First multi-proxy record of Jurassic wildfires from Gondwana

0 comentarios Publicado por Leonardo Filippi en 16:46



Leszek Marynowski, Andrew C. Scott, Michał Zatoń, Horacio Parent, Alberto C. Garrido


Wildfires play a crucial role in recent and ancient ecosystem modeling but their detailed history on the Earth is still not well recorded or understood. The co-occurrence of charcoal and pyrolytic polycyclic aromatic hydrocarbons (PAHs) is used for the recognition of wildfires in geological record that may have implications for the analysis of the terrestrial environment, ecosystems, climate and the level of atmospheric oxygen. Here we present the first multi-proxy evidence of wildfires on the Gondwana continent during the Jurassic, based on the occurrence of charcoal and pyrolytic PAHs in the Middle Jurassic of the Neuquén Basin, Argentina. This is the first evidence of wildfire in the Aalenian, the lowest stage of the Middle Jurassic, and one of the few records of wildfires in the Bathonian. Temperature interpretations, derived from charcoal reflectance data, show that charcoals formed in low temperature surface fires that only sporadically reached the higher temperatures, possibly related to crown fires. The occurrence of charcoals in the Middle Jurassic deposits confirms recent results that the atmospheric oxygen level reached at least 15% during the Middle Jurassic times.

Marynowski, L., Scott, A. C., Zatoń, M., Parent, H. & Garrido, A. C. 2011. First multi-proxy record of Jurassic wildfires from Gondwana: Evidence from the Middle Jurassic of the Neuquén Basin, Argentina. Palaeogeography, Palaeoclimatology, Palaeoecology 299 (2011) 129–136.

 

El Museo Municipal Argentino Urquiza, retoma las actividades de campo

0 comentarios Publicado por Leonardo Filippi en 5:27


Después de cuatro años de inactividad real, el Museo Municipal Argentino Urquiza, retoma las actividades de campo en uno de los sitios de interés. Este lugar llamado Loma de los Jotes, es un yacimiento de gran importancia por la abundancia de los materiales hallados y por la información relevante que esta comenzando a aportar. En este sitio, se descubrieron los restos de al menos tres ejemplares de dinosaurios saurópodos titanosaurios, los cuales no solo corresponden a diferentes tallas, sino, a diferentes formas, entre las que se destacan un ejemplar con caracteres primitivos y un ejemplar que correspondería a un clado no registrado hasta el momento en el área. Por el momento, se estan realizando algunas tareas para proteger algúnos de los materiales que no fueron extraídos en campañas paleontológicas anteriores, pero se estima, pronto, realizar trabajos para recuperar estos importantes ejemplares.

 

Biological Implications of the bone microstructure of the Gasparinisaura cincosaltensis.

0 comentarios Publicado por Leonardo Filippi en 15:50



Ignacio A. Cerda and Anusuya Chinsamy

Here we present the bone histology of Gasparinisaura cincosaltensis, a basal ornithopod from the Late Cretaceous of Patagonia, and discuss its biological implications. The sample includes axial and appendicular elements from several specimens of different ontogenetic stages. The cortex of most bones consists of fibro-lamellar tissue, with mainly longitudinally oriented vascular spaces, which suggests rapid osteogenesis and fast growth. However, the fibro-lamellar bone is commonly interrupted by lines of arrested growth and/or annuli composed of parallel-fibered bone that indicates that the rapid growth was periodic. Although a true outer circumferential layer was not recorded in any of the sampled elements, in several of the larger samples the woven-fibered matrix of the inner and middle cortex grades into a parallel-fibered tissue, which suggests that the attainment of sexual maturity occurred before skeletal maturity. The growth dynamics of Gasparinisaura are similar to those reported in other basal ornithopods. Inter-elemental, as well as intraspecific, variations in histology were observed in Gasparinisaura. Such variation could be the result of sexual dimorphism, or the effect of localized conditions of growth, or perhaps plasticity in growth in response to local environmental conditions.

Cerda, I. A. and Chinsamy, A. 2012. Biological Implications of the bone microstructure of the Late Cretaceous ornithopod dinosaur Gasparinisaura cincosaltensis. Journal of Vertebrate Paleontology 32(2):355–368.






 

New alvarezsaurid from uppermost Cretaceous of north-western Patagonia

0 comentarios Publicado por Leonardo Filippi en 15:37

Federico L. Agnolin, Jaime E. Powell, Fernando E. Novas  and Martin Kundrát

The Alvarezsauridae represents a branch of peculiar basal coelurosaurs with an increasing representation of their Cretaceous radiation distributed worldwide. Here we describe a new member of the group, Bonapartenykus ultimus gen. et sp. nov. from Campanian-Maastrichtian strata of Northern Patagonia, Argentina. Bonapartenykus is represented by a single, incomplete postcranial skeleton. The morphology of the known skeletal elements suggests close affinities with the previously described taxon from Patagonia, Patagonykus, and both conform to a new clade, here termed Patagonykinae nov. Two incomplete eggs have been discovered in association with the skeletal remains of Bonapartenykus, and several clusters of broken eggshells of the same identity were also found in a close proximity. These belong to the new ooparataxon Arriagadoolithus patagoniensis of the new oofamily Arriagadoolithidae, which provides first insights into unique shell microstructure and fungal contamination of eggs laid by alvarezsaurid theropods. The detailed study of the eggs sheds new light on the phylogenetic position of alvarezsaurids within the Theropoda, and the evolution of eggs among Coelurosauria. We suggest that plesiomorphic alvarezsaurids survived in Patagonia until the latest Cretaceous, whereas these basal forms became extinct elsewhere.

Agnolin, F. L, Powell, J. E., Novas, F. E., and Kundránt M., 2012. New alvarezsaurid (Dinosauria, Theropoda) from uppermost Cretaceous of north-western Patagonia with associated eggs. Cretaceous Research 35: 33-56.


 

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