Fossil Record

Tupuxuara, Pteranodon skeleton & skeletal plaque, and Quetzalcoatlus arm

American Museum of Natural History, New York, USA

Pterosaurs lived during the Triassic, Jurassic, and Cretaceous, the three periods of the Mesozoic Era, poularly known as the "Age of Dinosaurs." They were the dominant form of flying vertebrate for millions of years, though they shared their ecospace with birds beginning in the Late Jurassic.

Triassic * Jurassic * Cretaceous


 

Eudimorphodon amid the canopy of an Araucarioxylon forest (Chinle Formation, Arizona, USA)

By Douglas Henderson; used with permission

 Triassic

248-206 million years ago

Pterosaurs appear very suddenly in the fossil record, and their ancestry is very poorly understood. They are close relatives of dinosaurs, but what precisely did they evolve from? Perhaps the most likely candidate so far is a small archosaur from the Lossiemouth Sandstone of Scotland known as Scleromochlus. It has a skull similar to those of pterosaurs and it may have been arboreal. It is also possible that Scleromochlus was a glider, a mode of life that could have given rise to pterosaur flight. However, the proportions of its limbs (long legs and short arms) are exactly opposite the condition in pterosaurs. Until more evidence comes to light, the origin of pterosaurs will remain a major unknown.

The earliest known true pterosaur is Eudimorphodon. It was first identified in ~220 million year old rocks from Northern Italy. Since then, it has also been identified in Austria, Luxembourg, Greenland, and possibly Texas. There are three other known genera of Triassic pterosaur (Austriadactylus, Peteinosaurus, and Preondactylus), all from Central Europe. All were fairly small and probably subsisted on fish and insects.

 

Two pterosaurs soar above a herd of Camarasaurus (Morrison Formation, Colorado, USA)

By Douglas Henderson; used with permission

 Jurassic

206-144 million years ago

The Jurassic saw a major diversification of pterosaurs both morphologically and geographically, as widespread adaptation to new sizes, niches, and environments occurred. Most of the main groups of pterosaurs evolved at this time, and many well-known genera such as Dimorphodon, Pterodactylus, and Rhamphorhynchus lived in the Jurassic.

The Solnhofen Limestone of the Late Jurassic of Germany is one of the best sites in the world for pterosaur fossils both in terms of diversity and the quality of the fossil record. The formation probably represents a low-oxygen lagoonal environment which allowed soft tissues such as wing membranes to be preserved in extraordinary detail.

 

Pteranodon over the Western Interior Seaway (Two Medicine Formation, Montana, USA)

By Douglas Henderson; used with permission

 Cretaceous

144-65 million years ago

The Cretaceous saw the evolution of the largest pterosaurs, as well as the appearance of fully toothless forms. One of the best known pterosaurs is Pteranodon from the Cretaceous of the Central United States, famous both for its long crest and large size (up to as much as 9 metres in some species). The more recently discovered Quetzalcoatlus, discovered in Texas and named for an Aztec god, would have dwarfed this though, with a wingspan of up to 12 metres. Even more spectacularly, scattered remains from Mexico and Israel hint at forms with wingspans greater than 18 metres!

The Santana Formation of Brazil has become internationally famous for its well-preserved pterosaur remains (as well as for their presumed food, a wide diversity of fish). Among the genera discovered here are the spectacularly-crested Tapejara and a number of ornithocheroid pterosaurs.

Pterosaurs went extinct at the end of the Cretaceous Period, 65 million years ago, along with many other organisms.



Author: John D. Orcutt

Last Updated: 11/2005

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