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Palaeoecology of the Spathian Virgin Formation (Utah, USA) and its implications for the Early Triassic recovery

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Hofmann R., Hautmann M., Wasmer M., Bucher H.
Acta Palaeontologica Polonica
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2013
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tom 58
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nr 1
The Spathian (late Early Triassic) Virgin Formation of south−western Utah (USA) yields a comparatively diverse benthic fauna that flourished ~2 Ma after the end−Permian mass extinction. In this study, we present quantitative palaeoecological data, which are analysed in the context of depositional environments. This integrated approach helps to discriminate between effects of the end−Permian mass extinction event and local environmental factors on alpha diversity and ecological structure of the Virgin Fauna. Shallow subtidal environments yield the highest species richness and lowest dominance val− ues as recorded in two benthic associations, the Eumorphotis ericiusAssociation and the Protogusarella smithi Association, both ofwhich contain 20 benthic species (bivalves, gastropods, brachiopods, echinoderms, and porifers). Tidal inlet deposits yield a low diverse fauna (Piarorhynchella triassica Association) with a very high dominance of filter feeders adapted to high energy conditions.Another comparably low diverse fauna is recorded by the Bakevellia exporrecta Association, which occurs in deposits of the offshore transition zone,most likely reflecting unconsolidated substrates. A single sample contain− ing five bivalve species (Bakevellia costata Assemblage) is recorded from a marginal−marine setting. The Virgin fauna yields a bulk diversity of 30 benthic species (22 genera) of body fossils and 14 ichnogenera and, thus, represents the most di− verse marine bottom fauna known so far from the Early Triassic. Our results suggest that oceanographic conditions during the early Spathian enabled ecosystems to rediversify without major abiotic limitations. However, taxonomical differentia− tion between habitats was still low, indicating a time lag between increasing within−habitat diversity (alpha diversity) and the onset of taxonomical differentiation between habitats (beta diversity). We suggest that taxonomical habitat differentia− tion after mass extinction events starts only when within−habitat competition exceeds a certain threshold, which was not yet reached in the Spathian of the investigated area. This interpretation is an alternative to previous suggestions that the preva− lence of generalistic taxa in the aftermath of mass extinction events reflects protracted environmental stress. The onset of in− creasing beta diversity is a potential criterion for distinguishing two major recovery phases, the first ending with habitat satu− ration and the second ending with the completion of ecosystem differentiation.
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A new large capitosaurid temnospondyl amphibian from the Early Triassic of Poland

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Sulej T., Niedzwiedzki G.
Acta Palaeontologica Polonica
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2013
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tom 58
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nr 1
The Early Triassic record of the large capitosaurid amphibian genus Parotosuchus is supplemented by new material from fluvial deposits of Wióry, southern Poland, corresponding in age to the Detfurth Formation (Spathian, Late Olenekian) of the Germanic Basin. The skull of the new capitosaurid shows an “intermediate” morphology between that of Paroto− suchus helgolandicus from the Volpriehausen−Detfurth Formation (Smithian, Early Olenekian) of Germany and the slightly younger Parotosuchus orenburgensis from European Russia. These three species may represent an evolutionary lineage that underwent a progressive shifting of the jaw articulation anteriorly. The morphology of the Polish form is dis− tinct enough from other species of Parotosuchus to warrant erection of a new species. The very large mandible of Parot− osuchus ptaszynskii sp. nov. indicates that this was one of the largest tetrapod of the Early Triassic. Its prominent anatomi− cal features include a triangular retroarticular process and an elongated base of the hamate process.
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A new Early Triassic gastropod genus and the recovery of gastropods from the Permian-Triassic extinction

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Nutzel A.
Acta Palaeontologica Polonica
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2005
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tom 50
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nr 1
The common Early Triassic (Olenekian) gastropod Turbo rectecostatus from the upper Werfen Formation of the Alps is placed in the new genus Werfenella. Elimination of the wrong or outdated generic assignments of Late Palaeozoic and Early Mesozoic gastropods to archetypical genera such as Turbo, Trochus, or Natica (all with Recent type species) represents an important step toward understanding the evolutionary history of the gastropods across the Permian/Triassic mass−extinction event. The first appearance of Werfenella in the Olenekian, as well as the origination of other groups of gastropods, suggests an early turnover in the aftermath of the end−Permian mass extinction event. The relatively large size of Werfenella (up to 35 mm) sheds doubt on assertions that all Early Triassic gastropods are microgastropods (Lilliput effect). The new genus is placed in the caenogastropod family Purpurinidae and represents its earliest occurrence. However, a placement of Werfenella in the Archaeogastropoda (Vetigastropoda) is also possible because it resembles the paraturbinid genus Chartronella. The characteristic Werfenella rectecostata–Natiria costata gastropod association from the Werfen Formation is not found in the approximately contemporaneous Sinbad Limestone of the Moenkopi Formation (Utah, USA) nor elsewhere outside Europe. This suggests that the similarities between Olenekian gastropod faunas from the Tethys and western North America are more limited than previously thought.
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A basal archosauriform from the Early Triassic of Poland

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Borsuk-Bialynicka M., Evans S. E.
Acta Palaeontologica Polonica
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2003
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tom 48
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nr 4
Basal Archosauriformes had a wide geographic distribution through the Lower to Middle Triassic. Osmolskina czatkowiensis gen. et sp. nov. from Early Olenekian karst deposits at Czatkowice, west of Cracow, provides the first record from Poland. The reconstructed skull and attributed postcranial elements show a morphology closely resembling that of the Early Anisian African genus Euparkeria Broom, 1913, while differing at generic level. Both genera display the same mosaic of plesiomorphic and apomorphic character states, but share no unique apomorphic character state. They might thus be combined in the family Euparkeriidae Huene, 1920, but could also constitute two plesions of the same grade lying just below the Archosauria + Proterochampsidae node. Currently, Euparkeriidae remains monotypic because no other genus can be assigned to it with confidence. Until this problem is resolved, the term “euparkeriid” essentially denotes a grade of Lower to Middle Triassic non−archosaurian archosauriforms that are more derived than proterosuchid grade taxa, but lack the specializations of either erythrosuchids or proterochampsids. They were probably Pangaean in their distribution.
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The scapulocoracoid of an Early Triassic stem-frog from Poland

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Borsuk-Bialynicka M., Evans S. E.
Acta Palaeontologica Polonica
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2002
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tom 47
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nr 1
The scapulocoracoid of Czatkobatrachus polonicus Evans and Borsuk−Białynicka, 1998, a stem−frog from the Early Triassic karst locality of Czatkowice (Southern Poland), is described. The overall type of scapulocoracoid is plesiomorphic, but the subcircular shape and laterally oriented glenoid is considered synapomorphic of Salientia. The supraglenoid foramen is considered homologous to the scapular cleft of the Anura. In Czatkobatrachus, the supraglenoid foramen occupies an intermediate position between that of the early tetrapod foramen and the scapular cleft of Anura. The cleft scapula is probably synapomorphic for the Anura. In early salientian phylogeny, the shift in position of the supraglenoid foramen may have been associated with an anterior rotation of the forelimb. This change in position of the forelimb may reflect an evolutionary shift from a mainly locomotory function to static functions (support, balance, eventually shock−absorption). Laterally extended limbs may have been more effective than posterolateral ones in absorbing landing stresses, until the specialised shock−absorption pectoral mechanism of crown−group Anura had developed. The glenoid shape and position, and the slender scapular blade, of Czatkobatrachus, in combination with the well−ossified joint surfaces on the humerus and ulna, all support a primarily terrestrial rather than aquatic mode of life. The new Polish material also permits clarification of the pectoral anatomy of the contemporaneous Madagascan genus Triadobatrachus.
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