This Cleoniceras is an excellent example of one of the most beautiful of all fossil groups, the ammonites. Much like a submarine, ammonites employe🧸d gas- and liquid-filled chambers to regulate their position in the water column. The animals themselves lived only in the outermost compartment, employing its tubular siphuncle to connect its chambers along the shell's ventral surface.

The now-extinct ammonites are some of the oldest cephalopods — a grꦅoup that includes today's octopus, squid, cuttlefish, and nautilus — and are of central importance to the study of paleontology. Acting as a "defining biological marker," they provide a reference for determini💝ng the age of select sedimentary rock layers.