Paleontologists have discovered remains of about 40 male and female individuals of a new pterosaur species with five exceptionally well-preserved 3D eggs in the Early Cretaceous deposit in northwestern China. The discovery reveals that the pterosaurs lived together in gregarious colonies.
Life restoration of Hamipterus tianshanensis. Image credit: Chuang Zhao.
The pterosaur fossil record is generally poor, with little information about their populations. To date, only four isolated and flattened pterosaur eggs were known to the paleontological science.
Discovered in 2005 in the Turpan-Hami Basin, northwestern China, the new pterosaur fossil-rich site harbors thousands of bones, including male and female skulls and the first three-dimensional eggs.
“It was most exciting to find many male and female pterosaurs and their eggs preserved together. Five eggs are three-dimensionally preserved, and some are really complete,” said Dr Xiaolin Wang from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, who is the lead author of a paper published in the journal Current Biology.
Sediments in the area suggest that the colony died in a large storm in the Early Cretaceous period, about 120 million years ago.
Colony of Hamipterus tianshanensis. Image credit: Chuang Zhao.
Dr Wang’s team decided that the fossils belong to a previously unknown genus and species of pterosaur – Hamipterus tianshanensis.
The generic name, Hamipterus, is a combination of a reference to the region where the specimens were found and the Greek word ‘pteros’ (wing). The specific name, tianshanensis, refers to the Tian Shan Mountains in Xinjiang, China.
The paleontologists also examined the well-preserved pterosaur eggs to find that they were pliable, with a thin, calcareous eggshell outside and a soft, thick membrane inside, similar to the eggs of some modern-day snakes.
Fossil egg of Hamipterus tianshanensis. Scale bar – 2 cm. Image credit: Xiaolin Wang et al.
Their analysis of 40 pterosaur individuals suggests differences between the sexes in the size, shape, and robustness of their head crests. The combination of many pterosaurs and eggs strongly indicates the presence of a nesting site nearby and indicates that this species developed gregarious behavior.
Hamipterus tianshanensis most likely buried their eggs in sand along the shore of an ancient lake to prevent them from drying out.
While the new fossils shed light on the reproductive strategy, development, and behavior of pterosaurs, there is still plenty left to learn about them.
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Xiaolin Wang et al. Sexually Dimorphic Tridimensionally Preserved Pterosaurs and Their Eggs from China. Current Biology, published online June 05, 2014; doi: 10.1016/j.cub.2014.04.054
