Ornithocheirus (from Greek "ορνις", meaning bird, and "χειρ", meaning hand) was a pterosaur from the Cretaceous period of Europe and South America. Based on poor fossil material, the genus has caused enduring problems of zoological nomenclature.
Fossil remains currently classified as Ornithocheirus have been recovered mainly from the Cambridge Greensand of England, dating to the beginning of the Albian stage of the late Cretaceous period, about 110 million years ago.Additional fossils from the Santana Formationof Brazil, dating to 112-108 million years ago, have been classified as species of Ornithocheirus.The original material of Ornithocheirus simus, recovered from England, indicates a mid-sized species with a wing span of 2.5 m (8 ft). Referred specimens attributed to Ornithocheirus simus(alternately called Criorhynchus simus) can reach 5 m (16 ft). Tropeognathus mesembrinus is also usually considered a part of the Ornithocheirus genus as O. mesembrinus, and reached over 6 m (20 ft) in wingspan.Both O. simus and O. mesembrinus bore distinctive convex "keeled" crests on their snouts.The upper crests arose from the snout tip and extended back to the nostril. An additional, smaller crest projected down from the lower jaw at the symphysis ("chin" area). While many ornithocheirids had a small, rounded bony crest projecting from the back of the skull, this was particularly large and well-developed in Ornithocheirus.Unlike the related Anhanguera and Coloborhynchus, which had an expanded rosette of teeth at the jaw tips, Ornithocheirus had straight jaws that narrowed toward the tip. Also unlike related pterosaurs, the teeth of Ornithocheirus were mostly vertical, rather than set at an outward-pointing angle. They also had fewer teeth than related species.The type specimen of Ornithocheirus simus is represented only by a broken piece of the upper jaw tip. While it does preserve several characteristic features of Ornithocheirus, it is nearly identical to comparable bones in o. mesembrinus, making clear distinction between these two species impossible.During the 19th century, in England many fragmentary pterosaur fossils were found in the Cambridge Greensand, a layer from the early Cretaceous, that had originated as a sandy seabed. Decomposing pterosaur cadavers, floating on the sea surface, had gradually lost individual bones that sank to the bottom of the sea. Water currents then moved the bones around, eroding and polishing them, until they were at last covered by more sand and fossilised. Even the largest of these remains were damaged and difficult to interpret. They had been assigned to the genus Pterodactylus, as was common for any pterosaur species described in the early and middle 19th century.
