Molecular evidence for a terrestrial origin of snakes

Abstract

Biologists have debated the origin of snakes since the nineteenth century. One hypothesis suggests that snakes are most closely related to terrestrial lizards, and reduced their limbs on land. An alternative hypothesis proposes that snakes are most closely related to Cretaceous marine lizards, such as mosasaurs, and reduced their limbs in water. A presumed close relationship between living monitor lizards, believed to be close relatives of the extinct mosasaurs, and snakes has bolstered the marine origin hypothesis. Here, we show that DNA sequence evidence does not support a close relationship between snakes and monitor lizards, and thus supports a terrestrial origin of snakes.

The skull of the round Island boa, Casarea dussumieri Schlegel, based on high‐resolution X‐ray computed tomography

“…2;Tchernov et al, 2000;Apesteguia and Zaher, 2006). These phylogenetic hypotheses stand in stark contrast to the recent findings based on molecular data, which place bolyeriids as sister-taxon to a clade that includes the uropeltines (traditionally considered non-macrostomatan), Acrochordus and colubroids, whereas the tropidophiids were found to be the sister-taxon of the non-macrostomatan genus Anilius (Vidal and Hedges, 2004; see also Vidal and David, 2004).…”

“…There is no morphological evidence known that supports the heterodox placement of tropidophiids at the base of alethinophidian snakes, as is obtained using molecular data (Vidal and Hedges, 2004; see also Vidal and David, 2004). The position of Casarea dussumieri (and implicitly of bolyeriids: Anthony and Guibé, 1952) relative to tropidophiids on the one hand, and to the Acrochordus-colubroid clade on the other, remains equivocal as far as cranial characters are concerned.…”

Snake Venomics and Antivenomics of the Arboreal Neotropical Pitvipers Bothriechis lateralis and Bothriechis schlegelii

“…Panels A and B show, respectively, reverse-phase separations of soluble B. lateralis venom proteins recovered after incubation of the venom with rabbit anti-horse IgG antiserum (control sample), and with polyvalent (Crotalinae) antivenom followed by rabbit anti-horse IgG antiserum and immunoprecipitation. HPLC fractions labelled with asterisks in panel A were quantitatively immunodepleted from the venom sample incubated with the polyvalent antivenom, whereas fractions labelled in panel B with numbers (following the same numbering as in Figure 1) were not affected at all (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)20), or were only partially recognized (13)(14)(15)(16)(17)22), by the antivenom (see Figure 7). The insert in panel B shows an SDS-PAGE analysis of -mercaptoethanol-reduced fractions a-g. CID-MS/MS of tryptic peptide ions from these fractions (601.7 2+ : LSVPTSEWQR; 545.6 2+ : VVSTLPI-AHQDWLR; 621.6 3+ : TTPAVLDSDGSYFLYSK) identified them as rabbit IgGs.…”

Earliest world record of green lizards (Lacertilia, Lacertidae) from the Lower Miocene of Central Europe

“…Recent molecular analyses using DNA sequences suggest it may be the sister-group of the Amphisbaenia, the worm lizards (Townsend et al 2004;Vidal & Hedges 2004). This paper deals with the oldest occurrences of lizards close to the Lacerta viridis group (green lizards) from the Lower Miocene of the Dolnice locality near Cheb in westernmost Bohemia (Czech Republic).…”