Sunday, 10 December, 2017

Over 200 fossilized eggs found in China reveal how pterosaurs breed

The discovery of 215 eggs of the pterosaurs species Hamipterus tianshanensis in China is providing new insights into the development and nesting habits of pterosaurs Scroll down for video
Theresa Hayes | 03 December, 2017, 05:38

They report that one of the eggs had a hatchling that was at least 2 years old, which supports a previous hypothesis: Pterosaurs need to develop in the egg for longer periods of time, similar to how human babies develop in the womb for nine months.

"It's the first time that embryos have been found in a three-dimensional and uncompromised condition, which has allowed many (embryological) details to be seen regarding these flying animals", said Brazilian paleontologist Alexander Kellner, one of the leaders of the research team. They also believe that some of these eggs and the individuals discovered were washed away from their colony due to the storm and eventually landed into the lake, where they were preserved and fossilized.

Kellner emphasised the importance of the large quantity of eggs: "They're very fragile, which always makes their preservation hard".

There are many more mysteries that remain about pterosaurs, Deeming writes, such as whether the eggs were buried as they developed and how many eggs were in each clutch.

The latest invention in northwestern China of hundreds of fossilised pterosaur eggs is giving a fresh knowledge of the flying reptiles that lived alongside the dinosaurs, including a sign that their babies were born flightless and needed parental care. Unfortunately, research for this species is hard due to the lack of pterosaur eggs discovered with their embryos clearly preserved. If pterosaurs hatched without teeth, then the young reptiles may have needed additional care or help with feeding. This, too, is an embarrassment of riches because it means scientists now have more information about how pterosaurs progressed from egg to adult than ever before.

Xiaolin Wang, the study's lead author and a paleontologist at the Chinese Academy of Sciences, described the site as a sort of "pterosaur Eden".

Neither birds nor bats pterosaurs were reptiles who ruled the skies in the Jurassic and Cretaceous periods

To understand why Unwin and others are freaking out about the discovery, published Thursday in the journal Science, you have to first appreciate how rare pterosaur eggs are.

As the waters raged on that ancient Chinese lake, numerous pterosaur eggs split open, letting in sediments that ultimately preserved their oblong shapes. There may be even more of them, but scientists haven't had time to properly analyze all the eggs, and CT scans are only partially useful.

"What's on my wish list?" says coauthor Alexander Kellner, a paleontologist at the Federal University of Rio de Janeiro.

Five of the eggs were also found in the Turpan-Hami Basin, where a huge lake once existed in the Cretaceous period. Each embryo varied in its stage of development, but all the eggs had well-developed thigh bones and underdeveloped pectoral muscles.

"We learned a lot", Kellner said "For example, the bones associated with wings were less developed compared to the embryos development with their legs".

In an accompanying article, Denis Deeming of University of Lincoln in Britain, touted the work as "a crucial advance in understanding pterosaur reproduction". Instead, Unwin thinks it more likely that a bunch of female pterosaurs simply laid their eggs in the same general area, much like female sea turtles returning to the same beaches year after year. Only a handful of isolated occurrences of eggs and embryos have been reported so far. Others boasted wild and insane crests, which may have been used to attract the opposite sex, as has been suggested with H. tianshanensis.