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Tributo a Ignacio Aureliano Machado Brito: Um Professor de Paleontologia

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Ossos de pterosauro da Formação Portezuelo (Cretáceo), Grupo Neuquén, Patagônia, Argentina

The Futalognko quarry, located 90km northwest of Neuquén city, Argentina, has yielded several fossil vertebrates. All come from the upper part of the Portezuelo Formation (Turonian-Early Coniacian) and include some pterosaur remains, the first ones from the Cretaceous strata of the Neuquén Group. The material consists of a proximal end of a large ulna (MUCPv-358), the proximal part of a wing-phalanx (MUCPv-359), and another ulna associated with a radius (MUCPv-600). All specimens are referred to the Pterodactyloidea, and possibly represent members of the Azhdarchoidea. Histological sections of the large ulna (MUCPv-358) indicate that it belonged to an animal that was still growing at time of death. Comparisons with more complete specimens indicate that MUCPv-358 represents an animal with a wingspan of six meters, making it the largest pterosaur known from Argentina.O jazigo Futalognko está situado 90km a noroeste da cidade de Neuquén, Argentina, e forneceu uma grande quantidade de vertebrados fósseis, todos da parte superior da Formação Portezuelo (Turoniano- Eoconiaciano). Dentre os exemplares recuperados encontram-se alguns exemplares de pterossauros indicando a primeira ocorrência deste grupo para as rochas cretácicas do Grupo Neuquén. O material está representado pela parte proximal de uma ulna de grandes proporções (MUCPv-358), a parte proximal de uma primeira falange alar (MUCPv-359), e uma segunda ulna associada com o rádio (MUCPv-600). Todos estes exemplares são referidos a Pterodactyloidea e possivelmente representam formas de Azhdarchoidea. Seções histológicas da ulna maior (MUCPv-358) indicam que ela representa um animal jovem que estava em fase de crescimento quando morreu. Comparações com outros exemplares mais completos sugerem que MUCPv-358 tenha pertencido a um pterossauro com uma abertura alar em torno de seis metros, fazendo dele o maior réptil voador coletado até o presente momento na Argentina

Discovery of a Very Nearby Brown Dwarf to the Sun: A Methane Rich Brown Dwarf Companion to the Low Mass Star SCR 1845-6357

We present VLT/NACO SDI images of the very nearby star SCR 1845-6357 (hereafter SCR 1845). SCR 1845 is a recently discovered (Hambly et al. 2004) M8.5 star just 3.85 pc from the sun (Henry et al. 2006). Using the capabilities of the unique SDI device, we discovered a substellar companion to SCR 1845 at a separation of 4.5 AU (1.170''+-0.003'' on the sky) and fainter by 3.57+-0.057 mag in the 1.575 um SDI filter. This substellar companion has an H magnitude of 13.16+0.31-0.26 (absolute H magnitude of 15.30+0.31-0.26), making it likely the brightest mid-T dwarf known. The unique Simultaneous Differential Imager (SDI) consists of 3 narrowband filters placed around the 1.6 um methane absorption feature characteristic of T-dwarfs (Teff < 1200 K). The flux of the substellar companion drops by a factor of 2.7+-0.1 between the SDI F1(1.575 um) filter and the SDI F3(1.625 um) filter, consistent with strong methane absorption in a substellar companion. We estimate a spectral type of T5.5+-1 for the companion based on the strength of this methane break. The chances that this object is a background T dwarf are vanishing small -- and there is no isolated background T-dwarf in this part of the sky according to 2MASS. Thus, it is a bound companion, hereafter SCR 1845-6357B. For an age range of 100 Myr - 10 Gyr and spectral type range of T4.5-T6.5, we find a mass range of 9 - 65 MJup for SCR 1845B from the Baraffe et al. 2003 COND models. SCR 1845AB is the 24th closest stellar system to the Sun (at 3.85 pc); the only brown dwarf system closer to the Sun is Eps Indi Ba-Bb (at 3.626 pc). In addition, this is the first T-dwarf companion discovered around a low mass star.Comment: 8 pages, 3 figures. Accepted to the Astrophysical Journal Letter

Sobre uma coluna vertebral de um titanossaurídeo (Dinosauria, Sauropoda) do grupo Bauru, Neocretáceo do Brasil

A new titanosaurid dinosaur from the Late Cretaceous continental deposits of the Bauru Group is described. Trigonosaurus pricei n.gen., n.sp., is based on two specimens, both collected at the Caieira Quarry near Peirópolis, Minas Gerais. The holotype consists of the five most posterior cervical vertebrae, 10 dorsals, six sacrals and the left ilium (MCT 1488-R). The second specimen (paratype) consists of 10 caudal vertebrae that according to a quarry map, were found isolated but show a similar morphology and compatible size suggesting that they belonged to one individual (MCT 1719-R). Trigonosaurus pricei is diagnosed by a combination of characters such as elongated cervicals and middorsals, dorsal vertebrae 9 and 10 with incipient postzygodiapophyseal lamina and transverse processes well developed throughout the sequence formed by anterior and medial caudals. The occurrence of this new taxon indicates a higher diversity of titanosaurids in the Brazil during the Cretaceous period.Um novo titanossaurídeo procedente dos depósitos continentais do grupo Bauru (Neocretáceo) é descrito. Trigonosaurus pricei n.gen., n.sp. é baseado em dois exemplares coletados na localidade Caieira na região de Peirópolis, Minas Gerais. O holótipo é composto das últimas cinco vértebras cervicais, 10 vértebras dorsais, seis sacrais e o ílio esquerdo (MCT 1488-R). O segundo exemplar (parátipo) é formado por 10 vértebras caudais que, de acordo com um mapa da escavação, foram encontradas isoladas, mas apresentam o mesmo padrão morfológico e um tamanho compatível, sendo, deste modo, consideradas como pertencentes a um mesmo indivíduo (MCT 1719-R). Trigonosaurus pricei é diagnosticado por uma combinação de caracteres tais como vértebras cervicais e dorsais médias alongadas, vértebras dorsais 9 e 10 com uma incipiente lâmina diapopós-zigapofisiária e processos transversos bem desenvolvidos por toda seqüência anterior e média da série caudal. A ocorrência deste novo táxon demonstra a existência de uma maior diversidade de titanosaurídeos no Brasil durante o período Cretáceo

Floresta dos Borbas, uma nova localidade com pistas de dinossauros na Bacia de Sousa, Paraíba, Brasil.

A new site with dinosaur tracks from the Sousa Basin, Lower Cretaceous of Northeast Brazil is presented. Floresta dos Borbas is the sixth dinosaur tracksite found in the Antenor Navarro Formation. Two theropod trackways are described as well as three sauropod tracks. The sauropod record in this region indicates a restriction to the northern portion of the basin, mostly found in the Antenor Navarro Formation and probably the basal portion of the Sousa Formation. A preliminary analysis indicates that the lower portion of the stratigraphic sequence that forms the Sousa Basin was deposited in a different paleoenvironmental condition than the upper part, being possibly more favorable for sauropods.Uma nova localidade com pistas de dinossauros da Bacia de Sousa, parte do complexo de bacias do Rio do Peixe, Cretáceo Inferior do Nordeste do Brasil, é apresentada. A região, conhecida como Floresta dos Borbas, forma a sexta localidade com pistas e pegadas de dinossauros encontrada na Formação Antenor Navarro. Duas pistas de terópodes e três pegadas de saurópodes são descritas. O registro de pegadas de saurópodes está restrito à parte norte da bacia, procedente da Formação Antenor Navarro e possivelmente à base da Formação Sousa. Uma análise ainda bastante preliminar sugere a existência de diferentes condições paleoambientais na base da seqüência estratigráfica que forma esta bacia, possivelmente mais favorável ao desenvolvimento de uma comunidade de saurópodos do que a parte superior

The Fringe Detection Laser Metrology for the GRAVITY Interferometer at the VLTI

Interferometric measurements of optical path length differences of stars over large baselines can deliver extremely accurate astrometric data. The interferometer GRAVITY will simultaneously measure two objects in the field of view of the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO) and determine their angular separation to a precision of 10 micro arcseconds in only 5 minutes. To perform the astrometric measurement with such a high accuracy, the differential path length through the VLTI and the instrument has to be measured (and tracked since Earth's rotation will permanently change it) by a laser metrology to an even higher level of accuracy (corresponding to 1 nm in 3 minutes). Usually, heterodyne differential path techniques are used for nanometer precision measurements, but with these methods it is difficult to track the full beam size and to follow the light path up to the primary mirror of the telescope. Here, we present the preliminary design of a differential path metrology system, developed within the GRAVITY project. It measures the instrumental differential path over the full pupil size and up to the entrance pupil location. The differential phase is measured by detecting the laser fringe pattern both on the telescopes' secondary mirrors as well as after reflection at the primary mirror. Based on our proposed design we evaluate the phase measurement accuracy based on a full budget of possible statistical and systematic errors. We show that this metrology design fulfills the high precision requirement of GRAVITY.Comment: Proc. SPIE in pres