Dinosaurs' gradual rise to dominance.Fossil finds in the southwestern United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. suggest that dinosaurs didn't quickly supplant sup·plant tr.v. sup·plant·ed, sup·plant·ing, sup·plants 1. To usurp the place of, especially through intrigue or underhanded tactics. 2. the creatures they evolved from, as many paleontologists have assumed. The first dinosaurs evolved from reptiles called dinosauromorphs about 235 million years ago. Until recently, scientists hadn't uncovered any dinosauromorph fossils from much after that time, fueling speculation that dinosaurs had swiftly eclipsed their ancestors, says Randall B. Irmis, a paleontologist at the University of California, Berkeley The University of California, Berkeley is a public research university located in Berkeley, California, United States. Commonly referred to as UC Berkeley, Berkeley and Cal . Now, however, Irmis and his colleagues have unearthed Unearthed is the name of a Triple J project to find and "dig up" (hence the name) hidden talent in regional Australia. Unearthed has had three incarnations - they first visited each region of Australia where Triple J had a transmitter - 41 regions in all. remains of several known dinosauromorph species, and of a previously undescribed one, from the 215-million-year-old rocks of a quarry in north-central New Mexico New Mexico, state in the SW United States. At its northwestern corner are the so-called Four Corners, where Colorado, New Mexico, Arizona, and Utah meet at right angles; New Mexico is also bordered by Oklahoma (NE), Texas (E, S), and Mexico (S). . All these creatures lived alongside many types of dinosaurs whose remains are in the same rock strata, the researchers note in the July 20 Science. The team's findings suggest that dinosaurs and dinosauromorphs coexisted in some locales for between 15 million and 20 million years, says Irmis. Excavations in rocks of similar ages at fossil-rich sites in Arizona and Texas bolster the notion that the two reptile groups shared an ecosystem for significantly longer than had been recognized.--S.P. |
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