Darwinopterus

Darwinopterus (meaning "Darwin's wing") is a genus of pterosaur, discovered in China and named after Charles Darwin. It is the first known pterosaur to display features of both long-tailed (rhamphorhynchoid) and short-tailed (pterodactyloid) pterosaurs. Darwinopterus is a transitional fossil between the two groups.Dell'Amore, C. (2009). "Odd new pterosaur: 'Darwin's wing' fills evolution gap." National Geographic News, 13 October 2009. 

Between 30 and 40 fossil specimens have been found,Hecht J. 2011. Did pterosaurs fly out of their eggs?" New Scientist online edition, 20 Jan 2011. all collected from the Tiaojishan Formation, which dates to the Middle Jurassic, 160 million years ago (mya). The type species, D. modularis, was described in February 2010.Lü J. Unwin D.M. Jin X. Liu Y. and Ji Q. 2010. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society B, 277(1680): 383-389.  PMID 19828548 

Two additional species, D. linglongtaensis and D. robustodens, were described from the same fossil beds in December 2010 and June 2011, respectively.Lü J. Xu L. Chang H. and Zhang X. 2011. A new darwinopterid pterosaur from the Middle Jurassic of western Liaoning, northeastern China and its ecological implications. Acta Geologica Sinica - English Edition, 85(3): 507–514. 

The specimens showed sexual dimorphism: the males had crests on their heads, and narrower hips than the females.

 Mosaic features 
This genus, and its near relatives, show a combination of 'primitive' (basal) and 'advanced' (derived) pterosaurian features. This is characteristic of transitional fossils ('missing links'), and is called modular evolution or mosaic evolution.

Darwinopterus had long tails and other features of rhamphorhynchoids, they also had distinct pterodactyloid features, such as long vertebrae in the neck and a single skull opening in front of the eyes.

 Eggs 
The specimen preserved along with an egg gave information on the reproductive strategies of Darwinopterus and pterosaurs in general.Lü J. Unwin D.M. Deeming D.C. Jin X. Liu Y. and Ji Q. 2011. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324.  PMID 21252343 

Like the eggs of later pterosaurs and modern reptiles, the eggs of Darwinopterus had a parchment-like, soft shell. In modern birds, the eggshell is hardened with calcium carbonate, completely shielding the embryo from the outside environment.Except for the diffusion of gases. Soft-shelled eggs are permeable to water, and allow significant amounts to be absorbed into the egg during development. Eggs of this type are more vulnerable to the elements and are typically buried in soil. 

David Unwin, a co-author of the paper, suggested that Darwinopterus probably laid many small eggs at a time and buried them. Juveniles could fly upon hatching, and required little to no parental care. 

These results imply that reproduction in pterosaurs was more like that in modern reptiles and significantly differed from reproduction in birds.

 References 

Category:Pterosaurs