A juvenile hadrosaurine dinosaur, Kritosaurus notabilis (Lambe), is described from the Oldman Formation, Upper Cretaceous, Alberta. It is evident that the characteristically broad skull-roof of this genus is not developed until the individual is more than half-grown, and that this is probably true for other hadrosaurines. The status of the species of Kritosaurus is reviewed, and it is considered that K. incurvimanus may be an immature K. navajovius. The nomenclature of the anterior part of the neurocranium is discussed briefly, the element formerly described as a presphenoid being now designated as the septosphenoid interorbital septum.

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