Lambeosaurus

Lambeosaurus (/ˌlæmbiəˈsɔːrəs/ LAM-bee-ə-SOR-əs) is a genus of hadrosaurid dinosaur that lived during the Late Cretaceous period of western North America. The first skull of Lambeosaurus found was used by palaeontologist Lawrence M. Lambe to justify the creation of the new genus Stephanosaurus, although it was not part of the latter's original material. Its incomplete nature led William A. Parks to name Lambeosaurus lambei for this skull in 1923 to honour Lambe. Multiple species of Lambeosaurus have been named since, including L. clavinitialis and L. magnicristatus in 1935, and L. laticaudus in 1981 which was later moved to its own genus Magnapaulia. It has also been identified that some species earlier identified as belonging to Tetragonosaurus and Corythosaurus are now considered juveniles of Lambeosaurus. It is the eponymous member of the subfamily Lambeosaurinae and tribe Lambeosaurini. Lambeosaurins, which also includes Corythosaurus and Hypacrosaurus from western North America, are understood to be some of the most specialized ornithopods.

Adult Lambeosaurus would have grown to around 7–7.7 m (23–25 ft) long and weighed 2.6–3.4 t (2.6–3.3 long tons; 2.9–3.7 short tons). It was able to move on two or four legs, with a deep tail, long limbs, and a highly distinct, hollow cranial crest. This crest, which can be used to separate the three recognized species of Lambeosaurus, projects well above the eye and slightly over the snout, and adults of some species possess a backwards spur. The function of the crest, which is also found in other lambeosaurines, is debated historically, but modern studies show that it could have been used as a resonating device for vocalisation, with a secondary function of sexual or species identification. The crest also allows for the identification of juveniles, which are otherwise nearly indistinguishable from those of Corythosaurus. It is through this identification that the growth of Lambeosaurus is well-known, with the crest developing late but expanding in height by an order of magnitude by the time individuals reached adulthood. Skin impressions are known and show that it had unornamented scales across the entire body.

The species of Lambeosaurus are only known from the middle Campanian of the Dinosaur Park Formation of Alberta. L. clavinitialis is known from a restricted range as the oldest species, overlapping with L. lambei which lived for around 0.3 million years before L. magnicristatus evolved later in the Campanian. This temporal separation suggests that L. clavinitialis, which was previously believed to be a female of either L. lambei or L. magnicristatus, is a separate species or at least earlier population. Lambeosaurus would have lived alongside the lambeosaurines Corythosaurus and Parasaurolophus, and also the saurolophine Prosaurolophus. Dental wear suggests that Lambeosaurus would have avoided competition with Prosaurolophus by occupying different feeding niches, preferring more closed habitats and browsing lower to the ground with a more generalised diet. The habitat Lambeosaurus lived in was a coastal plain where meandering rivers separated regions of dense vegetation, covered in a diversity of conifers, ferns and other shrubs, and occupied by diverse invertebrates, fish, mammals and reptiles, especially other megaherbivorous dinosaurs.