London: Dinosaurs lived on Earth almost 10
million years earlier than previously thought, a new discovery
has suggested.
An international team has in fact based its conclusion
on the discovery of a four-legged ancestor of the prehistoric
creatures that hails from 250 million years ago, the 'Nature'
journal reported.
The large dog-sized creature, which ate meat
and vegetation, seems to be a similar relation to dinosaurs as
chimps are to humans, say palaeontologists who have analysed
the fossils found in Tanzania and dubbed it a "proto-saur".
According to the of palaeontologists, dinosaurs and
other close relatives such as pterosaurs -- flying reptiles
often described as pterodactyls -- might have also lived much
earlier than previously thought.
"Everyone loves dinosaurs. But this new evidence
suggests that they were really only one of several large and
distinct groups of animals that exploded in diversity in the
Triassic, including silesaurs, pterosaurs, and several groups
of crocodilian relatives.
"This goes to show that there are whole groups of
animals out there that we've never even found evidence of that
were very abundant during the Triassic. It's exciting because
it means there is still so much chance for discovery," team
leader Dr Sterling Nesbitt of Texas University said.
The new species, called Asilisaurus kongwe, is part
of a sister group to dinosaurs known as silesaurs. Silesaurs
are considered dinosaur-like because they share many dinosaur
characteristics but still lack key characteristics all
dinosaurs share.
Even though the oldest dinosaurs discovered so far
are only 230 million years old, the presence of their closest
relatives 10 million years earlier implies that silesaurs and
the dinosaur lineage had already diverged from common
ancestors by 240 million years ago.
Silesaurs continued to live side by side with early
dinosaurs throughout much of the Triassic Period (between
about 250 and 200 million years ago). And, this is the first
dinosaur-like animal recovered by palaeontologists from the
Triassic Period in Africa.
Fossil bones of at least 14 individuals were recovered
from a single bone bed in southern Tanzania making it possible
to reconstruct a nearly entire skeleton. Each individual stood
about 1.5 to 3 feet tall at the hips and were three to 10 feet
long. They weighed about 22 to 66 pounds.
PTI
First Published: Saturday, March 06, 2010, 10:00