Field of Science

Could it Be? An Non-Archosaurian Archosauriform that is Actually a Dinosaur?

The past eight years have seen quite a few cases where purported Triassic dinosaurs actually turned out to be non-dinosaurian archosauriforms...Revueltosaurus, Shuvosaurus, Azendohsaurus... finally the dinosaurs get one back. Moreover there are no Jurassic or Chinese phytosaur specimens. 

Barrett, P. M., and X. Xu. 2012. The enigmatic reptile Pachysuchus imperfectus Young, 1951 from the lower Lufeng Formation (Lower Jurassic) of Yunnan, China. Vertebrata PalAsiatica 50:151-159. [Free download here]

Abstract - Phytosaurs are generally considered to have become extinct at the end of the Triassic Period, but several records have suggested that they survived into the basal Jurassic in Europe and Asia. The Asian record consists of Pachysuchus imperfectus from the lower Lufeng Formation (?Hettangian-Sinemurian) of Yunnan, China. However, this specimen differs from phytosaurs in numerous aspects and is more likely a poorly preserved, indeterminate sauropodomorph dinosaur skull. The referred specimens of this species are also regarded as indeterminate, thereby removing the post-Triassic record of phytosaurs from Asia. The European records of Jurassic phytosaurs are also shown to be doubtful, suggesting that this clade was restricted to the Late Triassic. 

9 comments:

  1. Other supposed non-dinosaurian archosauriforms that ended up being dinosaurs- "Ornithocheirus" hilsensis, Poekilopleuron, Streptospondylus, Suchosaurus, Scansoriopteryx (ha!) and any bird described by BANDits.

    Very cool paper though. I love when old specimens are re-examined. The abstract's more accurate than your summary though in the sense that Barrett and Xu don't disprove all other Jurassic phytosaurs. While they do show Pachysuchus isn't a phytosaur, and the fragment described by Maisch and Kapitzke (2010) is Triassic, the teeth described by Huene and Mauberge (1954) and "Megalosaurus" terquemi are merely suggested to be similar to Dakosaurus based on personal communication. They might be right these are crocodyliforms insead, but that would need to be shown with actual morphological comparisons and reasons besides stratigraphy that they are more similar to Dakosaurus than to phytosaurs.

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  2. Don't forget Cetiosaurus, known to Richard Owen, but not included in his Dinosauria because he thought it was crocodilian.

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  3. By know means was my list meant to be exhaustive. There is also Scutellosaurus from the Kayenta Formation. Osteoderms found were thought to be aetosaur, even as late as 1989, and therefore the Kayenta (including Dilophosaurus) was Triassic. These were later shown by Kevin Padian to belong to Scutellosaurus rather than aetosaurs and thus the Kayenta could be Jurassic.

    Mickey is right that someone should reexamine the Jurassic 'phytosaur' teeth using an apomorphy based approach.

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  4. Bill, regarding the Kayenta, I think you mean Scelidosaurus, not Scutellosaurus.

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  5. Talking of apomorphy based approaches, theKayenta scutes are not Scelidosaurus...

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  6. Indeterminate thyreophoran ...

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  7. As an interesting (perhaps just to me) aside, have you noticed how often Archosauromorpha lately ends up as a toilet in phylogenetic analyses of diapsids, sucking in numerous odd taxa? ;)

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