WASHINGTON (Reuters) - A spectacular
fossil find in China - a prehistoric egg extravaganza from 120 million
years ago - is providing unique insight into the lifestyle and gender
differences of pterosaurs, the flying reptiles that lived alongside the
dinosaurs.
Until now, only four pterosaur eggs had ever been found, and all
were flattened during the process of fossilization.
But Chinese scientists said on Thursday they had unearthed five
pterosaur eggs preserved beautifully in three dimensions at a site
in northwestern China that also includes no fewer than 40 adult
individuals of a newly identified species that lived in a bustling
colony near a large freshwater lake.
"This is definitely the most important pterosaur site ever found,"
said paleontologist Zhonghe Zhou, director of the Chinese Academy of
Sciences' Institute of Vertebrate Paleontology and
Paleoanthropology.
The creature, Hamipterus tianshanensis, had a crest atop its
elongated skull, pointy teeth for catching fish and a wingspan of
more than 11 feet (3.5 meters).
The five oblong eggs were "pliable" with a thin, hard outer layer
marked by "cracking and crazing" covering a thick membrane inner
layer, making them resemble the soft eggs of some modern snakes and
lizards, said paleontologist Xiaolin Wang, another of the
researchers.
"They are the best-preserved pterosaur eggs ever found," Wang said.
The site was remarkable for what it reveals about how pterosaurs
lived. At least 40 male and female individuals have been identified,
and there may be hundreds in all, Wang said.
The site indicates pterosaurs lived in large colonies, in this case
nesting near the lake and burying eggs in moist sand to prevent them
from becoming desiccated, Wang said.
"One of the significant (aspects) of this discovery - hundreds of
individuals and eggs together from one site - is that it confirmed
that pterosaurs were gregarious, and the population size is
surprisingly large," Zhou said.
The fossils illustrated important sex differences in pterosaurs. For
example, males possessed distinctly larger head crests.
"In Hamipterus, size, shape and robustness are decided by the
gender," Wang said, adding that this contradicts a previous notion
that "sexual dimorphism in pterosaurs was only reflected in the
absence or presence of the crests."
The site, discovered in Xinjiang province in 2005, was preserved
probably after the Cretaceous period creatures perished together in
a large storm, Zhou said.
Pterosaurs were Earth's first flying vertebrates, with birds and
bats appearing much later. They thrived from about 220 million years
ago to 65 million years ago, when they were doomed by the asteroid
that also killed the dinosaurs.
Knowledge about pterosaurs has been spotty, with their fragile
skeletons not lending themselves well to fossilization. Little has
been known about their behavior.
"I have been truly amazed by the abundance of bones and the number
of eggs as well the great potential of more discoveries from the
site," Zhou said.
The genus name, Hamipterus, means "Hami wing," honoring nearby Hami
City. The species name, tianshanensis, refers to the nearby Tian
Shan mountains.
The study appears in the journal Current Biology.
(Reporting by Will Dunham; Editing by Jonathan Oatis)
Stunning
fossil eggs provide insight on ancient flying reptiles
