Predator “dawn runner” dinosaur found in the Valley of the Moon

A lanky predator roamed South America in search of prey as the age of the dinosaurs began, approximately 230mya. This dinosaur, named Eodromaeus (the “dawn runner”), sported a long neck and tail, and weighed only 4.5kg to 6.8kg. A team of palaeontologists and geologists from Argentina and the USA announced the discovery of dawn runner in January 2011.


Reconstruction of Eodromaeus,
by Todd Marshall.

“It really is the earliest look we have at the long line of meat eaters that would ultimately culminate in Tyrannosaurus rex near the end of the dinosaur era,” said Paul Sereno, University of Chicago palaeontologist and National Geographic Explorer-in-Residence. “Who could foretell what evolution had in store for the descendants of this pint-sized, fleet-footed predator?”
Sereno and his colleagues described a near-complete skeleton of the new species, based on the rare discovery of two individuals found side-by-side, in the 14 January 2011 issue of the journal Science. The paper presents a new snapshot of the dawn of the dinosaur era – a key period that has garnered less attention than the dinosaurs’ demise. “It’s more complex than some had supposed,” Sereno said.


Dr Paul Sereno. Photo by Mike Hettwer.

Set in picturesque foothills of the Andes, the site of the discovery is known as the “Valley of the Moon,” said the report’s lead author, Ricardo Martinez of Argentina’s National University of San Juan. For dinosaur palaeontologists, it is like no other. “Two generations of field work have generated the single best view we have of the birth of the dinosaurs,” Martinez said. “With a hike across the valley, you literally walk over the graveyard of the earliest dinosaurs, to a time when they ultimately dominate.”
The area was once a rift valley in the southwest corner of the supercontinent Pangaea. Sediments covered skeletons over a period of five million years, eventually accumulating a thickness of more than 700m. Volcanoes associated with the nascent Andes Mountains occasionally spewed volcanic ash into the valley, allowing the team to use radioactive elements in the ash layers to determine the age of the sediments.


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