PTEROSAURS

These winged reptiles originated about 220 million years ago (mya) during Late Triassic, and they went extinct about 66 mya, at the end of the Cretaceous Period; thus, they lived during a span of approximately 155 million years (see Fig. 1).

Figure 1. Geologic time scale (2012, via the Geologic Time Scale Foundation). Pterosaurs ranged from the middle Triassic (in purple color at the bottom of this figure) to the end of Cretaceous time (Maastricthian time) (in light green color at the top of this figure).  

Pterosaurs have been commonly referred to as pterodactyls, but the term pterosaurs is most commonly used one these days. Their bones are hollow, thus they do not preserve well. As a result, their fossil record is rather poor. Nevertheless, their remains are found on every continent. 

Currently, there are 281 reported genera or pterosaurs; see Wikipedia for a list. 

Based on wing structure, it is known that pterosaurs did not evolve into birds. For a comparison of the wing-bone structure of pterosaurs versus other flying animals, see Fig. 2. Nevertheless, pterosaurs were the earliest vertebrates known to have evolved powered flight. Some species of pterosaurs had long reptilian tails.

Figure 2. Wing comparisons of a bird, a bat, and a pterosaur.   

Pterosaur wings were not feathered. Instead, they were formed by a membrane of skin and muscle. Their skeleton was lightweight but very strong, with their bones about 80 percent stronger than similar mammal bones. Pterosaurs were strong fliers and had powered flight. They ranged in size from Nemicolopterus, with a 10 inch (25 cm) wingspan, to the largest known species of pterosaurs, which was Quetzalcoatus northropi (pronouonced “its-so-quat-a-lus), from West Texas (Figure 3). 

Figure 3. Quetzalcoatus northropi. It is estimated that Q. northropi weighed about 200 to 500 pounds, with a long head and a strong neck. A crest on its nose most likely allowed subtle changes in body to adjust for variable flight patterns. As it was bipedal, it could walk along shorelines and eat dead fish and mollusks, etc.

Figure 4. Pteranodon was another large Cretaceous-age pterosaur (Fig. 4).  It had a very large crest on its skull, the function of which is unknown; nevertheless, it has been speculated as being an “air brake” or a demonstration as to rank, or etc. etc. Many pterosaurs, however, did not even have a crest (Wellnhofer, 1991). It had a wingspan of 30 feet (9 m) and is reported as probably being a glider (soarer) that flapped its wings infrequently (Langstone, 1981).

References Cited

Langstone, W. Jr. 1981. Pterosaurs. Scientific American, v. 244, no. 2, pp. 122-135.

Monastersky, R. National Geographic, May, 2001. Pp. 87-103.

Wellehofer. P. 1991. The illustrated encyclopedia of pterosaurs. Crescent Book, New York. 192 pp.