Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
Dipartimento di Scienze della Terra e Geologico-Ambientali, Alma Mater Studiorum, Università di Bologna, Bologna, Italy.
PLoS One. 2022 Feb 2;17(2):e0262824. doi: 10.1371/journal.pone.0262824. eCollection 2022.
The Wapiti Formation of northwest Alberta and northeast British Columbia, Canada, preserves an Upper Cretaceous terrestrial vertebrate fauna that is latitudinally situated between those documented further north in Alaska and those from southern Alberta and the contiguous U.S.A. Therefore, the Wapiti Formation is important for identifying broad patterns in vertebrate ecology, diversity, and distribution across Laramidia during the latest Cretaceous. Tracksites are especially useful as they provide a range of palaeoecological, palaeoenvironmental, and behavioural data that are complementary to the skeletal record. Here, we describe the Tyrants Aisle locality, the largest in-situ tracksite known from the Wapiti Formation. The site occurs in the lower part of Unit 4 of the formation (~72.5 Ma, upper Campanian), exposed along the southern bank of the Redwillow River. More than 100 tracks are documented across at least three distinct track-bearing layers, which were deposited on an alluvial floodplain. Hadrosaurid tracks are most abundant, and are referable to Hadrosauropodus based on track width exceeding track length, broad digits, and rounded or bilobed heel margins. We suggest the hadrosaurid trackmaker was Edmontosaurus regalis based on stratigraphic context. Tyrannosaurids, probable troodontids, possible ornithomimids, and possible azhdarchid pterosaurs represent minor but notable elements of the ichnofauna, as the latter is unknown from skeletal remains within the Wapiti Formation, and all others are poorly represented. Possible social behaviour is inferred for some of the hadrosaurid and small theropod-like trackmakers based on trackway alignment, suitable spacing and consistent preservation. On a broad taxonomic level (i.e., family or above), ichnofaunal compositions indicate that hadrosaurids were palaeoecologically dominant across Laramidia during the late Campanian within both high-and low-latitude deposits, although the role of depositional environment requires further testing.
加拿大阿尔伯塔省西北部和不列颠哥伦比亚省东北部的 wapiti 组保存了一套上白垩统陆生脊椎动物群，其地理位置位于阿拉斯加北部和阿尔伯塔省南部以及美国接壤地区记录的动物群之间。因此，wapiti 组对于确定拉腊米迪亚在白垩纪晚期脊椎动物生态、多样性和分布的广泛模式非常重要。足迹遗址特别有用，因为它们提供了一系列与骨骼记录互补的古生态学、古环境学和行为学数据。在这里，我们描述了 tyrants aisle 遗址，这是已知来自 wapiti 组的最大原地足迹遗址。该遗址位于该组下部第 4 单元（约 7250 万年前，上坎潘期），暴露在 redwillow 河南岸。至少有三个不同的含足迹层记录了 100 多个足迹，这些层是在冲积洪泛平原上沉积的。鸭嘴龙足迹最为丰富，根据足迹宽度超过足迹长度、宽趾和圆形或双叶状足跟边缘，可归入 hadrosauropodus。我们根据地层背景推测，鸭嘴龙足迹的制造者是埃德蒙顿龙。暴龙类、可能的驰龙类、可能的似鸟龙类和可能的翼手龙类代表了该足迹动物群的次要但显著的组成部分，因为在 wapiti 组的骨骼遗骸中没有发现翼手龙类，而其他的则很少见。一些鸭嘴龙和小型似兽脚类足迹制造者的足迹轨迹排列、合适的间距和一致的保存情况表明，它们可能具有社会行为。在广泛的分类学水平（即科或以上）上，足迹动物群组成表明，在白垩纪晚期，鸭嘴龙类在拉腊米迪亚的高纬度和低纬度沉积环境中都是古生态优势种，尽管沉积环境的作用还需要进一步的测试。
