Ammonite - The aptychus

Ammonites are an extinct group of marine animals (subclass Ammonoidea) in the phylum Mollusca and class Cephalopoda. Their closest living relative is probably not the modern Nautilus, whom they resemble, but rather the Subclass Coleoidea (octopus, squid, and cuttlefish). Their fossil shells take the form of flat spirals (though there are some rarer helically spiraled and non-spiraled forms, called heteromorphs) and are responsible for the animals' name as they somewhat resemble a tightly coiled ram's horn (the god Ammon was com ...

Including:

• Ammonite - Classification
• Ammonite - Life
• Ammonite - Shell anatomy and diversity
• Ammonite - Basic shell anatomy
• Ammonite - Sexual dimorphism
• Ammonite - Variations in shape
• Ammonite - The aptychus
• Ammonite - Size
• Ammonite - Ammonite distribution
• Ammonite - Trivia
• Ammonite - References and further reading

Read more here: » Ammonite: Encyclopedia - Ammonite

Ammonite - Basic shell anatomy. The chambered part of the ammonite shell is called a phragmocone. The phragmocone contains a series of progressively larger chambers, called camerae (sing. camera) that are divided by thin walls called septa (sing. septum). Only the last and largest chamber, the body chamber, was occupied by the living animal at any given moment. As it grew, it adde ...

See also:

Ammonite, Ammonite - Classification, Ammonite - Life, Ammonite - Shell anatomy and diversity, Ammonite - Basic shell anatomy, Ammonite - Sexual dimorphism, Ammonite - Variations in shape, Ammonite - The aptychus, Ammonite - Size, Ammonite - Ammonite distribution, Ammonite - Trivia, Ammonite - References and further reading

Read more here: » Ammonite: Encyclopedia II - Ammonite - Shell anatomy and diversity

Originating from within the bactritoid nautiloids, Ammonites first appeared in the Late Silurian to Early Devonian (~400 million years ago) and became extinct at the close of the Cretaceous along with the dinosaurs (65 million years ago). The classification of ammonites is based in part on the ornamentation and structure of the septa comprising their shells' gas chambers; by these and other characteristics we can divide this subclass into three orders and eight known suborders. While nearly all nautiloids show gently curving sutures, the ammonite suture line (the intersection of the septum with the outer shell) was folded, forming ...

See also:

Ammonite, Ammonite - Classification, Ammonite - Life, Ammonite - Shell anatomy and diversity, Ammonite - Basic shell anatomy, Ammonite - Sexual dimorphism, Ammonite - Variations in shape, Ammonite - The aptychus, Ammonite - Size, Ammonite - Ammonite distribution, Ammonite - Trivia, Ammonite - References and further reading

Read more here: » Ammonite: Encyclopedia II - Ammonite - Classification

In medieval times, ammonites were believed to be petrified snakes. They were frequently fitted with carved snake-like heads and sold to pilgrims. A famous example of this links the ammonite fossils common in the Jurassic sediments around Whitby, North Yorkshire with the legend that St. Hilda turned a plague of snakes into stone. Even today, tourists can buy ammonite fossils with heads carved onto them to make them look more snake-like. It is said that the original discus used by the ancient Greeks in their Olympics was in fact a fossilized ammonite; a number of ammonite generic names include an explicit reference to the discus ...

See also:

Ammonite, Ammonite - Classification, Ammonite - Life, Ammonite - Shell anatomy and diversity, Ammonite - Basic shell anatomy, Ammonite - Sexual dimorphism, Ammonite - Variations in shape, Ammonite - The aptychus, Ammonite - Size, Ammonite - Ammonite distribution, Ammonite - Trivia, Ammonite - References and further reading

Read more here: » Ammonite: Encyclopedia II - Ammonite - Trivia

Starting from the late Silurian, ammonites were extremely abundant, especially in the Mesozoic seas. Many genera evolved and ran their course quickly, becoming extinct in a few million years. Due to their rapid evolution and widespread distribution, ammonites are useful for geologists and paleontologists for biostratigraphy. They are excellent index fossils, and it is often possible to link the rock layer in which t ...

See also:

Ammonite, Ammonite - Classification, Ammonite - Life, Ammonite - Shell anatomy and diversity, Ammonite - Basic shell anatomy, Ammonite - Sexual dimorphism, Ammonite - Variations in shape, Ammonite - The aptychus, Ammonite - Size, Ammonite - Ammonite distribution, Ammonite - Trivia, Ammonite - References and further reading

Read more here: » Ammonite: Encyclopedia II - Ammonite - Ammonite distribution

Because ammonites and their close relatives are extinct, little is known about their way of life. Their soft body parts are practically never preserved in any detail. Nonetheless, a lot has been worked out by examining ammonite shells and by using models of these shells in water tanks. Many ammonites probably lived in the open water of ancient seas, rather than at the sea bottom; this is suggested by the fact that their fossils are often found in rocks that were laid down under conditions where no benthic (bottom-dwelling) life is fou ...

See also:

Ammonite, Ammonite - Classification, Ammonite - Life, Ammonite - Shell anatomy and diversity, Ammonite - Basic shell anatomy, Ammonite - Sexual dimorphism, Ammonite - Variations in shape, Ammonite - The aptychus, Ammonite - Size, Ammonite - Ammonite distribution, Ammonite - Trivia, Ammonite - References and further reading

Read more here: » Ammonite: Encyclopedia II - Ammonite - Life

Originating from within the bactritoid nautiloids, Ammonites first appeared in the Late Silurian to Early Devonian (~400 million years ago) and became extinct at the close of the Cretaceous along with the dinosaurs (65 million years ago). The classification of ammonites is based in part on the ornamentation and structure of the septa comprising their shells' gas chambers; by these and other characteristics we can divide this subclass into three orders and eight known suborders. While nearly all nautiloids show gently curving sutures, the amm ...

See also:

Ammonite, Ammonite - Classification, Ammonite - Life, Ammonite - Shell anatomy and diversity, Ammonite - Basic shell anatomy, Ammonite - Sexual dimorphism, Ammonite - Variations in shape, Ammonite - The aptychus, Ammonite - Size, Ammonite - Ammonite distribution, Ammonite - Trivia, Ammonite - References and further reading

Read more here: » Ammonite: Encyclopedia II - Ammonite - Classification