Field of Science

Sedimentology of Dinosauriform-bearing Triassic Rocks in Poland

I have been away dealing with a personal issue (the sudden passing of my mother), but am taking a much needed break to check messages and such and found this paper in my mailbox (thanks Randy)so I decided to do some therapeutic blogging. It is from last year but provides an important sedimentological and depositional system study of Triassic rocks in Poland which contain the Krasiejow fauna, which is famous for the presence of the dinosauriform Silesaurus opolensis. One of the key aspects of this paper is the support of a Norian age for this fauna rather than a Carnian age as previously supposed. This study removes another "Carnian" record from the record of dinosauriforms demonstrating a global survival of non-dinosaurian dinosauriforms into the Norian (at least in Laurasia)where they were contemporaneous with dinosaurs. This paper also provides evidence that the Krasiejow environment was subtropical and wet, but punctuated with dry periods, thus the climate was monsoonal as has been proposed for the Chinle Formation.

Note: Someone e-mailed me asking about the recent Chinese Jurassic theropod paper. I accidentally deleted your message so please resend.

Gruszka, B. and T. Zielinski. 2008. Evidence for a very low-energy fluvial system: a case study from the dinosaur-bearing Upper Triassic rocks of Southern Poland. Geological Quarterly 52:239-252.

The Upper Triassic succession in S Poland in which dinosaur bones have been found consists predominantly of siltstones and claystones. Three units are distinguished. The lowermost and the upper most units reflect an alluvial environment, whereas the middle one represents lacustrine facies. The lower alluvial unit is interpreted as a record of ephemeral, sinuous, suspended-load channels with rapid vertical accretion. Channel barforms are lacking. The environment is interpreted as a low-energy anastomosing fluvial system. The clayey middle unit is interpreted as having formed in a wide long-lived lake. The top of the lacustrine deposits shows signs of vertisol-type pedogenesis, most probably under subtropical conditions, with seasonally-in duced wet and dry intervals. The upper unit reflects a low-energy meandering river system. Silty point bars were abundant and the channels migrated freely. The energy level of this fluvial system was slightly higher than that of the earlier one, which is interpreted as an effect of base-level lowering in combination with an increasingly humid climate. The almost exclusively silty/clayey alluvial deposits represent an exceptionally rare facies. The drainage basin must have been an extremely flat lowland. The presence of vertebrate bones within the anastomosing and meandering river deposits indicates that low-energy alluvial plains were apparently favourable habitats for both reptiles and amphibians during the Late Triassic: under the subtropical, seasonally dry conditions, the animals must have preferred moist low areas, i.e. the flood basins and abandoned channels on the flat valley floors.

11 comments:

  1. Hi Bill. My condolences on your mother. Good to see you blogging.

    -Joanna

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  2. Hi Bill,

    I'm sorry to hear about your mother. I haven't forgotten your kind support when we had trouble with our daughter, I just wish I could say something as uplifting to you at this time but I really can't think of anything other than you have my sympathy. I agree with Joanna it is good to see you continue blogging.

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  3. My thoughts are with you and your family.

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  4. So sorry about your mother, sir. My deepest consolences.

    On to the topic at hand...where the heck is a redescription of Silesaurus with the new material included? And a proper phylogenetic analysis? It's a basal ornithischian, dammit!

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  5. Thank you to everyonefor their condolences. If you sent an email I will reply when I return home.

    Zach,

    I hate to break it to you but Silesaurus is not a basal ornithischian. No phylogenetic analysis has recovered it as such including a forthcoming detailed proper one (from his dissertation) by Randall Irmis.

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  6. Zach - some of the new material is figured in this publication:

    Dzik, J., and T. Sulej. 2007. A review of the early Late Triassic Krasiejów biota from Silesia, Poland. Palaeontologia Polonica 64:1-27. [PDF]

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  7. That's the one I read where Dzik & Sulej propose it's a basal ornithischian! :-(

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  8. Yes, but unfortunately Dzik and Sulej do not test this hypothesis with a phylogenetic analysis.

    They proposed this relationship based on two characters, the presence of a "predentary" (see below) and three sacral vertebrae (a dinosaur plesiomorphy). Irmis et al. 2007 argued that the "predentary" in Sacisaurus (another "Silesaurid") is not a seperate ossification and that the "suture" is a groove.

    Besides this "predentary" and the tooth morphology there are no other characters that support ornithischian affinities for "silesaurids".

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  9. Jonathan WeinbaumMarch 7, 2009 at 9:15 AM

    Bill,

    I'm very sorry to hear about your loss. My condolences to you and your family. Hope you're doing ok.

    Jonathan

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  10. I think, that... there is still problem with the age of Krasiejow locality. Such findings like a conchostraca, ostracoda, and poorly preserved palynomorph suggest rather late Carnian age for this strata! Also new lithostratigraphical data confirm this point of view.
    With the best
    Grzegorz, Poland

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