Albertosaurus looked like a smaller more slender version of T. rex. It was lighter and more similar in size, speed and appearance to Daspletosaurus and slightly bigger than Gorgosaurus. It lived earlier than most of its big relatives but it possibly died out, got extinct the same time.
Albertosaurus was a Tyrannosaur, a smaller relative of T. rex. It lived earlier and was the top predator on land in North America 75-70 million years ago. Unlike it's more powerful relatives, Albertosaurus was faster and more agile like Gorgosaurus. It had a narrower skull and longer arms than Tyrannosaurus. It was first found in Alberta in 1905, giving it it's name. Even though Albertosaurus was built for speed and hunted duckbills, it was powerful enough to hunt and eat horned dinosaurs such as Pachyrhinosaurus.