Pterosaurs: dragons of the air
The Jurassic: birds take flight
A global rise in sea level and an adaptive radiation of pretty well everything that survived the end Triassic extinction saw the beginning of the Jurassic. Famous for its dinosaurs like Stegosaurus, and the super abundant ammonites, the Jurassic was a period of great diversification of life. Some bony fishes, such as Leedsichthys achieved sizes comparable with today’s baleen whales, while gigantic marine reptiles like the pliosaur, Liopleurodon, one of the star animals in the BBC’s Walking With Dinosaurs TV series, were top predators in the seas. The Jurassic saw global sea levels going up and down on several occasions, and the beginning of the opening of the Atlantic Ocean. The Tethys Ocean widened and spread west. There is little evidence for any ice caps during this period, and tropical climates persisted much further north than they do today.
Global reconstruction courtesy of Professor Ron Blakey, Northern Arizona University, Geology.
Photograph of the Eichstätt specimen courtesy of Robert Loveridge
Archaeopteryx lithographica: the early bird
Archaeopteryx is a small theropod dinosaur with feathers. It also has a mouthful of sharp, recurved teeth and fingers with claws on its wings. It lacks the avian pelvis or shoulder girdle, and without its feathers, it would not have attracted much attention at the time of its discovery in 1860.
Archaeopteryx is a classic example of a ‘transitional fossil’ exhibiting features found in meat-eating dinosaurs, but also possessing features shared by birds, in this case, most notably feathers.
Anchiornis: the oldest feathered dinosaur
This image shows a small dinosaur (about 40cm long) from Mid to Late Jurassic rocks in Liaoning Province, China. An analysis of its feathers revealed evidence of colour patterning and, for the first time in a dinosaur, the preservation of pigment cells that enabled the original colour to be established. It had mainly grey and white wing feathers with spots and stripes. The crown of the head was rufous grading into grey, while the legs were grey and the feet black.
Anchiornis is somewhat older than Archaeopteryx, usually credited with being the first dino-bird. Furthermore, it is a very different type of dinosaur to Archaeopteryx, belonging to a group called the troodontids (pronounced true oh dont id). It is unclear if Anchiornis was capable of sustained flight.
Picture kindly supplied by Michael A. DiGiorgio. See more of his artwork at www.natureartists.com/michael_digiorgio.asp
Drawing from Owen, 1870
The first British pterosaur
Dimorphodon macronyx (Buckland, 1829) was not the first pterosaur to be found in Britain, but it was the first to be named.
It fell to the eccentric Dean William Buckland of the University of Oxford to recognise that a specimen discovered by Mary Anning, a commercial fossil dealer of Lyme Regis, was a new species of pterosaur. Mary Anning found the specimen in 1828 and, a year later, Buckland named it Pterodactylus macronyx.
Later, Sir Richard Owen reappraised Buckland’s specimen and quickly realised that it was a completely new type of pterosaur and renamed it Dimorphodon.
Since 1829 only one other specimen with a skull has been found of this animal. Dimorphodon therefore is an extremely rare pterosaur, and although it has only been found in marine rocks, it probably was not a coastal animal: its rarity reflecting the infrequence with which terrestrial animals were blown out to sea.