Doran Brownstein Chase
Stamford Museum and Nature Center, Stamford, CT, USA.
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA.
R Soc Open Sci. 2021 Aug 25;8(8):210127. doi: 10.1098/rsos.210127. eCollection 2021 Aug.
During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the early Late Cretaceous has concealed how dinosaurs and other terrestrial vertebrates responded to these events. I describe two dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous dinosaurs. This skeleton is associated with the first small juvenile dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance.
在白垩纪时期，物种的多样化和更替影响着经历全球地理变化的陆地脊椎动物。然而，晚白垩世早期化石记录的匮乏掩盖了恐龙和其他陆地脊椎动物对这些事件的反应方式。我描述了来自北美鲜为人知的古陆块阿巴拉契亚地区桑托阶至坎帕阶早期的两种恐龙。对一种大型的、可能是新的兽脚亚目恐龙的重新审视表明，它可能属于仅来自阿巴拉契亚地区的暴龙超科新分支。另一个部分骨骼化石属于鸭嘴龙科的早期成员，鸭嘴龙科是一类非常成功的草食性恐龙分支。这具骨骼化石与来自大西洋沿岸平原的首批小型幼年恐龙标本有关。这种暴龙超科恐龙和鸭嘴龙科恐龙证实了仅有的晚桑托阶恐龙动物群之一，并有助于确定两个广泛分布的恐龙谱系中重要解剖学创新的时间。暴龙超科恐龙和鸭嘴龙科恐龙的系统发育位置表明，桑托阶阿巴拉契亚恐龙动物群与同时期的欧亚大陆动物群相当，并且仅由阿巴拉契亚恐龙类群形成的分支的存在，表明阿巴拉契亚恐龙组合中存在一定程度的特有性，这归因于隔离事件。
