Nyctosaurus

Genus of nyctosaurid pterosaur from the Late Cretaceous

Nyctosaurus (meaning "night lizard" or "bat lizard") is a genus of nyctosaurid pterosaur from the Late Cretaceous period of what is now the Niobrara Formation of the mid western United States, which, during the time Nyctosaurus was alive, was covered in an extensive shallow sea. Some remains belonging to a possible Nyctosaurus species called N. lamegoi have been found in Brazil, making Nyctosaurus more diverse. The genus Nyctosaurus has had numerous species referred to it, though how many of these may actually be valid requires further study. At least one species possessed an extraordinarily large antler like cranial crest. Later that year, Marsh reclassified the species in its own genus, which he named Nyctosaurus, meaning "night lizard" or "bat lizard", in reference to the wing structure somewhat paralleling those of bats. In 1881, Marsh incorrectly assumed the name was preoccupied and changed it into Nyctodactylus, which thus is now a junior synonym. In 1902, Samuel Wendell Williston described the most complete skeleton then known (P 25026) discovered in 1901 by H. T. Martin. In 1903, Williston named a second species, N. leptodactylus, but this is today considered identical to N. gracilis. In 1953, Brazilian paleontologist Llewellyn Ivor Price named a partial humerus, DGM 238 R found in Brazil, N. lamegoi; the specific name honours the geologist Alberto Ribeiro Lamego. This species has an estimated wingspan of four metres; today, it is generally considered to be a form different from Nyctosaurus, but has not yet been assigned its own genus name. In 1972, a new skeleton, FHSM VP 2148, in 1962 discovered by George Fryer Sternberg, was named N. bonneri; today, it is generally seen as identical to N. gracilis. In 1978, Gregory Brown prepared the most complete Nyctosaurus skeleton currently known, UNSM 93000. In 1984, Robert Milton Schoch renamed Pteranodon nanus (Marsh 1881), "the dwarf", Nyctosaurus nanus. In the early 2000s, Kenneth Jenkins of Ellis, Kansas collected two specimens of Nyctosaurus, which were the first to demonstrate conclusively that not only was this species crested, but that the crest in mature specimens was very large and elaborate. The specimens were purchased by a private collector in Austin, Texas. Despite being in private hands rather than a museum collection, paleontologist Chris Bennett was able to study the specimens and gave them the manuscript reference numbers KJ1 and KJ2 (for Kenneth Jenkins). Bennett published a description of the specimens in 2003. Despite the unusual crests, the specimens were otherwise indistinguishable from other specimens of Nyctosaurus. However, the then currently named species were extremely similar and Bennett declined to refer them to a specific one pending further study of the differences, or lack thereof, between species of Nyctosaurus.

Some skull specimens preserve a distinctively large crest, at least tall in the older adults, and was relatively gigantic compared to the rest of the body, while also being 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 long and the backward pointing spar was at least long. In 2018, a topology by Nicholas Longrich and colleagues had made the clade Pteranodontoidea the more inclusive group, while Pteranodontia was restricted to only pteranodontids and nyctosaurids. In this analysis, three species of Nyctosaurus were included: N. lamegoi, N. nanus and N. gracilis; all three of which were placed as derived members of the Nyctosauridae.

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 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. However, in the actual description of the fossils, paleontologist Christopher Bennett argued against the possibility of a membrane or soft tissue extension to the crest. Bennett noted that the edges of each prong were smooth and rounded, and showed no evidence for any soft tissue attachment points. He also compared Nyctosaurus with large crested tapejarids, which do preserve soft tissue extensions supported by prongs, and showed that, in those species, the attachment points were obvious, with jagged edges where the transition from bone to soft tissue occurred. Bennett concluded that the crest was most likely used solely for display, citing similar structures in modern animals. The ecosystem preserved in this zone was unique in its abundance of vertebrate life. Nyctosaurus shared the sky with the bird Ichthyornis and with Pteranodon longiceps, though the second Niobrara Pteranodon species, P. sternbergi, had disappeared from the fossil record by this point. In the waters of the Western Interior Seaway below swam mosasaurs such as Clidastes, Ectenosaurus, Eonatator, Halisaurus, Platecarpus and Tylosaurus, several remains of the plesiosaurs Dolichorhynchops and Polycotylus, cephalopods like Baculites and Tusoteuthis, and the sea turtles such as Ctenochelys and Toxochelys were also found. Flightless diving birds such as Parahesperornis were also known from the fossil site, and a wide variety of fish including swordfish like Protosphyraena, as well as the predatory fishes Pachyrhizodus, Xiphactinus, Ichthyodectes, Gillicus, Leptecodon, Enchodus and Cimolichthys, the filter feeding Bonnerichthys, the dorsal finned Bananogmius, and the cartilaginous fishes Cretolamna, Ptychodus, Rhinobatos and Squalicorax were also found within the formation.