Sceloporus tristichus Cope in Yarrow, 1875 - plateau fence lizard in northeastern Utah, USA. (9 June 2012) (also known as Sceloporus undulatus tristichus)

This is an outcrop of eolian sandstones in Dinosaur National Monument, Utah. It's locally called the Glen Canyon Sandstone, but it's the same unit as the Navajo Sandstone (elsewhere, it's called the Nugget Sandstone). The Navajo/Nugget/Glen Canyon is a thick quartzose sandstone succession with abundant cross-bedding. Cross-bedding refers to tilted layers between horizontal layers, and forms in a one-directional current by wind or water (in this case, wind). The sandstone is part of a sand dune deposit in an ancient, vast desert, or "sand sea", technically called an "erg".

I saw this lizard trailside while walking back to my vehicle after examining some ~1000 year old Uinta Fremont Indian petroglyphs at a nearby cliff. The most interesting petroglyphs there were lizards! (see: <a href="https://www.flickr.com/photos/jsjgeology/22954590855">www.flickr.com/photos/jsjgeology/22954590855</a> ) I think this is Sceloporus tristichus, the plateau fence lizard.

Classification: Animalia, Chordata, Vertebrata, Reptilia, Squamata, Phrynosomatidae

Stratigraphy: Glen Canyon Sandstone, Upper Triassic-Lower Jurassic

Locality: outcrop next to Cub Creek Road, Dinosaur National Monument, northern Uintah County, northeastern Utah, USA (vicinity of 40° 25' 13.54" North latitude, 109° 11' 14.41" West longitude)

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