Eight-Armed Animal Preceded Dinosaurs

Garimelda writes "Scientists have discovered what they believe is an eight-armed creature which colonized a large section of the world's oceans over 300 million years before the first dinosaurs emerged."

four accidental or metabolically efficient?

[peter303]

Maybe four limbs gives you more bang for the buck in terms of the energy of development and survival locomotion. However insects and relatives have been more creative with all even numbers - 2, 4, 6, 8 and dozens.

computer evolution experiments

[peter303]

I recall people studying the evolution of locomotion by allowing any kind of movement- walking, tumbling, slithering, wheels, etc. Computer programs "evolve" trying random mutations and look at resulting locomotive efficiency. Some clever, unexpected solutions result which you dont see in nature. I forget the reference, but may be associated with the Sante Fe Artificial Life Institute, etc.

Re:four accidental or metabolically efficient?

[OzPeter]

I have always wondered where we got our 5-fold symmetry from. Our core body sprouts 5 elements (head, 2 arms and 2 legs), and the arms and legs at least sprout 5 fingers and toes.

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Re:four accidental or metabolically efficient?

[lartful_dodger]

The basic mammalian model, I always thought, was a 6-element system - most mammals have a tail, even some humans are born with one, albeit vestigial.

Bilateral symmetry by pure chance

[timholman]

To me, the most interesting aspect of these early, pre-Cambrian-Explosion fossils was that bilateral symmetry (which is the norm for practically all animal life today) was nothing special. You had lots of organisms that were radially symmetric or just plain asymmetric. Whatever mass extinction event wiped out the majority of the Ediacaran biota gave a foothold to the bilaterally symmetric ancestors of modern animal life, which then dominated the Cambrian Explosion. It is just a fluke of evolution that we are not radially symmetric or asymmetric. Shades of Niven & Pournelle's Moties!

who says .....

[Brigadier]

i'm off topic on this one, but I never did understand why the assumption was always made that got created creatures the way they exist today. When the Bible says man who says they were refering to the first bi-ped. Who isn't to say the Bible wasn't refering to the final iteration of homosapain. Just food for thought here not trying to start a new religion.

Re:Are those really limbs?

[GleeBot]

Those 'limbs' are in an exceptionally regular spiral pattern. If you fossilized an octopus, you'd expect the limbs to be all crossed over and tangled up. I'm guessing that those 'limbs' couldn't move independently, and are more like ridges in a sheet of material.

More to the point, a soft-tissued creature like an octopus almost never leaves a fossil record. If you find a fossil, it's because of some sort of skeletal structure the creature has left behind, which of course would naturally be rigid. Think of something like an eight-branched exoskeletal structure.