Ammonoidea

3D Model

An ammonite, subclass of the class Cephalopoda. This specimen is in the teaching collection of the Department of Invertebrate Paleontology.

Cephalopods are extant (living) marine mollusks characterized by tentacles attached to a cone-shaped body. The name cephalopod comes directly from the Greek kephalopoda, “head-feet.” Most fossil cephalopods formed a calcareous (made of calcium carbonate) shell around their conical body. The shell may be straight (orthoconic), curved (cyrtoconic), or coiled. As cephalopods grow, shells are sealed off into increasingly large chambers, with the body remaining connected by soft tissue in a thin tube called the siphuncle. Many cephalopods live today, including cuttlefish, squid, and octopus, but only the Nautilus has a coiled shell. (David and Mapes 1996, “Phylum Mollusca, Class Cephalopoda”)

Image by Jacob Kordeleski, CMNH Dept of Archaeology // Hawken School