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Geisonoceras Ammonoid


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Excellent study Geisonoceras, orthocerid, a member of the nautiloids group found in the western desert of Africa. This example shows a very interesting feature to the inner whorls of the early stages of growth read more about this unique feature below...

We shall select a Geisonoceras ammonoid from our stock, that shall be the closest match to the illustrations to the left and fall within the size parameters stated. The ammonoids in the images are of an average size, colouration and condition of what you shall expect to receive.

Genus: Geisonoceras (orthocerid), described by Hyatt 1884.
Age: Palaeozoic era, Devonian period, approximately 417 to 354 million years.
Origin: Er-rachidia province, Western Sahara desert, Morocco, North Africa.

Geisonoceras ammonite measurements.
Height: 14.5 cm
Width: 18.2 cm
Depth: 3 cm

Approximate weight: 0,734 g

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Supplied with documentation including age, genus type and geological discovery location on a certificate of authenticity, just as every other fossil and mineral on our web site.

The Geisonoceras ammonoid is an extinct orthocerid genus origianlly described by Hyatt, circa 1884, and type for the Geisonoceratidae established by Zhuravleva in 1959. Geisonoceras fossil shells are found in marine strata from the Ordovician some four hundred and sixty million years ago through to the Devonian period which ended around three hundred and fifty four million years ago. The remains off fossil Geisonoceratidae are known from location across the globe from Europe, North America, Asia and Africa where this fine example was discovered.

When the ammonoid was young its shell formed defence strategies, this is evident from the tubercles visible only on the outer ridge of the inner central whorls of this (these look like cogs of a drum), fossilised shell. Where the fossil preparatory work has created a sectional view of the phragmacone (shell), as the individual cephalopod grew in size the tubercles did not develop and so these do not appear on the advancing whorls. An excellent study fossil, recommended.

Additional Information

Age Devonian
Origin Morocco
Colour Green