LOCALITY:
Baishin Tsav, Gobi Desert, Southeastern Mongolia

AGE:
Late Cretaceous (Santonian), Bayn Shireh Formation, 85 million years ago

SIZE:
This skull is 140 mm.  Adults would grow up to 6-7 metres tall and up to 15 metres in length

MEANING OF NAME:
'Reptile from Arstan well'

PRONUNCIATION:
Ahr-stan-oh-SAWR-us

CLASSIFICATION:
ORNITHOPODA: Hadrosauridae; Hadrosaurinae

This skull is that of a young hadrosaurid or duck-billed dinosaur, possibly aged 3-4 years. Adults were probably 6-7 metres high and up to 15 metres long.

Studies of the microstructure of the bones suggest that the young grew rapidly attaining a height of 40-50 centimetres in the first year after hatching.