A new genus and species of hadrosaur (duck-billed) dinosaur the oldest duck-billed dinosaur known from North America has been named by scientists who expect the discovery to shed new light on dinosaur evolution.
The most striking feature of Acristavus gagslarsoni, the name given to the new dinosaur, is that its head lacked the distinctive ornamentation common to later duck-billed relatives. Acristavus means "non-crested grandfather." The genus name is symbolic of the animal's unadorned skull and the fact that it preceded later hadrosaurs.
All other hadrosaur fossils come with some kind of adornment on their skulls (with one exception from the end of the Cretaceous Period, the time just before the K-T extinction.) Ornamentation varied among hadrosaurs. Some adornments were hollow and part of the creatures' breathing apparatus, whereas others were solid. Scientists speculate the crests played a role in species recognition where one species could tell another apart by unique embellishments.
The new fossil hints that the two different styles of hadrosaur headgear evolved independently from an ancestor that did not possess ornamentation.
Especially exciting is that the two fossils of the 79.3 million-year-old dinosaurs were discovered in different locations, suggesting that earlier species of duck-billed dinosaurs roamed over a much larger region of North America than their successors four million years later.
"To find two specimens 650 miles apart that lived at virtually the same time, and were discovered within one year of one another is extremely rare in dinosaur paleontology," said Terry Gates, a research associate at Chicago's Field Museum, and a member of the team that documents the discovery in the July issue of the Journal of Vertebrate Paleontology.
The first fossil specimen was found in Montana in 1999 by the Old Trail Museum staff and volunteers, including a group of "junior paleontologists" from the Unive
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