Kerian's Theories - Orthocone Eyesight

Kerian's Theories: Orthocone Eyesight

In the Walking with Dinosaurs special, Sea Monsters, Nigel Marvin; zoologist, paleontologist (and bad actor); visits seven of the world's deadliest seas of prehistory.  It was the show where I learned of the term 'Hell's Aquarium,' which is the name used to describe most of the Late Cretaceous oceans.  In the first part, he goes to the Ordovician where he meets a 'giant orthocone,' which was likely one of the granddaddies of an equally large cephalopod called Cameroceras.

Cameroceras, like most Orthocones, was a cephalopod.  It was unique among cephalopods in that it had a hard shell covering its mantle much like snails do; a trait it shares with Ammonites and modern Nautiluses.  Unlike its cousins, however, this shell points straight like a cone, hence the name.  It is theorized that these shells, much like today's Nautiloids, were used to aid in buoyancy underwater.  There have been a lot of theories surrounding these guys, but the biggest involves their size; at one time it was theorized it could grow up to 11 meters (36 feet) in length, including both shell and tentacles.  Such a deep sea creature would likely have lived most of its life in deep water where it could both support its bulk and allow room for it to swim around, as reefs at that time would likely have constrained its movement.

Now Cameroceras depictions have led to some confusion among a few scientists.  In the film Sea Monsters it was depicted as having poor eyesight.  This is odd considering that cephalopods are most famous for their eyesight, which they use to be able to help depict colors easily as a form of communication between members of their own species.  No one's ever been able to find any eyes fossilized on these things yet (it is very hard to get soft tissue to fossilize, and when it does it is a very rare find indeed), so how can they tell?

Except that Cameroceras has a modern relative today that had poor eyesight...

Nautiluses are the last known living cousins of the Ammonites and the Orthocones, making them a living fossil whose body type is older than any other cephalopod group living.  If you've ever seen a nautilus you'd recognize just how alien they look; they have a shell like a snail does, their tentacles don't have suction cups (and there's a lot of them) and they have very weird eyes.  Their eyes are, in fact, very poor altogether; primitive and practically useless in the depths where they like to call home.  Given that nautiluses have remained unchanged since the Triassic period there is a very good chance that Orthocones and even Ammonites shared a similar body composition; suction-less tentacles that were long and wiry and eyes that collected light but weren't very good at seeing it; and that their relatives, the squids and the octopuses, had taken on a much different route than they.  After all, the one thing that squids, octopuses, and cuttlefish have in common is that they have good eyes and they use them to see color as a form of communication.  If you don't communicate with color (courtesy of a big shell) then why would you need to have good eyesight?

-Kerian