Cymatoceras
Nautiloid
Phylum
Mollusca, Class Cephalopoda, Subclass Nautiloidea, Order Nautilida,
Family Cymatoceratidae
Geological
Time: Cretaceous
Size (25.4
mm = 1 inch): 51 mm diameter
Fossil
Site: Tulear, Madagascar
Fossil
Code: PP22
Price:
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Description:
A spectacular nautiloid from Madagascar which has been sagitally
split and polished to show wonderful detail within. Most of the
individual chambers are open and filled with greenish gray Calcite
crystals, with the septa (divisions) between each chamber preserved
as light gray Calcite, making for a superb display piece. The
primitive suturing pattern distinguishes these cephalopods from
the ammonites (I have posted it with the ammonites as they are
close relatives). This one shows the suturing well from the interior,
making it a striking piece. Additionally, they have the siphuncule
at the center of the chambers as opposed to the top as in the
ammonites. It is visible here as the spiral seen in some chambers.
The Nautilida have a rich evolutionary history which began in
the early Devonian. The order suffered a drastic decline in the
late Devonian, only to have an extensive radiation in the Carboniferous.
They suffered less than some other orders at the end of the Permian,
and did better than the ammonites by surviving the Cretaceous
extinction, leaving one descendant, the modern-day Nautilus,
of which there are 5 species. Nautiloids had stronger shells
than the ammonites, and were capable of descending deeper than
the ammonites could. Perhaps this allowed them to survive the
disaster at the end of the Cretaceous. This is a fine example
of a nautiloid from the Cretaceous deposits of Madagascar, one
that is sure to be a fine addition to any collection. |
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