Tuesday, December 10, 2013

Sexual Dimorphism in Carnian Triassic Ichthyosaur Shastasaurus



SHANG Qing-Hua and LI Chun

Summary:

Marine reptiles, especially large-sized long-snout ichthyosaurs are highly controversial in taxonomy in Guanling Biota (early Carnian, Guizhou, SW China).  A large number of large-sized long-snout ichthyosaur skeletons have been excavated from Guanling and adjacent areas since 2000.  Totally 14 specimens were used for taxonomical research and morphological description in previous works, which were originally named as different genera and species.  Based on the similarity of cranial morphology Shan et al referred all of these specimens to one species Shastasaurus tangae.

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It might be possible that the two morphotypes represent different species if those variations would be considered as interspecific differences.  However, we are inclined to believe that they are most probably resulted from sexual dimorphism on the basis of the similarity of the skill anatomy, although more specimens are needed to verify this.

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