Alectrosaurus is a genus of tyrannosaurid 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 thirdAmerican Museum of Natural History expedition to Mongolia. Both genus and species were named by American paleontologist Charles Gilmore in 1933. In a 2001 study conducted by Bruce Rothschild and other paleontologists, 23 foot bones referred to Alectrosaurus were examined for signs of stress fracture, but none were found.The holotype (AMNH 6554), or name-bearing specimen, of Alectrosaurus is 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.
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 thirdAmerican Museum of Natural History expedition to Mongolia. Both genus and species were named by American paleontologist Charles Gilmore in 1933. In a 2001 study conducted by Bruce Rothschild and other paleontologists, 23 foot bones referred to Alectrosaurus were examined for signs of stress fracture, but none were found.The holotype (AMNH 6554), or name-bearing specimen, of Alectrosaurus is 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 ofAlectrosaurus 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.Alectrosaurus is undoubtedly a tyrannosauroid, but due to its fragmentary nature, there is presently very little confidence in restoring its relationships with other tyrannosauroids and many recent cladistic analyses have omitted it altogether. One study recovered Alectrosaurus at no less than eight equally parsimonious positions in a tyrannosauroid cladogram.Some paleontologists have considered Alectrosaurus olseni to be a species of Albertosaurus.
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