domingo, janeiro 03, 2016

Notícias frescas... da Gronelândia

Três novos artigos científicos dão-nos notícias frescas sobre a paleontologia do Triásico da Gronelândia, resultado da expedição de 2012 e publicadas agora na Geological Society, Special Publications.

Lars Clemmensen e colegas fazem o sumário das descobertas de vertebrados e da geologia.

In Late Triassic (Norian–Rhaetian) times, the Jameson Land Basin lay at 40° N on the northern part of the supercontinent Pangaea. This position placed the basin in a transition zone between the relatively dry interior of the supercontinent and its more humid periphery. Sedimentation in the Jameson Land Basin took place in a lake–mudflat system and was controlled by orbitally forced variations in precipitation. Vertebrate fossils have consistently been found in these lake deposits (Fleming Fjord Formation), and include fishes, dinosaurs, amphibians, turtles, aetosaurs and pterosaurs. Furthermore, the fauna includes mammaliaform teeth and skeletal material. New vertebrate fossils were found during a joint vertebrate palaeontological and sedimentological expedition to Jameson Land in 2012. These new finds include phytosaurs, a second stem testudinatan specimen and new material of sauropodomorph dinosaurs, including osteologically immature individuals. Phytosaurs are a group of predators common in the Late Triassic, but previously unreported from Greenland. The finding includes well-preserved partial skeletons that show the occurrence of four individuals of three size classes. The new finds support a late Norian–early Rhaetian age for the Fleming Fjord Formation, and add new information on the palaeogeographical and palaeolatitudinal distribution of Late Triassic faunal provinces.

Jameson Land, na Gronelândia.

Malmos Klint na Gronbelândia (Clemmensen et al. 2015)

Geologia do Triásico da Gronbelândia (Clemmensen et al. 2015)

Pegadas de sauropodomorfos (Clemmensen et al. 2015)

Clemmensen, L.B., Milàn, J., Adolfssen, J.S., Estrup, E.J., Frobøse, N., Klein, N., Mateus, O. and Wings, O., 2015. The vertebrate-bearing Late Triassic Fleming Fjord Formation of central East Greenland revisited: stratigraphy, palaeoclimate and new palaeontological data. Geological Society, London, Special Publications434, pp.SP434-3. PDF

Bitten Hansen et al. (2015) abordam a descoberta de numerosos coprólitos de tubarão e outros animais do Triásico de Kap Stewart, nomeadamente a morfologia, classificação e alimentação.

A large collection of vertebrate coprolites from black lacustrine shales in the Late Triassic (Rhaetian–Sinemurian) Kap Stewart Formation, East Greenland is examined with regard to internal and external morphology, prey inclusions, and possible relationships to the contemporary vertebrate fauna. A number of the coprolites were mineralogically examined by X-ray diffraction (XRD), showing the primary mineral composition to be apatite, clay minerals, carbonates and, occasionally, quartz in the form of secondary mineral grains. The coprolite assemblage shows multiple sizes and morphotypes of coprolites, and different types of prey inclusions, demonstrating that the coprolite assemblage originates from a variety of different producers.


Localidade com coprólitos de tubarão na Gronelândia (Hansen et al., 2015)

Coprólitos de tubarão da Gronelândia (Hansen et al., 2015)

Coprólitos (Hansen et al., 2015)

Hansen, B.B., Milàn, J., Clemmensen, L.B., Adolfssen, J.S., Estrup, E.J., Klein, N., Mateus, O. and Wings, O., 2015. Coprolites from the Late Triassic Kap Stewart Formation, Jameson Land, East Greenland: morphology, classification and prey inclusions. Geological Society, London, Special Publications434, pp.SP434-12. PDF

Hendrik Klein e colegas anunciam a descoberta de pegadas de Brachychirotherium, normalmente atribuídas a arcossauros.

The Ørsted Dal Member of the Upper Triassic Fleming Fjord Formation in East Greenland is well known for its rich vertebrate fauna, represented by numerous specimens of both body and ichnofossils. In particular, the footprints of theropod dinosaurs have been described. Recently, an international expedition discovered several slabs with 100 small chirotheriid pes and manus imprints (pes length 4–4.5 cm) in siliciclastic deposits of this unit. They show strong similarities withBrachychirotherium, a characteristic Upper Triassic ichnogenus with a global distribution. A peculiar feature in the Fleming Fjord specimens is the lack of a fifth digit, even in more deeply impressed imprints. Therefore, the specimens are assigned here tentatively to cf. Brachychirotherium. Possibly, this characteristic is related to the extremely small size and early ontogenetic stage of the trackmaker. The record from Greenland is the first evidence of this morphotype from the Fleming Fjord Formation. Candidate trackmakers are crocodylian stem group archosaurs; however, a distinct correlation with known osteological taxa from this unit is not currently possible. While the occurrence of sauropodomorph plateosaurs in the bone record links the Greenland assemblage more closer to that from the Germanic Basin of central Europe, here the described footprints suggest a Pangaea-wide exchange.
Brachychirotherium (Klein et al. 2015) 

Brachychirotherium (Klein et al. 2015) 

Klein, H., Milàn, J., Clemmensen, L.B., Frobøse, N., Mateus, O., Klein, N., Adolfssen, J.S., Estrup, E.J. and Wings, O., 2015. Archosaur footprints (cf. Brachychirotherium) with unusual morphology from the Upper Triassic Fleming Fjord Formation (Norian–Rhaetian) of East Greenland. Geological Society, London, Special Publications434, pp.SP434-1. PDF


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