Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda, phylum Mollusca. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods. Ammonites' closest living relative is probably not the modern Nautilus (which they outwardly resemble), but rather the subclass Coleoidea (octopus, squid, and cuttlefish). Their fossil shells usually take the form of planispirals, although there were some helically-spiraled and non-spiraled forms (known as "heteromorphs"). Their spiral shape begot their name, as their fossilized shells somewhat resemble tightly-coiled rams' horns. Plinius the Elder (died 79 A.D. near Pompeii) called fossils of these animals ammonis cornua("horns of Ammon") because the Egyptian god Ammon (Amun) was typically depicted wearing ram's horns
see http://en.wikipedia.org/wiki/Ammonite
Ammonites first appeared during the Devonian Period within the Paleozoic Era.
Ammonites are considered body fossils because they are the preserved remains of an organism that lived millions of years ago. Trace fossils, on the other hand, are evidence of the activities of ancient organisms, such as footprints or burrows.
Ammonites and nautiloids are extinct marine mollusks with coiled partitioned shells. Ammonites were abundant during the Mesozoic era, while nautiloids have survived to the present day with only a few species remaining. These shells are characterized by their chambers, which were used for buoyancy control and housing the soft body parts of the organisms.
Yes, ammonites are good index fossils because they had a wide geographical distribution and existed for a long period of time. Their evolution is well-documented, making them useful for relative dating of rock layers.
Trilobites are older than ammonites, with trilobites appearing first in the fossil record about 521 million years ago during the Cambrian period, while ammonites appeared later, around 400 million years ago during the Devonian period. Scientists determine the age of fossils based on their position in rock layers and radiometric dating techniques.
ammonites are extinct
Ammonites are named for the Egyptian god Ammon, who had a ram's head. The shells of ammonites are spirals like the horns of a ram.
Various aquatic reptiles were predators of ammonites. Fossils of damaged ammonites have been found with teeth marks from Plesiosaurs.
Squid
Ammonites first appeared during the Devonian Period within the Paleozoic Era.
Ammonites went extinct at the end of the Cretaceous Period.
Ammonites went extinct at the same time as the dinosaurs, about sixty-five million years ago.
Ammonites are very common fossils from the Jurassic Period. They were dominant in the ocean during and before the Jurassic Period.
Ammonites are the most widely-known and abundant fossils in the world. The name "ammonites" came from the Greek god Ammon. Ammonites include squid, octopus, snails, cuttlefish, and nautilus.
ammonites
David
a size