Alectrosaurus (uh-LECK-truh-SAW-rus)

George Olsen, discovered the first specimens in 1923 on the third American Museum of Natural History expedition to Mongolia. Both genus and species were named by American paleontologist Charles Gilmore in 1933.


Alectrosaurus (uh-LECK-truh-SAW-rus)
Alectrosaurus (meaning "unmarried lizard") is a genus of tyrannosauroid theropod dinosaur from the Late Cretaceous Period of Inner Mongolia. It was a bipedal carnivore with a body shape similar to its much larger relative, Tyrannosaurus rex. Alectrosaurus was much smaller though, most likely less than five meters (17 ft) long.

The generic name Alectrosaurus can also be translated as "alone lizard," and is derived from the Greek words alektros ("unmarried") and sauros ("lizard"). At the time of its discovery, it was unlike any other Asian carnivore known. There is one named species (A. olseni), which is named in honor of George Olsen, who discovered the first specimens in 1923 on the third American Museum of Natural History expedition to Mongolia. Both genus and species were named by American paleontologist Charles Gilmore in 1933.

History of discovery
Right hind foot of Alectrosaurus olseni. No. 6368, A.M.N.H.The holotype (AMNH 6554), or original specimen, of Alectrosaurus was a hind limb discovered in the Iren Dabasu Formation of the Inner Mongolia Autonomous Region (Nei Mongol Zizhiqu) of the People's Republic of China. Forelimb material in the type specimen was later found to be misidentified therizinosauroid remains. The age of this geologic formation is not clear, but is commonly cited as the Campanian stage of the Late Cretaceous Period, about 83 to 74 million years ago.

More material, including comparable hind limb material as well as skull and shoulder elements, has been referred to Alectrosaurus. These fossils were found in the Bayan Shireh Formation of Outer Mongolia, a formation which is also of uncertain age. It may possibly extend into the early Campanian, but recent estimates suggest it was deposited from Cenomanian through Santonian times.

Iren Dabasu and Bayan Shireh dinosaur faunas are similar, but van Itterbeecka et al. claimed that the Iren Dabasu is probably Campanian-Maastrichtian in age and possibly correlated with the Nemegt Formation, so it is not surprising that a species of Alectrosaurus would be found there.

Furthermore, several more partial skeletons may have been found in both Inner and Outer Mongolia. These remain undescribed as of early 2007.