A locality in the Upper Cretaceous Two Medicine Formation of Montana preserves abundant and variable horseshoe crab tracks and trails of the ichnotaxon Kouphichnium isp. These specimens span six morphologies differing in track form and trail configuration. These differences likely reflect variations in track-maker locomotion and behavior, substrate consistency, epichnial versus hypichnial preservation, and undertrack versus true tracks. Several tracks preserve the first clear appendage impressions for an extinct horseshoe crab. This discovery adds new information to the fossil horseshoe crab diversity in the Cretaceous Period. Trackway dimensions, such as the external width across the pusher legs or of the prosomal drag mark, provide information on the track-maker size. Most trackways correspond with crabs 9–14 cm wide; the abundance but limited size range of the traces suggests the large assemblage corresponds to a mating aggregation. The trace fossil record of xiphosurids indicates that throughout their history, horseshoe crabs inhabited both marine and nonmarine settings. They were definitively present in freshwater habitats from the lower Carboniferous through at least the Paleogene. Horseshoe crab trace abundance is highest from the upper Carboniferous through the Jurassic and likely reflects two factors: true upper Carboniferous taxonomic diversity and a preponderance of suitable sites for trackway preservation in the Late Triassic and Jurassic. Cretaceous traces are uncommon, and this Two Medicine locality is the first occurrence of horseshoe crab traces in the Late Cretaceous worldwide. Overall, track abundance and diversity would seem to correspond well with the reported horseshoe crab body fossil record.

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美国蒙大拿州上白垩统二药组的鲎踪迹化石及剑鲛科物种学记录的简要回顾

蒙大拿州上白垩纪二药组的一个地方保存着丰富且多变的鲎踪迹和鱼鳞属的踪迹口蘑ISP。这些标本跨越六种形态，在轨道形式和轨迹配置上有所不同。这些差异可能反映了轨道制造商运动和行为、基质一致性、上胎与下胎保存以及下轨与真实轨道的差异。几条轨道保存了灭绝马蹄蟹的第一个清晰的附肢印象。这一发现为白垩纪鲎化石的多样性增加了新的信息。轨道尺寸，例如跨推腿的外部宽度或前体阻力标记的外部宽度，提供了有关轨道制造商尺寸的信息。大多数轨道对应9-14厘米宽的螃蟹；痕迹的丰富但有限的大小范围表明大组合对应于交配聚集。剑齿蟹的踪迹化石记录表明，在它们的整个历史中，鲎都居住在海洋和非海洋环境中。它们确实存在于从下石炭纪到至少古近纪的淡水栖息地。马蹄蟹痕量丰度从上石炭统到侏罗纪最高，可能反映了两个因素：真正的上石炭统分类多样性和晚三叠世和侏罗纪适合轨道保存的优势位置。白垩纪的痕迹并不常见，而这两个药的地方是世界上白垩纪晚期鲎痕迹的首次出现。总体而言，轨道丰度和多样性似乎与报道的鲎体化石记录相符。马蹄蟹栖息在海洋和非海洋环境中。它们确实存在于从下石炭纪到至少古近纪的淡水栖息地。马蹄蟹痕量丰度从上石炭统到侏罗纪最高，可能反映了两个因素：真正的上石炭统分类多样性和晚三叠世和侏罗纪适合轨道保存的优势位置。白垩纪的痕迹并不常见，而这两个药的地方是世界上白垩纪晚期鲎痕迹的首次出现。总体而言，轨道丰度和多样性似乎与报道的鲎体化石记录相符。马蹄蟹栖息在海洋和非海洋环境中。它们确实存在于从下石炭纪到至少古近纪的淡水栖息地。马蹄蟹痕量丰度从上石炭统到侏罗纪最高，可能反映了两个因素：真正的上石炭统分类多样性和晚三叠世和侏罗纪适合轨道保存的优势地点。白垩纪的痕迹并不常见，而这两个药的地方是世界上白垩纪晚期鲎痕迹的首次出现。总体而言，轨道丰度和多样性似乎与报道的鲎体化石记录相符。马蹄蟹痕量丰度从上石炭统到侏罗纪最高，可能反映了两个因素：真正的上石炭统分类多样性和晚三叠世和侏罗纪适合轨道保存的优势地点。白垩纪的痕迹并不常见，而这两个药的地方是世界上白垩纪晚期鲎痕迹的首次出现。总体而言，轨道丰度和多样性似乎与报道的鲎体化石记录相符。马蹄蟹痕量丰度从上石炭统到侏罗纪最高，可能反映了两个因素：真正的上石炭统分类多样性和晚三叠世和侏罗纪适合轨道保存的优势地点。白垩纪的痕迹并不常见，而这两个药的地方是世界上白垩纪晚期鲎痕迹的首次出现。总体而言，轨道丰度和多样性似乎与报道的鲎体化石记录相符。而这个“两药”产地是世界范围内白垩纪晚期首次发现鲎踪迹。总体而言，轨道丰度和多样性似乎与报道的鲎体化石记录相符。而这个“两药”产地是世界范围内白垩纪晚期首次发现鲎踪迹。总体而言，轨道丰度和多样性似乎与报道的鲎体化石记录相符。