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Serpentes Look for this name in NCBI Wikipedia Animal Diversity Web
http://palaeo-electronica.org/content/fc-6 Head, 2015
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OMNH 33520 and 33520 were both collected in the uppermost Cedar Mountain Formation (Mussentuchit Member), Emery County, Utah. The Cedar Mountain Formation spans the Early Cretaceous and Early-Late Cretaceous transition (Cifelli et al., 1997). 40Ar/39Ar dating of Sanidine phenocrysts from smetitic ash horizons directly overlying snake-bearing fossil localities produced a weighted mean age of 98.39 ± 0.07 Ma, which is used as the hard minimum age for Serpentes.
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The soft maximum age is based on uncertainty in age estimates for late Albian snakes from Algeria.
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These specimens possess unambiguous apomorphies of all known total clade Serpentes, including a well-developed zygosphene-zygantral articulation consisting of a transversely wide zygosphene with dorsolaterally angled articular facets and a medially convex anterior margin, and a deep zygantrum with distinct ventromedially angled articular facets. Additional characters include synapophyses with distinct para- and diapophyseal articular surfaces, and well-developed intergyapophyseal ridges. These characters do not differentiate between crown and stem taxa, and there are no diagnostic characters present, or defined, for Coniophis.
Gardner, J.D. and Cifelli, R.L. 1999. A primitive snake from the Cretaceous of Utah. Special Papers in Palaeontology, 60:87-100
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