Fossil range: Cretaceous
Nyctosaurus sp., with giant head crest.
| Scientific classification
Nyctosaurus is a genus of pterodactyloid pterosaur notable for its extraordinarily large cranial crest, otherwise known only in the distantly related tapejarids. Its remains have been found primarily in the mid-western United States, which during the late Cretaceous Period was covered in an extensive shallow sea.
Nyctosaurus is the only pterosaur to have lost its clawed "fingers", with the exception of the wing finger, which is likely to have impaired its movement on the ground, leading scientists to conjecture that it spent almost all of its time on the wing and rarely landed. In particular the lack of claws with which to grip surfaces would have made climbing, or clinging to cliffs or treetrunks, impossible for Nyctosaurus. Nyctosaurus appears to have outlasted its relative Pteranodon and may have survived until the great extinction 65 million years ago.
Nyctosaurus was similar in anatomy to its close relative and contemporary, Pteranodon. It had relatively long wings, similar in shape to modern seabirds. However, it was smaller overall than Pteranodon, with an adult wingspan of 2 meters (6.6 ft) and a maximum weight of about 1.86 kg. The overall body length was 37 cm. Some specimens preserve a distinctive crest, at least 55 cm tall in old adults, relatively gigantic compared to the rest of the body and over three times the length of the head. The crest is composed of two long, grooved spars, one pointed upward and the other backward, arising from a common base projecting up and back from the back of the skull. The two spars were nearly equal in length, and both were nearly as long or longer than the total length of the body. The upward-pointing crest spar was at least 42 cm long (1.3 ft) and the backward-pointing spar was at least 32 cm long (1 ft).
The jaws of Nyctosaurus were long and extremely pointed. The jaw tips were thin and needle sharp, and are often broken off in fossil specimens, giving the appearance that one jaw is longer than the other, though in life they were probably equal in length.
Nyctosaurus is the only pterosaur to have lost its clawed "fingers", with the exception of the wing finger (of which however the fourth phalanx was lost), which is likely to have impaired its movement on the ground, leading scientists to conjecture that it spent almost all of its time on the wing and rarely landed. In particular, the lack of claws with which to grip surfaces would have made climbing or clinging to cliffs and tree trunks impossible for Nyctosaurus.
Nyctosaurus, like its relative Pteranodon, appears to have grown very rapidly after hatching. Fully adult specimens are no larger than some immature specimens such as P 25026 (pictured below), indicating that Nyctosaurus went from hatching to adult size (with wingspans of 2 m or more) in under a year. Some sub-adult specimens have been preserved with their skulls in nearly pristine condition, and lack any trace of a head crest, indicating that the distinctively large crest only began to develop after the first year of life. The crest may have continued to grow more elaborate as the animal aged, though no studies have examined the age of the fully adult, large-crested specimens. These individuals may have been 5 or even 10 years old at the time of their deaths.
Early fossils of Nyctosaurus did not reveal an elaborate crest, only a smaller structure similar to the crest of the closely related Pteranodon.
A few scientists hypothesize that this crest, which resembles an enormous antler, may have supported a skin "headsail" used for stability in flight. While there is no fossil evidence for such a sail, studies have shown that a membranous attachment to the bony crest would have imparted aerodynamic advantages.
Wing loading and speedEdit
Sankar Chatterjee and R.J. Templin used estimates based on complete Nyctosaurus specimens to determine weight and total wing area, and to calculate its total wing loading. They also estimated its total available flight power based on estimated musculature. Using these calculations, they estimated the cruising speed of Nyctosaurus gracilis as 9.6 meters/second (34.5 kilometers/hour or 21.4 miles/hour).
- ^ Xing, L., Wu, J., Lu, Y., Lu, J., and Ji, Q. (2009). "Aerodynamic characteristics of the crest with membrane attachment on Cretaceous pterodactyloid Nyctosaurus." Acta Geologica Sinica, 83(1): 25-32.
- Nyctosauridae (scroll down) in The Pterosaur Database