BEIJING, Jan. 31 (Xinhuanet) -- A recent finding of a
Stegosaurus fossil in Europe -- the first ever outside of North America --
supports a widely accepted theory the two continents were connected at one time
by a series of temporary land bridges.
These land bridges surfaced when
sea levels dipped allowing the famous plated dinosaur -- and other dinosaur
species -- to cross.
"Both coasts were very close and the basins between
them could emerge occasionally," said study leader Fernando Escaso of the
University of Autonoma in Madrid, Spain.
All of the world's continents were clumped together
into one giant landmass called Pangaea when dinosaurs first roamed the planet.
At the end of the Jurassic Period, about 150 million years ago, the
supercontinent began slowly separating and North America, Europe and Africa
began to drift apart giving birth to the Atlantic Ocean.
There were times during this million-years long
transformation when sea levels rose and fell. Sometimes, land
bridges emerged between the newly sundered landmasses. It was then
dinosaurs like Stegosaurus would have been able to cross.
Easily recognized by any dinosaur enthusiast,
Stegosaurus was a bizarre looking herbivorous creature that had a back adorned
by a double row of vertical plates and a tail studded with spikes. It was once
thought these strange accessories were for protection or used to radiate heat
from the dinosaur's body.
But now most scientists think the body armor was
probably just an extreme example of the elaborate and colorful displays animals
use to recognize each other as the same species.
The scientists unearthed the new Stegosaurus fossils
-- which included a tooth and parts of the animal's spinal column and leg bones
-- near the city of Batalha, in central Portugal. Preliminary analyses show the
fossils to be indistinguishable from a species previously found only in North
America, called Stegosaurus ungulatus.
While the similarity bolsters the land-bridge case,
it provides no information on when the land bridges emerged.
"At present, it isn't possible to know the structure,
frequency and duration of these land bridges," Escaso told LiveScience.
Peter Makovicky, a paleontologist at the Field Museum
in Chicago who was not involved in the study, said the new Stegosaurus discovery
supports something largely suspected in the past and helps flesh out some of the
geological history of the region.
"It documents the second genus of dinosaurs that's
well-known from the Jurassic of North America to be present in Europe, and
thereby gives evidence that there was a fairly strong connection between these
areas during that time,"” Makovicky said in a telephone interview.
The only other dinosaur for which bones have been
found in both North America and Europe is a species of Allosaurus, a large
meat-eating dinosaur similar to Tyrannosaurus rex, but without the latter's
The new finding will be detailed in an upcoming issue
of the German science journal Naturwissenchaften.