Field of Science

Latest Literature: Triassic redbeds, footprints, and Eshanosaurus

Thanks to Jerry Harris for pointing these out...

Zaghloul, M.N., Critelli, S., Perri, F., Mongelli, G., Perrone, V., Sonnino, M., Tucker, M., Aiello, M., and Ventimiglia, C. 2009. Depositional systems, composition and geochemistry of Triassic rifted-continental margin redbeds of the Internal Rif Chain, Morocco. Sedimentology. doi: 10.1111/j.1365-3091.2009.01080.x.

ABSTRACT: The Middle to Upper Triassic redbeds at the base of the Ghomaride and Internal 'Dorsale Calcaire' Nappes in the Rifian sector of the Maghrebian Chain have been studied for their sedimentological, petrographic, mineralogical and chemical features. Redbeds lie unconformably on a Variscan low-grade metamorphic basement in a 300 m thick, upward fining and thinning megasequence. Successions are composed of predominantly fluvial red sandstones, with many intercalations of quartzose conglomerates in the lower part that pass upwards into fine-grained micaceous siltstones and massive mudstones, with some carbonate and evaporite beds. This suite of sediments suggests that palaeoenvironments evolved from mostly arenaceous alluvial systems (Middle Triassic) to muddy flood and coastal plain deposits. The successions are characterized by local carbonate and evaporite episodes in the Late Triassic. The growth of carbonate platforms is related to the increasing subsidence (Norian-Rhaetian) during the break-up of Pangea and the earliest stages of the Western Tethys opening. Carbonate platforms became widespread in the Sinemurian. Sandstones are quartzose to quartzolithic in composition, testifying a recycled orogenic provenance from low-grade Palaeozoic metasedimentary rocks. Palaeoweathering indices (Chemical Index of Alteration, Chemical Index of Weathering and Plagioclase Index of Alteration) suggest both a K-enrichment during the burial history and a source area that experienced intense weathering and recycling processes. These processes were favoured by seasonal climatic alternations, characterized by hot, episodically humid conditions with a prolonged dry season. These climatic alternations produced illitization of silicate minerals, iron oxidation and quartz-rich red sediments in alluvial systems. The estimated burial temperature for the continental redbeds is in the range of 100 to 160 °C with lithostatic/tectonic loading of ca 4 to 6 km. These redbeds can be considered as regional petrofacies that mark!the onseern Pangea (Middle Triassic) before the opening of the western part of Tethys in the Middle Jurassic. The studied redbeds and the coeval redbeds of many Alpine successions (Betic, Tellian and Apenninic orogens) show a quite similar history; they identify a Mesomediterranean continental block originating from the break-up of Pangea, which then played an important role in the post-Triassic evolution of the Western Mediterranean region.

Gierlinski, G.D. 2009. A preliminary report on new dinosaur tracks from the Triassic, Jurassic and Cretaceous of Poland; pp. 75-90 in Salas, C.A.-P. (ed.), Actas de las IV Jornadas Internacionales sobre Paleontologia de Dinosaurios y su Entorno. Colectivo Arqueológico-Paleontológico de Salas de los Infantes, Burgos.

ABSTRACT: Dinosaur tracks in Poland are mainly recognized in the Lower Jurassic (Hettangian) of the Holy CrossMountains. There are only few finds, so far reported, from the Upper Triassic of the Tatra Mountains and Silesia. Dinosaur footprints in the Upper Jurassic of the Holy Cross Mountains are also little recognized. Field investigations, in 2006 and 2007, revealed new finds of dinosaur footprints in the Upper Triassic (Norian), Lower Jurassic (Pliensbachian) and Upper Jurassic (Oxfordian) of the Holy Cross Mountains (central Poland), and the Upper Cretaceous (Maastrichtian) of the Roztocze region (southeastern Poland). Norian material comprises prosauropod tracks, which came from the coarse-clastic sequences exposed in the Skarszyny outcrops. New Jurassic finds, in the Holy Cross Mountains, are the Pliensbachian sauropod and small theropod footprints from the Smilow sandstone quarry, and the Oxfordian theropod, and small ornithopod tracks from Baltow limestones. Dinosaur footprints, in the Roztocze carbonates, are discovered in the lowermost part of Szopowe quarry on the Mlynarka Mount. The material from Mlynarka Mount resembles Asiatic ichnotaxa, a small didactyl maniraptoran track of Velociraptorichnus, bird-like ichnite similar to Saurexallopus and a large tetradactyl footprint of Macropodosaurus, a form recently supposed of the therizonosauroid origin.

Barrett, P.M. 2009. The affinities of the enigmatic dinosaur Eshanosaurus deguchiianus from the Early Jurassic of Yunnan Province, People's Republic of China. Palaeontology. doi: 10.1111/j.1475-4983.2009.00887.x.

ABSTRACT: Eshanosaurus deguchiianus is based on a single left dentary from the Lower Lufeng Formation (Lower Jurassic) of Yunnan Province, China. It was originally identified as the earliest known member of Therizinosauroidea (Theropoda: Coelurosauria), a conclusion that results in a significant downward range extension for this clade (>65 million years) and for many other major lineages within Coelurosauria. However, this interpretation has been questioned and several authors have proposed that the anatomical features used to refer Eshanosaurus to Therizinosauroidea are more consistent with attribution to a basal sauropodomorph dinosaur. Detailed consideration of the holotype specimen suggests that several features of the dentary and dentition exclude Eshanosaurus from Sauropodomorpha and support its inclusion within Therizinosauroidea. If accepted as an Early Jurassic coelurosaur, Eshanosaurus has important implications for understanding the timing and tempo of early theropod diversification. Moreover, its provenance also suggests that substantial portions of the coelurosaur fossil record may be missing or unsampled. However, the Early Jurassic age of Eshanosaurus requires confirmation if this taxon is to be fully incorporated into broader evolutionary studies.

3 comments:

  1. "However, the Early Jurassic age of Eshanosaurus requires confirmation if this taxon is to be fully incorporated into broader evolutionary studies."

    How certain is an Early Jurassic age? (Sorry, I don't have access to the paper.)

    ReplyDelete
  2. From the paper:
    "It may be noteworthy that the type area for Eshanosaurus, the Dianzhong Basin, contains a thick Mesozoic sequence that includes not only basal Jurassic sediments (referred to as the Lower Lufeng Formation or the Fengjiahe Formation by different authors: Ye 1975; Xu et al. 2001) but also Middle Jurassic and Early Cretaceous deposits (Bureau of Geology and Mineral Resources of Yunnan Province 1990). As the precise age of Eshanosaurus has profound implications for understanding the timing of the coelurosaur radiation, additional collecting and stratigraphical work is needed at the type locality in order to confirm or refute its Early Jurassic age. In the meantime, the potential importance of Eshanosaurus should be assessed critically and its unprecedented stratigraphical position should not be used as a criterion for excluding this taxon from analyses of coelurosaurian and theropod evolution."

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  3. Wowzers, it really is a therizinosaur, eh? That's pretty awesome, but it requires so many ghost lineages!

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