Dinosaur Paleoecology, Judith River Formation, South CentralMontana

蒙大拿州的朱迪斯河地层作为美国第一批恐龙化石的来源具有历史意义，约瑟夫·莱迪于1856年在费城描述了恐龙化石。然而，自那以后，作为恐龙化石的来源，这种地层一直令人沮丧。事实证明，阿尔伯塔省北部和蒙大拿州中北部更西边的类似年限的床层生产率更高。1981年在蒙大拿州中南部肖穆特附近的朱迪斯河沉积物中发现的恐龙骨床，是蒙大拿州朱迪斯河迄今发现的最丰富的恐龙骨床，也是该地层最南端的高产地点。在所代表的分类群中，有角龙的一个新属(爱氏角龙Lammersi Dodson 1986)，一种巨大的鸭嘴龙，非常罕见的厚头恐龙的后颅骨，以及幼年鸭嘴龙和角足龙，在这里出现的频率比大多数其他当代地点都要高。最初的工作集中在疏忽溪采石场，但勘探发现了该地区的一些地点，因此建议建立一个从西向东通往内海的环境样带。已经建立了一条25公里长的样带，在其东端发现了牡蛎、鲨鱼和硬骨鱼。分析整个样带的动物群变化将有助于更好地了解恐龙分布的生态决定因素。

The Judith River Formation of Montana has historical significance as the source of America's first dinosaur fossils, which were described in Philadelphia by Joseph Leidy in 1856. However, the formation has since been frustrating as a source of dinosaur fossils. Beds of similar age farther north in Alberta and farther west in north central Montana have proved to be more productive. A dinsosaur bonebed discovered in 1981 in Judith River sediments near Shawmut, south central Montana, is the richest yet found in the Montana Judith River, and the southernmost productive site from this formation. Among the taxa represented are a new genus of ceratopsid (Avaceratops lammersi Dodson 1986), a giant hadrosaur, very rare postcrania of a pachycephalosaurid, and juvenile hadrosaurs and ceratopsids that occur with a higher frequency here than at most other contemporary sites. Work initially focused on the Careless Creek Quarry, but prospecting has revealed a number of sites in the area, so it is proposed to establish an environmental transect from west to east towards the Interior Seaway. A 25 km transect has been established, at the eastern end of which are found oysters, sharks and teleost fishes. Analysis of faunal changes across the transect will permit a better understanding of the ecological determinants of dinosaur distribution.