Tikiguania and the antiquity of squamate reptiles (lizards and snakes)

Abstract

Tikiguania estesi is widely accepted to be the earliest member of Squamata, the reptile group that includes lizards and snakes. It is based on a lower jaw from the Late Triassic of India, described as a primitive lizard related to agamids and chamaeleons. However, Tikiguania is almost indistinguishable from living agamids; a combined phylogenetic analysis of morphological and molecular data places it with draconines, a prominent component of the modern Asian herpetofauna. It is unlikely that living agamids have retained the Tikiguania morphotype unchanged for over 216 Myr; it is much more conceivable that Tikiguania is a Quaternary or Late Tertiary agamid that was preserved in sediments derived from the Triassic beds that have a broad superficial exposure. This removes the only fossil evidence for lizards in the Triassic. Studies that have employed Tikiguana for evolutionary, biogeographical and molecular dating inferences need to be reassessed.

A reconsideration of Sphaerodactylus dommeliBöhme, 1984 (Squamata: Gekkota: Sphaerodactylidae), a Miocene lizard in amber

“…The external and internal anatomy of the holotype of S. dommeli confirms that this taxon is a member of the Family Sphaerodactylidae, providing a reliable calibration point for biogeo- (Hutchinson et al 2012).…”

“…The external and internal anatomy of the holotype of S. dommeli confirms that this taxon is a member of the Family Sphaerodactylidae, providing a reliable calibration point for biogeographical and molecular dating inferences, this is very important considering that using erroneously identified and dated fossils may result in incorrect divergence dates (Hutchinson et al. ).…”

Relationships of the Indian phytosaur Parasuchus hislopi Lydekker, 1885

“…Hutchinson et al . () argued that T ikiguania was a C enozoic agamid reworked into T riassic sediments; it is listed here for sake of completeness.…”

Shearing Mechanics and the Influence of a Flexible Symphysis During Oral Food Processing in Sphenodon (Lepidosauria: Rhynchocephalia)

“…The short distance between the pterygoid flange and medial surface of the lower jaw supports the hypothesis that the pterygoid flange acts as a brace to limit medial displacement of the lower jaw (Fig. 11; Iordansky,1964; Taylor,1992; Jones et al,2011; Porro et al,2011). Therefore, as well as being important for dealing with struggling prey this medial buttress may also help guide the jaws and ensure smoother shearing of heterogeneous food material.…”