[N] 2006 Sexual dimorphism Lambeosaurines reconsidered
Evans, D., Currie, P., Eberth, D. & Ryan, M. (2006) High-resolution Lambeosaurine dinosaur biostratigraphy Dinosaur Park Formation, Alberta: Sexual dimorphism reconsidered. JVP 26(3) Abstracts pp.59
Cranial crest morphotypes of the lambeosaurine hadrosaurids Corythosaurus and Lambeosaurus from the Campanian Dinosaur Park Formation are frequently cited as examples of sexual dimorphism in dinosaurs. Each taxon is known from over 15 skulls that comprise growth series. Distinctive crest morphs at presumed maturity have been linked to sexual dimorphism, with sexes identified by the relative prominence of the crest.
Employing new stratigraphic and GPS data we have established a biostratigraphic framework in which the sexual dimorphism hypotheses can be tested. Crest morphs of each genus are not randomly distributed within the formation. The two Corythosaurus morphs are stratigraphically segregated, with the large-crested presumed male (originally named C. casuarius) occurring stratigraphically below all specimens of the putative female morph (C. intermedius). Three adult-sized Lambeosaurus morphs have been recognized, but their interpretation is not consistent; L. clavinitialis has been posited as the female of L. lambei as well as of L. magnicristatus.
In addition, a high degree of crest variation makes the identification of some specimens difficult. Small-crested specimens that have a posteroventrally-directed spike cluster low in section relative to larger-crested specimens. L. magnicristatus, the largest crested morph, occurs stratigraphically higher than all other lambeosaurines. The biostratigraphic succession of these cranial morphotypes is not consistent with previously proposed sexual dimorphism, and, instead, indicates that the Dinosaur Park Formation hosts a taxonomically diverse assemblage of lambeosaurines that form two distinct lineages. Morphological change within each lineage is concentrated in subtleties of crest shape, and is consistent with an anagenetic interpretation where temporal ranges do not overlap significantly.