Italiano

I caimani (Crocodylia: Alligatoroidea) tardo miocenici della Formazione di Urumaco, Venezuela

La Formazione di Urumaco, stato di Falcón, Venezuela, è particolarmente ricca di coccodrilli estinti e rappresenta un hotspot per la diversità neotropicale di questo gruppo. In questo lavoro abbiamo revisionato i resti appartenenti ai camani prendendo in considerazione sia resti già descritti sia resti sino ad ora inediti. In molti casi è stato possibile confermare lo status specifico del resti. È questo il caso di Caiman brevirostris, Globidentosuchus brevirostris, e Purussaurus mirandai per cui sono state fornite nuove informazioni morfologiche al fine di corroborare le precedenti descrizioni anatomiche. In altri casi è stato necessario riassegnare il materiale a taxa diversi. Il materiale precedentemente assegnato a Caiman lutescens è stato riferito a Caiman latirostris o a Caiman wannlangstoni; quello attribuito a Melanosuchus fisheri è stato identificato come Caimaninae aff. Melanosuchus fisheri. Inoltre, Mourasuchus nativus è stato considerate essere un junior synonym di Mourasuchus arendsi. Questo suggerisce che nel Miocene del Sud America ci siano state solo tre specie di camanini dal "becco d'anatra" attribuibili a Mourasuchus. Questi avrebbero colonizzato il continente partendo da nordovest (Colombia e Perù) durante il Miocene medio e disperdendo successivamente, nel Miocene superiore, verso est e sudest (Venezuela, Brazil e Argentina). Altri esemplari, che erano stati precedentemente identificati come appartenenti al genere Caiman, sono stati invece riferiti a livello di famiglia, Caimaninae indet., in quanto mancano dei caratteri diagnostici del genere attuale. Oltre a migliorare la conoscenza dei coccodrilli del Miocene superiore del Sud America, i nostri risultati confermano l'alta diversità tassonomica dei coccodrilli della Formazione di Urumaco e l'eccezionale livello di simpatia che era stato raggiunto in quell'area.

 caimanini; Crocodylia; composizione faunistica; Globidentosuchus; Mourasuchus; Purussaurus

Resumen en Español

La fauna de Caimaninae del Mioceno tardío (Crocodylia: Alligatoroidea) de la Formación Urumaco, Venezuela

La Formación Urumaco del Mioceno tardío en Urumaco, estado de Falcón, Venezuela, es notablemente rica en crocodilios extintos, por lo que se puede considerar un punto caliente de diversidad de este grupo en el Neotrópico. En este sentido, revisamos la fauna de Caimaninae mediante la inclusión de nuevo material fósil, así como los ejemplares descritos anteriormente asignables a este clado. En muchos casos se pudo confirmar el estatus taxonómico de las especies, como es el caso de Caiman brevirostris, Globidentosuchus brevirostris, y Purussaurus mirandai, y se presentan nuevos datos osteológicos que corroboran las descripciones anatómicas anteriores. En otros casos, los especímenes tuvieron que ser reclasificados en otros taxones; material previamente identificado como Caiman lutescens ahora es considerado como perteneciente a Caiman latirostris o Caiman wannlangstoni, y material considerado como Melanosuchus fisheri es reasignado a Caimaninae aff. Melanosuchus fisheri. Además, Mourasuchus nativus se considera en este estudio una sinonimia de Mourasuchus arendsi. Esto sugiere que sólo hay tres especies del Caimaninae "pico de pato" del género Mourasuchus en el Mioceno de América del Sur, lo que implica una colonización del continente desde el noroeste (Colombia y Perú) durante el Mioceno medio y un desplazamiento hacia el este y sureste (Venezuela, Brasil y Argentina) en el Mioceno tardío. Otros especímenes, previamente identificados como pertenecientes al género Caiman, carecen de características diagnósticas del género actual y se consideran en cambio como Caimaninae indet. Además de mejorar el conocimiento de los crocodilios del Mioceno tardío de América del Sur, nuestros resultados confirman la alta diversidad taxonómica de la fauna y el nivel sobresaliente de simpatría anteriormente indicado para la Formación Urumaco.

Palabras clave: Caimaninae; Crocodylia; composición faunística; Globidentosuchus; Mourasuchus; Purussaurus

Traducción: Enrique Peñalver (Sociedad Española de Paleontología)

Résumé en Français

La faune de Caimaninae (Crododylia : Alligatoroidea) du Miocène récent de la formation d'Urumaco, Venezuela

La formation d'Urumaco (État de Falcón, Venezuela) date du Miocène récent et est remarquablement riche en crocodiliens éteints, représentant un point chaud de diversité pour ce groupe dans les Néotropiques. Dans cet article, nous révisons la faune de Caimaninae en incluant du nouveau matériel fossile ainsi que des spécimens décrits auparavant et attribués à ce clade. Dans de nombreux cas, le statut taxinomique d'espèces a pu être confirmé, notamment pour Caiman brevirostris, Globidentosuchus brevirostris, et Purussaurus mirandai, et de nouvelles données ostéologiques sont présentées pour corroborer les descriptions anatomiques précédentes. Dans d'autres cas, les spécimens ont dû être réattribués à différents taxons : le matériel précédemment identifié comme C. lutescens est considéré comme appartenant soit à C. latirostris, soit à C. wannlangstoni, et le matériel de Melanosuchus fisheri est réattribué à un Caimaninae aff. Me. fisheri. De plus, dans cet article, Mourasuchus nativus est considéré comme étant un synonyme junior de Mo. arendsi. Cela suggère qu'il n'y a que trois espèces de Mourasuchus, genre de Caimaninae à « bec de canard », présentes dans le Miocène d'Amérique du Sud, ayant colonisé le continent à partir du nord-ouest (Colombie et Pérou) pendant le Miocène moyen et se déplaçant vers l'est et le sud-est (Venezuela, Brésil, et Argentine) au Miocène récent. D'autres spécimens, précédemment identifiés comme appartenant au genre Caiman, ne présentent pas les caractères diagnostiques du genre actuel et sont plutôt considérés comme des Caimaninae indéterminés. En plus d'améliorer la connaissance des crocodiliens du Miocène récent d'Amérique du Sud, nos résultats confirment la diversité taxinomique élevée de la faune et le niveau exceptionnel de sympatrie précédemment signalé dans la formation d'Urumaco.

Mots-clés : Caimaninae ; Crocodylia ; composition faunique ; Globidentosuchus ; Mourasuchus ; Purussaurus

Translator: Antoine Souron

Deutsche Zusammenfassung

Die Kaimanfauna (Crocodylia: Alligatoridae) der spätmiozänen Urumaco Formation Venezuelas

Die spätmiozäne Urumaco Formation bei Urumaco im Staat Falcón, Venezuela, ist bemerkenswert reich an ausgestorbenen Krokodyliern und stellt somit einen Diversitätshotspot für diese Gruppe in der Neotropis dar. In dieser Arbeit revidieren wir die Caimaninae-Fauna auf Grundlage sowohl von bisher beschriebenen Fossilien als auch von Neufunden der Gruppe. In vielen Fällen konnte der taxonomische Status der Arten bestätigt werden, was beispielsweise bei Caiman brevirostris, Globidentosuchus brevirostris und Purussaurus mirandai der Fall war; die neuen osteologischen Daten ergänzen somit vorherige anatomischen Beschreibungen. In anderen Fällen wurden Fossilfunde anderen Arten oder Gattungen zugewiesen. So werden Fossilien, welche bisher Caiman lutescens zugeordnet wurden, nun als Vertreter der Arten Caiman latirostris und Caiman wannlangstoni betrachtet, und Material von Melanosuchus fisheri wird neu Caimaninae aff. Melanosuchus fisheri zugewiesen. Zudem betrachten wir Mourasuchus nativus als jüngeres Synonym von Mourasuchus arendsi. Dies bedeutet, dass nur drei Arten des Entenschnabelkaimans Mourasuchus im Miozän von Südamerika vorkommen, welche den Kontinent von Nordwesten (Kolumbien und Peru) während des mittleren Miozän kolonisierten und sich im späten Miozän nach Osten und Südosten (Venezuela, Brasilien und Argentinien) ausbreiteten. Anderes Material, welches bisher der Gattung Caiman zugeordnet wurde, lässt keine diagnostischen Merkmale dieser heutigen Gattung erkennen und ist daher nur als Caimaninae indet. identifizierbar. Neben der taxonomischen Revision der spätmiozänen Krokodylier Venezuelas bestätigen unsere Ergebnisse weiterhin die hohe taxonomische Vielfalt der Fauna und die ungewöhnlich hohe Anzahl sympatrischer Arten in der Urumaco Formation.

Schlüsselwörter: Kaimane; Crocodylia; Faunenzusammensetzung; Globidentosuchus; Mourasuchus; Purussaurus

Translator: Author

Arabic

Translator: Ashraf M.T. Elewa

 

 

List of specimens studied.

Accession number Material Locality/Age
AMU-CURS-006 Purussaurus isolated tooth North of Urumaco Town, Urumaco Formation, Venezuela
AMU-CURS-022 Purussaurus isolated tooth North of El Picache, Urumaco Formation, Venezuela
AMU-CURS-033 Purussaurus mirandai isolated teeth Urumaco Formation, Venezuela
AMU-CURS-049 C. wannlangstoni (sensu Salas-G. et al., 2015; was labelled “ Caiman lutescens”) Corralito, Urumaco Formation, Venezuela
AMU-CURS-057 Purussaurus cf. mirandai (previously referred specimen of P. mirandai by Aguilera et al. 2006) Tío Gregorio, Urumaco Formation, Venezuela
AMU-CURS-067 Globidentosuchus brachyrostris additional specimen Playa Larga, Urumaco Formation, Venezuela
AMU-CURS-073 Mourasuchus sp. Tío Gregorio, Urumaco Formation, Venezuela
AMU-CURS-083 Globidentosuchus cf. G. brachyrostris Coquina Quebrada Bejucal, Urumaco Formation, Venezuela
AMU-CURS-084 Globidentosuchus cf. G. brachyrostris Coquina Quebrada Bejucal, Urumaco Formation, Venezuela
AMU-CURS-090 Caimaninae indet. (was Caiman) North of Mamon, Corralito, Urumaco Formation, Venezuela
AMU-CURS-100 Caimaninae indet. Norte El Picache, Urumaco Formation, Venezuela
AMU-CURS-101 Purussaurus isolated tooth North of El Picache, Urumaco Formation, Venezuela
AMU-CURS-105/106 Caimaninae indet. (was Caiman brevirostris) West of Quebrada Tío Gregorio, Urumaco Formation, Venezuela
AMU-CURS-113 Caimaninae indet. (was Caiman brevirostris in Riff et al. 2010 = Caiman sp. in Scheyer et al., 2013 from Loc. Puente Rio Urumaco/Playa Larga) just NE of ‘Northwest San Rafael’; Cerro Amarillo, Urumaco Formation, Venezuela
AMU-CURS-135 Purussaurus mirandai paratype material El Hatillo, Urumaco Formation, Venezuela
AMU-CURS-162 Purussaurus additional unprepared specimen 1.5 km north of El Hatillo, Urumaco Formation, Venezuela
AMU-CURS-212 Mourasuchus arendsi (previously identified as M. nativus) West of El Mamon, Urumaco Formation, Venezuela
AMU-CURS-217 Caimaninae indet. (previously identified as Melanosuchus fisheri) Puente Rio Urumaco/Playa Larga, Urumaco Formation, Venezuela
AMU-CURS-218 Mourasuchus arendsi (previously identified as M. nativus) Puente Rio Urumaco/Playa Larga, Urumaco Formation, Venezuela
AMU-CURS-222 Globidentosuchus brachyrostris holotype El Picache, Urumaco Formation, Venezuela
AMU-CURS-223 Globidentosuchus brachyrostris additional specimen El Picache, Urumaco Formation, Venezuela
AMU-CURS-224 Globidentosuchus brachyrostris additional specimen El Picache, Urumaco Formation, Venezuela
AMU-CURS-234 Caimaninae aff. Melanosuchus fisheri Medina, 1976 El Hatillo, Urumaco Formation, Venezuela
AMU-CURS -301 Globidentosuchus brachyrostris additional specimen Domo de Agua Blanca, Urumaco Formation, Venezuela
AMU-CURS -383 Globidentosuchus brachyrostris additional specimen Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-384 Purussaurus sp. Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-394 Purussaurus sp. Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-395 Mourasuchus sp. Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-396 Mourasuchus sp. Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-429 Caimaninae indet. (previously identified as Caiman brevirostris) El Mamón, Urumaco Formation, Venezuela
AMU-CURS-430 Mourasuchus sp. Loc Norte Las Huertas, SW of El Mamón, Urumaco Formation, Venezuela
AMU-CURS-442 Purussaurus sp., additional unprepared specimen Urumaco Formation, Venezuela
AMU-CURS -450 Globidentosuchus brachyrostris additional specimen Domo de Agua Blanca, Urumaco Formation, Venezuela
AMU-CURS-451 Caimaninae indet. Corralito Sur, Urumaco Formation, Venezuela
AMU-CURS-528 Purussaurus cf. P. mirandai Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-530 Mourasuchus sp. Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-537 Mourasuchus sp. Northwest San Rafael, Urumaco Formation, Venezuela
AMU-CURS-541 Purussaurus sp. North of El Picache, Urumaco Formation, Venezuela
AMU-CURS-601 Caimaninae indet. North of El Picache, Urumaco Formation, Venezuela
AMU-CURS-602 Purussaurus cf. P. mirandai North of El Picache, Urumaco Formation, Venezuela
AMU-CURS-606 Purussaurus sp. North of El Picache, Urumaco Formation, Venezuela
AMU-CURS-671 Purussaurus sp. Corralito east of Rio Urumaco, Urumaco Formation, Venezuela
AMU-CURS-685 Purussaurus cf. P. mirandai Urumaco Formation, Venezuela
AMU-CURS-695 Mourasuchus sp. Tío Gregorio, Urumaco Formation, Venezuela
AMU-CURS-748 Mourasuchus sp. El Hatillo, Urumaco Formation, Venezuela
AMU_CURS-768 Mourasuchus arendsi large posterior skull part El Vijiadero, ca. 6 km south west of Urumaco town, Lower Member, Urumaco Formation, Venezuela
MCNC-243 Melanosuchus fisheri holotype skull Corralito, Urumaco Formation, Venezuela
MCNC-1829 Caiman brevirostris El Picache, Urumaco Formation, Venezuela
MCNC-URU-76-72V Purussaurus mirandai referred specimen 0.5 km N of Quebrada Picache / 50 m E of Chiguaje Fault (sensu Patterson et al., 1972), Urumaco Formation, Venezuela
MCNC-URU-90-72V Purussaurus sp. 0.5 km N of Quebrada Picache / 50 m E of Chiguaje Fault (sensu Patterson et al., 1972), Urumaco Formation, Venezuela
MCNC-URU-110-72V lower jaw and skull of Mourasuchus sp. (heavily plastered/reconstructed specimen) 3.5 km N and 3? W of El Picache on up side of Chiguaje Fault (sensu Patterson et al., 1972), Urumaco Formation, Venezuela
MCNC-URU-111-72V Purussaurus sp. 3.5 km N and 3? W of El Picache on up side of Chiguaje Fault (sensu Patterson et al., 1972), Urumaco Formation, Venezuela
MCNC-URU-115-72V Purussaurus mirandai paratype material close to URU-76-72V, in bed of Quebrada Picache (sensu Patterson et al., 1972; ‘El Picache’ in Aguilera et al., 2006), Urumaco Formation, Venezuela
MCNC-URU-157-72V (was wrongly indicated as paratype material of Purussaurus mirandai, is postcranium of Purussaurus sp. instead) Capa de Tortugas/ Corralito (s sensu Patterson et al., 1972: locality data of 139-72V; ‘Tio Gregorio’ in Aguilera et al. 2006), Urumaco Formation, Venezuela
MCNC-URU-158-72V Purussaurus mirandai paratype material (was wrongly accessioned before) Capa de Tortugas/ Corralito, Urumaco Formation, Venezuela
MCNC-URU-2002-145 C. latirostris (was identified as “ Caiman lutescens”) Capa de Tortugas/ Corralito, Urumaco Formation, Venezuela
UNEFM-CIAAP-1297 Mourasuchus arendsi holotype Corralito, Urumaco Formation, Venezuela [‘Quebrada El Mamón. Río Urumaco / enero 1983‘ according to UNEFM catalogue]
UNEFM-CIAAP-1333 right maxilla from type loc. of M. arendsi - specimen missing Corralito, Urumaco Formation, Venezuela [‘Quebrada El Mamón. Río Urumaco / enero 1983‘ according to UNEFM catalogue]
UNEFM-CIAAP-1367 Purussaurus cranial and postcranial remains Right bank of Rio Urumaco, 1.5 (?) km N of El Hatillo?, Urumaco Formation, Venezuela
UNEFM-CIAAP-1368 large crocodylian teeth belonging to large gharial Right bank of Rio Urumaco, 1.5 (?) km N of El Hatillo?, Urumaco Formation, Venezuela
UNEFM-CIAAP-1368/1372 small Purussaurus skull fragment Right bank of Rio Urumaco, 1.5 (?) km N of El Hatillo?, Urumaco Formation, Venezuela
UNEFM-CIAAP-1369 Purussaurus mirandai holotype El Hatillo (sensu Aguilera et al., 2006), Urumaco Formation, Venezuela [same locality as -1368 according to UNEFM catalogue]
UNEFM-CIAAP-1378 Mourasuchus maxillary fragment Right bank of Rio Urumaco north of El Hatillo, Urumaco Formation, Venezuela [additional info: ‘octubre de 1983. (P-2: Pozo Dos)’ according to UNEFM catalogue]
UNEFM-CIAAP-1432 tooth of Purussaurus ? [‘P-2: Urumaco. Taparito. Este de la Quebrada Picacho / enero 1984‘ according to UNEFM catalogue]
UNEFM-CIAAP-1434 Purussaurus sp. lower jaw fragment Urumaco Formation, Venezuela
UNEFM-CIAAP-1445 Purussaurus mirandai paratype El Hatillo (sensu Aguilera et al., 2006), Urumaco Formation, Venezuela [‘Urumaco. Taparito. Este de la Quebrada Picacho / enero 1984‘according to UNEFM catalogue]
UNEFM-CIAAP-1447 Mourasuchus maxillary fragments [‘Urumaco. Taparito. Este de la Quebrada Picacho / enero 1984‘according to UNEFM catalogue]
UNEFM -VF-03 Mourasuchus sp. Urumaco Formation, Venezuela
UNEFM- VF-06 Caimaninae indet. Urumaco Formation, Venezuela
UNEFM- VF-017 Globidentosuchus cf. G. brachyrostris El Hatillo, Urumaco Formation, Venezuela
UNEFM- VF-019 Caimaninae indet. Urumaco Formation, Venezuela
UNEFM- VF-022 Caimaninae indet. Urumaco Formation, Venezuela

Additional specimens referred to in the text

MCN-USB no number Purussaurus cf. P. mirandai (Simon Bolivar Univ. specimen at the Museo Paleontológico Urumaco) Urumaco Formation, Venezuela
DGM 526-R Mourasuchus amazonensis holotype Solimões Formation, Acre, Brazil
MCZ 4336 Melanosuchus fisheri, referred skull Capa de Tortugas/ Corralito, Urumaco Formation
MLP 73-IV-15-8 Mourasuchus nativus holotype material Ituzaingó Formation, Paraná area, Argentina
MLP 73-IV-15-9 Mourasuchus nativus referred material Ituzaingó Formation, Paraná area, Argentina
MUSM 2377 Caiman wannlangstoni, holotype skull Pebas Formation, Iquitos area, Peru
MUSM 2378 Mourasuchus atopus (?) Pebas Formation, Iquitos area, Peru
UFAC-196 Caiman brevirostris holotype Solimões Formation, Acre, Brazil
UFAC-1424 was Mourasuchus nativus referred specimen, herein considered as M. arendsi Solimões Formation, Acre, Brazil
UCMP 39978 aff. Caiman wannlangstoni ?; “La Venta Caiman ” as “distinct entity of uncertain taxonomic affinities“ La Venta, Colombia
UCMP 38012 Mourasuchus atopus type specimen La Venta, Colombia
ZSM 76/1911 Melanosuchus niger, extant specimen extant species, no locality data
MACN PV 5416 C. latirostris, partial right rostrum Argentina
MACN PV 13551 C. lutescens, holotype (skull table) Argentina
 

FIGURE 1. Simplified phylogenetic framework based on Scheyer et al. (2013) and Salas-Gismondi et al. (2015). The caimanine taxa present in the Urumaco Formation are marked in bold face.

figure1 

FIGURE 2. Photographs of Caiman brevirostris (MCNC-1829). 1, right dorsolateral view. 2, left ventrolateral view. 3, right lateral view. Note that the specimen is strongly crushed and folded in on itself.

 figure2

FIGURE 3. Photographs (1, 3, 5) and interpretative drawings (2, 4, 6) of Caiman brevirostris (MCNC-1829). 1,2, close-up of the fronto-nasal contact in right dorsolateral view. 3, 4, close-up of the skull roof in dorsal view. 5, 6, close-up of the craniomandibular articulation in slanted right dorsolateral view. Abbreviations: an, angular, ar, articular; d, dentary; f, frontal; j, jugal, itf, infratemporal fenestra; mf, mandibular fenestra; n, nasal; o, orbit; oc, occipital condyle; po, postorbital; prf, prefrontal, q, quadrate; qj, quadratojugal; sa, surangular; so, supraoccipital; sq, squamosal; stf, supratemporal fenestra.

 figure3

FIGURE 4. Interpretative drawings of skull bone configuration in the rostro-orbital region of three small sized caimanines from the Urumaco Formation, in comparison to three living caimanines (anterior is to the top). 1, Melanosuchus fisheri based on holotype skull MCNC-243. 2, Globidentosuchus brachyrostris based on holotype skull AMU-CURS-222. 3, Caiman brevirostris based on MCNC-1829 from the late Miocene Urumaco Formation, Urumaco, Venezuela. 4, Caiman brevirostris from the Pleistocene of Acre, Brazil (UFAC-196) originally described by Souza Filho (1987, also figured in Fortier et al., 2014). Note that the anterior projection of the frontal appears much broader in the Venezuelan specimen than in the Pleistocene specimen. 5, extant Melanosuchus niger based on ZSM 76/1911 (picture courtesy: Julia Desojo; see also Foth et al., 2015). 6, extant Caiman crocodilus based on Iordansky (1973, figure 7A). 7, extant Caiman latirostris based on Bona and Desojo (2011, figure 2). 8, extant Paleosuchus trigonatus and 9, extant Paleosuchus palpebrosus based on Medem (1958, figure 36). The bridge of the ‘spectacles’ between the orbits is indicated in 1, 5, 6, and 7. Drawings not to scale. Abbreviations: f, frontal; n, nasal; o, orbit; prf, prefrontal.

figure4 

FIGURE 5. Photograph (1) and interpretative drawing (2) of Caiman brevirostris (MCNC-1829) in occipital view. Abbreviations: bo, basioccipital; eo, exoccipital; fm, foramen magnum; j, jugal; so, supraoccipital; sq, squamosal; stf, supratemporal fenestra; oc, occipital condyle; pt, pterygoid; q, quadrate; qj, quadratojugal.

 figure5

FIGURE 6. Photographs (1, 3, 5) and interpretative drawings (2, 4, 6) of Caiman wannlangstoni (AMU-CURS-49). 1,2, dorsal view. 3, 4, ventral view. 5, 6, right lateral view. Occlusion pits are marked in grey. The partially preserved teeth in the third premaxillary alveolus and the third and tenth maxillary alveoli are marked in dark grey. Note that the two occlusion pits anteromedial and posteromedial to the fourth premaxillary alveolus are preserved only as very faint impressions on the bone surface. Abbreviations: mx, maxilla; n, nasal; op, occlusion pit; pmx, premaxilla.

figure6 

FIGURE 7. Photographs (1, 3) and interpretative drawings (2, 4) of Caiman latirostris (MCNC-URU-145-72V). 1, 2, dorsal view. 3, 4, ventral view. Alveoli are marked with numbers, occlusion pits in dark grey. The internal trabecular space within the maxilla is marked in light grey. Abbreviations: en, external naris; mx, maxilla; n, nasal; op, occlusion pit; pmx, premaxilla.

figure7 

FIGURE 8. Photographs of Globidentosuchus brachyrostris (AMU-CURS-067). 1-3, left ramus of lower jaw in lateral (1), medial (2), and dorsal (3) view. 4-6, anterior, portion of right ramus in lateral (4), medial (5 ), and dorsal (6) view. 7, 8, fragment of a (right?) maxilla in ventral (7) and lateral (8) view. 9, 10, Fragment of a (left?) premaxilla in ventral (9 ) and dorsal (10) view. 11, indeterminate cranial fragment found associated with the other skeletal element and therefore referred to the same specimen.

figure8 

FIGURE 9. Photographs and interpretative drawings of Globidentosuchus brachyrostris lower jaw (AMU-CURS-067). 1, 2, assembled right and left ramus in dorsal view showing posterior crushing dentition and the splenials participating in symphysis. 3, 4, posterior part of left ramus in lateral view. 5, 6, posterior part of left ramus in medial view. Note that fragment of articular is still partially present, articulating with the angular ventrally. Abbreviations: a, angular; ar, articular; co, coronoid; d, dentary; fic, foramen intermandibularis caudalis; fme; external mandibular fenestra; path, area of pathology; sa, surangular; sed, sediment; sp, splenial.

 figure9

FIGURE 10. Photographs of Globidentosuchus cf. G. brachyrostris. 1-6, AMU-CURS-083. 7-18, AMU-CURS-084. 1, articulated left strongright associated dentary in dorsal view. 2,3, isolated right dentary in dorsal and angled medial view. 4-6, right dentary of (1) in lateral (4), dorsolateral (5) and angled medial view (6). 7, 8, right maxilla in angled lateral and angled medial view. 9, 10, right angular in medial and dorsal view. 11, 12, left articular and portion of surangular in angled medial and lateral view. 13, 14, right surangular sutured to part of dentary in angled medial and lateral view. 15, 16, left surangular in medial and lateral view. 17, 18, teeth. Abbreviations: d, dentary; ds, scar for dentary articulation; fic; foramen intermandibularis caudalis; fo, foramen; sa, surangular.

 figure10

FIGURE 11. Images of Globidentosuchus cf. G. brachyrostris (UNEFM-VF-017) including three right dentaries (1-4), one left dentary (5, 6), and one left angular in angled dorsal (7) and medial (8) view. Images of dentaries in 3, 4, and 5 in dorsal view, 2 and 6 in ventral view. Note splenial associated with dentary and reaching the symphysis in (4).

 figure11

FIGURE 12. Photographs of the holotype skull of Melanosuchus fisheri (MCNC-243; 1-4) and the skull and associated lower jaw assignable to Caimaninae aff. Melanosuchus fisheri (AMU-CURS-234, 5-8). 1, skull in dorsal view. 2, close-up of the sutures between the frontal, prefrontals and posterior portion of nasals. Compare to interpretative drawing in Figure 4.1. 3, skull in left lateral view. 4, skull in occipital view. 5,6, skull in dorsal and ventral view. 7,8, lower jaw in dorsal and ventral view. Abbreviations: f, frontal; n, nasal; prf, prefrontal.

 figure12

FIGURE 13. Photographs (1, 3, 4-6) and interpretative drawing (2) of the holotype skull and associated lower jaw remains (UNEFM-CIAAP-1297) (3) of Mourasuchus arendsi. 1, 2, skull in dorsal view. 3, right mandibular ramus in dorsal view. 4-6, Fragment of left mandibular ramus in dorsal (4), medial (5) and lateral (6) view. Abbreviations: f, frontal; j, jugal; la, lacrimal; mx, maxilla; n, nasal; p, parietal; pmx, premaxilla; po, postorbital; prf, prefrontal; pt, pterygoid; q, quadrate; qj, quadratojugal; so, supraoccipital; sq, squamosal.

 figure13

FIGURE 14. Photograph without (1) and with superimposed interpretative drawing (2) of the skull roof of holotype skull (UNEFM-CIAAP-1297) of Mourasuchus arendsi in left dorsolateral view. Abbreviations: f, frontal; mc, medial crest on parietal; p, parietal; po, postorbital; so, supraoccipital; sq, squamosal; stf, supratemporal fenestra.

 figure14

FIGURE 15. Photograph without (1) and with superimposed interpretative drawing (2) of the right side of the posterior portion of holotype skull (UNEFM-CIAAP-1297) of Mourasuchus arendsi in angled lateral view. Note clear notch of jugal and system of cracks (indicated by dotted white lines and arrows) leading to displacement of right posterolateral portion of skull. Abbreviations: j, jugal; po, postorbital; q, quadrate; qj, quadratojugal; sq, squamosal.

 figure15

FIGURE 16. Photograph (1) and interpretative drawing (2 of the holotype skull (UNEFM-CIAAP-1297) of Mourasuchus arendsi in occipital view. Note dorsoventral compaction of specimen. Abbreviations: bo, basioccipital; eo, exoccipital; oc, occipital condyle; pt, pterygoid; q, quadrate; so, supraoccipital; sq, squamosal.

 figure16

FIGURE 17. Photographs of skull and lower jaw (MCNC-URU-110-72V) assignable to Mourasuchus arendsi. 1, dorsal view. 2, ventral view. 3, dorsal view. 4, medial view. Note that large parts of the specimen have been heavily reconstructed and all tooth alveoli are covered by plaster-cast teeth.

 figure17

FIGURE 18. Photographs and interpretative drawing of weathered posterior skull portion (UNEFM-VF-03) and large skull part (AMU-CURS-768) of Mourasuchus arendsi. 1, 2, incomplete skull in dorsal view. 3, 4, incomplete skull in occipital view. 5, 6, large porterior skull part in dorsal and ventral view. Note squamosal eminences and posterior median ridge on parietal in UNEFM-VF-03 and both, the squamosal eminences and the knobs in front of the orbits in AMU-CURS-768. Abbreviations: eo, exoccipital f, frontal; mx, maxilla; oc, occipital condyle; ok, ornamental knob on prefrontal; pa, parietal; po, postorbital; pt, pterygoid; q, quadrate; se, squamosal eminences; so, supraoccipital; sof, suborbital fenestra; sq, squamosal; stf, supratemporal fenestra.

 figure18

FIGURE 19. Photographs and interpretative drawings of the posterior skull portion and orbitofrontal region as well as additional fragments (possibly jugal and lower jaw fragments) of Mourasuchus arendsi (AMU-CURS-218). 1,2, skull fragment in dorsal view. Note squamosal eminences and orbital bony excrescences. 3, 4, skull fragment in occipital view. 5-9, skull fragments (partially from jugals?) found associated with the larger skull portions. Abbreviations: bo, basioccipital; eo, exoccipital; f, frontal; j, jugal; la, lacrimal; oc, occipital condyle; o, orbit, ok, orbital knob; p, parietal; po, postorbital; prf, prefrontal; pt, pterygoid; q, quadrate; qj, quadratojugal; so, supraoccipital; sq, squamosal; stf, supratemporal fenestra.

 figure19

FIGURE 20. Photographs (1, 2, 5-12) and interpretative drawings (3, 4) of skull and lower jaw remains (AMU-CURS-073) of Mourasuchus sp. 1, 2, images of the largest fragment of the skull including the basioccipital-basisphenoid-pterygoid complex in dorsal (1) and occipital (2) view. 3, 4, interpretative drawings of the skull bones shown in 1 and 2. 5, 6, left quadrate in dorsal (5) and ventral (6) view. 7, fragment tentatively assigned to the postorbital bar of a right jugal in dorsal (?) view. 8, 9, large fragments of the maxillae in ventral view. 10, right lower jaw ramus in medial view. 11, small fragment of the left lower jaw ramus in dorsal view. 12, conical, slightly curved isolated tooth (the tip is set off by a break). Note different scale bar in 10 and 12. Abbreviations: bo, basioccipital; bs, basisphenoid; cf, carotid foramen; ec, ectopterygoid; eof, facet for exoccipital on basioccipital; ffm, floor of foramen magnum on basioccipital; oc, occipital condyle; pa, palatine; pt, pterygoid; vc, vertebral centra.

 figure20

FIGURE 21. Photographs of weathered skull and lower jaw remains (AMU-CURS-396) of Mourasuchus sp. 1, posterior portion of skull and braincase in occipital view. Note squamosal eminences. 2, right premaxilla in dorsal view with perforations for anterior-most teeth of lower jaw. 3, fragment of maxilla with seven alveoli in ventral view. 4, portion of dentary in medial view. 5, unidentified bone fragment. 6, fragment of maxilla with about 26 alveoli in ventral view. 7, straight portion of lower jaw in dorsal view. The exact number of alveoli could not be elucidated.

 figure21

FIGURE 22. Photographs of skull and lower jaw remains of several individuals of Mourasuchus sp. 1, heavily encrusted posterior portion of skull (AMU-CURS-530) in occipital view. Note squamosal eminences. 2, 3, maxillary fragment (UNEFM-CIAPP-1378) in dorsal (2) and ventral (3) view. 4, two maxillary fragments (UNEFM-CIAPP-1447) preserved in overlapping position in ventral view. 5, 6, right premaxilla (AMU-CURS-395) in dorsal (5) and ventral (6) view. 7, small fragment of lower jaw in dorsal view 13 alveoli (AMU-CURS-537). 8, posterior portion of skull (AMU-CURS-695) in dorsal view. Note massive squamosal eminences. 9, twelve fragments of a lower jaw (AMU-CURS-430), with at least the larger fragments belonging to the right ramus. The largest pieces are in dorsal view, showing alveoli.

 figure22

FIGURE 23. Photographs of lower jaw remains and associated left prefrontal of Mourasuchus sp. (AMU-CURS-748). 1, anterior and medial portion of lower jaw in dorsal view. Note lateromedial distortion of the right ramus and the break in the anterior portion of the left ramus. 2-6, posterior portions of the lower jaw in dorsal (2, 6), lateral (3, 5), and medial (4) view. 7-10, images and schematic interpretations of prefrontal in dorsal (7, 8) and lateral (9, 10) view. Abbreviations: a, angular; ar, articular; fme, external mandibular fenestra; ok, ornamental knob; prf.p, prefrontal pillar; prf.s, prefrontal shelf; ro, rim of orbit; rp, retroarticular process; sa, surangular.

 figure23

FIGURE 24. Photographs of skull of holotype (1-5: UNEFM-CIAAP-1369; associated lower jaw not shown) and paratypes UNEFM-CIAAP 1445 (6) and AMU-CURS-135 (7) of Purussaurus mirandai. 1-3, holotype skull in dorsal (1), ventral (2) and angled rostral view (3); the latter is not to scale. 4, 5, skull fragment labelled as “quadrate” of UNEFM-CIAAP-1369, which possibly constitutes a proximal fragment of the left quadrate/quadratojugal complex of the holotype skull. 6, right lower jaw in dorsal view. 7, largely unprepared skull and attached left and right lower jaw rami in dorsal view (picture courtesy: Jorge Moreno, Colombia).

figure24 

FIGURE 25. Photographs of skull and jaw material of Purussaurus. 1, right dentary fragment (MCNC-URU-115-72V) in dorsal view; 2-23, skull and lower jaw material belonging to several different individuals currently accessioned under a single collection number (MCNC-URU-158-72V). 2-3, anterior part of skull (electronically assembled to represent life position) in dorsal and ventral view. Only the right premaxilla and maxilla (2-4) were shown as part of the paratype series of P. mirandai by (Aguilera et al., 2006). 5, right part of skull table in dorsal view. 6, left part of skull table in lateral view. 7, isolated tooth. 8, 9, left quadrate in dorsal and ventral view. 10, right quadrate in dorsal view. 11, right ectopterygoid in posterolateral view. 12, lower jaw fragment in medial view with alveoli. 13, right jugal in lateral view. 14, 15, articulars with retroarticular processes in dorsal view. 16, 17, pterygoids? 18-21, lower jaw elements. 18, possible anterior fragment of left surangular in ventral view? 19, posterior fragment of surangular in lateral view? 20, fragment of right angular in medial view? 21, fragment of right surangular in medial view? 22, smaller skull table in the assemblage also assignable to Purussaurus in dorsal view. 23, anterior portion of lower jaw, initially referred to and figured as MCNC-URU-157-72V by (Aguilera, 2004).

 figure25

FIGURE 26. Photographs of specimens referable to Purussaurus cf. P. mirandai. 1, referred specimen AMU-CURS-057, right and left dentaries in dorsal view. 2, posterior skull fragment UNEFM-CIAAP-1368/1372 in dorsal view. 3, 4, premaxillae of UNEFM-CIAAP-1367 in dorsal and ventral view. 5, three isolated teeth of UNEFM-CIAAP-1367. 6, lower jaw of AMU-CURS-541 in dorsal view.

figure26 

FIGURE 27. Photographs of lower jaw material of Purussaurus cf. P. mirandai in the show room of Museo Paleontológico Urumaco. 1, right mandibular ramus in lateral view (AMU-CURS-685). 2, lower jaw in dorsal view (MCN-USB no number).

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FIGURE 28. Photographs of isolated right premaxilla of Purussaurus cf. P. mirandai (AMU-CURS-602). 1, specimen prior to collection in the field (dorsal view). 2-4, surface scan model of specimen (taken with an Artec Spider Surface Scanner) in (2) dorsal, (3) ventral, and (4 lateral view.

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FIGURE 29. Photographs of associated cranial material (AMU-CURS-528) of Purussaurus cf. P. mirandai. 1-2, right premaxilla in dorsal (1) and ventral (2) view. 3-4, right jugal in lateral (3) and medial (4) view. 5-6, right ectopterygoid in ventral (5) and dorsal (6) view. 7-8, left ectopterygoid in ventral (7) and dorsal (8) view. 9-10, dentary fragment in external (9) and internal (10) view. 11, isolated teeth (note different scale bar).

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FIGURE 30. Photographs of cranial bones of several individuals of Purussaurus. 1, Strongly weathered lower jaw ramus (UNEFM-CIAAP-1434) in medial view. 2-7, associated lower jaw fragments (MCNC-76-72V). 2, 3, dentary symphyseal region showing the symphyseal region in ventral (2) and dorsal (3) view. 4-6, posterior portions of the left (4) and right dentary, the latter in medial (5) and lateral (6) view. Note that part of splenial is still attached to dentary in (5). 7, left articular, surangular and portion of angular in medial view. 8, right articular and surangular in medial view. 9-16, associated skull and lower jaw fragments (MCNC-URU-90-72V). 9,10, left ramus in ventral and dorsal view. 11-14, two premaxillary fragments in dorsal and ventral view each. 15, 16, two dentary fragments in dorsal view. 17-25, skull and lower jaw fragments (MCNC-URU-111-72V), which were found in an assemblage of at least two individuals of different size. 17, partial skull in dorsal view. 18, smaller partial skull in dorsal view. 19, strongly weathered maxillary fragment (?) in ventral view. 20, left dentary fragment in dorsal view. 21, 22, right articular and surangular in dorsolateral (21) and dorsal (22) view. 23,24, left angular, surangular, and articular in medial (23) and lateral (24) view. 25, dentary symphyseal region and portion of right dentary in dorsal view.

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FIGURE 31. Cranial and lower jaw specimens of Purussaurus sp. 1-4, lower jaw fragments (AMU-CURS-384). 1, 2, left dentary in dorsal and medial view. 3, 4, left articular and angular in dorsal and lateral view. 5, 6, quadrate and skull table (AMU-CURS-606) in dorsal view. 7, dentaries of lower jaw (AMU-CURS-394) in dorsal view. Note the evident deformation of the left dentary.

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FIGURE 32. Photographs (1, 2) of the anterior portion of the lower jaw of Purussaurus sp. (AMU-CURS-671) and interpretative drawing of the natural cross-section (3) of the right dentary. Abbreviations: ab, alveolar bone; rf; functional tooth; rt1, first replacement tooth; rt2, second replacement tooth.

figure32 

FIGURE 33. Photographs of isolated giant crocodylian teeth assignable to Purussaurus sp. All but the smallest specimen (19 mm) show maximal cross-sectional diameters between 27 and 39 mm, which lie in the alveolar diameters of the largest Purussaurus specimens from Urumaco. 1, 2, tooth AMU-CURS-006 in rostral (1) and medial (2) view, carrying a wear facet. 3, 4, strongly weathered tooth AMU-CURS-046 in rostral (3) and medial (4) view. 5,6, two teeth labelled AMU-CURS-033. 7, tooth AMU-CURS-101. 8, small tooth AMU-CURS-022. 9, 10, tooth UNEFM-CIAAP-1432 in medial view.

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FIGURE 34. Photographs of caimanine lower jaw fragment (AMU-CURS-090) in lateral (1) and medial (2) view.

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FIGURE 35. Photographs of heavily encrusted anterior portion of a partial caimanine skull and lower jaw (AMU-CURS-100) in dorsal (1) and ventral (2) view.

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FIGURE 36. Photographs of skull (1-3, 5) and associated lower jaw fragment (4, 5) of small Caimaninae indet. (AMU-CURS105/106). 1, dorsal view. 2, ventral view. 3, occipital view. 4, left dentary in dorsal view. 5, Close-up of mounted specimen (not to scale) showing a preserved knob-like crushing tooth in the posterior part of the maxilla (marked by white arrow).

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FIGURE 37. Photographs of heavily weathered and altered caimanine lower jaw fragment (AMU-CURS-110) in lateral (1), medial (2), and dorsal (3) view.

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FIGURE 38. Photographs of strongly deformed partial caimanine skull (AMU-CURS-113) in dorsal (1) and ventral (2) view.

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FIGURE 39. Photographs of remains including an associated posterior skull and maxilla fragments (AMU-CURS-429: 1-4) and a weathered and partly encrusted, isolated skull table of a small caimanine (AMU-CURS-451: 5-7). Posterior skull table and braincase in 1, dorsal, 2, ventral, and 3, occipital view. Maxillary fragment (4) in ventral view. Isolated skull table in dorsal (5), ventral (6), and occipital (7) view showing small exposure of supraoccipital on the skull roof.

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FIGURE 40. Photographs of small caimanine skull part (AMU-CURS-601) consisting of an articulated left jugal and partial quadratojugal in lateral (1) and medial (2) view.

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FIGURE 41. Photographs of small caimanine skull roofs. A-C, UNEFM-VF-06 in dorsal (1), ventral (2), and occipital (3) view. 4, 5, UNEFM-VF-019 in dorsal and occipital view. 6, 7, UNEFM-VF-022 in dorsal and occipital view.

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author1Torsten M. Scheyer. Paläontologisches Institut und Museum, Universität Zürich, Karl Schmid-Strasse 4, CH-8006 Zürich, Switzerland This email address is being protected from spambots. You need JavaScript enabled to view it.

Torsten Scheyer is research associate and private lecturer of Palaeontology at the Palaeontological Institute and Museum of the University of Zurich (PIMUZ), Switzerland. He is mainly interested in the evolutionary morphology and palaeobiology of vertebrates, the development of skeletal tissues and the microstructures of bone, as well as the ecological adaptations of extant and extinct vertebrates, with a focus on reptiles.

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author2Massimo Delfino. Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, I-10125 Torino, Italy. This email address is being protected from spambots. You need JavaScript enabled to view it. and Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona. Edifici ICTA-ICP, Carrer de les Columnes s/n, Campus de la UAB, E-08193 Cerdanyola del Vallès, Barcelona, Spain

Massimo Delfino is Associate Professor of Palaeontology and Palaeoecology at the University of Turin (Italy). The focus of his research concerns aspects of palaeontology, evolutionary morphology, systematics, phylogeny and biogeography of the amphibians and reptiles. The main research lines deal with the contribution of fossils to the phylogeny of crocodilians and to the evolution of the herpetofaunas of Europe and the Mediterranean area. 

 

TABLE 1. Comparison of different species of Mourasuchus. Characters 1-8 are taken from the emended diagnosis of M. nativus of Bona et al. (2013a, b); characters 9 and 10 from Bocquentin Villanueva (1984). Data on M. amazonensis is based on holotype DGM 526-R as described and shown by Price (1964) and Langston (1966). Data on M. nativus is based on holotype MLP 73-IV-15-8 and specimen MLP 73-IV-15-9 as shown by Bona et al. (2013a, b), as well as on specimen UFAC- 1424 in Tineo et al. (2015). Data on M. atopus is based on holotype UCMP 38012 in Langston (1965, 1966). Data on M. arendsi is based mainly on holotype UNEFM-CIAAP-1297 as described by Bocquentin Villanueva (1984) 1, as well as on our revised interpretation of the holotype presented herein2. As noted in the discussion, some characters are deemed to be of little taxonomic utility (e.g., characters 9, 10) and need to be treated with caution.

Character

M. amazonensis (holotype)

M. atopus (holotype)

M. nativus (holotype)

UFAC-1424 (referred to M. nativus)

M. arendsi (holotype)

MCNC-URU-110-72V

AMU-CURS-218

1. prominent squamosal horns absent ? present present absent1,
present2
? present
2. marked knobs or bosses at orbital margin present present ? absent present present present
3. supratemporal fenestra surrounded rostrally by postorbital and parietal absent absent present present present ? present
4. dentary linear between 4th and 10th alveoli present present ? present present present (but obscured) ?
5. orbits smaller than infratemporal fenestrae present present ? present present present present
6. middle crest on posterior dorsal surface of parietal absent absent present present absent 1, present 2 ? present
7. pronounced notch at lateral edge of jugals present absent ? present absent 1, present 2 present ?
8. lateral border of maxillae extend parallel to each other absent present ? absent absent absent ?
9. premaxillary perforations 2

 

(1 st and 4 th)

2

 

(1 st and 4 th)

? 4? 4

 

(1 st -4 th)

 

 

right: 3

 

(1 st -3 rd)

 

left: 3

 

(2 nd -4 th)

?
10. palatine constriction weak? strong ? weak weak 1 weak? (area damaged) ?