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Dinosaur biostratigraphy studies the distribution of dinosaur taxa through rock layers. It can be useful for dating and correlating rock units and reconstructiong ancient ecosystems. Most dinosaur-bearing rock formations do not contain multiple distinct stratigraphically separated faunas.〔 Typically dinosaur faunas are static throughout a formation or change piecemeal over time.〔 Faunal turnover usually occurs between formations.〔 The fossil record can give an appearance of faunal turnover due to multiple causes including evolution, migration, or changing preservational biases.〔 Turnover events can have extremely minor causes like the migration of a taxon to a new area or extremely conspicuous ones like an ecosystem destroying catastrophe.〔 Since the fossil record is incomplete assessing the nature and causes of faunal turnovers is fraught with difficulty, except in cases where the fossil record is "unusually complete."〔 ==Dinosaur Park Formation== The Dinosaur Park Formation can be divided into at least two distinct faunas. The lower part of the formation is characterized by the abundance of ''Corythosaurus'' and ''Centrosaurus''. This group of species is replaced higher in the formation by a different ornithischian fauna characterized by the presence of ''Lambeosaurus'' and ''Styracosaurus''. The appearance of several new, rare species of ornithischian at the very top of the formation may indicate that a third distinct fauna had replaced the second during the transition into younger, non-Dinosaur Park sediments, at the same time an inland sea transgresses onto land, but there are fewer remains here. An unnamed pachyrhinosaur, ''Chasmosaurus irvinensis'', and ''Lambeosaurus magnicristatus'' may be more common in this third fauna.〔〔Evans, D.C., Bavington, R. and Campione, N.E. (2009). "(An unusual hadrosaurid braincase from the Dinosaur Park Formation and the biostratigraphy of ''Parasaurolophus'' (Ornithischia: Lambeosaurinae) from southern Alberta. )" ''Canadian Journal of Earth Sciences,'' 46(11): 791-800. 〕 The timeline below follows a synthesis presented by Arbour et al. 2009 with additional information from Evans et al. 2009 ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-76.6 till:-74.3 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:1 start:-76.6 ScaleMinor = unit:year increment:1 start:-76.6 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dinosaur biostratigraphy」の詳細全文を読む スポンサード リンク
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