|Extant erycine boas: An African Exyx colubrinus, and the North American Lichanura, and Charina|
This paper is of most interest because it clarifies the previous idea that Erycinae boas were common in the Paleogene of North America. Today in North America erycines are represented by the rosy boas (Lichanura) and the rubber boas (Charina). In the past many authors assigned most North American Paleogene snake taxa to the Erycinae (sand boas) Smith reports that there is no well-founded record of an erycine boa in North America prior to the Miocene. The mistake apparently resulted from the similarity of mid-body vertebrae in the extant North American Erycinae and the Paleogene snakes. Thus the Eocene North American snake fauna had small booid snakes, but they were in fact members of the loxocemid and ungaliophid clades, not the Eastern Hemisphere sand boas, the Erycinae.
Smith, K. T. 2012. New constraints on the evolution of the snake clades Ungaliophiinae, Loxocemidae and Colubridae (Serpentes), with comments on the fossil history of erycine boids in North America. Zoologischer Anzeiger - A Journal of Comparative Zoology, http://dx.doi.org/10.1016/j.jcz.2012.05.006