Description:
Parkinsonia are used as an index fossil to demarcate a geological
time zone in the Jurassic period. Presented is a beautiful and large
example of the classic species. It is wonderfully preserved, with
it’s calcite skin still intact. Note the white to brown colors
represented. There has been no crushing or distortion to the specimen.
It resides regally on a flat matrix base. This one would definitely
compliment any serious ammonite collection.
Background:
BAJOCIAN, in geology, the name proposed in 1849 by d'Orbigny for
the rocks of Middle Jurassic age which are well developed in the
neighborourhood of Bayeux, Calvados. The Bajocian stage is practically
equivalent to the Inferior Oolite of British geologists. It corresponds
fairly closely with the Lower and Middle Brown Jura of Quenstedt,
and with the Dogger of Oppel. By means of the fossil ammonites the
Bajocia strata have been subdivided into the following zones, in
descending order: Zone of Parkinsonia Parkinsoni and Cosmoceras
garantianum "Coeloceras subcoronatum (Humphriesianum)"
Sonninia Romani "Stephaeoceras Sowerbyi" Harpoceras concavum
Murchisonae _ Substage Aalenien opalinum = of Mayer-Eymar.
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