New Predator 'Dawn Runner' Discovered in Early Dinosaur Graveyard.

A team of paleontologists and geologists from Argentina and the United States on Jan. 13 announced the discovery of a lanky dinosaur that roamed South America in search of prey as the age of dinosaurs began, approximately 230 million years ago.

Sporting a long neck and tail and weighing only 10 to 15 pounds, the new dinosaur has been named Eodromaeus, the "dawn runner."

"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 paleontologist 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 describe a near-complete skeleton of the new species, based on the rare discovery of two individuals found side-by-side, in the Jan. 14, 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.

Set in picturesque foothills of the Andes, the site of 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 paleontologists, 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 2,000 feet (700 meters).
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.

"Radioisotopes -- our clocks in the rocks -- not only placed the new species in time, about 230 million years ago, but also gave us perspective on the development of this key valley," said Paul Renne, director of the Berkeley Geochronology Center in California. "About five million years of time are represented in these layers, from one end to the other."

In the oldest rocks Eodromaeus lived alongside Eoraptor, a similar-sized, plant-eating dinosaur that Sereno and colleagues discovered in the valley in 1991. Eoraptor's descendants would eventually include the giant, long-necked sauropods. Eodromaeus, with stabbing canine teeth and sharp-clawed grasping hands, is the pint-sized precursor to later meat-eaters called theropods, and eventually to birds.

"We're looking at a snapshot of early dinosaur life. Their storied evolutionary careers are just unfolding, but at this point they're actually quite similar," Sereno said.

Eodromaeus at the root of the dinosaur family tree
Vexing scientific questions at the dawn of the dinosaur era include what gave them an edge over competitors, and how quickly did they rise to dominance? In Eodromaeus' day, other kinds of reptiles outnumbered dinosaurs, such as squat lizard-like rhynchosaurs and mammal-like reptiles. The authors logged thousands of fossils unearthed in the valley to find, as Martinez remarked, that "dinosaurs took their sweet time to dominate the scene."

Their competitors dropped out sequentially over several million years, not at a single horizon in the valley.

In the red cliffs on the far side of the valley, larger plant- and meat-eating dinosaurs had evolved many times the size of Eoraptor and Eodromaeus, but it would be even later when they dominated all land habitats in the succeeding Jurassic and Cretaceous periods.

"The story from this valley suggests that there was no single advantage or lucky break for dinosaurs but rather a long period of evolutionary experimentation in the shadow of other groups," Sereno said. Other researchers on the paper tracked climate change and other conditions across the layers of the valley. "The dawn of the age of dinosaurs," Martinez remarked, "is coming into focus."

Pint-sized Eodromaeus (“dawn runner”) weighed only 10 to 15 pounds and measured about 4 feet in length from snout to tail tip. It lies very close to the ancestor of all meat-eating dinosaurs, including Tyrannosaurus. (Credit: Illustration by Todd Marshall)

One of France's Largest Dinosaur Fossil Deposits Found in the Charente Region

 The first excavations at the Audoin quarries in the town of Angeac, in the Charente region of south-western France, have confirmed that the site is one of the richest dinosaur fossil deposits in the country. Coordinated by the Musée d'Angoulême and the Géosciences Rennes laboratory (CNRS / Université de Rennes 1), the project involved researchers from CNRS and the Muséum National d'Histoire Naturelle (French Natural History Museum). With more than 400 bones brought to light, this site is remarkable both for the quantity of discoveries and their state of preservation.

The quarries have yielded a wide variety of fossils dating from the Lower Cretaceous Period, dating back 130 million years. The most impressive is a femur exceeding 2.2 meters, which could have belonged to the largest sauropod known in Europe. Unusually, the paleontologists at the site also discovered fossilized wood, leaves and seeds that will enable them to reconstitute the flora in which the animals lived. Based on these exceptional finds, the scientists hope to gain a clearer picture of the terrestrial ecosystems of the Lower Cretaceous, a little-known and insufficiently documented period in this region of Europe.

Although its existence had been suspected for years, the dinosaur fossil deposit in Angeac-Charente, near Angoulême, was only discovered in the Audoin quarries in January 2010, and turned out to be one of the largest paleontological sites in France. Covering several hundred square meters, the site consists of argillaceous strata from the Lower Cretaceous Period buried under the ancient quaternary alluvial deposits of the Charente River. The first excavation campaign, which took place over 20 days from late August to early September this year, was conducted by a team led by the Musée d'Angoulême and the Géosciences Rennes laboratory (CNRS / Université de Rennes 1), in collaboration with scientists and technicians from the Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (Paleobiodiversity and Paleoenvironmental Research Center, CNRS / MNHN), the Université de Lyon and the Musée des Dinosaures in Esperaza (Aude region, south-western France).

Remains of herbivorous and carnivorous dinosaurs mixed with aquatic species
These initial excavations have already unearthed more than 400 bones, over 200 of which are of great scientific interest. The latter come from at least 3 dinosaur species, found alongside the remains of two types of turtle and three species of crocodile. The find is all the more exceptional as the bones are not only present in large numbers, but are also remarkably well preserved, having been buried rapidly in the argillaceous sediments of a marsh that covered the Angeac-Charente region during the Lower Cretaceous.

The most impressive finds are indisputably the remains of the largest known sauropod in Europe. Its femur, which has for the moment been left in situ, exceeds 2.2 meters in length, suggesting a weight of some 40 tons and a body length of about 35 meters. The biological links between this giant herbivore and other species have yet to be determined, but its anatomy is not dissimilar to examples found in Spain and dating from the same period. The presence of small herbivorous dinosaurs has also been evidenced by the discovery of a tooth and a few bones. The most abundant fossil material gathered this summer (nearly 80% of the bones exhumed) belongs to a large carnivorous dinosaur with a body length of about 9 meters. The number of femurs found points to no fewer than five individuals, young and adult.

Dinosaurs from the Lower Cretaceous are rarely found in France, and are usually identified on the basis of fragmentary remains. So far only three dinosaur genera have been identified: the ornithopod Iguanodon and the two theropods Genusaurus and Erectopus. Richer faunas, most likely contemporary with that of the Angeac site, have been described in Britain (in particular on the Isle of Wight) and Spain (Cuenca Province). The most remarkable animal remains from the period, including feathered carnivorous dinosaurs, were found in the Liaoning Province of China. The newly-found Angeac dinosaurs will be compared to these other specimens to determine their shared and distinctive characteristics.

For the paleontologists involved in the project, the next step will be to study and analyze their discoveries, whether it be the animal bones or the fossilized plants. In parallel with this scientific research, a project will be undertaken to enhance the site, enabling the public to view each phase of the operation, from excavation to museum display, over the next few years.

On the right, part of the giant femur (more than 2.2 meters long) of a sauropod, and on the left a section of a humerus from the same animal. (Credit: Copyright Didier Néraudeau (CNRS/Université de Rennes 1))