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Stenopterygius (Ichthyosauria) species

From: Ben Creisler
New in January 2012 Journal of Paleontology:
 Erin E. Maxwell (2012)
New Metrics To Differentiate Species of Stenopterygius (Reptilia: 
Ichthyosauria) from the Lower Jurassic of Southwestern Germany.
Journal of Paleontology 86(1):105-115 
doi: http://dx.doi.org/10.1666/11-038.1
Ichthyosaurs represent one of the most highly specialized lineages of marine 
reptiles, but our understanding of the evolution of this group is based on 
specimens found at a surprisingly small number of stratigraphic intervals and 
localities. The Lower Jurassic (Toarcian) Posidonia Shale of southwestern 
Germany is one of the richest ichthyosaur-bearing formations in the world and 
has produced thousands of skeletons, including specimens with preserved soft 
tissue, and fetal remains inside the body cavity. The most abundant ichthyosaur 
genus in the Posidonia Shale is Stenopterygius. In spite of almost 200 years of 
research effort, the number of species in this genus is still a point of active 
disagreement in the literature. Here, bivariate and multivariate analyses are 
used to classify both articulated and disarticulated skeletons to the level of 
species, using measurement data from individual cranial and postcranial 
elements. Unlike previous classification
 attempts, this technique pinpoints ontogenetically conserved differences in 
size and proportion between the species, and so can be applied to adult, 
subadult, and neonatal specimens. Using this method, three species of 
Stenopterygius, S. quadriscissus, S. triscissus, and S. uniter are