[dinosaur] Gryposaurus cranial variation from Dinosaur Park Formation of Alberta

Ben Creisler
[email protected]

A new paper:

Talia Michelle Lowi-Merri & David C. Evans (2019)
Cranial variation in Gryposaurus and biostratigraphy of hadrosaurines
(Ornithischia: Hadrosauridae) from the Dinosaur Park Formation of Alberta,
Canada.
Canadian Journal of Earth Sciences (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1139_cjes-2D2019-2D0073&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=wpMEEoeowW_57Y_XSx2iE9_KGN_tg0Lm4Usk5MThkNI&s=KoOaLz3rgo7hzb411vzt-FgWKvV6KeodC2mkPd-M0uY&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.nrcresearchpress.com_doi_abs_10.1139_cjes-2D2019-2D0073-23.Xa8hO5JKjX4&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=wpMEEoeowW_57Y_XSx2iE9_KGN_tg0Lm4Usk5MThkNI&s=drNCGCL-RyG16CK-d_x0RJ20ywk6IeboVJvY_nTrBKQ&e= 


The Dinosaur Park Formation (Campanian) of Alberta documents one of the
most diverse assemblages of hadrosaurine dinosaurs. Historically, two
species of the genus Gryposaurus have been recognized in the Dinosaur Park
Formation, G. notabilisand G. incurvimanus, which are differentiated
primarily on their nasal arch morphology. These two species have recently
been suggested to represent either variable morphs within G. notabilis
(e.g., ontogeny) or two distinct taxa within an evolving Gryposaurus
lineage (e.g., anagenesis). These alternative hypotheses have never been
adequately tested via detailed morphological comparisons, morphometrics, or
biostratigraphy. A geometric morphometric analysis of hadrosaurine skulls
from the Dinosaur Park Formation was performed to assess the influence of
ontogeny on skull morphology. G. incurvimanus skulls were found to be
distinctly smaller, and morphologically divergent from those of G.
notabilis, with larger G. notabilis skulls having higher nasal arches set
farther back on the skull, a feature commonly seen in adult individuals of
other hadrosaurids, such as Brachylophosaurus and lambeosaurines.
Stratigraphic data were used to map this morphology through time, to
evaluate the anagenesis hypothesis. The stratigraphic distributions of the
two species showed considerable overlap, indicating that the sampled
individuals lived over a short period of time (< 0.5 mya). Overall, our
results suggest that the hypothesis that G. incurvimanus and G. notabilis
represent different ontogenetic stages within a single species cannot be
rejected. This study improves our understanding of the extent of potential
individual variation within a single Gryposaurus species, which can be
useful in assessing the validity of other hadrosaurines.

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