Aiolosaurus

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

Aiolosaurus
Temporal range: Late Cretaceous, 80 Ma
↓
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Varanidae
Genus: †Aiolosaurus
Gao and Norell, 2000
Species:
†A. oriens
Binomial name
†Aiolosaurus oriens
Gao and Norell, 2000
Not to be confused with Aeolosaurus.

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
  1. Gao, K.; Norell, M.A. (2000). "Taxonomic composition and systematics of Late Cretaceous lizard assemblages from Ukhaa Tolgod and adjacent localities, Mongolian Gobi Desert". Bulletin of the American Museum of Natural History. 249: 1–118. doi:10.1206/0003-0090(2000)249<0001:tcasol>2.0.co;2. hdl:2246/1596.
  2. Conrad, J.L. (2008). "Phylogeny and systematics of Squamata (Reptilia) based on morphology" (PDF). Bulletin of the American Museum of Natural History. 310: 1–182. doi:10.1206/310.1. hdl:2246/5915.
  3. Norell, M.A.; Gao, K.-Q.; Conrad, J. (2008). "A new platynotan lizard (Diapsida: Squamata) from the Late Cretaceous Gobi Desert (Ömnögov), Mongolia" (PDF). American Museum Novitates. 3605: 1–22. doi:10.1206/0003-0082(2008)3605[1:ANPLDS]2.0.CO;2. hdl:2246/5910.
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