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Hornerstown Formation
The Hornerstown Formation is a Paleogene or latest Mesozoic geologic formation.〔Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.〕 The age of these deposits have been controversial. While most fossils are of animals types known from the earliest Cenozoic era, several fossils of otherwise exclusively Cretaceous age have been found. These include remains of the shark ''Squalicorax'', the teleost fish ''Enchodus'', several species of ammonite, and marine lizards referred to the genus ''Mosasaurus''. Some of these remains show signs of severe abrasion and erosion, however, implying that they are probably re-worked from older deposits. Most of these fossils are restricted to the lowest point in the formation, one rich in fossils and known as the Main Fossiliferous Layer, or MFL. Other explanations for the out-of-place fossils in the MFL is that they represent a time-averaged assemblage that built up and remained unburied during a time of low sediment deposition, or that they were stirred up from deeper in the sediment and deposited together during a tsunami.〔Gallagher, W.B. (2005). "Recent mosasaur discoveries from New Jersey and Delaware, USA: stratigraphy, taphonomy and implications for mosasaur extinction." ''Netherlands Journal of Geosciences — Geologie en Mijnbouw'', 84(3): 241-245. ()〕
==Vertebrate paleofauna==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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