Probactrosaurus

Probactrosaurus Temporal range: Late Cretaceous, 96–88 Ma PreЄ Є O S D C P T J K Pg N
Mounted casts
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Superorder:	Dinosauria
Order:	Ornithischia
Suborder:	Cerapoda
Infraorder:	Ornithopoda
Superfamily:	Hadrosauroidea
Genus:	Probactrosaurus
Binomial name
Probactrosaurus gobiensis Rozhdestvensky, 1966

Probactrosaurus (meaning "before Bactrosaurus") is an early herbivorous hadrosauroid iguanodont dinosaur. It lived in China during the Late Cretaceous period. It is often known as the Asian Iguanodon.

In 1959 and 1960 a Soviet-Chinese expedition uncovered the remains of a euornithopod in Inner-Mongolia near Maortu. The type species is Probactrosaurus gobiensis, described and named by A. K. Rozhdestvensky in 1966. The generic name refers to Rozhdestvensky's hypothesis that Probactrosaurus would be the direct ancestor of Bactrosaurus, a notion today discarded. The specific name refers to the Gobi desert. The holotype specimen, PIN 2232/1, a partial skeleton with skull, was found in layers of the Dashuigou Formation. Another partial skeleton was found, PIN 2232-10, along with numerous other fragments.

In 1966 Rozhdestvensky also named a second species, Probactrosaurus alashanicus, based on fragmentary material. Its specific name refers to the Alxa League. In 2002 David Bruce Norman published a revision of the genus, in which he reported the holotype specimen of P. alshanicus, the back of a skull, had been lost after being dispatched from Moscow to Beijing. He concluded that the species was a synonym of P. gobiensis.

In 1997 Lü Junchang named a third species, Probactrosaurus mazongshanensis, based on holotype IVPP V.11333 found in 1992. The specific name refers to the Mazong Shan region. Today, this form is seen as more closely related to Equijubus and Altirhinus rather than to P. gobiensis and is therefore commonly referred to as "Probactrosaurus" mazongshanensis.