Huge haul of rare pterosaur eggs excites palaentologists.
NYT Syndicate A remarkable fossil slab containing hundreds of
pterosaur eggs and some embryos has been discovered in China. The find
looks set to transform palaeontologists' understanding of these
enigmatic creatures. The early life of pterosaurs " the first
vertebrates to evolve powered flight " has been a mystery. It was
only in 2004 that scientists even confirmed that they laid eggs, and
until now, only a handful of eggs had been found. The newly discovered
trove, belonging to a species called Hamipterus tianshanensis that lived
around 120 million years ago, offers clues into the development and
anatomy of freshly hatched pterosaurs. It also provides the first solid
evidence that, like many dinosaur species, these animals nested in
groups. The fossils, reported in the December 1 issue of Science, were
discovered in the Turpan-Hami Basin in Xinjiang, northwestern China.
From 2006 to 2016, Wang Xiaolin of the Chinese Academy of Sciences'
Institute of Vertebrate Paleontology and Paleoanthropology in Beijing
and his colleagues excavated a 3 square-metre sandstone block to reveal
at least 215 squashed and cracked eggs among jumbled pterosaur bones.
They think that up to 300 eggs could be present, some buried below the
upper layers of fossils. The team used computed tomography scanning to
peer inside 42 eggs, and found 16 that contained the remains of embryos
at various stages of development, with partial skulls and limb bones.
Other experts say that the find will be significant for understanding
pterosaur reproduction. It's"a crucial advance," writes
Charles Deeming, who studies bird and reptile reproduction at the
University of Lincoln, UK, in a commentary also published in Science.
Mark Witton, who researches the reptiles at the University of
Portsmouth, UK, says that H tianshanensis now"has the potential to
be one of the most completely known pterosaurs of all." GROUP
NESTING Although the eggs are not in their original nest positions
" they were probably washed together by a storm event " the
authors argue that the series of embryos and juveniles at different
developmental stages strongly suggests that they nested as a
group."This is something we've long suspected might happen,
but it's neat to see it confirmed with fossils," says Witton.
Further examination of the microscopic structure of the embryonic bones
also revealed a surprise, says Wang. Until now, the consensus has been
that hatchling pterosaurs could fly almost from birth. The team found
well-developed femur (thigh) bones, which are important for walking
" but the animals' forelimbs, which are necessary for flight,
were underdeveloped."We conclude that 'baby' pterosaurs,
at least Hamipterus, can walk on the ground, but not fly in the
sky," says Wang. But Witton isn't convinced. He thinks that
most pterosaurs probably had well-developed wings upon hatching, but
that some features were made of cartilage, which is less likely to
fossilise."These animals would weigh just a few grams when hatched,
and almost certainly didn't need crisply sculpted, well-ossified
wing bones to fly," he says."Cartilage would be strong
enough." His own team's work, presented in September at the
Symposium on Vertebrate Palaeontology and Comparative Anatomy in
Birmingham, UK, have found that hatchling fossils of two other pterosaur
species do look flight-ready, with bones that appear robust and have
high bending strength. Deeming also cautions against inferring too much
from what remains a limited data set " perhaps the embryos studied
by Wang weren't close to hatching after all, he suggests.
Paleontologist and co-author of the Science paper Alexander Kellner, of
Brazil's National Museum at the Federal University of Rio de
Janeiro, hopes that other eggs already being unearthed from the Xinjiang
site will fill some gaps."We hope to find embryos in different
stages," he says,"to have a complete embryological
[c] Copyright Qatar Tribune. All Rights Reserved. Provided by
SyndiGate Media Inc. ( Syndigate.info ).