El primer caparazón completo de la pleurodira Eocenochelus eremberti: primera evidencia en España

El registro de tortugas pleurodiras es muy abundante en niveles del Eoceno de Europa. Este linaje está principalmente representado por miembros de Podocnemididae, atribuibles a dos géneros. El más abundante y diverso es Neochelys. Neochelys correspondía a una tortuga que habitó en ambientes continentales, en medios de agua dulce. La otra forma es Eocenochelus, cuyo registro es muy escaso. Eocenochelus era el único representante del linaje hasta ahora conocido, de manera informal, como “tortugas del grupo de Erymnochelys” que habitó en ambientes litorales, así como el único identificado fuera de África. Dicho grupo de tortugas es conocido desde el Cretácico hasta la actualidad. Un nuevo trabajo, que acaba de ser publicado en la revista Historical Biology, define formalmente ese linaje como el grupo Erymnochelyini. De hecho, uno de estos representantes de Erymnochelyini es detalladamente analizado en esa publicación, mediante la presentación y el estudio del único caparazón completo de Eocenochelus hasta ahora identificado. El ejemplar analizado proviene del yacimiento de Castejón de Sobrarbe-41, en la Cuenca de Ainsa (Huesca, España). Se trata de un yacimiento del Eoceno medio, es decir, de hace unos 45 millones de años. El ambiente sedimentario interpretado para este yacimiento es compatible con la atribución previa de Eocenochelus a una forma litoral.

El nuevo ejemplar analizado es atribuido a la especie de referencia del género, Eocenochelus eremberti. Esta especie era, hasta ahora, conocida exclusivamente por dos caparazones parciales, procedentes de niveles estratigráficamente equivalentes, pero no de yacimientos españoles sino de la Cuenca Franco-Belga: un hallazgo procedente del norte de Francia y el otro de la propia ciudad de Bruselas. Por lo tanto, el conocimiento sobre la distribución paleobiogeográfica de esta especie de tortuga marina litoral es notablemente incrementado gracias al nuevo estudio, siendo identificada desde la región sur del Mar del Norte hasta el Golfo de Vizcaya. El nuevo hallazgo aporta nuevos datos sobre la anatomía del género Eocenochelus en general, y sobre su especie de referencia en particular.

Más información:

• Imágenes: Mapa de Europa suroccidental durante e Eoceno medio, en el que se muestran tanto la posición de los dos hallazgos previamente conocidos de la tortuga Eocenochelus eremberti (1 y 2) como la del ejemplar presentado en el nuevo trabajo (3) / Fotografías y dibujos interpretativos del nuevo ejemplar, en vista dorsal (A) y ventral (B).
• Referencia: A. Pérez-García, E. Díaz-Berenguer, A. Badiola & J.I. Canudo (2019): An unexpected finding: identification of the first complete shell of the Franco-Belgian middle Eocene littoral pleurodiran turtle Eocenochelus eremberti in Spain, Historical Biology, DOI: 10.1080/08912963.2019.1644330

Análisis del único galápago fósil hallado en El Salvador en el XVII Annual Meeting de la EAVP

El registro de tortugas más reciente defendido por miembros de Grupo de Biología Evolutiva de la UNED en el XVII Annual Meeting de la EAVP corresponde al análisis del único galápago (emídido) hallado en el registro fósil de El Salvador, en niveles del Plioceno superior-Pleistoceno inferior.

El resumen es el siguiente:

The late Pliocene-early Pleistocene fossiliferous area of Río Tomayate (Apopa Municipality, El Salvador) represents the richest vertebrate locality in Central America. A diverse fauna was recorded, especially considering the record of reptiles and mammals. The greatest diversity of reptiles corresponds to the turtles. A terrestrial form, belonging to a large-sized testudinid, and two freshwater taxa, identified as a kinosternid and an emydid, were reported. The available information on these taxa was very limited, due to the scarce material attributed to each taxon in the study in which the Río Tomayate fauna was presented, and to the absence of subsequent publications. In the case of the emydid, only an almost complete nuchal (the only figured plate), a partial one, and an epiplastron were recognized. However, the potential belonging of many other unspecified elements to it was suggested. Abundant remains of the emydid from Río Tomayate are recognized here. In this sense, even the single plate (attributed here to a hypoplastron instead of a hyoplastron) previously assigned to a kinosternid (the only report of Kinosternon in a Central American fossil site), is reassigned to the emydid. The almost complete plastral morphology of this emydid is reconstructed, and many elements of the carapace are identified. Based on this new information, which also allows the documentation of intraspecific variability, we perform an accurate approach to the systematic position of the emydid from Río Tomayate, being the only one recognized in the fossil record of El Salvador. Thus, its potential attribution to Deirochelyinae is discussed.

-----

Más información:

• Imagen: Fotografía de una de las campañas de excavación en Tomayate (El Salvador), donde fueron hallados los ejemplares presentados en este trabajo. Imagen tomada de aquí.
• Referencia: A. Pérez-García, E. Vlachos, M.A. Molina-Leddy. 2019. On the anatomy and systematics of the only emydid turtle recognized in the fossil record of El Salvador. XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 90.

Nuevos datos sobre las tortugas pleurodiras de Sobrarbe en el XVII Annual Meeting de la EAVP

Volviendo al registro de tortugas fósiles españolas, en el recientemente celebrado XVII Annual Meeting de la EAVP, en Bruselas, se presentó un trabajo en el que se discutía la presencia de un segundo miembro de Pleurodira en el Eoceno medio de Sobrarbe, en Huesca, donde, hasta ahora, únicamente la forma de agua dulce Neochelys había sido reconocida.

El resumen es el siguiente:

The record of pleurodiran turtles is relatively abundant and diverse in the Eocene levels of Western Europe. Most of these findings correspond to members of Podocnemididae. Among them, the diverse Neochelys is the best represented. In addition to the finding of several forms of terrestrial and freshwater cryptodires, the presence of Neochelys had been recognized in the Spanish Lutetian (middle Eocene) Sobrarbe Formation of the Ainsa Basin (southern Pyrenees, Huesca). This freshwater turtle has been identified in several sites of that Basin. The first complete shell of a turtle from this Formation is presented here. It can be attributed to a podocnemidid pleurodiran turtle. However, it does not correspond to a member of Neochelys. This finding has been performed in the Castejón de Sobrarbe-41 fossil site which corresponding to an intertidal floodplain, where several littoral fossils have been recognized, including sirenian marine mammals. The systematic position of this turtle is discussed, especially taking into account the available information about the poorly known European littoral form Eocenochelus, whose type species (i.e. Eocenochelus eremberti), from the Franco-Belgian Basin, also comes from Lutetian levels.

-----

Más información:

• Imagen: Caparazón de la pleurodira litoral del Eoceno de Europa Eocenochelus.
• Referencia: A. Pérez-García, E. Díaz-Berenguer, A. Badiola, J.I. Canudo. 2019. Identification of a second member of Pleurodira at the middle Eocene levels of the Spanish Ainsa Basin. XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 88.

Discutiendo sobre sinonimias (o no) de sauropterigios triásicos en el XVII Annual Meeting de la EAVP

El registro de sauropterigios triásicos también ha tenido un huequito entre los trabajos presentados por los miembros del Grupo de Biología Evolutiva de la UNED en en el XVII Annual Meeting de la EAVP celebrado recientemente en Bruselas. Allí se presentó un póster en el que se re-evaluaba la validez de Partanosaurus zitteli, un taxón de sauropterigio poco conocido del Triásico Medio de Austria, que había sido considerado durante décadas un sinónimo de Simosaurus gaillardoti.

Aquí tenéis el resumen:

For more than two decades, Simosaurus gaillardoti, from the Ladinian (Middle Triassic) of France and Germany, was considered the only valid taxon within the sauropterygian clade Simosauridae. Thus, Partanosaurus zitteli, a problematic sauropterygian taxon whose remains were found in the 19th century in the Ladinian of the Austrian Alps, has been considered a junior synonym of Simosaurus gaillardoti. However, the discovery of new simosaurian remains, including the recently described Paludidraco multidentatus, from the Upper Triassic of Central Spain, as well as other fragmentary remains from the Middle and Upper Triassic of Europe and the Middle East, allows us to re-evaluate the validity of Partanosaurus zitteli. An exclusive combination of characters not present in Simosaurus gaillardoti or Paludidraco multidentatus supports the hypothesis that Partanosaurus zitteli is a valid taxon within the sauropterygian clade Simosauridae. The diversity of the clade Simosauridae is recognized as higher than previously expected.

-------
Más información:

• Imagen: Alejandro Serrano posa delante del póster de turno en el congreso, en representación de los autores ausentes.
• Referencia: Miguel Chaves, C. de; Ortega, F.; Pérez-García, A. 2019. Re-evaluating the validity of Partanosaurus zitteli (Sauropterygia), from the Middle Triassic of Austria. XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 72.

El caparazón de una Pleurodira del Cretácico Superior de Niger en el XVII Annual Meeting de la EAVP

Siguiendo con los trabajos sobre tortugas fósiles presentados por miembros del Grupo de Biología Evolutiva de la UNED en el XVII Annual Meeting de la EAVP, llega el turno de las faunas de Niger. Concretamente en esta presentación se discuten las implicaciones sobre la diversidad de Pleurodira derivadas del hallazgo del primer caparazón relativamente completo hallado en el Cretácico Superior de dicho país.

El resumen es el siguiente:

The Maastrichtian (uppermost Cretaceous) levels of the south-western region of Niger have provide several remains of pleurodiran turtles. The large Nigeremys gigantea, represented by a skull, comes from those levels. It corresponds to a member of Bothremydidae, belonging to the abundant and diverse clade Taphrosphyini. A second representative of Bothremydidae has recently been recognized at these levels, corresponding to a new form of Taphrosphyini, currently under study. The analysis of unpublished material allow us to recognize the diversity of turtles from the Maastrichtian levels of that region as greater than that described so far. In this sense, the first almost complete shell identified in this area is presented here. It can also be attributed to a member of Pleurodira. However, its availability of characters is not compatible with that of the members of Taphrosphyini. The detailed anatomical description of this specimen allows us to discuss its systematic position. Its attribution to a new form cannot be ruled out.

-----

Más información:

• Imagen: Caparazón de un miembro de Taphrosphyini (Pleurodira, Bothremydidae) del Maastrichtiense.
• Referencia: A. Pérez-García, S.D. Chapman. 2019. Implications on the uppermost Cretaceous diversity of Pleurodira in Southwest Niger based on the finding of the first almost complete shell. XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 87.

La evolución de las cavidades intracraneanas en cocodrilos eusuquios en el XVII Annual Meeting de la EAVP

Las cavidades intracraneanas son unas estructuras muy conservativas, y no son diferentes en el linaje de los cocodrilos. Sin embargo, a partir de una variada base de datos, se han descrito varias diferencias en las cavidades en los distintos linajes que componen el grupo.

Además, se han realizado medidas lineales y volumétricas de estas cavidades para estimar las capacidades neurosensoriales de estos animales, comparándolas con las observadas mediante estudios etológicos y citológicos para comprobar su efectividad, de cara a extrapolarlos a los taxones fósiles.

Aquí el resumen:

Eusuchia is the only extant lineage of Crocodylomorpha, spanning 129 million years from its origin in the Early Cretaceous to present day. Eusuchian remains are common in numerous Mesozoic and Cenozoic fossil sites across the world. However, the structure of their inner skull cavities remains poorly known. The basal eusuchians from Lo Hueco (Late Cretaceous, Cuenca, Spain) are noteworthy because of their abundance and exquisite state of preservation. The skull of several specimens from this site and of various extant crocodylians representing major lineages were CT-scanned and their brain and pneumatic cavities were 3D reconstructed and analysed in order to assess sensory and cognitive capabilities. The results show that the inner skull cavities of eusuchians are conservative structures. Those of extant taxa are very similar to those of basal members of the group. However, there are a few characters that appear to have varied during the course of evolution, such as the shape of the caudodorsal surface of the cerebrum, the relative size of the intertympanic diverticula and the relative length of the median pharyngeal sinus. Our results also suggest that the neurosensory and cognitive capabilities of extant crocodylians, including good olfactory and visual abilities, and a specialization for low-frequency hearing, were already present in early members of Eusuchia.

-----
Más información:

• Referencia: Serrano-Martínez, A., Knoll, F., Ortega, F. 2019. Evolution of the inner skull cavities in Eusuchia. XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 79.
• Imagen: Alejandro Serrano, durante su charla.

Primeros datos sobre las tortugas basales de Ariño en el XVII Annual Meeting de la EAVP

El Grupo de Biología evolutiva de la UNED ha defendido varios trabajos relativos al estudio de tortugas fósiles europeas, africanas y centroamericanas en el recientemente celebrado el XVII Annual Meeting de la EAVP. Las cronologías de los yacimientos analizados son muy diversas, correspondiendo al Cretácico Inferior (Albiense de Teruel), Cretácico Superior (Maastrichtiense de Niger), Paleógeno (Eoceno de Huesca) y Neógeno (Plio-Pleistoceno de El Salvador).

Siguiendo un orden de exposición cronológico, presentamos ahora el resumen correspondiente a las tortugas basales (Solemydidae o Helochelydridae) del Cretácico Inferior de Ariño (Teruel):

The lower Albian (Lower Cretaceous) Spanish vertebrate locality of Santa María Quarry, in Ariño (Teruel Province, Aragón), provided abundant remains of several individuals that were attributed to a new freshwater turtle, Toremys cassiopeia. This taxon corresponds to the youngest representative of Paracryptodira Pleurosternidae so far identified. Although this turtle is the only one from the Santa María Quarry studied so far, it does not correspond to the only representative identified in the site. Thus, a clade of terrestrial primitive turtles (i.e. stem Testudines) is also well represented. It is Solemydidae. As in the case of the pleurosternids, the solemydids are known both in North America and in Europe. The solemydids are scarce at the Upper Jurassic levels, but relatively abundant in the European Cretaceous record, its greatest diversity being recorded during the Lower Cretaceous. The Iberian record of Solemydidae hitherto known is composed of fragmentary remains, those from the Lower Cretaceous being scarce. The findings of Solemydidae performed in Ariño are an exception. Thus, sets of disjointed or partially articulated elements, including partial skeletons and relatively complete shells, are recognized. A shell of Solemydidae from Ariño is here presented for the first time. It shows an ornamental pattern composed of tubercles. The arrangement of these tubercles, as well as other anatomical characters, especially those related to the morphology and disposition of some of its plates and scutes, allow us to make a first approximation on the systematic position of this Spanish form, taking into account the European Lower Cretaceous record.

-----
Más información:

• Imagen: Detalle de la ornamentación de una placa de Solemydidae del Cretácico Inferior de Europa.
• Referencia: A. Pérez-García, E. Espílez, L. Mampel, L. Alcalá. 2019. First data about the solemydidae turtles from the Lower Cretaceous of Ariño (Teruel, Spain). XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 89.

Nuevos restos de dinosaurios ornitópodos de la cantera de Mas de la Parreta (Morella) en el XVII Annual Meeting de la EAVP

Desde su ubicación en la Cantera del Mas de la Parreta, llegó al XVII EAVP Annual Meeting la presentación del yacimiento CMP-5 localizado en el Mas de Sabaté en Morella. A pesar de que se continua con la preparación del material extraídos de este importante yacimiento, el análisis preliminar de los restos localizados indican la presencia de restos asignables a tiburones, peces, tortugas, cocodrilos, pterosaurios y dinosaurios. En este encuentro se han presentado estos resultados preliminares. Aquí va el resumen:

Mas de la Parreta quarry (CMP), located at the southwest of the locality of Morella (Castellón province, Spain), is a richly fossiliferous area of the Arcillas de Morella Formation that commonly yields vertebrate fossils. Seventeen vertebrate fossil sites have been documented so far. Nowadays, the identified vertebrate fauna includes sharks, bony fishes, plesiosaurs, turtles, crocodiles and dinosaurs. Among this diverse fauna highlights the discovery of more than 2.000 styracosternan ornithopod dinosaur remains, including some partial skeletons of distinct medium to large individuals. We provide information on CMP-MS-05 site, located at Mas de Sabaté area in the Mas de la Parreta quarry. The vertebrate fauna identified in CMP-MS-05 site includes semionotiform fishes, turtles, non- eusuchian neosuchian crocodiles, pterosaurs and dinosaurs. The fossil accumulation includes teeth of spinosaurid and allosauroid theropods, and remains of, at least, three styracosternan individuals. Two of these partial skeletons, including skull material, belong to a large-sized and robust styracosternan ornithopod that shares many similarities with Iguanodon bernissartensis. The third partial skeleton represents a medium, lightly built styracosternan dinosaur, similar in body proportions to Morelladon beltrani.

-----
Más información:

• Imagen: José Miguel Gasulla en un momento de su interlocución en una de las sesiones de científicas del congreso.
• Referencia: J. M. Gasulla, F. Escaso, I. Narváez J. L. Sanz & F. Ortega. A new styracosternan ornithopod-bearing fossil site from the upper Barremian Morella Formation in Morella (Spain). XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 44.

El gran monstruo marino con caparazón del monte Ilatarda

Con el título de esta entrada no nos referimos a una película de serie B, pero tampoco a ningún otro tipo de película u obra literaria de terror. “El gran monstruo marino con caparazón del monte Ilatarda” es, nada más y nada menos, que el significado del nombre con el que acaba de ser denominada una nueva especie de tortuga, Ilatardia cetiotesta, en la revista científica Journal of African Earth Sciences. Lo “monstruoso” de este animal era su tamaño, ya que la longitud de su cráneo era de cerca de 20 centímetros. Ilatardia pertenecía al linaje de pleurodiras extintas Bothremydidae, y habitó al final del Cretácico, en la región suroccidental de Niger. Así, sus restos han sido hallados en la región del monte Ilatarda, de donde procede su nombre genérico. Se trata de una de las especies de pleurodiras mesozoicas de mayor tamaño hasta ahora conocidas. Ilatardia forma parte de un linaje que se adaptó al medio marino. Como varias de las otras formas con la que estaba cercanamente emparentada, la nueva tortuga estaba dotada de un paladar muy robusto, que le permitiría alimentarse de presas duras.

-----
Más información:

• Referencia: Pérez-García, A. 2019. A new member of Taphrosphyini (Pleurodira, Bothremydidae) from the Maastrichtian of Niger. Journal of African Earth Sciences 158: 103548
• Imágenes: Cráneo de la nueva tortuga gigante Ilatardia cetiotesta.

Nuevos individuos de Morelladon beltrani en el XVII Annual Meeting de la EAVP

Qué no sólo hay uno, que no sólo hay dos, que no sólo hay tres, que sí que son cuatro… los yacimientos de la Formación Arcillas de Morella donde se han localizado restos del estiracosterno Morelladon beltrani. En el XVII Annual Meeting of the European Association of Vertebrate Paleontologists celebrado en Bruselas se han presentados los nuevos restos asignados a Morelladon procedentes de tres yacimientos localizados en la Cantera del Mas de la Parreta.

Aquí va el resumen:

The most representative dinosaur group of the late Barremian Arcillas de Morella Formation are styracosternan ornithopods, which are also very abundant throughout the Iberian Lower Cretaceous. Among the more than 20 vertebrate fossil sites documented in this formation the Mas de la Parreta quarry (CMP), located at the southwest of the locality of Morella (Castellón province, Spain) is particularly noteworthy. Currently, three styracosternan species have been recognized in this quarry: Iguanodon bernissartensis, Mantellisaurus atherfieldensis and Morelladon beltrani. Up to the present, Morelladon was just represented by the holotype specimen located in CMP-MS-03 site. Here, new postcranial bones of Morelladon beltrani from three different sites (CMP-3c, CMP-MS-03 and CMP- MS-05) within the Mas de la Parreta quarry are examined for the first time. These bones correspond to nearly complete and partial sacra of three new individuals. These sacra can be confidently referred to Morelladon beltrani based on the autapomorphic midline ventral keel of the centrum in sacrals 2 and 3 of CMP-3c and CMP-MS-05 specimens and in sacral 4 of CMP-MS-03 and CMP-MS-05 specimens. These new occurrences confirm that remains of this species were more common than previously thought in the Arcillas de Morella Formation.

-----
Más información:

• Imagen: José Miguel Gasulla en otro momento de su interlocución en una de las sesiones de científicas del congreso.
• Referencia: F. Escaso, J. M. Gasulla, I. Narváez J. L. Sanz & F. Ortega. New sacral material of Morelladon beltrani from the upper Barremian Morella Formation in Morella (Spain). XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 37.

La posición filogenética de Duerosuchus piscator, cocodrilo del Eoceno medio de la Cuenca del Duero, en el XVII Annual Meeting de la EAVP

Duerosuchus piscator es un cocodrilo de pequeño tamaño del Eoceno medio definido por L. Alonso-Santiago y L. Alonso-Andres en 2009 a partir de diferentes restos craneales y postcraneales procedentes de la localidad zamorana de Corrales del Vino (Castilla y León, España). Aunque los autores realizaron una descripción preliminar y una diagnosis para esta nueva especie, no proporcionaron un análisis de sus relaciones de parentesco dentro del grupo Crocodylia. Ahora, se presenta en el XVII Annual Meeting de la EAVP que se está celebrando en Bruselas una comunicación con el título "On the systematic position of the eusuchian Duerosuchus piscator (middle Eocene, Spain)", a partir de los análisis filogenéticos llevados a cabo tras una revisión detallada de la especie. El resumen es el siguiente:

Duerosuchus piscator is a middle Eocene eusuchian crocodile only known by several remains from Corrales del Vino (Zamora, Spain). The species was defined based on an incomplete skull, the partial lower jaws, several osteoderms and some vertebrae. A detailed study of these remains allows us to question the attribution of all these remains to the same form. Just the cranial remains are considered as indisputably attributable to it, the validity of this species being supported. The phylogenetic relationships of Duerosuchus piscator within Crocodylia was not been, until now, analyzed. The present study provides a detailed description and an amended diagnosis for Duerosuchus piscator, which is included for the first time in a phylogenetic analysis in order to establish its systematic position. As a result of this study, the Eocene crocodyliform paleobiodiversity in the Duero Basin is recognized as composed by a notosuchian (Iberosuchus macrodon), as well as three forms of Crocodylia, belonging to three different clades: the alligatoroid Diplocynodon tormis, the crocodyloid Asiatosuchus sp., and Duerosuchus piscator, which is here identified as being part of another lineage up to now unrecognized in the Iberian fossil record.

Más información:

• Imagen: Daniel Vidal, uno de los representantes del Grupo de Biología Evolutiva de la UNED presente en el congreso, posa con el póster de la comunicación.
• Referencia: Narváez, I., De Celis, A., Martín de Jesús, S., Pérez-García, A., Rodríguez, A., Ortega, F. 2019. On the systematic position of the eusuchian Duerosuchus piscator (middle Eocene, Spain). XVII Annual Meeting of the European Association of Vertebrate Paleontologists, Abstract Book, 79.

Dinosaurios del yacimiento de Gnatalie (Utah) en el 11th North Paleontological Conference (California, USA)

Recientemente se ha presentado en el 11th North Paleontological Conference, NAPC 2019, en Riverside (California, USA) una comunicación oral sobre el trabajo paleontológico desarrollado en colaboración con el Dinosaur Institute do Natural History Museum of Los Angeles County y el Instituto Dom Luiz, en el yacimiento de Gnatalie del Jurásico Superior de la Formación Morrison (EE.UU.). 

Aquí va el pequeño resumen titulado “Gnatalie Quarry, a window to understand the dinosaurian paleodiversity of the Late Jurassic of Southeastern Utah (Morrison Fm., USA)”: 

A new Morrison Fm. bone-bed (Brushy Basin Member) from San Juan County (Utah) has been reported. The 'Gnatalie quarry' (locality LACM 7683; all specimens are housed at the Dinosaur Institute of the Natural History Museum of Los Angeles County) is one of the most important bone accumulations from the Upper Jurassic of Utah yielding multiple partial skeletons in anatomical connection or with a low dispersion of their skeletal elements in a moderate to low degree of articulation. More than 400 bones were found belonging to crocodylomorphs and dinosaurs including theropods (Allosaurus sp.), sauropods, ornithopods and thyreophorans (Ankylosauria indet. and Stegosauria indet.). Sauropods are represented by two taxa, one diplodocine and one camarasaurid. This fossil-site has produced several partially complete diplodocine individuals (at least five individuals), and the performed phylogenetic analyses place all these sets within the clade Barosaurus+Diplodocus, sharing the presence of a double posterior centroparapophyseal lamina on posterior dorsal vertebrae, straight ventral surface with projected chevrons facets in midcaudal vertebrae, or high twisted humeral shaft (>40º). The presence of pneumatic foramina until the 16th caudal vertebra (and perhaps beyond), deep ventral hollow in anterior- and middle-caudal vertebrae, or hook-like ambiens process, all support the inclusion of these specimens within Diplodocus. The recovered phylogenetic hypothesis and the detailed comparative analyses support a close relationship of the Gnatalie diplodocines with Diplodocus hallorum. In addition, the camarasaurid specimen found in Gnatalie comprises skull remains, dorsal, sacral and caudal vertebrae, dorsal ribs, chevrons and some partial appendicular elements. The detailed study of several specimens attributed to Camarasaurus reveals a possibly closer  relationship with the type specimen of Camarasaurus lewisi. Both specimens share the presence of (i) posterior centroparapophyseal lamina (that can be double in some vertebrae) in the middle-posterior dorsal vertebrae; (ii) sacral neural spines with transversely concave anterior and posterior face; (iii) bridged chevrons; (iv) dorsoventrally short neural canal; and (v) and anterior tuberosities on the ventral face of the middle caudal vertebrae. However, the Gnatalie camarasaurid is also characterized by an exclusive set of features, which might justify the establishment of a new taxon, and includes the presence of a dorsoventrally short quadrate fossa; markedly robust anterior chevrons with an anteroposteriorly compressed distal end and a very short haemal canal; and a robust fourth trochanter displaced to the midline of the femoral posterior face. For the moment, the Gnatalie assemblage appears to comprise only one diplodocine and one camarasaurid form, corresponding to the most  southwestern occurrence of Diplodocus hallorum and Camarasauridae in the Morrison Formation, west to the paleo-lake T'oo'dichi'.

-----

Más información:

• Mocho P, Escaso F, Chiappe L. 2019. Gnatalie quarry, a window to understand the dinosaurian paleodiversity of the Late Jurassic of Southeastern Utah (Morrison Fm., USA), pp. 251-252. In: Droser M, Hughes N, Bonuso N, Bottjer D, Eernisse D, Gaines R, Hendy A, Jacobs A, Miller-Camp J, Norris R, Roy K, Sadler P, Springer M, Wang X, Vendrasco M (eds.), 11th North American Paleontological Conference Program with Abstracts. PaleoBios36 (Supplement 1)