Pterosaurs: dragons of the air
After more than 200 years of collecting pterosaurs, palaeontologists now know of slightly more than 60 different genera containing around 100 species. Counts vary because the validity of some species based on fragmentary remains is in doubt. About half of these pterosaurs have been discovered in the last 30 years. This sudden increase is certainly in part due to the rapid increase in palaeontological research by museums and universities, but it is also due to three or four major discoveries. In Brazil two new horizons have been found with pterosaur remains in abundance: the Crato and Santana formations in the Araripe Basin. A similar story applies to China where three formations – the Daohugou Beds (including the Tiaojishan Formation) and the Yixian and Jiufotang formations – have all yielded exciting new pterosaur remains. Elsewhere too, new pterosaurs have been found, including in Morocco, Argentina and Mongolia. And quite remarkably, several new pterosaurs have been found in the Solnhofen Limestone in Germany, 200 years after the first specimen was discovered there in 1784.
Traditionally, pterosaurs were divided into two groups, the so-called ‘rhamphorhynchoids’ with long tails and the pterodactyloids with short tails, but this classification was oversimplistic and tended to obscure their true evolutionary relationships. Indeed, some long-tailed ‘rhamphorhynchoids’ like Anurognathus had short tails and recently a new pterosaur called Darwinopterus has been found with a pterodactyloid head and neck, but a long tail more typical of earlier pterosaurs, making us change our ideas about pterosaur evolution.
The pterosaur tree of life (above) shows the current classification of pterosaurs. It is based on an analysis of more than 100 characters from 57 different pterosaurs and was presented recently in a paper published by the Royal Society by Lü Junchang, David Unwin and others in 2009. It is the most up-to-date and thorough analysis of pterosaurs yet undertaken.