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Cenomanian micromorphic ammonites from the Western Interior of the USA

Abstract:

Calcareous concretions from middle and upper Cenomanian (Cretaceous) shale sequences in Montana and Wyoming yield, on rare occasions, abundant minute ammonites. Some are juveniles of large species, and give valuable evidence on early ontogeny and evolutionary affinities of these taxa. They provide evidence for the probable evolutionary origins of a series of hitherto undescribed progenic dwarf genera, adult at 4.5-16.5 mm diameter that are a remarkable feature of these assemblages. Five new g...

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Institution:
University of Oxford
Department:
Oxford, MPLS, Earth Sciences
Role:
Author
Journal:
Palaeontology
Volume:
33
Issue:
2
Pages:
379-422
Publication date:
1990-01-01
ISSN:
0031-0239
URN:
uuid:68112446-53fa-4187-bcf1-e88aa547c38f
Source identifiers:
81916
Local pid:
pubs:81916
Language:
English

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