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Image: Head scan of a Texas Horned Lizard, part of a series of 3-D head scans showing clear skin and solid bone.<BR> <BR> The images were created at the High-Resolution X-ray Computed Tomography Facility (UTCT) at the University of Texas, Austin. The UTCT--a National Science Foundation-supported shared multi-user facility—gives researchers a nondestructive technique for visualizing features in the interior of opaque solid objects as well as obtain digital information on their 3-D geometries and properties. The scans were taken as part of on-going research by Wendy Hodges, a University of California-Riverside biologist who is attempting to reconstruct the physical features of the common ancestor of the 13 species of North American horned lizards.<BR> <BR> Between 23 and 30 million years ago, the first North American horned lizards branched off from sand lizards, becoming stockier and spinier and evolving their distinctive crowns of horns. A single common ancestor gave rise to the 13 North American species, each developing a unique set of cranial horns and spikes. Researchers are trying to determine what this prehistoric, common ancestor may have looked like and how the horns of these species developed. <I>[This image is 2 in a series of 3; see also, <B>Head Scan – Clear Skin and Bone, Image 2 and 3</B>. This image is also one of several related images pertaining to Dr. Hodges research on horned lizards. See related images: <B>Color Head Scan - External Skin and Internal Skeleton, Image 1 through 5</B>, <B>Basking Coast Horned Lizard</B> and <B>Coast Horned Lizard</B>.]</I><BR> <BR> <U><B>More about this Image</B></U><BR> With the assistance of Reuben Reyes, a visualization expert from the Texas Advanced Computing Center (UT-Austin), Wendy Hodges is applying advanced computer analysis and graphics techniques to three-dimensional data sets acquired through computed tomography (CT). CT reconstruction allows the analyses and comparison of the morphologies of different species of horned lizards. The final goal of the project is the visualization of the evolution of horns in this group of lizards and determining how horn number increased through evolutionary time.<BR> <BR> Hodges and Reyes have been applying
Eventually, images of each horned lizard species’ head will be created from the CT data using visualization software, to reveal both the external configurations and the internal structures of the specimens. One visualization application depicts the external skin and internal skeleton using a color-mapping scheme that represents the distance from the skin to the bone, giving some of the lizard head reconstructions a polychromatic, "tie-dyed" appearance.

[This research is funded in part by the NSF through a Postdoctoral Fellowship in Biological Informatics, awarded to Hodges.]

CREDIT for this Image Should Read:
Research by Wendy Hodges, Timothy Rowe, and Reuben Reyes; X-ray CT scans by High Resolution X-ray CT Facility, Univ. of Texas, Austin, Dept. of Geological Sciences; Specimen courtesy of the Texas Memorial Museum of Science and History; Graphics and 3D models from Univ. of Texas, Texas Advanced Computing Center, ACES Visualization Lab. Thumbnail">

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