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Using portable 3D laser technology, scientists have preserved electronically a rare 110 million-year-old fossilized dinosaur footprint that was previously excavated and built into the wall of a bandstand at a Texas courthouse in the 1930s.

The laser image preserves what is called a “type specimen” footprint — an original track used many years ago to describe a new species of dinosaur, says paleontologist Thomas L. Adams at SMU.

Portable 3D laser scanners capture original fossil morphology and texture, making it possible to use the data for rapid 3D prototyping in foam or resin, Adams says.

The footprint embedded in the bandstand has been exposed to the elements for nearly 75 years, causing portions of it to erode, Adams says. Erosional loss has affected the outer edge of the toes and heel, altering the initial shape of the track impression.

The track of the ichnospecies Eubrontes glenrosensis was excavated in 1933 from a main track layer in a riverbed in what is now 1,500-acre Dinosaur Valley State Park in Somervell County near Glen Rose. Not long after the track was excavated, the citizens of Glen Rose built a stone bandstand and embedded the track within one of its walls.

The track was described in 1935 by Ellis W. Shuler, SMU’s first geology professor.

Adams says the footprint is that of a three-toed, bipedal, meat-eating dinosaur, with the most likely candidate being the theropod named Acrocanthosaurus, found mostly in Texas, North Carolina and Oklahoma.

“The track is scientifically very important,” says Adams, who is earning his doctoral degree in paleontology at SMU. “But it’s also a historical and cultural icon for Texas.”

Dinosaur Valley State Park boasts the ancient shoreline of a 113 million-year-old sea and is renowned for some of the best preserved dinosaur footprints in the world. The bandstand track is a popular draw for tourists passing through Glen Rose, which is one hour southwest of Dallas.

In an effort to preserve the specimen, as well as to compare its present state with the original description, Adams used a portable 3D laser scanner to perform in situ digitization of the track.

The scans were post-processed to generate high-resolution 3D digital models of the track. Finally the models were rendered in various media formats such as Quicktime VR Virtual Reality and Tagged Image File Format for viewing, publication and archival purposes.

Adams will make the raw scan data and industry-standard 3D object files format available for download.

The research demonstrates the advantages of using portable laser scanners to capture field data and create high-resolution, interactive models that can be digitally archived and made accessible to others via the Internet for further research and education.

“It’s a nice way to share scientific data,” Adams says.

Adams’ research was funded by the Institute for the Study of Earth and Man at SMU. He presented the research at a scientific session of the 2009 annual meeting of The Geological Society of America in Portland, Ore., Oct. 18-21. His co-researchers are Christopher Strganac, Michael J. Polcyn and Louis L. Jacobs, all three in the Roy M. Huffington Department of Earth Sciences at SMU. — Margaret Allen

Fossil land snail shells found in ancient soils on the subtropical eastern Canary Islands show that the Spanish archipelago off the northwest coast of Africa has become progressively drier over the past 50,000 years.

Isotopic measurements performed on fossil land snail shells resulted in oxygen isotope ratios that suggest the relative humidity on the islands was higher 50,000 years ago, then experienced a long-term decrease to the time of maximum global cooling and glaciation about 15,000 to 20,000 years ago, according to new research by Yurena Yanes, a post-doctoral researcher, and Crayton J. Yapp, a geochemistry professor, both in the Roy M. Huffington Department of Earth Sciences at SMU.

With subsequent post-glacial climatic fluctuations, relative humidity seems to have oscillated somewhat, but finally decreased even further to modern values.

Consequently the eastern Canary Islands experienced an overall increase in dryness during the last 50,000 years, eventually yielding the current semiarid conditions. Today the low-altitude eastern islands are characterized by low annual rainfall and a landscape of short grasses and shrubs, Yanes says.

The research advances understanding of the global paleoclimate during an important time in human evolution, when the transition from gathering and hunting to agriculture first occurred in the fertile Middle East and subsequently spread to Asia, North Africa and Europe.

“In the Canary Archipelago, land snails are one of the rare ‘continuous’ records of paleoclimatic conditions over the last 50,000 years,” Yanes says. “The results of this study are of great relevance to biologists and paleontologists investigating the evolution of plants and animals linked to climatic fluctuation in the Islands.”

The researchers’ isotopic evidence reflects changing atmospheric and oceanic circulation associated with the waxing, waning and subsequent disappearance over the past 50,000 years of vast ice sheets at mid- to high latitudes on the continents of the Northern Hemisphere.

The research also is consistent with the observed decline in diversity of the highly moisture-sensitive land snails.

Land snail shells are abundant and sensitive to environmental change and as fossils they are well-preserved. Measurement of variations in oxygen isotope ratios of fossil shells can yield information about changes in ancient climatic conditions.

The shells are composed of the elements calcium, oxygen and carbon, which are combined to form a mineral known as aragonite. Oxygen atoms in aragonite are not all exactly alike. A small proportion of those atoms is slightly heavier than the majority, and these heavier and lighter forms of oxygen are called isotopes of oxygen.

Small changes in the ratio of heavy to light isotopes can be measured with a high degree of accuracy and precision. Variations in these ratios are related to climatic variables, including relative humidity, temperature and the oxygen isotope ratios of rainwater and water vapor in the environments in which land snails live.

Yanes presented the research at a scientific session of the 2009 annual meeting of The Geological Society of America in Portland, Ore., Oct. 18-21.

The research was funded by the government of Spain’s Ministry of Science and Innovation and the National Science Foundation.

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