About Ammonite
Ammonites were predatory mollusks that resembled squid. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus.
Ammonite Characteristics
Common Name: Ammonites/Ammonoids
Scientific Name: Ammonoidea
Type: Prehistoric Animals, Diet: Carnivore
Size: From less than an inch to more than nine feet in diameter, relative to a 6-ft man.
Ammonites were predatory mollusks that resembled squid. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus. Ammonites first appearing in the fossil record 240 million years ago, descending from straight shelled cephalopods. The last lineages disappeared 66 million years ago at the end of the Cretaceous.
Apparience
Based on the fossil record, ammonites came in a wide range of sizes and shapes, from smaller than an inch to as large as nine feet wide. Some ammonites had long, straight shells, while others had helix-shaped shells. Most species, however, had coiled shells lined with progressively larger chambers separated by thin walls called septa.
The animals constantly grew new shell material as they aged, but the their bodies always remained in the outer chamber. The walls that separated each chamber helped protect the shell from being crushed. They were connected to the shell by intricate lines known as sutures—the complexity of which varied tremendously throughout this animal’s evolution.
Cephalopods
The many chambers of their shells likely helped these cephalopods glide through the planet’s warm, shallow seas. A thin, tubelike structure called a siphuncle pumped air through the interior chambers of the shell, which scientists believe helped provide buoyancy and move ammonites through the water. It’s unclear whether ammonites were very efficient swimmers, though.
Scientists believed that ammonites, like modern cephalopods, had soft body tissue with tentacles attached to their heads for catching prey. Fossil evidence indicates they had sharp, beaklike jaws to snare prey such as plankton, crustaceans, and other ammonites. They were also preyed on by larger reptiles and fish.