Alioramus

***Alioramus*** (meaning "different branch") is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. It currently contains two species. The type species, ***A. remotus*** is known from a partial skull and three foot bones recovered from the Mongolian Nemegt Formation, which was 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. Its relationships to other tyrannosaurid genera are unclear, with some evidence supporting a hypothesis that *Alioramus* is closely related to the contemporary species *Tarbosaurus bataar*.

*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 remotus* was estimated at 5 to 6 m (16 to 20 ft) in length when originally described by Sergei Kurzanov in 1976. In 1988 Paul gave a similar length of 6 m (20 ft) and a weight of 700 kg (1,500 lb). In 2016 Molina-Pérez and Larramendi estimated A. remotus at 5.5 m (18 ft) and 500 kg (1,100 lb), and *A. altai* at 5 m (16 ft) and 385 kg (849 lb). 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 cm (1.48 ft) 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 ornamented with a row of five irregular bony crests that protrude upwards from the midline, where the nasal bones are sutured together. These crests all measure more than 1 cm (0.39 in) tall.

At the back of the skull there is a protrusion, called the *nuchal crest*, arising from the fused parietal bones, a feature shared with all tyrannosaurids. In *Alioramus*, the nuchal crest is greatly thickened, similarly to *Tarbosaurus* and *Tyrannosaurus*. Like the rest of the skull, the lower jaw of *Alioramus* was long and slender, another possible juvenile characteristic. As in *Tarbosaurus*, a ridge on the outer surface of the angular bone of the lower jaw articulated with the rear of the dentary bone, locking the two bones together and removing much of the flexibility seen in other tyrannosaurids. Other tyrannosaurids had four premaxillary teeth, *D*-shaped in cross section, on each side. Including 16 or 17 in each maxilla, and 18 in each dentary, *Alioramus* had 76 or 78 teeth, more than any other tyrannosaurid. The braincase of *A. altai* was intermediate between the basal theropod and avialan conditions.

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.

## *Alioramus* in The Amazing Dinosaur Adventure

*Alioramus*, from the opening narration to *The Great Mountain Adventure*