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Plesiosaur tail fins and Stenopterygius (ichthyosaur) specimen in Italy (free pdfs)



From:  Ben Creisler
bcreisler@gmail.com

Two recent marine reptile papers not yet mentioned on the DML. The
links are to pdfs available on the web but not from the original
journal pages:



Adam S. Smith (2013)
Morphology of the caudal vertebrae in Rhomaleosaurus zetlandicus and a
review of the evidence for a tail fin in Plesiosauria.
Paludicola 9(3): 144-158
(not yet posted on Paludicola website)
pdf available at:
http://www.plesiosauria.com/pdf/smith_2013_plesiosaur_tail_fin.pdf

The holotype of the large plesiosaurian Rhomaleosaurus zetlandicus
from the Toarcian (Lower Jurassic) of England comprises an almost
complete skeleton, including the caudal vertebral series. The
osteology of the tail is described and two morphological
characteristics are interpreted as evidence for a caudal fin in
Rhomaleosaurus: 1. A distinct node consisting of two relatively
anteroposteriorly shortened vertebrae; and 2. Laterally compressed
terminal caudal centra. This inference is based on osteological
correlates derived from other marine reptile groups that possessed a
vertically oriented bilobed dermal tail fin in life (ichthyosaurs,
thalattosuchian crocodylomorphs, and mosasaurs). This corroborates
evidence from other plesiosaurian taxa and suggests that a caudal fin
may have been widespread among plesiosaurians, with implications for
locomotion and behavior.
==


Chiarenza, A.A., Dalla Vecchia, F.M., Rosso, A. & Sanfilippo, R. (2013)
The Early Jurassic ichthyosaur Stenopterygius in the collections of
the Museo di Scienze della Terra, Università di Catania (Italy).
Bollettino della Società Paleontologica Italiana 52: 19-25.
http://paleoitalia.org/media/u/archives/03_Chiarenza_et_al_2013_BSPI_521.pdf


The “Bonaventura Gravina” Collection of the Earth Science Museum of
Catania (Italy) includes an ichthyosaur specimen of unknown geographic
and stratigraphic provenance, age, and taxonomic determination. On
comparison with other fossils from the same collection it was
established that the specimen is from Böll, southwestern Germany; the
ammonites preserved on the same slab indicate an early Toarcian age.
Based on the available information it is suggested that it comes from
the Early Jurassic Posidonia Shale (Posidonienschiefer), which is
known worldwide for its ichthyosaur remains. A morphological
comparison with Toarcian ichthyosaurs allowed the fossil remains to be
referred to an adult specimen of Stenopterygius, a mid-sized
ichthyosaur genus common in the Toarcian of Southern Germany. The
phylogenetic analysis by parsimony supports this conclusion.