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Cold-Blooded Myth
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Dateline: 04/27/00

Researchers at North Carolina State University have made an amazing discovery that could change the way we think about dinosaurs. They have discovered that the remains of a dinosaur found in 1993 contain a fossilized heart in the chest cavity. The findings are reported in Science (Apr 21 2000: 503-505).

"This challenges some of our most fundamental theories about how and when dinosaurs evolved."

- Dr. Dale Russell

"Fossilized heart in the chest cavity, Photo by Jim Page - NCMNS."

Willo, the dinosaur in question, is believed to be a Thescelosaurus. These large herbivores lived over 60 million years ago, weighed over 650 pounds and were about 13 feet long. The fossil remains were found in South Dakota. Willo is the first and only Thescelosaurus found with a complete skull and preserved tissues and organs.

"Artist's rendition of Willo in the flesh, Illustration by Ed Heck."

Upon examination of Willo's chest cavity, researchers and cardiologists concluded that the heart contained four chambers and a single aorta. This would likely indicate that Willo had double circulation and oxygen rich blood was kept separate from oxygen poor blood. Most modern reptiles have a three-chambered heart with two arches leading from the heart to the body. Oxygen rich blood is able to mix with oxygen poor blood in the reptilian heart. These findings suggest that Willo's heart was more similar to the mammalian or avian heart than the reptilian heart.

The researchers believe that Willo's four-chambered heart and single aorta strongly indicate that dinosaurs were warm-blooded and were able to maintain their body temperature by conserving heat generated from metabolism. This is in stark contrast to the prevalent belief that dinosaurs were most likely ectothermic (cold-blooded).

"3-D reconstruction of Willo's thorax, Paul Fisher - NCSU College of Veterinary Medicine Biomedical Imaging Resource Facility."

"CT scan of Willow's heart, Paul Fisher - NCSU College of Veterinary Medicine Biomedical Imaging Resource Facility."

Willo is currently on display at the North Carolina Museum of Natural Sciences in the "Prehistoric North Carolina" exhibit.

What do you think? Were dinosaurs warm-blooded? Come on over to the Biology Forum and share your thoughts, opinions and feelings.

For additional information see:

Willo, the Dinosaur With A Heart
Original news release about the findings.

Information and resources about dinosaurs.
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