
Cephalopods may be divided morphologically into:
ECTOCOCHLIAN FORMS
- have external shells
- encompass the vast majority of
fossil cephalopods
- for example, Nautilus
Figure 4: A Nautilus pompilius.
ENDOCOCHLIAN FORMS
- have internal shells or other solid internal
structures, although they include forms without
solid internal parts; for example, an octopus
- most living cephalopods today are endocochlians whose fossil relatives
include the Belemnites
Figure 5: Octopus rubescens.
© Sarah Vandervlugt.1998