2011-12-14 17:38:47
Pterosaurs, flying reptiles related to dinosaurs, ruled the skies during the Mesozoic era, between 230 and 65 million years ago. They lived with the dinosaurs, and they were ahead of the birds by about 75 million years. Until recently, pterosaurs were divided into two distinct groups, the ranforhynches and the pterodactyls.
The more primitive ranforhynches appeared in the Late Triassic and became extinct at the beginning of the Cretaceous, about 125 million years ago. They are characterized by their small size and long tail. They generally lack a bony crest on their heads, and their jaws are well-supplied with teeth.
Pterodactyls, descendants of the ranforhynches, appeared in the Middle Jurassic, about 160 million years ago, and did not become extinct until the end of the Cretaceous. They are distinguished mainly by having a short tail and longer wing bones. Many were toothless and had bony ridges on their skulls.
In the fossil record, the two groups were completely separate; no intermediate forms were known. But in 2009, an international group of paleontologists from the University of Leicester (England) and the Beijing Geological Institute (China) discovered the fossil remains of a new pterosaur that fits neatly between the two groups, the darwinoptera. This is the same site where the remains of Anchiornis were found, which we already talked about a few months ago.
Baptized with the name of Darwinopterus modularis, the Darwinoptera lived 160 million years ago. It was an animal the size of a crow, with long jaws, sharp teeth, and a flexible neck, fast in flight, and hunted other flying animals: small gliding mammals, feathered dinosaurs ancestors of birds, and other pterosaurs.
The anatomy of the Darwinoptera is intermediate between that of the ranforhynches and that of the pterodactyls, but not because their characters are intermediate as a whole, but because it is a mosaic of “archaic” characters, of a ranforhynchus (the trunk, the short wings and the long tail), and “advanced” characters, of pterodactyl (head and neck). Thus, it seems that the evolution of pterosaurs was carried out in a “modular” way, by blocks. Hence the specific name (modularis) given to the new fossil. Among the dozens of Darwinoptera specimens found, a female with an egg has been discovered, which represents the fourth known pterosaur egg in the world.
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