Aiolosaurus is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of monitor lizard

Monitor lizard

Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

 from the Late Cretaceous

Late Cretaceous

The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 of Mongolia

Mongolia

Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

. The type

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 and only species, A. oriens, was named in 2000 from Ukhaa Tolgod

Djadochta Formation

The Djadochta Formation is situated in central Asia and dates from the Late Cretaceous Period. Laid down in the early Campanian, possibly starting in the latest Santonian, it is dated somewhat uncertainly at about 84-75 mya...

, a rich fossil site in the Campanian

Campanian

The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

-age Djadochta Formation

Djadochta Formation

The Djadochta Formation is situated in central Asia and dates from the Late Cretaceous Period. Laid down in the early Campanian, possibly starting in the latest Santonian, it is dated somewhat uncertainly at about 84-75 mya...

.

Description and history

Aiolosaurus was named in 2000 on the basis of a single holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 specimen cataloged as IGM

Mongolian Academy of Sciences

The Mongolian Academy of Sciences is Mongolia's first centre of modern sciences. It was founded in 1921, when the government established an Institute of Literature and Script, which was later upgraded to Institute of Science. Later, in 1961, it was reconstituted as the Mongolian Academy of Sciences...

 3/171. This specimen includes a partial skull and parts of the postcranial skeleton. Aiolosaurus is named after Aeolus

Aeolus

Aeolus was the ruler of the winds in Greek mythology. In fact this name was shared by three mythic characters. These three personages are often difficult to tell apart, and even the ancient mythographers appear to have been perplexed about which Aeolus was which...

, the Greek god

Greek mythology

Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

 of wind, while the specific name of A. oriens means "east." Diagnostic features of Aiolosaurus are found mainly in the skull. They include:

• The division of the nasals
  Nasal bone
  The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
  
   into two bones (they form one bone in living monitors).
• A small hole in the snout between the premaxilla
  Premaxilla
  The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
  
   and maxilla
  Maxilla
  The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
  
   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
  Coronoid process
  The Coronoid process can refer to:* The coronoid process of the mandible, part of the ramus mandibulae of the mandible...
  
   of the upper jaw.

Classification

Aiolosaurus was initially classified as a basal member of Varanoidea

Varanoidea

Varanoidea is a superfamily of lizards, including the well-known family Varanidae . Also included in the Varanoidea are such extinct marine and semi-aquatic forms as mosasaurs and dolichosaurs, the venomous helodermatids , the Lanthanotidae , and the extinct Necrosauridae.Throughout their long...

, the superfamily that includes monitor lizards, helodermatids, and mosasaur

Mosasaur

Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...

s. Cherminotus

Cherminotus

Cherminotus is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, C. longifrons, was named in 1984.-Description and history:...

, 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

Varanidae

Varanidae is a group of lizards of the superfamily Varanoidea. The family is a group of carnivorous lizards which includes the largest living lizard, the Komodo dragon, and the crocodile monitor. Varanidae contains the living genus Varanus and a number of extinct taxa...

. It was placed in the subfamily Lanthanotinae along with Cherminotus and the living Earless monitor lizard. 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

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 varanid. As some of the earliest monitor lizards, Aiolosaurus, Cherminotus, and the related Ovoo

Ovoo (genus)

Ovoo is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. It is one of the smallest and earliest monitor lizards. The type and only species, Ovoo gurvel, was named in 2008...

are representative of the first evolutionary radiation

Evolutionary radiation

An evolutionary radiation is an increase in taxonomic diversity or morphological disparity, due to adaptive change or the opening of ecospace. Radiations may affect one clade or many, and be rapid or gradual; where they are rapid, and driven by a single lineage's adaptation to their environment,...

of varanids.