Hadrosaurids are among the most recognizable dinosaurs, thanks to their flamboyant head ornamentation and duck-billed visage. Although it is well-known that these herbivorous creatures lived in what is now Asia, Europe, and North America, paleontologists have long-debated where exactly these beasts first came from. Now, a new study published in the Journal of Vertebrate Paleontology has revealed that the eastern United States was in fact their place of origin.
Researchers know that hadrosaurids are descendants of the Upper Jurassic (161 to 146 million years ago) iguanadontian dinosaurs, and that they flourished during the end of the Upper Cretaceous (100 to 66 million years ago), with some living right up until the cataclysmic asteroid impact that brought the age of the non-avian dinosaurs to a dramatic close. Many unanswered questions surround this large group, however, particularly with regards to where and when the first primitive hadrosaurids evolved.
The answer was found alongside an unassuming creek in Montgomery County, Alabama. Buried in marine sediment, the remains of an unusual-looking ornithischian (“bird-hipped”) dinosaur, washed out to sea upon dying, was found. The fossilized skeletal remains included a complete skull – a rare find in dinosaurian paleontology.
It was a juvenile that would have reached up to 9 meters (30 feet) in length as an adult. It likely walked on its hind legs until it found some low-lying vegetation, when it would come down on all four of its legs to graze with its grinding teeth. Its skull proved to be particularly striking: It had a large crest protruding from its nose.
In terms of its skeleton, presumed diet and gait, it appeared to be a form of hadrosaurid. However, it was its age and location of discovery that provided the greatest revelations to the research team. The researchers named it Eotrachodon orientalis, which means “dawn rough tooth of the east,” highlighting the fact that, at 83 million years old, it is likely to be one of the very first hadrosaurids ever to have evolved.
Eighty-five million years ago, North America was divided into two distinct land masses – Laramidia to the west and Appalachia to the east – separated by the 1,610 kilometer (1,000 mile) long West Interior Sea connecting the Arctic Ocean to the Gulf of Mexico. “For roughly 100 million years, the dinosaurs were not able to cross this barrier,” Jun Ebersole, director of collections at McWane Science Center in Birmingham, Alabama, and co-author on the paper, said in a statement.
The fact that E. orientalis was found in what used to be Appalachia, but its descendants have popped up all across the world, implies that at some point the duck-billed dinosaurs managed to cross this watery chasm and diversify, presumably when the sea level lowered. Appalachia, therefore, may be where the hadrosaurids first evolved.