Tetragonosaurus is an invalid name for Lambeosaurus, a duck-billed dinosaur with a large crest from the late Cretaceous period . This plant-eater was about 30 feet (9 m) long. 
Tetragonosaurus This nomenclature (“square (head) lizard”) is no longer recognized by scientists because they found that it described an animal that was previously given another name which is Lambeosaurus. Named by William Arthur Parks in 1931.