Note: Phil welcomes discussion on this article in the Cephalopod Fossils forum.
Fossils of octopuses are by far the most enigmatic and mysterious of all the ancient groups of cephalopods. Due to their delicate structure fossils of these animals are exceptionally rare, as the soft-bodied nature of the animal does not lend itself to fossilisation. They are so unusual that there is just one known from Illinois, one from France, a handful from Lebanon and a couple of jaw fragments from Japan and Vancouver Island. In almost three hundred million years of octopod existence, the fossil record currently comprises just eight species in six genera - our entire record would fit inside a suitcase!
Very little is known about ancient octopus history, how they evolved and developed, or their lifestyle. Following is a brief look at some of the theories surrounding them, the octopus fossils themselves and the sites they were found in. These ancient forms almost certainly do not represent a single line of descent.
A little background may be of assistance in trying to understand these fossils. If we travel back in time to the Late Devonian period (408-360m) practically all the cephalopods we would find were the externally-shelled nautiloids. The very earliest ammonoids were starting to appear in forms known as goniatites, and living alongside them were a strange off shoot of the nautiloids known as the bactritids. These bactritids had long straight conical shells and share similarities with not only the ammonoids, but also the belemnoids...
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