Were dinosaurs cold-blooded or hot-blooded? In other words, were they like reptiles or like mammals and birds? New evidence shows that they may have been cold-blooded after all--but turbocharged for maximum sustained levels of activity.
According to a late January 1999 media report, Oregon State University's John A. Ruben and his associates utilized ultraviolet light to study fossilized impressions found in Salerno, Italy. These imprints had been made by a baby Scipionyx, a little carnivorous therapod of 110 million years ago which resembled velociraptors, and were very useful, as they showed indications of not usually preserved soft tissues, such as of muscles, intestines--even the liver. More importantly, they showed a partition which kept apart the liver and guts from the heart and lungs--a sort of rudimentary diaphragm. This feature allowed the lungs to be ventilated at times of heavy activity.
Previously, Ruben had maintained that the respiratory structures of dinosaurs were so simple that they would not work with a warm-blooded system. The new evidence indicated to Ruben that they had especially effective cold-blooded physiologies, giving them the metabolism for the types of activities of which both birds and mammals--being makers of their own body heat--were and are capable. This worked for dinosaurs as long as Earth's climate was of a high enough temperature. When global cooling came, they could no longer compete.
Terry D. Jones, another member of the team at Oregon State University, called the amazing fossil of the Scipionyx to be "like a Rosetta stone for palaeontology, and [it] shows us more about dinosaur biology than we ever knew before."
Source: The Independent, 1/22/99; The Washington Post, 1/25/99; Science magazine website