CHICAGO The discovery and analysis of an early carnivorous dinosaur, Sinovenator changii, are clarifying the evolutionary relationship between dinosaurs and birds, according to a paper to be published in Nature Feb. 14, 2002.
The small, relatively complete fossil was found in the rich Yixian Formation of western Liaoning in China, where scientists have recently discovered many groundbreaking fossils, including feathered dinosaurs.
This new dinosaur, which was probably feathered, is closely related to and almost the same age as the oldest known bird, Archaeopteryx, says Peter Makovicky, PhD, assistant curator of dinosaurs at The Field Museum and co-author of the paper. It demonstrates that major structural modifications toward birds occurred much earlier in the evolutionary process than previously thought.
Furthermore, these findings help counter, once and for all, the position of paleontologists who argue that birds did not evolve from dinosaurs, he adds.
The fossil is more than 130 million years old and sheds light on dinosaurs during the transition from the Jurassic period to the Cretaceous period. Sinovenator changii (sigh-no-ven-ay-tor chang-eye) is a troodontid (tro-don-tid), a type of theropod (tare-a-pod). Although many theropods, such as Tyrannosaurus, are large animals, theropods close to the ancestry of birds show an evolutionary trend toward small body size.
Accordingly, an adult Sinovenator changii would have been less than a meter long. This particular specimen, almost fully grown, is slightly larger than a chicken.
Although big dinosaurs may be more spectacular, we can actually learn more about evolution from the often overlooked smaller dinosaurs because they tend to be more primitive, says Dr. Makovicky. Sinovenator changii is more basal or primitive than any other known troodontid.
Troodontids are a type of theropod d
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Contact: Greg Borzo
312-665-7100
Field Museum
13-Feb-2002