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ABSTRACT-The fossil snake species Haasiophis terrasanctus Tchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description of Haasiophis. The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges. Haasiophis cannot be considered a juvenile specimen of Pachyrhachis. The implications of the presence of well-developed hind limbs in Haasiophis, Pachyrhachis, and Podophis for the cladistic analysis of the phylogenetic interrelationships of these fossil snakes is discussed. The presence of well-developed hind limbs in Pachyrhachis and Haasiophis also creates methodological problems for the cladistic analysis of the phylogenetic relationships of these fossil snakes. Scenarios of snake origins are reviewed and found to be deficient in the absence of a well-corroborated hypothesis of snake relationships within Squamata.
INTRODUCTION
THE ORIGIN of snakes, as well as the reconstruction of phylogenetic interrelationships among basal snakes, has been a long standing problem in herpetology and paleoherpetology (Rieppel, 1988), but one that has seen an important recent resurgence of interest (Caldwell, 1999, 200Oa, 2000b; Caldwell and Lee, 1997; Coates and Ruta, 2000; Cundall and Greene, 2000; Evans and Barbadillo, 1998; Graham and McGonnel, 1999; Greene and Cundall, 2000; Hallermann, 1998; Lee, 1997a, 1997b, 1998, 2000; Lee and Caldwell, 1998, 2000; Lee, Caldwell et al., 1999; Lee, Bell et al., 1999; Rage and Escuillie, 2000; Rieppel and Kearney, 2001, 2002; Rieppel and Zaher, 200Oa, 2000b, 2001; Rieppel et al., 2002; Scanlon and Lee, 2000; Scanlon et al., 1999; Tchernov et al., 2000; Zaher, 1998; Zaher and Rieppel, 1999a, 1999b, 2000, 2002). This renewed interest in snake origins and evolution was triggered primarily by the re-description of Pachyrhachis problematicus as a fossil snake with well-developed hind limbs from the early Upper Cretaceous of 'Ein Yabrud, a locality near Ramallah, approximately 20 km north of Jerusalem (Caldwell and Lee, 1997; Lee...