Pterodaustro
Pterodaustro is a genus of ctenochasmatid pterodactyloid pterosaur from South America. Its fossil remains dated back to the Early Cretaceous period, about 105 million years ago. The most distinctive characteristic that separates Pterodaustro from other ctenochasmatids is its bristle-like teeth, a feature not seen in any other pterosaur.
The first fossils, among them the holotype PVL 2571, a thigh bone, were in the late sixties discovered by Bonaparte in the Lagarcito Formation, situated in the San Luis Province of Argentina, and dating from the Albian. The genus has later also been found in Chile in the Santa Ana Formation.[citation needed] At the Argentine site, the just 50 square meters (540 sq ft) large "Loma del Pterodaustro", since then, during several expeditions, over 750 Pterodaustrospecimens have been collected, 288 of them having been catalogued until 2008. This makes the species one of the best known pterosaurs, with examples from all growth stages, from egg to adult.
The genus was named in 1969 by José Bonaparte as an as yet undescribed nomen nudum. The first description followed in 1970, making the name valid, the type species being Pterodaustro guiñazui.[2] The generic name is derived from Greek pteron, "wing" and Latin auster, "south (wind)". The elements are combined as a condensed pteron de austro, "wing from the south". The specific name honors paleontologist Román Guiñazú. It was amended in 1978 by Peter Wellnhofer into guinazui, because diacritical signs such as the tilde are not allowed in specific names.
Pterodaustro has a very elongated skull, up to 29 centimeters (11 in) long. The portion in front of the eye sockets comprises 85 percent of skull length. The long snout and lower jaws curve strongly upwards; the tangent at the point of the snout is perpendicular to that of the jaw joint. Pterodaustro has about a thousand bristle-like modified teeth in its lower jaws that might have been used to strain crustaceans, plankton, algae, and other small creatures from the water.[3] These teeth stand for the most part not in separate alveoli but in two long grooves parallel to the edges of the jaw. They have a length of 3 centimeters (0.098 ft) and are oval in cross-section, with a width of just 0.2 to 0.3 millimeters (0.0079 to 0.0118 in). At first it was suspected these structures were not true teeth at all, but later research established they were built like normal teeth, including enamel, dentine and a pulp. Despite being made of very hard material, they might still have been flexible to some extent due to their extreme length-width ratio, a bend of up to 45 degrees being possible.[4]The upper jaws also carried teeth, but these were very small with a flat conical base and a spatula-formed crown. These teeth also do not have separate tooth sockets but were apparently held by ligaments in a special tooth pad, that was also covered with small ossicles, or bone plates.
The back of the skull was also rather elongated and in a low position; there are some indications for a low parietal crest.
Pterodaustro had an adult wingspan of approximately 2.5 meters (8.2 ft).[5] Its hindlimbs are rather robust and its feet large. Its tail is uniquely elongated for a pterodactyloid, containing twenty-two caudal vertebrae, whereas other members of this group have at most, sixteen.
