DIAGNOSIS AND REMARKS Seven vertebrae are assigned to Viperidae (see appendix 11.1). These specimens have an ex tremely elongate hypapophysis that is predominantly postero-ventrally oriented (more ventrally directed than posteriorly directed; figure 11.4). Several North American viperid taxa (Agkistrodon, Crotalus, and Sistrurus) share this general characteristic. In our experience, the vertebral characters purported to separate these taxa (e.g., Holman, 1979) are subject to such variation that we question their utility in identifying fossil snakes. Both Crotalus and Sistrurus inhabit Colorado today but are not reported from Park County (Hammerson, 1999).
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