the Evo of Ceph Armature


Sep 26, 2005
Hey all. As most of you are no doubt aware of my studiers at the moment, I have decided to start researching the evolutionary history of Cephalopods' armature, with some help from Phil's family tree to help me along. I have thusfar discovered that Belemnites had hooks, but not suckers, which is fine (although Kat said the paper was a bit dubious at times- Engeser & Clarke Cephalopod Hooks, both recent and fossil[1988]) and from a few other sources.
I know also that Nutiloids don't have armaure except maybe a row of cirri or something? and they come almost directly from the Orthocone branch. Did ammonites have suckers or hooks, or is it just a characteristic of the Coleoidea?
Also, I suppose this means that hooks evolved before suckers then, or did they evolve alongside, just in a different branch? Most likely a responce to prey?
Any comments are appreciated.

Your answer probably lies in the Devonian Bactritids, if you find that they had hooks or suckers then the orthocerids may have had them. It is widely accepted that the Ammonoids and the Belemnoids both came from the Bactritids, so Bactritids could have passed them on to both or just the Belemnoids. Or, like you say, hooks may have started with the Belemnoids. Also up in the air is wether "ten arms" started with the Coleoids or "many arms" started with the Nautilids, and if armature started with "ten arms".

The Origin of the Cephalopoda (Dzik 1981) may help a little.

or The Fossil Coleoid Page
Crikey, that's a good question.

As far as I know arm hooks are purely a characteristic of the advanced coleoids, and are not present in ammonoids. I'm fairly sure that squid hooks are a derived secondary characteristic of suckers, therefore suckers in this lineage must have evolved first. However, according to Engeser (see Kevin's link above) Belemnite hooks do not stem from rings and are primary formations.

You are absolutely right that Nautilus does not have suckers, instead it has sticky pads arranged in ridges allowing it to cling to surfaces, but without any soft-bodied fossils (as far as I know) it is impossible to say if orthoconic nautiloids had the same arrangement. As Kevin has suggested, I expect that the evolution of the earliest sticky rings that went on to evolve into suckers took place amongst the Bactritids.
Hmmm, are there any fossils of coleoids, excluding belemnoids, at all? Even what would be hard parts? I've seen plenty belemnoids with their hooks!

Graeme said:
Hmmm, are there any fossils of coleoids, excluding belemnoids, at all? Even what would be hard parts? I've seen plenty belemnoids with their hooks!


See Phils Fossil Octopuses article. It has Paleoctopus with suckers (as hard as I look I cannot see them) from the Cretaceous. Also there are fossil squid from Lebanon with most of the tentacles painted on if I remember correctly.

There is a report of squid gladii and fossil tentacle hooks from the Permian here is Utah. As for the hooks, I have not seen pics of them :sad:, and as hard as I search through the beds they were reported in I cannot find any. I found some bivalves I thought were maybe jaws, but I am quite sure they are bivalves.

For the tentacle hooks and some ammonoids see:
Yochelson, E. L., 1968, Biostratigraphy of the Phosphoria, Park City, and Shedhorn Formations, U.S.G.S. Professional Paper 313-D, 660 p.

For the squid gladius see:
Gordon, Mackenzie, Jr., 1971, Primative Squid Gladii from the Permian of Utah, U.S.G.S. Professional Paper 750-C, p. C34-C38

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