Evidence of reworked Cretaceous fossils and their bearing on the existence of Tertiary dinosaurs

The Paleocene Shotgun fauna of Wyoming includes marine sharks as well as mammals. It has been suggested that the sharks were introduced from the Can-nonball Sea. It is more likely that these sharks were reworked from a Cretaceous rock sequence that included both marine and terrestrial deposits as th...

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Bibliographic Details
Published in:Palaios 1989-06, Vol.4 (3), p.281-286
Main Authors: Eaton, Jeffrey G, Kirkland, James I, Doi, Kentaro
Format: Article
Language:English
Subjects:
Abrasion
biostratigraphy
Cenozoic
Chordata
Cretaceous
Dinosaurs
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fauna
Fort Union Formation
Fossils
Geology
Mammals
Mesaverde Group
Mesozoic
Paleogene
Pisces
Raven Ridge
Reptilia
Research Letters
reworking
San Juan Basin
Shales
Sharks
Shotgun Member
Shotguns
Stratigraphy
Taxa
Tertiary
Tetrapoda
United States
Upper Cretaceous
Utah
Vertebrata
Wasatch Formation
Western U.S
Wyoming
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Summary:The Paleocene Shotgun fauna of Wyoming includes marine sharks as well as mammals. It has been suggested that the sharks were introduced from the Can-nonball Sea. It is more likely that these sharks were reworked from a Cretaceous rock sequence that included both marine and terrestrial deposits as there is a mixture of marine and freshwater taxa. These taxa have not been recorded elsewhere after the Cretaceous and are not known from the Cannonball Formation. Early Eocene localities at Raven Ridge, Utah, similarly contain teeth of Cretaceous marine and freshwater fish, dinosaurs, and Eocene mammals. The Cretaceous teeth are well preserved, variably abraded, and serve to cast doubts on criteria recently used to claim that dinosaur teeth recovered from the Paleocene of Montana are not reworked. Another Eocene locality in the San Juan Basin has produced an Eocene mammalian fauna with diverse Cretaceous murine sharks. Neither the nature of preservation nor the degree of abrasion could be used to distinguish reworked from contemporaneous material. The mixed environments represented by the fish taxa and recognition of the extensive pre-Tertiary extinction of both marine and freshwater fish were employed to recognize reworked specimens.
ISSN:0883-1351
1938-5323
DOI:10.2307/3514776