Important set of three unwound ammonites with... Lot 1
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Important set of three unwound ammonites with spines on rock matrix. Ammonites are cephalopods like squid or cuttlefish. While most cephalopods today have a more or less reduced internal shell, or even disappeared, fossil cephalopods have mostly external shells. Ammonites existed from the Silurian to the Cretaceous (410 to 65 million years ago), but it is during the Mesozoic (250 to 65 million years ago) that they had the greatest specific richness. They totally disappeared at the end of the Mesozoic era, during the Cretaceous-Tertiary crisis, famous for having also seen the end of dinosaurs and marine reptiles. The name ammonite comes from the god Ammon, who wore ram's horns reminiscent of the spiral shell of the ammonite. Pliny the Elder used the term ammonis cornua, the horns of Ammon, to refer to these animals. The group of Ammonidea includes species with the most diverse shells, rolled up in the manner of a snail shell or presenting on the contrary a more or less strong degree of unrolling. Certain species have even a rolling in the shape of screw; others, completely unrolled, are right. The body is housed in the chamber open to the outside, the largest, which is called the living chamber. The animal could retract in its shell in case of danger and close it by means of its operculum. Ammonites are found in sedimentary rocks, where there was the ocean, so this fossil is very important for paleontologists. This particularly decorative piece consists of three very large uncoiled ammonites characteristic of the Moroccan Cretaceous levels. With shells that deviate from the classical spiral coiling with joined turns, the uncoiled ammonites are certainly among the most beautiful and rare of the group. Long considered as an evolutionary degeneration, scientists are now realizing that these new shell forms were in fact attempts to adapt to environmental and climatic variations as we know them today. They will however become extinct during the great crisis of the end of the Cretaceous, 65 million years ago at the same time as all the other ammonites. Originally, most of the shells of uncoiled ammonites more fragile than the spiral forms, were bristling with long spines to protect themselves from predators (sharks, Ichthyosaurs ...) Name of ammonites : Ancyloceras van den heckii (2 specimens) and Gassendiceras alpinum (top left). Dating from the Upper Barremian (Cretaceous) 115 million years ago. From the region of Tamanar (Morocco) located between Essaouira and Agadir on the Atlantic coast. Measuring 90 of height on 90 cm of width. (Restoration of use.)
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