Data from: The ‘duck-billed’ dinosaurs of Careless Creek (Upper Cretaceous of Montana, USA), with comments on hadrosaurid ontogeny

The Careless Creek Quarry (CCQ) is a multitaxic bonebed in the Campanian Judith River Formation of south-central Montana (USA) that produced a diverse assemblage of vertebrates, including several dinosaurian clades. We describe the morphology of the CCQ hadrosaurid material and reevaluate its taxonomic affinities. Our osteological comparative observations, coupled with maximum parsimony phylogenetic analyses, indicate that the majority of the hadrosaurid material is referable to kritosaurin saurolophines. Only an ischium is unambiguously referable to Lambeosaurinae. Most of the kritosaurin specimens likely represent a taxon that forms a polytomy with species of Gryposaurus and Rhinorex condrupus Gates and Sheetz, 2015. This form may represent individuals of either G. latidens Horner, 1992 or G. notabilis Lambe, 1914, or a new species cogeneric or not with Gryposaurus. The juvenile material exemplifies several patterns of mandibular and appendicular osteological variation previously observed in other hadrosaurids. However, it also shows some departures from the common trends, supporting the fact that not all skeletal growth changes can be generalized to all hadrosaurids.

粗心溪采石场（Careless Creek Quarry, CCQ）是一处位于美国蒙大拿州中南部坎潘期朱迪思河组的多类群骨层，产出了包含多个恐龙演化支在内的多样脊椎动物组合。本研究描述了CCQ产出的鸭嘴龙类（hadrosaurid）标本的形态特征，并重新评估了其分类亲缘关系。通过骨骼形态比较观察结合最大简约法系统发育分析，研究结果显示绝大多数鸭嘴龙类标本可归入克里特龙类（kritosaurin）栉龙亚科（saurolophines），仅1件坐骨（ischium）可明确归属于兰伯龙亚科（Lambeosaurinae）。多数克里特龙类标本大概率代表一个与格里芬龙属（Gryposaurus）物种及2015年Gates与Sheetz命名的短吻龙（Rhinorex condrupus Gates and Sheetz, 2015）构成多歧支（polytomy）的类群；该类群可能属于1992年Horner命名的宽齿格里芬龙（G. latidens Horner, 1992）或1914年Lambe命名的显著格里芬龙（G. notabilis Lambe, 1914），亦或是一个与格里芬龙属同属或不同属的新物种。本次研究的幼年个体标本展现了此前在其他鸭嘴龙类中观察到的多种下颌与附肢骨骼形态变异模式，但同时也存在部分与普遍趋势不符的特征，这佐证了并非所有骨骼生长变化都能在所有鸭嘴龙类中通用这一结论。