Fossil feces from a carnivorous dinosaur. Specimen was found in southwestern Saskatchewan, Canada. Scale bar is 15 centimeters (approximately 6 inches) long. (Click on photo for higher resolution image and link to PhotoCD file)

An exceptionally large coprolite (fossilized feces) discovered in Saskatchewan, Canada provides direct evidence of dinosaurian carnivory. The specimen was found in the 65 million year old Frenchman Formation near the town of Eastend by crews of the Royal Saskatchewan Museum. Dinosaur dung is not common, so Timothy T. Tokaryk (supervisor of the RSM Fossil Research Station, a satellite facility of the Royal Saskatchewan Museum) contacted paleobiologist Karen Chin (a visiting scientist with the U.S. Geological Survey) who applied her expertise in coprolite research to the analysis of the specimen.

The Saskatchewan coprolite is an elongated, fractured mass of rock that is approximately 44 by 16 by 13 centimeters (about 17 by 6 by 5 inches). About 200 associated fragments weathered downslope from the larger mass and would have contributed to the original volume of the feces-- estimated to have been over 2.4 liters (about 2 1/2 quarts). The specimen contains fragments of bone, and its great size distinguishes it as the largest individual carnivore coprolite yet described. It is usually very difficult to determine the identity of the producer of a coprolite, but the great size and geologic and temporal context of this specimen indicate a tyrannosaur origin; of the carnivorous dinosaurs (theropods) and crocodilian species known from the Frenchman Formation, only Tyrannosaurus is likely to have produced such a sizable fecal mass.

As the first indisputable example of large theropod feces, this coprolite provides a unique perspective on ancient feeding habits. To extract paleobiological information from the specimen, ultra-thin sections were prepared and microscopically examined with the assistance of comparative anatomist Gregory M. Erickson (formerly at the University of California, Berkeley, now a Post-Doctoral Fellow at Stanford University; read about his research on Tyrannosaurus bite force) and electron probe specialist Lewis C. Calk (now retired from the U.S. Geological Survey). These analyses indicated that the soft fecal material was preserved as lithified (turned to rock) phosphate with included bone fragments that represent incompletely digested dietary residues.

This photograph was taken through a microscope and shows that the coprolite is composed of small chunks bone (upper left portion of the photo) suspended in a phosphatic groundmass. The distribution of bone fibers and blood vessels in the bone indicates that the ingested animal was a sub-adult dinosaur. This images is about 3 millimeters (1/8 inch) across. (Click on photo for higher resolution image and link to PhotoCD file)

This photomicrograph shows a chunk of bone that was partially digested by stomach acids. Most modern carnivores digest bone to some extent, and this coprolite provides a snapshot of ancient dinosaur digestion. This images is about 1.5 millimeters (1/16 inch) across.   (Click on photo for higher resolution image and link to PhotoCD file)

The microstructure of the bone fragments is characteristic of sub-adult dinosaurs and resembles the bone structure of herbivorous dinosaurs. This find thus suggests that a Tyrannosaurus ingested a lot of bone while feeding on a juvenile dinosaur that was probably around the size of a cow. Although tyrannosaurs could not chew like mammals, their teeth and jaws were so strong that bitten bones would have been shattered, and the fragments easily consumed.

Discovery of the specimen

This most unusual discovery was made in 1995 by the staff of the Royal Saskatchewan Museum, when they were taking a break from a Tyrannosaurus excavation. About 2 kilometers (1 1/4 miles) south of the T. rex, and slightly higher in section, Wendy Sloboda (then with the Royal Saskatchewan Museum) and Tim Tokaryk were surveying the floodplain deposits that characterize the Frenchman Formation. While Tokaryk discovered scattered remains of a Triceratops, Sloboda discovered broken, white blobs weathering out of the grey-green mud. Closer inspection revealed bone fragments within the material. The original source of the material was easy to find and was still in place. A quick assessment of the evidence suggested that it was a coprolite of unusually large proportions. Sloboda and Don Stoffregen returned to the site to excavate the specimen and take it to the Eastend Fossil Research Station, a satellite facility of the Royal Saskatchewan Museum.

What can scientists learn from coprolites?

As fossilized fecal material, coprolites have the potential to reveal new clues about the diets of ancient animals. Of course, the amount of information available from a specimen depends on the quality of preservation and on whether the source animal can be identified. In most cases, it is very difficult to pinpoint the producer of a coprolite, but the contents of a specimen may reveal a variety of organisms that coexisted in the paleoenvironment. Fragments of bone, teeth, fish scales, mollusks, wood, leaves, and seeds are some of the dietary residues that have been found in different well-preserved coprolites.

Coprolites may also tell us something about the community of organisms that colonized ancient feces. For example, distinctive burrows in herbivorous dinosaur coprolites indicate that several types of dung beetles helped recycle some of the copious quantities of dung that dinosaurs surely produced.

Thus, although we may not always be able to determine the specific identity of the animal that produced a coprolite, these trace fossils (fossils that indicate the activity of organisms) can provide valuable paleobiological information on the dynamic nature of ancient ecosystems.

Paleontology in southern Saskatchewan

The small town of Eastend, Saskatchewan is approximately 150 kilometers (90 miles) southwest of the city of Swift Current, 200 kilometers (125 miles) southeast of the Alberta city of Medicine Hat, and 50 kilometers (30 miles) north of the Saskatchewan/Montana border. Cretaceous deposits are found in the valley of the Frenchman River which flows through Eastend. Tertiary deposits, mostly late Eocene to early Miocene, are found a few kilometers further northwest, closer to the Cypress Hills.

The southern part of Saskatchewan has seen much traffic by paleontologists for over a century, but most early visitors collected only sporadically en route to the rich dinosaur fields of Alberta. The few early paleontologists (notably Charles M. Sternberg and Loris S. Russell) who spent substantial time in Saskatchewan were rewarded with a diversity of fossils from upper Cretaceous and Tertiary deposits.

The Royal Saskatchewan Museum began to collect from these deposits in the early 1960’s and now has an active research program in both the Tertiary and Cretaceous deposits of southwestern Saskatchewan. These Cretaceous beds are latest Maastrichtian in age, deposited at the very end of the reign of the non-avian dinosaurs, 65 million years ago. In 1991, local school teacher Robert Gebhardt discovered the weathered remains of a Tyrannosaurus in the Frenchman River Valley, while on a prospecting trip with Tim Tokaryk and John Storer of the Royal Saskatchewan Museum. Excavation of this site in 1994 revaled a skeleton at least 65% complete, including most of the skull. The tyrannosaur coprolite was found about 2 kilometers (1 1/4 miles) south of this site.

For additional information on this research, please contact:

Karen Chin
United States Geological Survey, 345 Middlefield Rd. MS 975, Menlo Park, California 94025

Timothy T. Tokaryk
Eastend Fossil Research Station, Royal Saskatchewan Museum, Box 460, Eastend, Saskatchewan, Canada S0N 0T0 (or Harold Bryant, Curator of Earth Sciences Royal Saskatchewan Museum, Regina, 2340 Albert Street, Regina, Saskatchewan, Canada S4P 3V7)

Gregory M. Erickson
Biomechanical Engineering Division, Mechanical Engineering Department & Rehabilitation R & D Center, VA Health Care System, Stanford University, Stanford California 94305

Lewis C. Calk
United States Geological Survey, 345 Middlefield Rd. MS 975, Menlo Park, California 94025

Links

Educational resources on the USGS Learning Web:

http://www.usgs.gov/education/

Royal Saskatchewan Museum:

http://www.royalsaskmuseum.ca

The Great Canadian Fossil Trail site describes different Canadian paleontological sites:

http://www.fossiltrail.org

Saskatchewan's fossils can be seen at:

http://www.dinocountry.com

More about Gregory M. Erickson's work on Tyrannosaurus bite force can be seen at:

http://www.calacademy.org/wild/pacdis/issues/winter97/horw97.htm

More about Karen Chin's work on coprolites can be found in the article "What the Dinosaurs Left Us" in the June, 1996 Discover magazine - search on the title in the Discover archive site:

http://www.discover.com/archive/index.html

 

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