Askeptosaurus

Extinct genus of reptiles

Askeptosaurus is an extinct genus of askeptosauroid, a marine reptile from the extinct order Thalattosauria. Askeptosaurus is known from several well preserved fossils found in Middle Triassic marine strata in what is now Italy and Switzerland.

Askeptosaurus, and its only known species Askeptosaurus italicus, were first named and described in 1925 by Hungarian paleontologist Franz Nopcsa von Felső Szilvás. It was most recently redescribed by Dr. Johannes Müller in 2005. Askeptosaurus is known from several disarticulated and articulated skeletons preserved at the MSNM (Museo Civico di Storia Naturale di Milano) in Milan, Italy, and the PIMUZ (Paläontologisches Institut und Museum der Universität Zürich, Paleontological Institute and Musée paléontologique de Zurich of the University of Zurich) in Zurich, Switzerland. These specimens were discovered in the Grenzbitumenzone of Monte San Giorgio, a UNESCO World Heritage Site on the Swiss Italian border. Also known as the Besano Formation in Italy, the Grenzbitumenzone has produced many well preserved fossils from the Anisian Ladinian boundary within the Middle Triassic.

The skull was low and somewhat broad at the back, though the snout was long and slender. Nearly half of the snout is formed by the large premaxillae, which send back a long triangular projection into the frontals along the midline of the snout. Each premaxilla has up to 12 sharp and slightly curved teeth. They are implanted in a pleurothecodont manner, meaning that they lie in shallow sockets along a groove which has a lowered edge on the lingual (tongue) side of the tooth row. The premaxilla is followed by the low and smaller maxilla, and an elongated naris (nostril) is present at the border between the two bones. The maxilla has 16 teeth, which are similar to those of the premaxilla, albeit slightly smaller. Unlike thalattosauroids, the teeth have the same general shape and there is no diastema (gap) between the premaxillary and maxillary tooth rows. Like other thalattosaurs, the nasals are separated from each other by midline projections of the premaxilla and frontal. The nasals have a small contribution to the border of the naris, and the sharp rear tip of each nasal projects into the frontal. Apart from the triangular notches incised by the premaxillae and nasals, the frontals have a simple and subrectangular form. argument that Endennasaurus is more closely related to Askeptosaurus than to other thalattosaurs. It is now commonly agreed that a monophyletic group is formed by Anshunsaurus and Askeptosaurus. To be more specific, Askeptosaurus belongs to the family Askeptosauridae, a division of the suborder Askeptosauroidea. Within Askeptosauridae, Askeptosaurus is considered to be the sister taxon of Anshunsaurus, from Middle Triassic deposits in Guizhou, China. At present, the Askeptosauroidea is only known from the Alpine Triassic and southern China, and Askeptosaurus represents the oldest record for this clade.

A. italicus was found in the Middle Triassic of Switzerland and Italy, with most specimens recovered from sites on Monte San Giorgio. It lived alongside many other fish and marine reptiles, including two other genera of thalattosaurs: Clarazia and Hescheleria.