The timing of non-avian dinosaur decline is one of the most debated subjects in dinosaur palaeontology. Dinosaur faunas from the last few million years of the Mesozoic appear far less diverse than those from earlier in the Cretaceous, a trend that could suggest non-avian dinosaur extinction occurred gradually. However, the limited nature of the latest Cretaceous dinosaur record outside western North America has obscured patterns in dinosaur diversity just before the extinction. Here, I describe two associated skeletons and several isolated fossils recovered from the New Egypt Formation of New Jersey, a latest Maastrichtian unit that underlies the K–Pg boundary. The larger skeleton appears to be a small-bodied adult from a lineage outside Hadrosauridae, the dominant group of these animals during the Maastrichtian, that persisted along the eastern coast of North America. Smaller specimens are identifiable as juvenile hadrosauromorphs. These results substantiate an important assemblage of herbivorous dinosaurs from the poorly-known Cretaceous of eastern North America. The marine depositional setting for these skeletons demonstrates that proposed ecosystem preferences among hadrosauromorphs may be biased by post-mortem transportation, and the adult skeleton has implications for assessing the proposed relictual nature of Late Cretaceous eastern North American vertebrates.

中文翻译：

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白垩纪末期海洋组合体中小型鸭嘴龙形态的骨学和系统发育

非禽类恐龙衰落的时机是恐龙古生物学中争议最大的主题之一。中生代最近几百万年的恐龙动物群远没有白垩纪早期的动物群多样化，这种趋势可能表明非禽类恐龙的灭绝正在逐渐发生。但是，北美西部以外地区最新白垩纪恐龙记录的有限性质，在灭绝之前就掩盖了恐龙多样性的格局。在这里，我描述了两个相关的骨骼和从新泽西州新埃及组（位于K–Pg边界之下的最新的马斯特里赫特单元）中发现的几个孤立的化石。较大的骨骼似乎是Hadrosauridae外的血统的小体成年动物，在Maastrichtian时期这些动物占主导地位，在北美东部沿海地区一直存在。较小的标本可鉴定为少年类鸭嘴龙。这些结果证实了北美东部鲜为人知的白垩纪的草食性恐龙的重要组合。这些骨骼的海洋沉积环境表明，尸走类动物在拟议中的生态系统偏好可能会因尸体运输而产生偏差，而成年骨骼对评估晚白垩世北美东部脊椎动物的拟议遗迹性质具有影响。