Ben Creisler
New Mesozoic turtle papers:
Pleurosternon moncayensis sp. nov.
A partial skeleton of a pleurosternid turtle (Paracryptodira), from the Jurassic-Cretaceous transition at the Spanish locality of Ãgreda (Moncayo Region, Soria Province), is presented here. Its partial skull represents the third of this lineage to be recognised in the European record, with the previously known specimens corresponding to British species. The specimen of Pleurosternidae studied here is attributed to a new species, Pleurosternon moncayensis. This lineage of stem turtles is identified as the most abundant and diverse group of freshwater aquatic turtles in Europe for the stages adjacent to the Jurassic-Cretaceous transition. Its presence decreased radically at post-Berriasian levels, when freshwater lineages of Eucryptodira, of Asian origin, are identified as the dominant forms at these aquatic turtle faunas. The confirmation of Pleurosternidae as freshwater inhabitants is made here, through the first neuroanatomical study for this lineage. Thus, the neuroanatomical reconstruction of Pleurosternon moncayensis sp. nov. is the first to be carried out for a freshwater stem turtle, and it allows us to identify convergent adaptations with freshwater members of the crown Testudines.
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News (in Spanish)
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Plesiochelys prebetica com. nov.
Two unpublished shells of thalassochelydian turtles from Tithonian (Late Jurassic) outcrops of the Lusitanian Basin (west central Portugal) are studied here. They are recognised as attributable to the plesiochelyid littoral genus Plesiochelys. They show characters unknown for the so far available Portuguese record of Plesiochelys, exclusively based on a partial shell, also from the Tithonian. The comparison between all these specimens and the only remains of Plesiochelys from the Spanish Tithonian record allow us to recognise several differences, compatible with the intraspecific variability reported for the genus. One of the oldest references to Thalassochelydia for the global record corresponds to that of the enigmatic taxon 'Hispaniachelys prebetica', from the Oxfordian of JaÃn (Spain), hitherto recognised as a nomen dubium. Its holotype is identified here as belonging to the oldest member of Plesiochelys, the new combination Plesiochelys prebetica being proposed. Thus, the presence of at least two forms of Plesiochelys is recognised for the Iberian record, one of them corresponding to the only one identified at levels older than the middle Kimmeridgian, and the other being younger than the two species of which the shell was known (i.e. Plesiochelys etalloni and Plesiochelys bigleri).
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News: (in Spanish)
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