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（Campanian Judith River Formation）的多分类群骨层，其产出了种类丰富的脊椎动物化石组合，涵盖多个恐龙演化支。本研究描述了CCQ所产鸭嘴龙科（Hadrosauridae）化石的形态特征，并重新评估其分类亲缘关系。本研究的骨骼学比较观察结合最大简约法系统发育分析结果显示，绝大多数鸭嘴龙科化石可归入克里特龙族（Kritosaurini）的赖氏龙亚科（Saurolophinae）；仅有一块坐骨（ischium）可明确归入兰伯龙亚科（Lambeosaurinae）。多数克里特龙族标本大概率隶属于一个与灰鸭龙属（Gryposaurus）物种及雷克斯鼻龙（Rhinorex condrupus Gates & Sheetz, 2015）构成多歧支（polytomy）的演化类群。该类群可能对应宽齿灰鸭龙（G. latidens Horner, 1992）或显著灰鸭龙（G. notabilis Lambe, 1914）的个体，亦或是一个与灰鸭龙属同属或不同属的新物种。该批次的幼年个体化石展现了此前在其他鸭嘴龙科类群中已被观察到的下颌及附肢骨骼的多种变异模式，但同时也存在一些与普遍生长趋势相悖的特征，这佐证了并非所有骨骼生长变化都能推广至所有鸭嘴龙科类群这一结论。