Size and Weight:
When they were first discovered (on a 1923 expedition to China by paleontologists from New York's American Museum of Natural History), the bones of Alectrosaurus were mixed up with those of another type of dinosaur, a segnosaur (a type of therizinosaur), provoking much confusion. After the mixup was finally sorted out, the researchers announced that they had discovered a previously unknown genus of tyrannosaur--at that time, the first ever dug up in Asia.
To date, paleontologists have had little luck figuring out the obscure Alectrosaurus' exact position on the tyrannosaur family tree, a situation that can only be improved by further fossil discoveries. (One theory is that Alectrosaurus was actually a species of Albertosaurus, but not everyone subscribes to this idea.)