Aiolosaurus

Aiolosaurus is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, A. oriens, was named in 2000 from Ukhaa Tolgod, a rich fossil site in the Campanian-age Djadochta Formation.

Description and history

Aiolosaurus was named in 2000 on the basis of a single holotype specimen cataloged as IGM 3/171. This specimen includes a partial skull and parts of the postcranial skeleton. Aiolosaurus is named after Aeolus, the Greek god of wind, while the specific name of A. oriens means "east."^[1] Diagnostic features of Aiolosaurus are found mainly in the skull. They include:

• The division of the nasals into two bones (they form one bone in living monitors).
• A small hole in the snout between the premaxilla and maxilla bones called the premaxillary fenestra.
• The separation of the premaxilla and septomaxilla bones by a projection of the maxilla bone.
• The small size of another hole in the snout called the septomaxillary foramen.
• Near the jaw joint, a hole in the surangular bone of the lower jaw that is positioned underneath the coronoid process of the upper jaw.^[1]

Classification

Aiolosaurus was initially classified as a basal member of Varanoidea, the superfamily that includes monitor lizards, helodermatids, and mosasaurs. Cherminotus, another Late Cretaceous varanoid from Mongolia, was also classified in this way. In a 2008 phylogenetic analysis, Aiolosaurus was classified as a member of Varanidae. It was placed in the subfamily Lanthanotinae along with Cherminotus and the living Earless monitor lizard.^[2] Another 2008 analysis supported the placement of Aiolosaurus in Varanidae but did not find it to be a member of Lanthanotinae. Instead, it was found to be a more basal varanid. As some of the earliest monitor lizards, Aiolosaurus, Cherminotus, and the related Ovoo are representative of the first evolutionary radiation of varanids.^[3]

References