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16 August 2011 A Large Predatory Archosaur from the Late Triassic of Poland
Grzegorz Niedźwiedzki, Tomasz Sulej, Jerzy Dzik
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Abstract

We describe a new large predatory archosaur, Smok wawelski gen. et sp. nov., from the latest Triassic (latest Norian—early Rhaetian; approximately 205–200 Ma) of Lisowice (Lipie Śląskie clay-pit) in southern Poland. The length of the reconstructed skeleton is 5–6 m and that of the skull 50–60 cm, making S. wawelski larger than any other known predatory archosaur from the Late Triassic and Early Jurassic of central Europe (including theropod dinosaurs and “rauisuchian” crurotarsans). The holotype braincase is associated with skull, pelvic and isolated limb-bones found in close proximity (within 30 m), and we regard them as belonging to the same individual. Large, apparently tridactyl tracks that occur in the same rock unit may have been left by animals of the same species. The highly autapomorphic braincase shows large attachment areas for hypertrophied protractor pterygoideus muscles on the lateral surface and a wide, funnel-like region between the basal tubera and basipterygoid processes on the ventral surface. The skeleton (cranial and postcranial) possesses some features similar to those in theropod dinosaurs and others to those in large crocodile-line archosaurs (“rauisuchians”), rendering phylogenetic placement of S. wawelski difficult at this time.

Introduction

A new vertebrate-bearing locality of Late Triassic (latest Norian—early Rhaetian) age was recently reported from near Lisowice village (Lipie Śląskie clay-pit) in southern Poland (Dzik et al. 2008a, b). Since then, numerous vertebrate fossils have been collected from the clay-pit, including remains of a dicynodont and bones of archosauromorphs. Among the fossils, probably the most intriguing are the remains of a large predatory archosaur, which was tentatively identified by Dzik et al. (2008a) as a theropod dinosaur from features of the braincase and frontal. More material of the archosaur, including additional postcranial bones, was collected from this site in 2009 and 2010. Bones were found as three accumulations in a 2 m thick rock body, one accumulation including the skull bones and the others accumulations of postcranial elements. Because the bones match each other in size and preservation, and because there are no overlapping elements, these three accumulations seem to represent the disarticulated skeleton of a single individual (Fig. 1). We present here a short description of the new predatory archosaur, in which we compare it with other carnivorous Triassic archosaurs and provide evidence that it is a new species. The primary purpose of this paper is to name and diagnose this new taxon, which is clearly distinct from all known Triassic archosaurs. As this is an initial report, we do not extensively discuss the phylogenetic position of this taxon here (this task will be the subject of the first author's Ph.D. thesis), and for the time being we refrain from assigning it to one of the major predatory archosaur groups common in the Late Triassic (Ornithosuchidae, “Rauisuchia” or perhaps Theropoda; see Gower and Wilkinson 1996; Langer and Benton 2006; Brusatte et al. 2010a, b; Langer et al. 2010; Nesbitt 2011).

Institutional abbreviation.—ZPAL, Institute of Paleobiology, Polish Academy of Sciences, Warsaw, Poland.

Systematic palaeontology

Diapsida Osborn, 1903
Archosauromorpha von Huene, 1946
Archosauria Cope, 1869
Genus Smok nov.

  • Type species: Smok wawelski sp. nov.; see below.

  • Etymology: From Polish smok, a dragon.

  • Diagnosis.—As for the type and only species.

  • Fig. 1.

    Field sketch showing distribution of Smok wawelski gen. et sp. nov. bones within the dark fine-grained mudstone lens at Lipie Śląskie clay-pit at Lisowice and their inferred routes of dislocation from the cadaver, presumably by scavengers or by water currents. Particular bone outlines are enlarged to show their orientation. Large tridactyl footprints were found somewhat above this level and outside the mapped area.

    f01_267.jpg

    Smok wawelski sp. nov.
    Figs. 26, 7A.

  • Etymology: In reference to Wawel Hill in Kraków. Smok wawelski was a legendary dragon living in the cave at the Wawel Hill in Kraków in the region of southern Poland near the excavation site.

  • Holotype: ZPAL V.33/15, ventral part of the braincase with basioccipital and basisphenoid and a separate articulating piece of the right exoccipital-opisthotic, including approximately half of the paroccipital process (Figs. 2D, 3). This specimen is associated with a partially preserved skeleton; probably representing a single individual (see below; Fig. 1).

  • Type locality: Lisowice (Lipie Śląskie clay-pit) about 2 km west of Lubliniec, Silesia, southwestern Poland (Dzik et al. 2008a).

  • Type horizon: The strata exposed in the Lipie Śląskie clay-pit are correlatable with the upper part of the subsurface Zbąszynek Beds and lower part of the Wielichowo Beds (Late Triassic: latest Norian—early Rhaetian). These formations apparently continue into the Exter Formation of the Upper Keuper in the east German part of the Germanic Basin (see Franz et al. 2007a, b). Well-preserved vertebrate bones occur in a lenticular body of clayish, grey mudstone in the northern part of the Lipie Śląskie clay-pit. They are mostly covered with a calcareous and pyritic crust or embedded in limestone concretions. The fossil assemblage includes a large dicynodont, a small dinosauromorph, small archosaurs (pterosaur, poposauroid), a large capitosaur, a small plagiosaurid amphibian, dipnoan fish, a hybodont shark, and palaeonisciform fish (Dzik et al. 2008a, b).

  • Referred mat