The imagery on this page is the basis for two papers. The most recent is entitled Naming and rediagnosing the Cretaceous gekkonomorph (Reptilia, Squamata) from Öösh (Övörkhangai, Mongolia) by J.L. Conrad and J.D. Daza, 2015 (Journal of Vertebrate Paleontology, 35, e980891). The abstract is as follows:

Although AMNH FR 21444 is an important early and relatively basal lizard whose internal skull structure was first described more than eight years ago (Conrad and Norell, 2006), this specimen has never been formally diagnosed or named. Several papers (Conrad, 2008; Daza et al., 2008, 2012, 2013; Daza and Bauer, 2010; Gauthier et al., 2012) have used AMNH FR 21444 to help reconstruct ancestral states for various squamate groups, especially Gekkonomorpha, its constituent clades, and basal squamate anatomy. Here, we formally describe, diagnose, and name AMNH FR 21444.

An earlier paper was entitled High-resolution X-ray computed tomography of an Early Cretaceous gekkonomorph (Squamata) from Öösh (Övörkhangai; Mongolia), by J. L. Conrad and M. A. Norell, 2006 (Historical Biology 18:405-431). The abstract is as follows:

We describe the braincase of AMNH FR 21444, a gecko-like squamate from the Early Cretaceous of Mongolia, based on high-resolution x-ray computed tomography scans (CT scans) and incorporate it in a phylogenetic analysis of 36 squamate taxa scored for 226 morphological characters. Our analysis corroborates the Eublepharidae-Gekkonoidea split as the basal gekkotan dichotomy, but retrieves Teratoscincus as the sister-taxon to pygopodines + diplodactylines. The combination of plesiomorphic and apomorphic character states within AMNH FR 21444 demonstrates a decoupled evolutionary history between the braincase and the rest of the skull and mandible within gekkonomorph squamates. Enclosure of the lateral head vein and mandibular branch of the trigeminal nerve are both plesiomorphic for gekkonomorphs. The mechanisms responsible for the transition from the plesiomorphic skull roof of basal gekkonomorphs to the modern gekkotan condition cannot be anticipated given the current data.

Click here for a Winzipped 8-bit TIFF version of the original CT dataset (267 mb).

This specimen was collected from Red Mesa, Öösh Basin, Mongolian People’s Republic. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Jack Conrad of the American Museum of Natural History. Funding for scanning and image processing was provided by a National Science Foundation Dissertation Improvement grant (DEB-0408064) to Dr. Conrad. Funding for additional image processing was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.

Dorsal view of specimen	Ventral view of specimen

The specimen was scanned by Matthew Colbert on 1 December 2004 along the coronal axis for a total of 645 1024x1024 pixel slices. Each slice is 0.027 mm thick, with an interslice spacing of 0.027 mm and a field of reconstruction of 12.5 mm.

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