Moiana M.,Museu Nacional de Geologia |
Dias P.,University of Minho |
Leal Gomes C.,University of Minho
Comunicacoes Geologicas | Year: 2014
Granitic gneisses hosting the Licungo Pegmatite Field (LPF) show, relatively, high light rare earth elements contents (LREE=257 ppm average), low heavy rare earth contents (HREE=18 ppm) and negative Eu anomalies. Similar patterns are displayed by granites with relatively low content of rare earth elements (LREE=74 ppm, HREE=5 ppm average), but without Eu negative anomalies. The compositional range of these rocks with metaluminous to peraluminous and subalkaline trends, plots between A and I&S type granites fields. The REE content of amphibolites is variable (LREE=30-151 ppm, HREE=12-29 ppm) and presents characteristic patterns of normal mid ocean ridge basalts (N-MORB) with variations probably corresponding to an arc volcanic setting. These geochemical variation patterns of felsic and mafic rocks suggest that the LPF country rocks were formed in transitional context between mid ocean ridge with expansion and volcanic arc settings following subduction, which is coherent with the variability of Ga and Ta+Nb contents. © 2014 LNEG – Laboratório Nacional de Geologia e Energia IP.
Castanhinha R.,Instituto Gulbenkian Of Ciencia |
Araujo R.,Museu da Lourinha |
Araujo R.,Southern Methodist University |
Junior L.C.,Museu Nacional de Geologia |
And 9 more authors.
PLoS ONE | Year: 2013
Dicynodontia represent the most diverse tetrapod group during the Late Permian. They survived the Permo-Triassic extinction and are central to understanding Permo-Triassic terrestrial ecosystems. Although extensively studied, several aspects of dicynodont paleobiology such as, neuroanatomy, inner ear morphology and internal cranial anatomy remain obscure. Here we describe a new dicynodont (Therapsida, Anomodontia) from northern Mozambique: Niassodon mfumukasi gen. et sp. nov. The holotype ML1620 was collected from the Late Permian K5 formation, Metangula Graben, Niassa Province northern Mozambique, an almost completely unexplored basin and country for vertebrate paleontology. Synchrotron radiation based micro-computed tomography (SRμCT), combined with a phylogenetic analysis, demonstrates a set of characters shared with Emydopoidea. All individual bones were digitally segmented allowing a 3D visualization of each element. In addition, we reconstructed the osseous labyrinth, endocast, cranial nerves and vasculature. The brain is narrow and the cerebellum is broader than the forebrain, resembling the conservative, "reptilian-grade" morphology of other non-mammalian therapsids, but the enlarged paraflocculi occupy the same relative volume as in birds. The orientation of the horizontal semicircular canals indicates a slightly more dorsally tilted head posture than previously assumed in other dicynodonts. In addition, synchrotron data shows a secondary center of ossification in the femur. Thus ML1620 represents, to our knowledge, the oldest fossil evidence of a secondary center of ossification, pushing back the evolutionary origins of this feature. The fact that the specimen represents a new species indicates that the Late Permian tetrapod fauna of east Africa is still incompletely known. © 2013 Castanhinha et al.