The Breadth and Depth of Asian Dinosaurs

Dr. Thomas R. Holtz

>Sorry to bug everyone with this but I need answers. I'm
>looking to find out what age range(s) the Gobi/Mongolia/China area
>covers. From the fauna uncovered from there, I'm figuring it's at
>least Upper Jurassic and (the lower side of)Upper Cretaceous, but I
>would like to know for sure.

China, especially, has many diverse faunas from throughout the age of Dinosaurs. Chinese dinosaurs include some rare Late Triassic forms, abundant Early Jurassic forms (the so-called Lufengosaurus fauna), the best Middle Jurassic fauna known (containing Huayangosaurus, Gasosaurus, Shunosaurus, and Omeisaurus, to name a few) and excellent Late Jurassic assemblages (containing Sinraptor, Mamenchisaurus, other sinraptorids and euhelopodids, and a buttload of stegosaurians).

With regards to the Cretaceous, there are late Early Cretaceous units (the Psittacosaurus fauna, probably Aptian-Albian stages), and various Senonian age (Coniancian, Santonian, Campanian, and Maastrichtian) units, although the ages of each particular unit is not yet well constrained. The Nanxing basin contains latest Maastricthian-early Paleocene deposits, making it one of the few regions in which the K-T boundary is preseved on land.

Mongolian dinosaurs, at least those I'm aware of, are all Cretaceous. (By "Mongolian", I refer to the old Mongolian People's Republic, and not Inner Mongolia, which is an autonomous region in the People's Repbulic of China) .

The Psittacosaurus fauna is well known from Mongolia. According to Dave Norman, the type specimen of Iguanodon orientalis (which is NOT the big-nosed Mongolian iguanodontian often illustrated) cannot be distinguished from I. bernissartensis. IF I. orientalis belongs to the European species, and IF I. bernessiartensis had a typically short species duration (two big "IF"s), then there are older Barremian deposits somewhere in Mongolia.

The Bayn Shire fauna, once considered to be early Late Cretaceous, may in fact be early Campanian (i.e., tens of millions of years younger than previously supposed). All the Late Cretaceous faunas of Mongolia may be Campano-Maastrichtian (~86-65 million years ago), but the exact date is far from certain. Although the Djadochta-Barun Goyot-Nemegt series of faunas has been interpreted as a temporal sequence (incidentally, indicating increasing humidity in Mongolia at the end of the Cretaceous), these units might only be generally contemporaneous, but from different environments. In fact, part of the AMNH work in Mongolia is to sort out this problem.

Hope that answered your question. To add a final note, the old southern Asian Soviet Republics (Tajikistan, Kazakhstan, etc.) contain dinosaurs which have been interpreted as Turonian age: that is, occuring between the Psittacosaurus fauna and the Bayn Shire.