Description: !! WOW, Very Nice !! 27.4g Natural AMMONITE Fossil Specimen In Display Case 300 million years old !!! Before we understood what they were, one of the explanations for ammonites was that they were coiled-up snakes that had been turned to stone, earning them the nickname 'snakestones'. But ammonites weren't reptiles: they were ocean-dwelling molluscs, specifically cephalopods. Ammonites were born with tiny shells and, as they grew, they built new chambers onto it. They would move their entire body into a new chamber and seal off their old and now too-small living quarters with walls known as septa. Ammonites' growing shells typically formed into a flat spiral, known as a planispiral, although a variety of shapes did evolve over time. Shells could be a loose spiral or tightly curled with whorls touching. They could be flat or helical. Some species would begin growing their shell in a tight spiral but straighten it out through later growth phases. There were also some more unusual shapes - the species Nipponites mirabilis, which is found in Japan, is exceptionally rare and looks a bit like a knot. The subclass Ammonoidea, a group that is often referred to as ammonites, first appeared about 450 million years ago. Ammonoidea includes a more exclusive group called Ammonitida, also known as the true ammonites. These animals are known from the Jurassic Period, from about 200 million years ago. Most ammonites died out at the same time as the non-avian dinosaurs, at the end of the Cretaceous Period, 66 million years ago. Like modern cephalopods, ammonites displayed sexual dimorphism, which is the noticeable difference in appearance between sexes. But when ammonite fossils that looked unique were found in the past, they tended to be recorded as new species instead of as the microconch (male) or macroconch (female) of an existing species, as this difference between the sexes was not yet known about.However, it is estimated that over 10,000 species of ammonite - possibly even over 20,000 have been discovered. Ammonites can be a useful tool for scientists. Because they are so common and evolved so rapidly, they are excellent to help determine the age of the rocks they were fossilised in. Much of the Mesozoic aged rock in Europe has been sectioned into 'ammonite zones', where rocks in different areas can be associated with each other based on the ammonite fossils found in them.
Price: 25 USD
Location: Port Saint Lucie, Florida
End Time: 2024-10-25T14:59:27.000Z
Shipping Cost: 7.68 USD
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