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Re: Shastasaurus as suction-feeding ichthyosaur



What happened to Shastasaurus alexandrae?

-------- Original-Nachricht --------
> Datum: Mon, 23 May 2011 21:03:22 -0400
> Von: "bh480@scn.org" <bh480@scn.org>
> An: dinosaur@usc.edu
> Betreff: Shastasaurus as suction-feeding ichthyosaur

> From: Ben Creisler
> bh480@scn.org
> 
> New in PLoS ONE:
> 
> Sander, P.M., Chen X., Cheng L., Wang X. (2011)
> Short-Snouted Toothless Ichthyosaur from China Suggests Late Triassic
> Diversification of Suction Feeding Ichthyosaurs. 
> PLoS ONE 6(5): e19480. doi:10.1371/journal.pone.0019480
> http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0019480
> 
> 
> ABSTRACT
> Background
> Ichthyosaurs were an important group of Mesozoic marine reptiles and
> existed from the Early Triassic to the early Late Cretaceous. Despite a
> great diversity in body shapes and feeding adaptations, all share greatly
> enlarged eyes, an elongated rostrum with numerous conical teeth, and a
> streamlined body.
> 
> Methodology/Principal Findings
> Based on new material from China and the restudy of Shastasaurus
> pacificus,
> we here reinterpret the classical large-bodied Late Triassic ichthyosaur
> genus Shastasaurus to differ greatly from the standard ichthyosaurian body
> plan, indicating much greater morphological diversity and range of feeding
> adaptations in ichthyosaurs than previously recognized. Phylogenetic
> analysis indicates a monophyletic clade consisting of the giant
> Shonisaurus
> sikanniensis, Guanlingsaurus liangae, and Shastasaurus pacificus to which
> the genus name Shastasaurus is applied. Shastasaurus liangae comb. nov. is
> from the Late Triassic (Carnian) Xiaowa Formation of Guizhou Province,
> southwestern China. The species combines a diminutive head with an
> entirely
> toothless and greatly reduced snout. The species also has by far the
> highest vertebral count among ichthyosaurs (86 presacral vertebrae and
> >110
> caudal vertebrae), a count that is also very high for tetrapods in
> general.
> A reduced toothless snout and a diminutive head is also apparently present
> in the giant S. sikanniensis and presumably in S. pacificus.
> 
> Conclusions/Significance
> In analogy to many modern odontocetes, Shastasaurus is interpreted as a
> specialized suction feeder on unshelled cephalopods and fish, suggesting a
> unique but widespread Late Triassic diversification of toothless,
> suction-feeding ichthyosaurs. Suction feeding has not been hypothesized
> for
> any of the other diverse marine reptiles of the Mesozoic before, but in
> Shastasaurus may be linked to the Late Triassic minimum in atmospheric
> oxygen.
> 
> 
> 
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