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Rare Fossil Preserves Pterosaur Mom and Egg

Enlarge Image credit: Image courtesy of Lu Junchang, Institute of Geology, Beijing MORE IMAGES

About 160 million years ago a female pterosaur with an injured wing dropped from the sky into a watery grave. She was carrying a single, nearly mature egg. "After this she drowned, her carcass became waterlogged, sank to the bottom and, as decay processes began, the egg was expelled from her body," wrote researchers who described the fossil in the January 21 issue of Science.

The specimen, recovered from the Tiaojishan Formation in Liaoning Province, China, preserves an adult female of the genus Darwinopterus with a 0.78-meter wingspan and an egg the size of an elongated quarter just below her pelvis.

Determining fossil gender is a challenge, but the presence of the egg is strong evidence this individual was a mature female. Her unadorned skull lends support to the hypothesis that Darwinopterus displayed sexual dimorphism, with males sporting a bony Mohawk-like crest. The crumpled but uncracked appearance of the egg suggests that it had a soft, parchment-like shell. It is likely that pterosaurs buried their eggs in underground nests, allowing the eggs to soak up water and gain mass during incubation, a technique used by modern lizards and snakes. Although some features of pterosaur physiology, such as the extent of body temperature regulation, resemble those found in birds and even bats, pterosaurs were "demonstrably reptilian" in their parental duties, the new paper suggests.

The fossil, dubbed "Mrs. T" by the researchers, is one of 11 Darwinopterus specimens that have been recovered from the formation. It is currently housed in the Zhejiang Museum of Natural History, which purchased Mrs. T from a local farmer.

Nina Bai

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