segunda-feira, 23 de fevereiro de 2015

Diversidade de equinóides do Mesozóico da Bacia Lusitânica na Paleo3

Está in press desde da semana passada um novo trabalho sobre a diversidade de equinóides do Mesozóico da Bacia Lusitânica na revista Palaeogeography, Palaeoclimatology, Palaeoecology. Este trabalho foi liderado pelo geólogo Bruno Pereira da Universidade de Bristol. Bruno Pereira é um dos geológicos responsáveis pelo estudo da famosa Praia Jurássica em Porto-de-Mós.

Abstract: Several analyses of diversity through geological time use global, synoptic databases, and this practice often makes it difficult to distinguish true signals in changing diversity from regional-scale sampling and/or geological artefacts. Here we investigate how echinoid diversity changed through the Mesozoic of the Lusitanian basin in Portugal based on a comprehensive, revised database, and seek to distinguish biological signal from geological or environmental constraints. The observed diversity pattern is far from having a defined trend, showing many fluctuations that appear to be linked with gaps in the geological record. This study revealed that, independently of the method used, whether correlation tests or model fitting, the diversity signal is not completely explained by the studied sampling proxies. Among the different proxies, marine facies variation in combination with outcrop area best explains the palaeodiversity curve.


terça-feira, 10 de fevereiro de 2015

Portugalophis lignites, a cobra da Guimarota.

Foi recentemente publicada um novo género e espécie de cobra proveniente da Guimarota (Leiria), Portugalophis lignites, que constitui um dos registos mais antigos deste grupo de vertebrados no registo fóssil.

Abstract: The previous oldest known fossil snakes date from ~100 million year old sediments (Upper Cretaceous) and are both morphologically and phylogenetically diverse, indicating that snakes underwent a much earlier origin and adaptive radiation. We report here on snake fossils that extend the record backwards in time by an additional ~70 million years (Middle Jurassic-Lower Cretaceous). These ancient snakes share features with fossil and modern snakes (for example, recurved teeth with labial and lingual carinae, long toothed suborbital ramus of maxillae) and with lizards (for example, pronounced subdental shelf/gutter). The paleobiogeography of these early snakes is diverse and complex, suggesting that snakes had undergone habitat differentiation and geographic radiation by the mid-Jurassic. Phylogenetic analysis of squamates recovers these early snakes in a basal polytomy with other fossil and modern snakes, where Najash rionegrina is sister to this clade. Ingroup analysis finds them in a basal position to all other snakes including Najash.


domingo, 8 de fevereiro de 2015

Registo icnofóssil da Formação da Desejosa (NE Portugal, Câmbrico Inferior).

Nem tudo são dinossáurios. Deixamos aqui uma referência a um trabalho saído no passado ano sobre o registo icnofóssil da Formação da Desejosa (Câmbrico Inferior) a NE de Portugal. O presente estudo foi liderado pelo geólogo português Ícaro Dias da Silva do Instituto Geológico y Minero de España

Abstract: "Trace fossils from a new locality in the Desejosa Formation, Freixo de Espada à Cinta area, northeast Portugal, are described, including Teichichnus rectus and the first Cambrian record from Iberia of the ichnogenus Rosselia, identified as R. cf. socialis. A literary review of the Cambrian record of Rosselia reveals no occurrences older than Cambrian Age 3. The occurrence of Rosselia in the Desejosa Formation therefore adds evidence to that of earlier reports on trilobite remains from the upper part of the Desejosa Formation for a Cambrian age of this unit. Both Rosselia and Teichichnus are indicative of the Cruziana ichnofacies, which is representative of a shallow-marine depositional environment, consistent with earlier interpretations for the depositional conditions of the upper part of the Desejosa Formation in this sector, and in the equivalent Cambrian units in Spain."