Pterosaur hatchlings needed their parents, trove of eggs reveals (Update)

November 30, 2017

Hundreds of pterosaur bones lying on the surface, demonstrating the richness of these sites. Credit: Alexander Kellner (Museu Nacional/UFRJ)
The largest collection of fossilized pterosaur eggs ever found has shown that pterosaurs, the airborne cousins of dinosaurs, could not fly right away and needed care from their parents, researchers said Thursday.

Pterosaurs were reptiles, and the first creatures—after insects—to evolve powered flight, meaning they flapped their wings to stay aloft instead of simply jumping and gliding.

First known to exist as many as 225 million years ago, they went extinct along with the dinosaurs about 65 million years ago.

Until now, scientists had found some pterosaur eggs with remains inside, including three in Argentina and five in China.

But the latest report in the peer-reviewed US journal Science is based on the biggest collection to date—215 fossilized eggs that were found in a 10-foot (three-meter) long sandstone block in northwestern China's Hami City, Xinjiang Uygur Autonomous Region.

"Since these are extremely fragile fossils, we were very surprised to find so many in the same place," Brazilian paleontologist Alexander Kellner told AFP.

"Because of this discovery, we can talk about the behavior of these animals for the first time."

Needed their parents

Sixteen of the eggs contained fossilized remains of a pterosaur species known as Hamipterus tianshanensis.

Rotation along the long (polar) axis of the egg. Credit: Wang et al., Science (2017)

As adults, these creatures would have stood about four feet tall, with a wingspan of 11 feet.

None of the eggs held a full set of pterosaur bones, likely because pieces were lost over the years due to storms and floods.

But scientists did find partial wing and skull bones, along with one complete lower jaw, which fill in aspects of pterosaurs' life cycle that have been poorly understood until now.

Using three-dimensional computed tomography scans, they discovered intact and well-developed thigh bones suggesting the creatures "benefited from functional hind legs shortly after hatching," said the report.

But their chest muscles were weak.

Pterosaur lower jaw eroding on the surface. Note the large teeth, one of the characteristics of Hamipterus tianshanensis. Credit: Alexander Kellner (Museu Nacional/UFRJ)
"This shows that when pterosaurs hatched, they could walk but not fly," said Kellner.

"They needed their parents. This is one of the biggest discoveries we have made."

Exceptionally preserved eggs and embryos reveal the life history of a pterosaur
Embryo 12, the most complete one, containing a partial wing and cranial bones, including a complete lower jaw. Photo and line drawing showing the lower jaw exposed in ventral view (A, B), scale bar 10 mm; (C) Close-up of the lower jaw, scale bar 5 mm; (D) Close-up of the anterior portion of the lower jaw in left view, scale bar 1 mm. Credit: WANG Xiaolin
Nesting behavior

Adult pterosaur bones were also scattered across the site, a sign that they returned to the same nesting spots over time, much the same as modern day sea turtles.

The massive numbers of eggs and bones point to major storms thrashing the site, submerging the eggs in a lake where they floated briefly before sinking and becoming buried alongside adult skeletons.

Pterosaur egg in the field. Note the fragility of this material. Credit: Alexander Kellner (Museu Nacional/UFRJ)

Researchers also noted that the cracked exterior of the eggs resembled the fragile softness of lizard eggs.

"All are deformed to a certain extent, which indicate their pliable nature," said the study.

One of the young pterosaurs was estimated to be "at least two years old and still growing at the time of its death, supporting the growing body of evidence that pterosaurs had long incubation periods."

Pterosaur eggs, preserved. Credit: Wang et al., Science (2017)

An accompanying article in the journal Science, written by D. Charles Deeming of the University of Lincoln, called the study "remarkable for the number of eggs in association with adults and juvenile pterosaurs that it reports on."

However, many questions remain, including whether the size of each clutch was really two as previous studies have suggested, just how the pterosaurs concealed their eggs, whether beneath vegetation or sand or soil, and why so many of the eggs appear dehydrated.

Life reconstruction of Hamipterus tianshanensis. Credit: ZHAO Chuang
"Hopefully additional finds of equally spectacular fossils will help us answer such questions," he wrote.

More than 200 eggs of Hamipterus tianshanensis preserved in sandstones (IVPP V 18941 to 18943), scale bar 200 mm. Credit: Wang Xiaolin

Explore further: First 3D pterosaur eggs found with their parents

More information: X. Wang el al., "Egg accumulation with 3D embryos provides insight into the life history of a pterosaur," Science (2017). science.sciencemag.org/lookup/ … 1126/science.aan2329

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7 comments

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TheGhostofOtto1923
5 / 5 (1) Dec 03, 2017
Why is nobody commenting on this? This is spectacular. There may be soft tissue and proteins there as well-
Captain Stumpy
not rated yet Dec 03, 2017
There may be soft tissue and proteins there as well-
one can only hope that there is and that it's viable

I don't expect that there will be, however
Captain Stumpy
not rated yet Dec 03, 2017
In a 2.2-m section, eight layers with pterosaur bones have been identified, four of which show egg concentrations in a vertical distance of 1.4 m. This sedimentological data, associated with the exceptional quantity of eggs and bones, indicate that events of high energy such as storms have passed over a nesting site, causing the eggs to be moved inside the lake where they floated for a short period of time, becoming concentrated and eventually buried along with disarticulated skeletons. Our findings further demonstrate the exceptional conditions necessary for the preservation of such fragile material and can explain the notable paucity of pterosaur eggs and embryos in the paleontological record compared to other reptiles (25), because the preservation potential of soft-shelled specimens is regarded as very poor (26). Furthermore, this occurrence implies colonial breeding for Hamipterus tianshanensis, as demonstrated by the osteohistological identification of individuals ...
-SCIENCE
TheGhostofOtto1923
5 / 5 (1) Dec 03, 2017
I don't expect that there will be, however
Why not?

"Acid dissolution
Acids can be used to learn more about fossil eggs... Even fossilized soft tissue like muscle and cartilage as well as fat globules from the original egg yolk can be uncovered using this method.[68] Amateur paleontologist Terry Manning has been credited with groundbreaking work developing this technique... First, the paleontologist must submerge the egg in a very dilute phosphoric acid..." etc

And

"The rib of a long-necked, plant-eating dinosaur that lived 195 million years ago has yielded what may be the oldest remains of soft tissue ever recovered..."
the exceptional conditions necessary for the preservation of such fragile material and can explain the notable paucity of pterosaur eggs
-Right. But since these eggs were in fact preserved, this might mean that under these rare conditions soft tissue and proteins could also have survived.
TheGhostofOtto1923
5 / 5 (1) Dec 03, 2017
Nope, thank You - I'm after dinner already.
Was it by chance chicken?
https://drakewolf...64612745

-I just had some salad bar chicken wings that may have been that old.
Captain Stumpy
not rated yet Dec 03, 2017
@Otto
Why not?
see below
But since these eggs were in fact preserved, this might mean that under these rare conditions soft tissue and proteins could also have survived.
True, and I remain hopeful, but I also know it is a difficult task because a phosphoric acid bath can also harm the sample

there is no guarantee
-I just had some salad bar chicken wings that may have been that old.
where were you eating?
I would like to avoid that place at all costs! LMFAO
https://drakewolf95.deviantart.com/art/Chickenosaurus-664612745
that is a cool pic!
great artist!
TheGhostofOtto1923
5 / 5 (1) Dec 03, 2017
where were you eating?
Acme market I think? Soft tissue barely discernable. Fossilization in progress. Salt and vinegar embalming solution.

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