Tag Archives: Allosaurus

Spending time in Purgatoire

One of the many places that I have been fortunate to spend time in is Purgatoire. Perhaps not the same thing you are thinking, but I am referring to the Purgatoire River Canyon in southeastern Colorado. Located south of La Junta, this area is an often-overlooked gem. The scenic vistas could be used for your desktop wallpaper!

Purgatoire River Canyon in southeastern Colorado

Purgatoire River Canyon in southeastern Colorado

The many names applied to the region can be confusing. The Purgatoire River has cut a dramatic canyon in this part of the plains, and with the Rocky Mountain Front Range far to the west, it can be almost startling to come upon the deep canyon in an otherwise rolling plains landscape. Anglo settlers bastardized the name of the river, and instead of the eloquent Purgatoire, ended up calling the area Picket Wire, so both names alternately apply.

The area is managed predominately by two federal agencies, the United States Department of Agriculture’s Forest Service and the Department of Defense through the Army. The military uses their lands for maneuver practice, as I understand it, tanks and other mechanized equipment. Some years ago the Army carved off some of their land and gave it to the Forest Service to manage as part of the Comanche National Grassland. The Forest Service land is used for recreation and also the preservation of significant historic and prehistoric resources.

Petroglyph of human and horse figures

Petroglyph of human and horse figures

Rourke Ranch house in the Purgatoire Canyon

Rourke Ranch house in the Purgatoire Canyon

The historic resources include Native American petroglyphs and other archeological sites, early Spanish homestead sites and churches, early American homesteads. The prehistoric resources include dinosaurs and other prehistoric animals, both body fossils and trace fossils. I was very fortunate to have been involved in the documentation of some of the first dinosaur fossils from the region (Schumacher and Liggett 2004).

Dinosaur trace fossils, in particular dinosaur tracks, are well preserved in one section of the Morrison Formation in the bottom of the canyon. These tracks were discovered in 1935 by a young girl as can be seen in this newspaper clipping from the Topeka Capital Journal. However, the tracks are most definitely not those of a Tyrannosaurus rex (mentioned in the clipping) as that beast did not stalk the Earth for at least 90 million years after the track-makers walked here. This track site is the largest continuous track site of dinosaurs known from North America, and contains over 1,400 prints.

Newspaper clipping announcing the discovery of the Purgatoire track site

Newspaper clipping announcing the discovery of the Purgatoire track site

However, because of the remoteness of the site, scientists turned their attention to other dinosaur tracks found in Texas, and the Colorado tracks were essentially forgotten for many decades. However, a newer generation of scientists have re-examined the track site. Of interest is the fact that the site shows five parallel sauropod tracks, suggesting that at least in this case, the animals walked along together spread out, not walking in a line (Lockley 1991).

There are actually several track layers in the rocks. Also preserved are several three-toed theropod, or meat-eating dinosaur. While it is difficult to exactly match the track to the species of dinosaur that made them, the large sauropod tracks were made by an animal like Apatosaurus (Brontosaurus of old) and the meat-eating tracks are similar to what an Allosaurus would make.

A well-preserved theropod dinosaur track in the Purgatoire Canyon

A well-preserved theropod dinosaur track in the Purgatoire Canyon

View of the Purgatoire River track site using low altitude photography

View of the Purgatoire River track site using low altitude photography

In addition to the tracks, the canyon is also now yielding body fossils of dinosaurs. It is really no surprise since the Morrison Formation is extensively exposed along the river canyons. The Morrison is the name given to a wide-spread formation that is the most prolific producer of Jurassic dinosaurs in North America. The formation outcrops in North Dakota, South Dakota, Montana, Wyoming, Colorado, Oklahoma, Texas, New Mexico, Arizona, Utah, and Idaho. Every Jurassic dinosaur you have ever heard of comes from the Morrison; animals such as Allosaurus, Apatosaurus, Diplodocus, Stegosaurus, and Camarasaurus all come from this formation. (See Formations for information about what that means.)

Stratigraphic section of the Purgatoire River Canyon showing the geologic formations that outcrop

Stratigraphic section of the Purgatoire River Canyon showing the geologic formations that outcrop

Given the Purgatoire River’s remoteness, and the fact that it was controlled for many years by the Army, few people were able to explore the region until more recent decades. Thus, now it is one of the last areas of the Morrison Formation exposures to be explored. And it is proving to be as rich as expected.

Over the last decade, the Forest Service has been conducting Passport in Time (PIT) programs in the canyons, looking for new dinosaur sites, and excavating sites. Many people, scientists, graduate students, and the lay public have enjoyed excavating dinosaurs in this beautiful and remote canyon. And several significant specimens have come out of the area. The Forest Service has partnered with many museums from the region to study this treasure-trove and to allow people to enjoy this amazing region.

Volunteers excavate dinosaur fossils from the Woody site

Volunteers excavate dinosaur fossils from the Woody site

Dinosaur vertebra from the Woody Site being prepared at the Sternberg Museum of Natural History

Dinosaur vertebra from the Woody Site being prepared at the Sternberg Museum of Natural History

Plastered dinosaur bone being carried out of the LC Site

Plastered dinosaur bone being carried out of the LC Site

Volunteers excavate dinosaur bones from the Morrison Formation at the LC site

Volunteers excavate dinosaur bones from the Morrison Formation at the LC site

The Forest Service offers tours of the canyon and track site. If you are interested contact the Forest Service Office at 1420 East 3rd, La Junta, CO 81050, 719-384-2181. If you plan to visit the area on your own, be aware of a couple of things. You cannot drive into the canyon without prior authorization. You can hike in on your own, but it is several miles in and out, and the summer temperatures can be brutal, so bring plenty of water and plan accordingly.

A large section of Dakota Formation slumping away from the main block provides a dramatic hiking experience

A large section of Dakota Formation slumping away from the main block provides a dramatic hiking experience

Lockley, M. G. 1991. Tracking Dinosaurs: A New Look at an Ancient World. Cambridge University Press, New York.

Schumacher, B. A., and G. A. Liggett. 2004. The dinosaurs of Picketwire Canyonlands, a glimpse into the Morrison Basin of southeastern Colorado. Journal of Vertebrate Paleontology 24(Supplement to 3):110A. (Poster page 1 and page 2).

Many other dinosaur facts can be found here at Boneblogger. Just search or select the category.

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Scientifically Authenticated Dinosaur Model Kits Now Online

Guest Post

For the Dinosaur connoisseur and collector, you will find what you have been looking for at Dinosaur Model Toys.com. The creator of all the works featured on this site is not only a gifted sculptor, but actually works with dinosaur fossils as a paleontological reconstruction artist, fossil preparator, and field technician at the Natural History Museum of Los Angeles. His artwork is based on the latest scientific research, real fossil material, and years of hands on experience. This is why the work featured is regarded as some of the most scientifically accurate available to the public.

The new Dinosaur Galleries at the Natural History Museum of Los Angeles will feature many of the artist’s creations. Most notable is the baby Tyrannosaurus rex estimated to have been two years old when it died, for which nearly ninety percent of the skeleton will be recreated for this mount. This sculpted reconstruction will be featured with two real T-rex specimens, one a six-year old, and the other the sub adult specimen named “Thomas” which Doyle Trankina helped collect, and prepare. Thomas is estimated to be about seventy percent complete, making it one of the top five most complete in the world. Our initial offering will be a series of cast resin models and limited edition bronze sculptures with both a highly detailed exterior view, and a rendition of the internal skeletal anatomy of an adolescent T-rex similar to the Thomas find.

As part of the Dinosaur Institute at the Natural History Museum of Los Angeles Doyle Trankina has attended several field excavations in Montana, Utah, and the Mojave. While in the field Doyle prospected, and assisted in the collection of several specimens, most notably Thomas the sub adult Tyrannosaurus rex that will be gracing the museum’s new Dinosaur Gallery in 2011. Through his experiences with the museum with his private obsession with prehistoric life and the natural world, Doyle has produced several sculptures and illustrations for exhibition and publication. Doyle has an extensive list of sculptures to produce over the next two years. His work will require lots of observational study from the museum’s collection, and extensive extrapolation based on the latest research, and modern analogues like birds, and crocodiles.

After completing the preparation of Thomas, Doyle embarked on a half skeletal, half flesh reconstruction of an adolescent Tyrannosaurus rex at 1;24th scale. The detail and fidelity to the skeleton was accomplished by long study of the anatomy from several existing mounts, scientific publications, and photographs from the some of the best Tyrannosaurus specimens. The teeth were surfaced to provide the accurate thickness and semblance to where the tinny serrations would have lined the many teeth. Because the position of the serrations actually change on the teeth as they move back towards the throat, the ridge implies the appropriate location of the serrations. The scales were carved individually so that the skin wraps around the form in a realistic, and accurate way.

Doyle is currently working on a skeletal reconstruction of a baby Tyrannosaurus rex which will be mounted in the new Dinosaur Galleries with Thomas and an intermediate specimen as an illustration of age progression. The actual specimen is only known from a skull fragment from the snout of what is believed to be from a two-year-old Tyrannosaurus rex. There are no post cranial remains, and there are only a handful of examples that are believed to be that of baby dinosaurs. This project has just begun, and with Dr. Chiappe Doyle will be making history in presenting the worlds only mounted baby Tyrannosaurus rex specimen.

Fall of 2009 marked one of the biggest Paleontology news splashes, featuring N. America’s smallest dinosaur, Fruitadens haagarorum. Nearly 150 million year old, the tiny Fruitadens would have shared its life with such titanic beasts as Brachiosaursus, and Allosaurus in the late Jurassic. It is thought that the animal might have weighed as little as two pounds and measured only 28 inches in length. Fruitadens was discovered in Colorado in the late 1970s in a geological formation known as the Morrison, more specifically in an area called Fruita, for which the specimen was named after.

Artist reconstruction of the dinosaur Fruitadens

Artist reconstruction of the dinosaur Fruitadens

The strange dentition of this animal implies that Fruitadens might have been omnivorous, eating plants and at least insects if not small vertebrates. Doyle has produced the first and most accurate illustrated and sculpted reconstructions of this animal. Fruitadens belongs to a family of early dinosaurs called heterodontosaurids, which share many interesting features, one of which are the teeth. Fruitadens like other heterodontisaurids have varied dentition, and in the front of the mouth sits a canine like tooth on the lower jaw. His work was featured on every major news source in the world, and five of the sculpted Fruitadens will be featured in the new galleries in 2011. In his studio, Doyle is currently working on a scale Fruitadens, which will be approximately 30cm long . This will be the only scaled sculpture of the animal, and the first and only for sale. The full scale version is not for sale and can only be seen at the Museum.

Doyle is also concurrently working on Mamenchisaurus, a long neck dinosaur and part of the branch of Sauriscian (lizard hipped dinosaurs) known as Sauropods. As the prospects of obtaining a casting of the Chinese mamenchisaur skull proved too difficult, Doyle was charged with the task of reconstructing the skull from two dimensional reference and other dinosaurs like Camarasaurus for comparison, and to gain familiarirty with Sauropod skull anatomy. The rare skull was found in China and researchers provided a paper with a detailed description and several scientific illustrations. Sauropod skulls are rare because they are so frail in construction, have several small bones that usually disarticulated some time after the animal dies, and are not commonly preserved in fossilization, or are so disarticulated and in such small pieces that they are nearly impossible to find.

Doyle Trankina is a sculptor, illustrator and fossil preparator at the Los Angeles Museum of Natural History. For unique scientifically authenticated Dinosaur Art, Dinosaur Models and Dinosaur Resin Model Kits, visit his online store Dinosaur Model Toys.Com.

Many other interesting dinosaur facts can be found here at Boneblogger.

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