25.8.16 0 comentarios

Se encuentra un saurópodo hasta ahora desconocido fuera del Reino Unido en las colecciones clásicas del Museo Geológico de Lisboa

Húmero de cf. Duriatitan humerocristatus encontrado en Praia dos Frades (Peniche)

Durante los últimos 4 años hemos tenido la posibilidad de revisar las colecciones del Museo Geológico en Lisboa (Portugal). La revisión de este material es el resultado de un proyecto enfocado en el estudio de la historia evolutiva de los saurópodos del Jurásico Superior portugués y conducido por los miembros del Grupo de Biología Evolutiva de la UNED, Dinópolis, la Sociedade de História Natural (Portugal) y el Instituto Dom Luiz (Portugal).

Escápula de Lourinhasaurus alenquerensis

En el Jurásico Superior de la cuenca lusitánica el registro fósil de estos dinosaurios herbívoros es especialmente abundante. A lo largo de este estudio, se han revisado centenares de ejemplares del Museu Geológico como resultado de meses de trabajo, tragar mucho polvo y desarrollar algún musculo por la manipulación de semejantes bestias, ahora muertas. Para quien no esté familiarizado con este museo, el Museu Geológico en Lisboa alberga una de las colecciones de vertebrados mesozoicos mas importantes del continente europeo, incluyendo los holotipos de Lourinhasaurus, Lusotitan, Dracopelta o Aviatyrannis.

Estudiando las colecciones del Museu Geológico

Algunas de las piezas de dinosaurios saurópodos analizadas se encuentran en exposición, pero una parte importante de este material (incluyendo ejemplares nunca antes estudiados) se localizan en las reservas de este museo. Con este trabajo, se intenta actualizar el conocimiento existente sobre los saurópodos de esta colección, reconociendo representantes de casi todos los grupos de saurópodos ya identificados previamente en el Jurásico Superior de Portugal, como los camarasáuridos, turiasaurios, diplodócidos y braquiosáuridos. Además del reconocimiento de estos grupos, se destaca la presencia de un húmero aislado, encontrado en la primera mitad del siglo XX en Praia dos Frades (Peniche, Portugal). Este ejemplar ha pasado varios años sin llamar mucho la atención, pero el estudio detallado de este elemento permitió identificar una característica única en este tipo de dinosaurios: la presencia de una cresta marcada en la cara posterior del húmero. En 2014, en una visita a las colecciones del Natural History Museum (Londres, Reino Unido), hemos conseguido encontrar el significado de este carácter al identificar el mismo tipo de cresta en el húmero de Duriatitan humerocristatus, considerándose una autapomorfia de este taxón. El saurópodo Duriatitan fue descubierto en el Reino Unido en sedimentos contemporáneos a los sedimentos donde se descubrió el ejemplar portugués (datados en unos 145-150 millones de años). Este estudio permite identificar por primera vez, la presencia de una especie de dinosaurios saurópodos compartida entre Portugal y Reino Unido y añade así nueva información sobre las relaciones y distribución de las faunas europeas a lo largo del Jurásico Superior. 

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6.8.16 0 comentarios

La tortuga de Cuvier ibérica vs la tortuga de Cuvier parisina: la clave estaba en Bélgica


Abundante material de tortugas proveniente de una misma localidad, el yacimiento del Oligoceno inferior de Boutersem-TGV (Boutersem, Bélgica), es presentado en un trabajo que acaba de ser publicado. Hasta ahora no existía ninguna información sobre las tortugas que habitaron en esta localidad. Todo el material de tortugas analizado en esta publicación es atribuible a un único taxón, correspondiente a una forma acuática. Se trata de un miembro de Geoemydidae, Cuvierichelys. Este hallazgo supone la primera identificación de un representante del grupo ‘Palaeochelys s. l.–Mauremys’ en el registro del Paleógeno belga. Sin embargo, este material, que permite identificar todos los elementos tanto del espaldar como del plastrón, no puede ser atribuido a la única especie del género Cuvierichelys hasta ahora identificada en el Oligoceno, la forma española Cuvierichelys iberica. El taxón de Boutersem es identificado como correspondiente a Cuvierichelys parisiensis, una especie cuya anatomía era, hasta ahora, mal conocida. Su identificación fuera del registro eoceno francés permite ampliar tanto la distribución paleobiogeográfica como bioestratigráfica de esta especie, siendo reconocida, por primera vez, tanto en Bélgica como en Gran Bretaña, y en niveles post-eocenos. Por tanto, la distribución sincrónica de Cuvierichelys iberica y Cuvierichelys parisiensis es reconocida. Caracteres sometidos a variabilidad intraespecífica son identificados para ambas especies de Cuvierichelys. Así, la validez de varias formas europeas es refutada, como es el caso de Landreatchelys y Cuvierichelys crassa, y varios caracteres previamente reconocidos como diferentes entre Cuvierichelys iberica y Cuvierichelys parisiensis son justificados como sometidos a variabilidad. 

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22.7.16 0 comentarios

Pelorochelon y Fontainechelon en los medios


Las recientemente descritas nuevas tortugas terrestres primitivas del Eoceno de Europa Fontainechelon y Pelorochelon, publicadas en la revista Zoological Journal of the Linnean Society, han aparecido en numerosos medios de comunicación durante las últimas semanas, incluyendo prensa escrita, radio y televisión. A continuación dejamos un resumen de algunas de las noticias más destacadas sobre la publicación de estos nuevos testudínidos:


21.7.16 0 comentarios

De vuelta del XIV Annual Meeting of the EAVP, en Haarlem


Hace unos días tuvo lugar el XIV Annual Meeting of the European Association of Vertebrate Palaeontologists, un congreso que cada año recibe a más investigadores Europeos. Concretamente, la edición de este año se celebró en la ciudad holandesa de Haarlem, entre los días 6 y 10 de Julio. Su sede fue el Teylers Museum, el museo más antiguo de Holanda, que cuenta con importantes ejemplares entre sus colecciones, como es el caso de, entre muchos otros, mosasaurios y tortugas marinas del Maastrichtiense holandés.


Los hallazgos de vertebrados mesozoicos del Cretácico Superior del área de Maastricht son muy conocidos a nivel mundial. Es en esa región donde se designó el estratotipo del Maastrichtiense. Algunos de estos niveles son explotados comercialmente en grandes canteras. Los asistentes al congreso tuvieron la oportunidad de pasearse por una de ellas, demás de sumergirse en algunas de sus galerías subterráneas, en las que varias reconstrucciones de mosasaurios y otros seres antediluvianos se ocultan esculpidos en sus paredes.


El Grupo de Biología Evolutiva de la UNED ha participado en este congreso, mediante la presentación de los siguientes trabajos:


Imágenes (de arriba a abajo):
- Llegada de los miembros del Grupo de Biología Evolutiva a la estación de Haarlem, ciudad sede del congreso.
- Fotografía realizada durante las ponencias. Imagen tomada de aquí.
- Visita a una cantera situada en la localidad tipo del Maastrichtiense, en Maastricht.
- Modelo junto a una reconstrucción de un mosasaurio, realizada entre 1953 y 1954, en una galería subterránea de Maastricht, en los mismo niveles donde se encontraron fósiles de este animal.


13.7.16 0 comentarios

Revisión de restos de eosauropterigios en el XIV Meeting de la EAVP


Poco a poco vamos finalizando ya con los trabajos que presentaron varios miembros del Grupo de Biología Evolutiva de la UNED en el XIV Annual Meeting of the European Association of Vertebrate Palaeontologists  (EAVP), que tuvo lugar la semana pasada en la ciudad de Haarlem (Holanda). El caso que nos ocupa hoy trata sobre restos sin describir de eosauropterigios de la localidad de Canales de Molina (Guadalajara, España), que incluyen algunos elementos que podrían ser atribuidos al genéro Nothosaurus. Os dejamos con el abstract:

The Spanish record of Triassic sauropterygians is mostly composed of isolated elements of placodonts, pachypleurosaurs, nothosauroids and pistosauroids. These remains represent teeth, vertebrae, ribs, osteoderms and appendicular elements, recovered from several Spanish regions (i.e. Aragon, Catalonia, Balearic Islands, Castilla-La Mancha and Andalusia). We present here several undescribed sauropterygian remains from the Muschelkalk of Guadalajara (Castilla-La Mancha, Spain).
These remains were discovered in 1980 near the locality of Canales de Molina (Guadalajara) in dolomitic limestones from the Middle Triassic of the Royuela Dolostones, Marls and Limestones Formation (Muschelkalk Facies). The vertebrate remains from Canales de Molina include teeth and scales of fishes, and vertebrae, osteoderms, teeth and appendicular elements of placodonts and eosauropterygians.
Several platycoelous vertebral centra with the “cruciform” articular surface that is characteristic for the Eosauropterygia were identified. Neural arches with different sizes and morphologies attributable to this clade have also been recovered. The proximal and distal fragments of a humerus are also preserved, as well as some femoral remains. Several characters observed in the vertebral centra and in the appendicular elements exhibit a similar condition as forms such as Nothosaurus and thereby permit attribution of the Canales de Molina remains to Nothosauridae. In addition, the teeth recovered from Canales de Molina are curved and have ornamented enamel, as is also characteristic of the clade Nothosauridae. The isolated remains from Canales de Molina correspond to several individuals of nothosaurs that range from small to medium size. The attribution of these elements to different taxa or to different ontogenetic stages of a single taxon is evaluated here.

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Referencia: 
  • de Miguel Chaves, C.; Ortega, F.; Pérez-García, A. 2016. Eosauropterygian remains from the Middle Triassic of Canales de Molina (Guadalajara, Spain). In: Holwerda F, Madern A, Voeten D, van Heteren A, Meijer H, den Ouden N (eds.), XIV Annual Meeting of the European Association of Vertebrate Palaeontologists, 6-10 July 2016, Haarlem, The Netherlands, Programme and Abstract Book  Haarlem: 185.
11.7.16 0 comentarios

Nuevos datos sobre los saurópodos del Jurásico Superior de la sub-cuenca de Turcifal en el XIV Annual Meeting de la EAVP


Durante estos días se ha celebrado el XIV encuentro anual de la European Association of Vertebrate Paleontologists en Haarlem (Holanda), donde se ha presentado una nueva comunicación sobre dinosaurios saurópodos del Jurásico Superior de la cuenca lusitánica. Este trabajo liderado por Pedro Mocho (Grupo de Biología Evolutiva UNED / Sociedade de História Natural) se centra en el amplio registro fósil de saurópodos encontrado en la sub-cuenca de Turcifal. Gran parte de este material sigue inédito y en estudio, pero en este análisis preliminar se identifica la presencia de eusaurópodos basales, diplodócidos y macronarios en el Jurásico Superior de la sub-cuenca de Turcifal.

The Turcifal Sub-basin is located at the SW part of the Lusitanian Basin Central sector (Portugal), and is particularly rich in dinosaur fossil-sites, revealing a diverse dinosaur fauna composed by sauropods, theropods, thyreophorans and ornithopods. The sauropods are well represented in this sub-basin. However, relatively scarce information is so far available because most of these specimens are currently under study and/or in preparation. Most of the sauropod discoveries at the Turcifal Subbasin come from the Sobral and Freixial Formations. Many sauropod fossil-sites were located in the Torres Vedras municipality, highlighting the localities of Praia Azul, Cambelas, Assenta and Gentias. One of the most important sites is located in Casal da Costa (Cambelas). Appendicular and axial sauropod material, including dorsal vertebrae, was recovered there. The dorsal vertebrae share a similar morphology to those of Camarasaurus supremus, sharing the presence of bifurcated neural spines with camarasaurids. The presence of a circular spinoprezygapophyseal fossa suggests that this sauropod could be attributed to Lourinhasaurus alenquerensis. Another specimen found in Cambelas, known by axial and appendicular remains, was previously related to Diplodocidae based on the presence of a marked expansion of the ischiatic distal end. The presence of a pronounced lateral bulge, observed in the femur of this specimen, is generally considered as a synapomorphy of Titanosauriformes. However, it also occurs in Diplodocus. Other partial skeleton, also found in Cambelas, has an anterior caudal neural spine with a delta-shaped distal end, a feature common in camarasaurids. Other sauropod occurrences in this area include several teeth (heart-, spatulate- and compressed cone-chisel-shaped teeth), axial and appendicular elements. The Upper Jurassic sauropod fossil record is abundant in the Turcifal Sub-basin, and is still relatively unknown. A preliminary analysis of this record notes the presence of basal eusauropods (probably turiasaurs), diplodocids (a specimen with diplodocine affinities), and basal macronarians (including camarasaurids and titanosauriforms).
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9.7.16 0 comentarios

Megalosáuridos del Jurásico Superior portugues en el XIV Meeting de la EAVP

Una jornada más en el XIV Annual Meeting of the European Association of Vertebrate Palaeontologists  (EAVP) en Haarlem. En la sesión de posters de hoy tocará hablar de dinosarios terópodos del Jurásico Superior de Portugal. Uno de los grupos representados en este registro son los megalosáuridos. Estas formas son los dinosaurios carnívoros de mayor tamaño representados en el Jurásico Superior ibérico. Por el momento no son especialmente abundantes, pero cada vez es más frecuente la presencia de Torvosaurus.


The Portuguese record of Late Jurassic megalosaurids includes a set of cranial and postcranial elements traditionally interpreted as closely related to the North American species Torvosaurus tanneri, but more recently reinterpreted as a species so far exclusive of the Lusitanian Basin: T. gurneyi. Herein it is reported a set of unpublished axial and appendicular elements collected in Praia da Corva (Torres Vedras) that present a combination of shared characters with megalosaurid theropods including Torvosaurus and Megalosaurus. These remains, which show evidences of long weather exposure, were collected from surface along the cliff, in an area composed by upper Kimmeridgian sediments. Thus, and despite these elements present compatible morphology and size, it is not possible to determine if they belong to the same individual. The axial elements include three centra of posterior dorsal vertebrae, a fragment of the neural arch of a dorsal vertebra, and eight partial caudal vertebrae. Appendicular skeleton is represented by an almost complete left fibula and fragments of the tibial diaphysis. The general morphology of the dorsal centra is similar to that of Megalosaurus sharing a flat and transversely broad ventral surface. The great development of the pleurocoels is comparable with that of Torvosaurus, occupying almost the entire anteroposterior length of the lateral surface the centra. The caudal vertebrae present broad ventral grooves, a character sometimes considered as an autapomorphy of Ceratosaurus, but having a much wider distribution among theropods. These vertebrae share with Torvosaurus the wider than high articular facets and the presence of well-marked neurocentral depressions. The fibula is significantly more robust than those of any other known theropod from the Lusitanian Basin and more similar to Torvosaurus and to an indeterminate megalosauroid from the Tendaguru Formation. In summary, the specimens of Praia da Corva are assigned to Megalosauridae, with several elements suggesting a close relationship with Torvosaurus. Some distinct characters would be interpreted as autapormorphies of the skull-based species T. gurneyi or belonging to an unknown non-Torvosaurus megalosaurid taxon.
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Referencia
  •  Malafaia E, Mocho P, Escaso F, Ortega F. 2016. New postcranial elements of megalosaurids (Dinosauria, Tetanurae) from the Upper Jurassic of Portugal, p 210. In: Holwerda F, Madern A, Voeten D, van Heteren A, Meijer H, den Ouden N (eds.), XIV Annual Meeting of the European Association of Vertebrate Palaeontologists, 6-10 July 2016, Haarlem, The Netherlands, Programme and Abstract Book  Haarlem.
8.7.16 0 comentarios

Conservación de la Colección de Lo Hueco en el XIV Annual Meeting de la EAVP


Y siguiendo con el XIV Annual Meeting of the European Association of Vertebrate Palaeontologists que transcurre en  la ciudad holandesa de Haarlem entre el 6 y el 10 del Julio, ayer se habló (postereó) sobre el estado de conservación de las colección paleontológica de Lo Hueco y del control de los riesgos de deterioro.

The vertebrate fossils from the "Lo Hueco" fossil site (Late Cretaceous. Fuentes, Cuenca, central Spain) are generally well preserved. However, all of them are extremely fragile and susceptible to destabilization caused by the effects of both intrinsic and extrinsic factors, such as material composition and the processes that occur during extraction, storage and exhibition without proper control. An analysis of the conservational state of the paleontological collection was carried out with the aim of identifying deterioration agents that need to be controlled to reduce risks and to ensure the continued integrity of fossils over time.

Particular minerals filling the pores of the fossils can promote fragility. The surrounding matrix is predominantly composed of clay, which also fills the cavities in fossils. The integrity of these clay infillings is sensitive to external factors such as humidity. Gypsum is deposited as needles, lentils or superficial precipitates, which can disrupt the fossil structure and render the fossil susceptible to high humidity and UV levels. Iron oxides produce a red stain or, in more severe situations, a red crust that may reach several millimeters deep. Humidity fluctuations introduce instability through a varying dilation coefficient, which can produce circumferential microfractures near the bone surface, delaminating and destroying outer cortical layers.

The process of extraction and uncontrolled storage conditions may invoke fragility as well. Decompression resulting from removal of sediment pressure can destabilize the spatial relations between fossil remains or between fossil and matrix. Dehydration can change the integrity or even alter the composition of certain materials. The associated volume reduction produces cracks that, in the most severe scenario, can transform important parts of the fossil into dust.

All aforementioned factors need to be taken into account during collection control and storage climate control in order to avoid the loss of general cohesion that may cause disintegration, collapse and even pulverization of the fossils when all physical consistency is lost. Furthermore, the formation of fissures and cracks needs to be avoided, as they may lead to fractions and disjunctions. This can be achieved by understanding and respecting the compression and dilation coefficients of the materials involved.

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7.7.16 0 comentarios

Tortugas Europeas en el XIV Annual Meeting de la EAVP

Estamos en plena celebración de uno de los congresos de paleontología más relevantes de Europa, el Annual Meeting of the European Association of Vertebrate Palaeontologists. Se trata de su XIV edición, celebrada en la ciudad holandesa de Haarlem. Entre los trabajos presentados por los miembros del Grupo de Biología Evolutiva de la UNED figuran aquellos centrados en el análisis de varias tortugas europeas. Los resultados de estas investigaciones son defendidos hoy. Sus resúmenes son los siguientes:

A NEW GENUS FOR THE EUROPEAN MIDDLE EOCENE TURTLE ‘AFF. ERYMNOCHELYSEREMBERTI, AND STUDY OF TWO NEW CLOSELY RELATED FORMS

The European ‘aff. Erymnochelyseremberti is the only member of the Erymnochelys group of turtles (Pleurodira, Podocnemididae) so far defined in the Laurasiatic record. It is known by a single specimen, from the Lutetian (middle Eocene) of the French locality of Saint-Germain-en-Laye (Yvelines, Île-de-France). This specimen corresponds to a partial skeleton, including the skull and lower jaw, the fragmentary but partially reconstructed dorsal carapace, the relatively complete plastron, and various partial remains of the axial and appendicular skeleton. Its description and detailed study are completed here, a diagnosis for this species being proposed for the first time. It is attributed to a new genus, corresponding to both the first genus of the Erymnochelys group defined outside of Africa and the oldest unambiguous generic determination of a member of this group heretofore attested. It corresponds to a coastal form, all the African representatives being continental taxa. This middle Eocene species is not the only member of the Erymnochelys group identified in the European record, this group also being represented in the Early and Late Eocene. Thus, a Spanish specimen from the late Eocene (Priabonian) of Can Beuloví (Sobremunt, Osona, Catalonia), as well as an almost complete shell from the early Eocene (Ypresian) of the French locality of Soulane (Jonquières, Aude, Languedoc-Roussillon-Midi-Pyrénées), are studied. This French specimen is identified as attributable to a new species, being the oldest defined representative of the Erymnochelys group. The Spanish specimen also corresponds to a new species.

THE OLDEST EUROPEAN TESTUDINIDS: DESCRIPTION OF NEW TAXA AND REVISION OF POORLY-KNOWN FORMS


Testudinidae is the only extant clade of tortoises (i.e. terrestrial turtles). It is recognized as a very successful group, based on its abundance, diversity, and geographic distribution. It is relatively abundant in the fossil record. In this sense, the knowledge about its Neogene evolutionary history is relatively good. However, its Paleogene record is much more limited.
Testudinids are known in Europe from the early Eocene. Scarce information on the taxonomy and systematics of the European Eocene testudinids was so far available. The oldest testudinids from Europe, recovered in early and middle Eocene levels of several countries, are studied here. Some of them were previously known, being generally attributed to North American genera (i.e. Hadrianus and Achilemys). The hypothesis suggesting that the European Eocene genera are exclusive of this continent is confirmed. Thus, two new genera are proposed. The largest collection of European Paleogene testudinids, from the middle Eocene of Mazaterón (Soria, Spain), has been prepared for this study. A new species from Mazaterón is proposed. The validity of some European Eocene taxa is refuted, the French middle Eocene ‘Testudo castrensis’, the Austrian middle Eocene ‘Cheirogaster steinbacheri’, and the Spanish middle-late Eocene ‘Asturichelys multicostatus’ being proposed as nomina dubia. The diagnosis of several forms is emended. In addition, some of the taxa analyzed here are included for the first time in a phylogenetic hypothesis including, among others, the European medium to large testudinids.

ON THE PRESENCE OF BOTHREMYDIDAE (TESTUDINES, PLEURODIRA) IN THE EUROPEAN CENOZOIC RECORD


Pleurodira is a lineage of turtles originated in Gondwana. Several migrations of this group to Europe are known from the Upper Cretaceous, and especially, during the uppermost Cretaceous and the Eocene. In this regard, several representatives of Podocnemididae (Pelomedusoides) are known in the Eocene record of this continent, including the abundant and diverse European taxon Neochelys, as well as various forms of the Erymnochelys group, currently under study (e.g. ‘aff. Erymnochelys’ eremberti). A second Gondwanan lineage of Pelomedusoides also migrated from Africa to Europe: Bothremydidae. This group was very abundant and diverse on the uppermost Cretaceous record of this continent. However, it has not so far been unambiguously identified in the European Cenozoic record.
A new representative of Pleurodira is presented here. It comes from the early Eocene of Southwestern Europe. The new taxon is represented by two skulls. It is attributable to Pelomedusoides. Several characters shared with the members of Bothremydidae are recognized in this taxon. Its detailed study, together with the revision of poorlyknown specimens, provides new data to assess whether Bothremydidae was part of the turtle fauna of the European Eocene record.

THE OLDEST MEMBER OF THE CROWN PLEURODIRA IN LAURASIA

Pleurodira is one of the two major lineages of turtles known from the Early Cretaceous to the present. The first representatives of this clade are Gondwanic forms. In fact, extinct and extant pleurodires were restricted to relatively warm regions, their temperature requirements being much more extreme than those of the sister group Cryptodira. Although Pleurodira is now restricted to tropical and intertropical regions, changes in the global temperatures and in the relative position of the landmasses allow the dispersal of some representatives to Laurasia. Thus, these diachronic migrations were known from the Santonian, being especially relevant between the uppermost Cretaceous and the Eocene. In this sense, both Bothremydidae and Podocnemididae were relatively abundant and diverse in the European record (Bothremydidae in the Late Cretaceous and Podocnemididae in the Paleogene).
A new representative of Pleurodira, corresponding to a member of Bothremydidae, is presented here. The new taxon comes from pre-Santonian levels of Southwestern Europe. It is represented by abundant remains, highlighting a skull, relatively complete and partial shells, abundant plates, and appendicular elements. This discovery shows that the first migration of Pleurodira from Gondwana to Laurasia occurred earlier than hitherto proposed.
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30.6.16 0 comentarios

Hoy nos visita... Alan Turner



Esta semana visita el laboratorio del Grupo de Biología Evolutiva el Dr. Alan Turner de la Stony Brook University (Nueva York, Estados Unidos). La línea de investigación de Turner incluye el estudio de la filogenia, sistemática y anatomía de crocodilomorfos y dinosaurios terópodos, así como la evolución del tamaño corporal de arcosaurios.