September 16. The First Pterosaurs

By late Triassic time, reptiles had diversified a lot, and were occupying more and more ecological niches. We’ve already talked about some of the aquatic reptiles, and today our topic is the first reptiles – in fact the first vertebrates – that learned to fly. Pterosaurs’ name means “winged lizard” and they first appear in the rock record in the first part of the late Triassic, around 220 to 225 million years ago. 

Eudimorphodon, Triassic flying reptile. Photo by Tommy from Arad, under Creative Commons license

The first fossils, discovered in Jurassic rocks in 1784, were thought to be aquatic, but in 1801 Georges Cuvier suggested that they were flying animals, and that idea has survived the test of time. In pterosaurs, generally the fourth finger of the front legs is tremendously extended to support the flap of skin that served as the wing. Triassic varieties mostly had teeth – in some cases lots of teeth, even as many as 110 in a jaw only 6 centimeters (2½ inches) long. They are generally seen as fish-eaters, but they might have eaten insects as well. There’s some evidence that their bodies were at least partially covered by hair or fur.

Most of the known Triassic pterosaurs are from Europe, with most species represented by just one or two specimens. The first Triassic pterosaur wasn’t described until 1973. Their wingspans were small compared to the giants that would evolve by Jurassic and Cretaceous times – Triassic pterosaurs had wingspans ranging from about 1½ to 4 feet. One possible pterosaur from Brazil was about the size of a sparrow.

Because of the paucity of Triassic pterosaur specimens, their early heritage remains uncertain. They are definitely not dinosaurs, nor are they related to birds, which descended from dinosaurs. It’s not even clear whether they are descended from the common archosaurs, perhaps from a gliding variety, or from some other reptile lineage. They do appear relatively suddenly in the fossil record, during the Norian stage of the upper Triassic, but whether this represents a true sudden appearance or is a reflection of the poor preservation isn’t certain.

* * *

Today’s birthday is my professor of geophysics at Indiana University, Judson Mead, born September 16, 1917, in Madison, Wisconsin. He was part of the team during World War II that developed airborne submarine detectors using magnetometers. He taught geophysics at Indiana from 1949 to 1983, and was the director of the Indiana University Geologic Field Station in Montana from 1960 to 1980.

—Richard I. Gibson

Links:
Triassic pterosaurs 

Triassic pterosaurs (U of Bristol)

Photo by Tommy from Arad, under Creative Commons license