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Alioramus
Temporal range: Upper Cretaceous, 70–66Ma
Alioramus Life Restoration.jpg
Alioramus remotus
Scientific classification
Kingdom:
Class:
Superorder:
Order:
Suborder:
Superfamily:
Tyrannosauroidea
Family:
Subfamily:
Tarbosaurinae
Tribe:
Alioramini
Genus:
Alioramus
Type species
Alioramus remotus
Kurzanov, 1979
Species

A. remotus Kurzanov, 1976
A. altai Brusatte et al., 2009

Synonyms

Alioramus is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. The type species, A. remotus, is known from a partial skull and three foot bones recovered from Mongolian sediments which were deposited in a humid floodplain about 70 million years ago.

These remains were named and described by Soviet paleontologist Sergei Kurzanov in 1976. A second species, A. altai, known from a much more complete skeleton, was named and described by Stephen L. Brusatte and colleagues in 2009.

A possible third species, A. sinensis was described in 2014 on the basis of fossils found in the Nanxiong Formation of China.

Alioramus were bipedal like all known theropods, and their sharp teeth indicate that they were carnivores. Known specimens were smaller than other tyrannosaurids like Tarbosaurus bataar and Tyrannosaurus rex, but their adult size is difficult to estimate since both Alioramus species are known only from juvenile or sub-adult remains.

The recent discovery of Qianzhousaurus indicates that it belongs to a distinct branch of tyrannosaur. The genus Alioramus is characterized by a row of five bony crests along the top of the snout, a greater number of teeth than any other genus of tyrannosaurid, and a lower skull than most other tyrannosaurids.

Description

Alioramus skeletal steveoc
Size of A. remotus compared with a human

Alioramus remotus was estimated at 5 to 6 metres (16 to 20 ft) in length when originally described by Sergei Kurzanov in 1976. Kurzanov, however, did not correct for lengthening of the skull by deformation during fossilization, which may indicate a shorter overall body length for this individual. If this specimen is a juvenile, then adult Alioramus would have reached greater lengths, but no confirmed adult specimens are known.

The skull of A. remotus was approximately 45 centimetres (18 in) long. In general, it is long and low, a shape typical of more basal tyrannosauroids and juveniles of larger tyrannosaurids.

The premaxillary bones at the tip of the snout in Alioramus remotus have not been found, but are taller than wide in all tyrannosauroids for which they are known. The nasal bones are fused and have a row of five irregular bony crests that protrude upwards. These crests all measure more than 1 centimetre (0.39 in) tall.

At the back of the skull there is a protrusion, called the nuchal crest, a feature shared with all tyrannosaurids. In Alioramus, the nuchal crest is greatly thickened.

Like the rest of the skull, the lower jaw of Alioramus was long and slender, another possible juvenile characteristic. Alioramus had 76 or 78 teeth, more than any other tyrannosaurid.

The rest of the skeleton of Alioramus remotus is completely unknown except for three metatarsals (bones of the upper foot), but the discovery of A. altai, which is known from substantially more complete remains, has shed light on the anatomy of the genus.

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