Tetragonosaurus

Lambeosaurus Temporal range: Late Cretaceous, 76–75 Ma PreЄ Є O S D C P T J K Pg N ↓
Mounted L. lambei skeleton, Royal Ontario Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Order:	†Ornithischia
Suborder:	†Ornithopoda
Family:	†Hadrosauridae
Subfamily:	†Lambeosaurinae
Tribe:	†Lambeosaurini
Genus:	†Lambeosaurus Parks, 1923
Type species
†Lambeosaurus lambei Parks, 1923
Species
†L. lambei Parks, 1923 †L. magnicristatus Sternberg, 1935 †L. paucidens? (Marsh, 1889 [originally Hadrosaurus])
Synonyms
Genus Synonymy Didanodon Osborn, 1902 Procheneosaurus Parks, 1920 (conserved name) Tetragonosaurus Parks, 1931 (rejected name) Species Synonymy Trachodon altidens Lambe, 1902 Didanodon altidens (Lambe, 1902 [originally Trachodon]) Procheneosaurus altidens (Lambe, 1942 [originally Trachodon]) Tetragonosaurus praeceps Parks, 1931 (conserved name) (type) Procheneosaurus praeceps (Parks, 1931 [originally Tetragonosaurus]) (conserved name) (type) Tetragonosaurus cranibrevis Sternberg, 1935 Procheneosaurus cranibrevis (Sternberg, 1935 [originally Tetragonosaurus]) Lambeosaurus clavinitialis (Sternberg, 1935 [originally Tetragonosaurus]) Corythosaurus frontalis Parks, 1935

Lambeosaurus (/ˌlæmbioʊˈsɔːrəs/ LAM-bee-o-SAWR-əs; meaning "Lambe's lizard") is a genus of hadrosaurid dinosaur that lived about 75 million years ago, in the Late Cretaceous period (Campanian) of North America. This bipedal/quadrupedal, herbivorous dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a hatchet. Several possible species have been named, from Canada, the United States, and Mexico, but only the two Canadian species are currently recognized as valid.

Lambeosaurus was belatedly described in 1923 by William Parks, over twenty years after the first material was studied by Lawrence Lambe. The genus has a complicated taxonomic history, in part because small-bodied crested hadrosaurids now recognized as juveniles were once thought to belong to their own genera and species. Currently, the various skulls assigned to the type species L. lambei are interpreted as showing age differences and sexual dimorphism. Lambeosaurus was closely related to the better known Corythosaurus, which is found in slightly older rocks, as well as the less well-known genera Hypacrosaurus and Olorotitan. All had unusual crests, which are now generally assumed to have served social functions like noisemaking and recognition.