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Photo © Paul Sereno
The Eoraptor lunensis site
in Argentina
Location: Ishigualasto
badlands of Argentina
Age
of fossil beds: Middle
Triassic, 228 million years old
Primary
Goals: Continue
investigation of dinosaur origins; explore
most remote regions of Ishigualasto valley
Accomplishments:
Discovery of 3-foot long articulated Eoraptor skeleton by Argentinian team member Riccardo
Martinez.
Scientific
Announcements:
Eoraptor
lunensis- announced 1993
Highlights:
"We had only just re-opened the door on
early dinosaurs and their world with the 1988
expedition. The Ischigualasto valley streched
some 75 miles in length, and much of it we had
yet to visit. The goals of this return expedition
were to explore more remote regions of the valley,
to search for bones of other early dinosaurs and
dinosaurian precursors, and to attempt to date
radiometrically the age of the beds.
Halfway through the season, Argentine team member
Ricardo Martinez discovered a small 3 foot-long
skeleton just coming to the surface. After detailed
cleaning back in the laboratory, the hollowed
skeleton of a new and very primitive predator
emerged. We dubbed this dinosaur Eoraptor,
or "dawn raptor," because its size and
form differed little from what we estimate is
the ancestral condition at the root of the dinosaur
family tree.
Eoraptor and the contemporary larger
predator Herrerasaurus,
however, show specializations that place them
with other theropods. The dinosaurian radiation
was underway, despite the fact that dinosaurs
were outnumbered at this time by other kinds of
reptiles. Volcanic ash deposits allowed us to
determine an accurate radiometric age for the
Ischigualsto beds nearest the dinosaurs--228 million
years old, plus or minus 300,000 years.
Returning to this area in 1991, we discovered
a small skeleton belonging to a new species aptly
named Eoraptor ("dawn raptor"). A primitive cousin
of Herrerasaurus,
Eoraptor measures only three feet from snout to
tail tip. Ancient volcanic ash beds discovered
near these early dinosaurs allowed Sereno's team
to determine their age--228 million years old--and
date the dawn of the dinosaur era. These discoveries
shed light on the roots of the dinosaur family
tree and on how and when dinosaurs came to dominate
the land." - Paul
Sereno |
