16.10.17 , , , 0 comentarios

El registro fósil de allosauroides del Jurásico Superior de la cuenca lusitánica en la XXII Bienal de la RSEHN


Durante la XXII Bienal de la RSEHN celebrada en Coimbra (Portugal) se presentó un análisis de la diversidad de allosauroides conocida a partir del registro fósil del Jurásico Superior portugués. Este registro incluye diversos ejemplares que representan una gran diversidad, aunque con una posición filogenética problemática, lo que dificulta la interpretación paleobiogeográfica de este grupo de terópodos. Con todo, la interpretación de algunos taxones de terópodos como formas exclusivas del registro portugués y la reinterpretación de diversos ejemplares (previamente considerados como pertenecientes a especies compartidas con el registro de la Formación Morrison) como formas exclusivas de la cuenca lusitánica, sugiere procesos de vicarianza incipiente en la evolución de las faunas de terópodos del Jurásico Superior en ambos lados del proto-Atlántico Norte. El resumen es el siguiente:

Allosauroidea is a clade of large-bodied theropod dinosaurs that ranged from the Middle Jurassic to the Late Cretaceous (Brusatte & Sereno, 2008). This clade includes the Late Jurassic theropod Allosaurus, which is a well-known dinosaur genus, represented by hundreds of specimens from the North American Morrison Formation. Allosauroids represent an important group for the study of the Mesozoic palaeobiogeography because they comprise a long-lived and diverse group that evolved during the fragmentation of Pangaea (e.g. Pérez-Moreno et al., 1999; Sereno, 1999a,b; Upchurch et al., 2002).
The fossil record of allosauroid theropods from the Upper Jurassic of the Lusitanian Basin is abundant and diverse. Currently, this record includes Lourinhanosaurus (Mateus, 1998), Allosaurus (Pérez-Moreno et al., 1999; Mateus et al., 2006), and some specimens with an uncertain phylogenetic position that share some features, but also differences with Lourinhanosaurus and Allosaurus (Malafaia et al., 2016). Lourinhanosaurus antunesi is represented by a set of postcranial elements collected in Peralta (Lourinhã). It was originally described as an allosauroid (Mateus, 1998) and latter interpreted as a more basal tetanuran closely related with megalosaurids (Mateus et al., 2006). Subsequently, it was recovered as a member of the basal allosauroid clade Metriacanthosauridae by Benson (2010) and as a possible coelurosaur by Carrano et al. (2012). A recent phylogenetic analysis including some theropod specimens from the Upper Jurassic of Portugal supports the interpretation of Lourinhanosaurus as a member of Allosauroidea, but placed this taxon at the base of a more derived group comprising Allosaurus + Carcharodontosauria (Malafaia et al., 2016).
Allosaurus is the most abundant and well represented allosauroid taxon currently known in the Lusitanian Basin. This taxon is represented by a set of cranial and postcranial remains found in Praia de Vale Frades (Lourinhã), Andrés (Pombal), and Guimarota (Leiria) (Pérez-Moreno et al., 1999; Rauhut & Fechner, 2005; Mateus et al., 2006; Malafaia et al., 2010). A specimen collected in Andrés was assigned to the species Allosaurus fragilis described in the Morrison Formation. This specimen is the first evidence of Allosaurus outside North America and was considered in that moment the first dinosaur species present in two continents. This discovery triggered an intense discussion concerning the paleobiogeographic relationships of Late Jurassic dinosaur faunas from the Lusitanian Basin and the Morrison Fm. The presence of A. fragilis in both continents was interpreted as an evidence of faunal interchanges across the North Atlantic Ocean during the Late Jurassic. Later, a partial skull collected in Praia de Vale Frades was interpreted as belonging to a new Allosaurus species: Allosaurus europaeus (Mateus et al., 2006). In 2005, several osteological remains assignable to Allosaurus were found in the Andrés fossil site, including abundant cranial elements. These specimens show some differences when compared with A. fragilis, but also with the holotype of A. europaeus. The currently known Upper Jurassic record of allosauroid theropods from Portugal includes a relatively large number of specimens with a great diversity, but with an uncertain phylogenetic position, which difficult the study of the paleobiogeography of this group.
The identification of some theropod taxa interpreted as exclusive from the Portuguese record and the reinterpretation of several specimens previously considered as species shared with the Morrison Fm. as forms exclusive of the Lusitanian Basin suggest an incipient vicariant evolution of the Late Jurassic theropod faunas from both margins of the proto-North Atlantic Ocean.

Referencia:
  • Malafaia, E., P. Mocho, F. Escaso, F. Ortega. 2017. The fossil record of Allosauroidea (Dinosauria, Theropoda) from the Upper Jurassic of the Lusitanian Basin: diversity and paleobiogeographic interpretation. XXII Bienal de La Real Sociedad Española de Historia Natural. Libro de Resúmenes 246–247.
11.10.17 , , , 0 comentarios

La tortuga de Porto de Mos en la XXII Bienal de la RSEHN


Como ha sido indicado en este blog, el ejemplar de Plesiochelyidae procedente del Oxfordiense de Porto de Mos (Portugal) ha sido presentado en la XXII Bienal de la RSEHN en Coimbra (Portugal). Este espécimen fue reconocido como uno de los pocos de un Plesiochelyidae hallados en niveles pre-kimmeridgienses y como el más antiguo representante de este grupo identificado a nivel genérico (ver aquí). El resumen es el siguiente:

The most abundant and diverse group of turtles in the Iberian record is Eucryptodira. It is represented by its crown group, Cryptodira, but also by several Mesozoic forms belonging to its stem group. The oldest lineage corresponds to Plesiochelyidae, a clade exclusive of the European Upper Jurassic record. These marine turtles were not adapted to a pelagic life, being inhabitants of coastal environments, mostly related to mid and inner shelf, open or rimmed carbonated systems. The plesiochelyids disappeared during the Jurassic–Cretaceous transition as result of the regression of the shallow shelf seas of Europe, probably due to a drastic reduction of their habitat.
Several plesiochelyid representatives have been recognized in the Kimmeridgian and Tithonian Iberian records, all of them being identified in the Portuguese Lusitanian Basin (see Pérez-García accepted and references therein). The first described member of Plesiochelyidae in the Iberian record was ‘Plesiochelys choffati’, from the Tithonian of Vila Franca do Rosario (Mafra, Portugal). It is now identified as belonging to Craspedochelys, a genus relatively common in the Kimmeridgian and Tithonian levels of the Lusitanian Basin. The presence of the genus Plesiochelys was subsequently confirmed in the Tithonian record of both Portugal and Spain. The presence of a third genus of Plesiochelyidae (i.e. Tropidemys) has recently been recognized in both the upper Kimmeridgian–lower Tithonian levels of Portugal and in the Tithonian record of Spain. This taxon is probably represented by two species.
The pre-Kimmeridgian record of Plesiochelyidae is poorly known. In fact, the only currently known specimens come from the Iberian record. The first one was found in upper Oxfordian beds from Sierra de Cazorla (Jaén, Spain). It corresponds to a relatively complete shell recognized to the holotype of a putative new taxon, ‘Hispaniachelys prebetica’. However, this taxon is now considered as nomen dubium, and the specimen is presently identified as belonging an indeterminate representative of Plesiochelyidae.
The second one is a shell from an upper Oxfordian section of the Lusitanian Basin (see Pérez-García et al., accepted). It comes from Alqueidão da Serra (Municipality of Porto de Mós). Several artisanal quarries have been working for a long time in this area, yielding a variety of Jurassic light grey limestones and the famous “black limestone”, a dark mudstone with quite dark, uniform color, mainly used to produce ubiquitous Portuguese cobblestone designs (“calçada portuguesa”), a traditional art internationally recognized. These carbonate layers also are quite fossiliferous and rich of invertebrate specimens, whichmostly belong to fresh to brackish, marginal marine environments. The turtle shell was found by Adolfo Correia de Carvalho (1934-2010), owner and worker of a local quarry, during the first months of 1989. It was carefully collected from its limestone cast and offered as a donation to the Museu Municipal de Porto de Mós, yet in process of constitution at that time.
Registered and incorporated as MMPM37 by Francisco Furriel (1925-2014), a local collector and first director of the museum, the turtle shell stood out side to side with many other fossil specimens and rocks, mostly collected from Middle and Upper Jurassic, and Upper Cretaceous outcrops of the nearby region. Despite to be separated in two pieces and exhibited without any previous preparation, this fossil merited through years the curiosity of the visitors.
Due to its rarity, the turtle shell from Porto de Mós also deserved a prominent place in the museum catalogue. However, until very recently, it has not been subjected to any detailed taxonomic study. Nowadays, a plan of the Council board to move the museum to another building with a new exhibition, was recently taken as an excellent opportunity to study this specimen, as a contribution to better understand this group of Jurassic vertebrates.
The specimen MMPM37 represents the oldest remain of a turtle identified in the Portuguese record, constituting the second identification of a plesiochelyid performed in pre-Kimmeridgian levels in all of Europe. This specimen can also be recognized as the only Oxfordian plesiochelyid identified at generic level.
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Referencia: 
  • Pérez-García, A., J. M. Brandão, P. M. Callapez, L. Machado, E. Malafaia, F. Ortega, and V. F. dos Santos. 2017. A plesiochelyid turtle from the upper Oxfordian of Porto de Mós (West Central Portugal). XXII Bienal de La Real Sociedad Española de Historia Natural. Libro de Resúmenes 268–269.
10.10.17 , , 0 comentarios

Una nueva visión sobre la enigmática tortuga primitiva Kallokibotion


Una de las tortugas más singulares del registro europeo es Kallokibotion. Esta tortuga, definida en Rumanía, corresponde a una especie que vivió muchos millones de años después de lo que cabría esperar. De hecho, se trata de una tortuga primitiva (es decir, de un linaje más basal que la divergencia Jurásica de Cryptodira como Pleurodira), que habitó al final de la “era de los dinosaurios”, durante el final del Cretácico Superior.


Kallokibotion fue descrita hace casi un siglo por el célebre paleontólogo Franz Nopcsa, quizá uno de los investigadores más pintorescos de cuantos han trabajado en esta disciplina científica, y cuya vida ha sido retratada tanto en libros como en el mundo cinematográfico. Esta tortuga fue un animal especial para Nopcsa ya que, a pesar de su descripción de numerosas especies fósiles, Kallokibotion bajazidi fue la escogida para homenajear a su amante Bajazid Doda, el nombre de esta tortuga significando “la caja hermosa de Bajazid”.

Aunque Nopcsa identificó varios ejemplares atribuibles a esta extraña tortuga, su preservación era mala. Por lo tanto, a pesar de ser muy relevante, la información detallada sobre esta forma era, hasta ahora, muy limitada. Muchos trabajos realizados en las últimas décadas y, especialmente, en tiempo reciente, han considerado esta tortuga. Sin embargo, la ausencia de hallazgos y estudios de nuevos ejemplares dificultó el avance en el conocimiento sobre la misma, así como sobre la evolución de estas tortugas primitivas. Así, su posición filogenética precisa estaba en discusión, formando parte de todas las filogenias generales de tortugas, así como de aquellas sobre formas primitivas.


Un nuevo trabajo, que acaba de ser publicado, presenta por fin nuevo y abundante material, muy bien preservado, atribuible a esta tortuga. Se reconocen caparazones, pero también elementos apendiculares, axiales y restos craneales, incluyendo un cráneo y gran parte del esqueleto de un ejemplar adulto. Los nuevos ejemplares aportan numerosa información nueva sobre la anatomía tanto craneal como del resto del esqueleto de esta tortuga. Además, permiten refutar numerosas interpretaciones anatómicas previas, que resultaban erróneas por haber sido deducidas a partir de ejemplares deformados y mal preservados. Este estudio permite caracterizar a Kallokibotion como una de las tortugas primitivas mejor conocidas a nivel mundial, estableciéndose su parentesco con las otras formas conocidas.
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Más información:
4.10.17 , , , 0 comentarios

Una de terópodos (o no) en la XXII Bienal de la RSEHN


La semana pasada se presentó en la XXII Bienal de la Real Sociedad de Historia Natural celebrada en la ciudad portuguesa de Coimbra la reevaluación de unos restos axiales articulados dentro de un bloque de arenisca que han formado parte hasta hace poco de la exposición permanente de dinosaurios del Museu Nacional de História Natural e da Ciência (MUHNAC) en Lisboa.

Los resultados preliminares presentados en este congreso indican que los restos presentes en este bloque de arenisca no pertenecen, como hasta ahora se había creído, al dinosaurio terópodo ‘Megalosaurus insignis’. Por el contrario, esta serie vertebral en articulación muestra una combinación de caracteres que relacionan a esta ejemplar con los dinosaurios ornitópodos cercanamente emparentados con formas como Camptosaurus.

Aquí está el resumen:

“Megalosaurus Buckland (1824) was the first non-avian dinosaur genus described and one of the three genera which Owen defined Dinosauria in 1842. Nevertheless, since its discovery, Megalosaurus is considered a waste-basket taxon for which more than thirty species have been described. Some of these controversial species were described in the Portuguese fossil record during the mid-twentieth century by Lapparent & Zbyszewski (1957) including Megalosaurus insignis, Megalosaurus pannoniensis, Megalosaurus pombali and Megalosaurus superbus.
One of the Portuguese specimen assigned to M. insignis consists of a sandstone block in which five articulated vertebrae are included, three of them having the proximal part of the left ribs in articulation. This specimen comes from the area of Praia de Areia Branca in Lourinhã municipality. Lapparent & Zbyszewski (1957) described and figured the specimen and identified it as a partial articulated set of five anterior caudal vertebrae of a the theropod dinosaur M. insignis. However, an ongoing re-evaluation of the specimen, housed at the Museu Nacional de História Natural e da Ciência in Lisbon, does not support the interpretation of Lapparent & Zbyszewski (1957).
The preserved dorsal series is characterized by low, cylindrical centra, clearly visible neurocentral sutures and parapophyses positioned at the base of the transverse processes. All of these features suggest that this specimen is related to ornithopod dinosaurs because the combination of them is unknown in theropod dinosaurs. In addition, the overall morphology of the vertebrae resembles that of camptosaur-grade ankylopollexians but pending further preparation of the specimen, it is tentatively referred to an indeterminate ankylopollexian.”

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Referencia:
  • Escaso, F., Malafaia, E., Mocho, P., Narváez, I., Ortega, F. 2017. ‘Megalosaurus insignis’ from Praia de Areia Branca (Lourinhã, Portugal): is it Theropoda or Ornithopoda?. Livro de Resumos da XXII Bienal da RSEHN - Coimbra, 227.
2.10.17 , 0 comentarios

Estuvimos en la XXII Bienal de la RSEHN en Coimbra (Portugal)


La Real Sociedad Española de Historia Natural ha celebrado su XXII reunión Bienal durante los días 6 al 9 de Septoiembre en distintas dependencias de la Universidad de Coimbra (Portugal). El tema central de la Bienal ha sido "Los mapas de la Nauraleza", por lo que la cartografía ha sido la protagonista del encuentro. Además, tambien ha habido comunicaciones y posters dedicados a la paleontologogía de vertebrados, en algunos de los cuales han participado colaboradores de este blog.
Estos han sido:
    Se pueden consultar los detalles de la reunión y los resúmenes publicados en las siguientes URLs:
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