Altirhinus

Altirhinus (/ˌæltɨˈraɪnəs/; "high snout") is a genus of iguanodontian ornithopod dinosaur from the Early Cretaceous Period of Mongolia.

Description
Altirhinus was herbivorous and bipedal when walking or running, but probably became quadrupedal when feeding from the ground. According to the original description, the entire body probably extended 26 feet (8 m) from snout to tail tip. In 2010 Gregory S. Paul estimated the length at 6.5 metres (21 ft), the weight at 1.1 tonnes.[1] The skull alone is about 30 inches (760 mm) long, with a wide mouth and a distinctive tall arch on top of its snout, from which this dinosaur derives its name.

History of discovery
All known specimens of Altirhinus were recovered in 1981 during collaborative expeditions organized by Soviet and Mongolian scientists, from the Khukhtek Formation in the Dornogovi Province of Mongolia. The Khukhtek was formed in the Aptian to Albian stages of the Early Cretaceous Period, which lasted from between 125 and 100 million years ago. Psittacosaurus and the primitive ankylosaurid Shamosaurus have also been found in these rocks.

Several fossil specimens of different ages and sizes are known. The holotype, PIN 3386/8, is a skull which is well preserved on the left side, as well as some postcranial material consisting of pieces of the hands, feet, shoulder and pelvic girdles. A more fragmentary skull was also recovered, associated with some ribs, fragmentary vertebrae, and a complete forelimb. A third specimen preserves many limb bones and a series of 34 tail vertebrae from a smaller individual. Two even smaller fragmentary skeletons, presumably of young individuals, were uncovered nearby.

The remains of this animal were originally referred to the species Iguanodon orientalis, which was first described in 1952. However, I. orientalis has since been shown to be fragmentary, nondiagnostic, and virtually indistinguishable from the European I. bernissartensis (Norman, 1996). As no features of I. orientalis are shared exclusively with the 1981 specimens, which are clearly distinguishable from Iguanodon, a new name for those specimens was required. British paleontologist David B. Norman named them Altirhinus kurzanovi in 1998.

The name was created from a Latin word, altus ("high") and a Greek word, ῥίς, rhis, genitive rhinos ("nose" or "snout"). There is one known species (A. kurzanovi), which honors Sergei Kurzanov, the influential Russian paleontologist who originally found the specimens in 1981.