- Joined
- Nov 19, 2002
- Messages
- 3,031
GPO87 said:
Joy, GP087,
Yep, that's right.
Vampyroteuthis is the last surviving member of the vampyromorpha, a cephalopod group that really had its heyday in the Jurassic. It is neither squid or octopus but probably stemmed from that murky period about 350 million years ago in when the earliest belemnites, teuthids and octopods were all beginning to appear.
Evolving from a ten-armed common ancestor back in the late Devonian or early Carboniferous, the different groups took the body plan in different ways. The belemnites kept their ten arms, the octopuses slowly lost an arm pair leaving them with eight. The decapodiformes (later cuttlefish, squid) converted one arm pair to tentacles. The vampyromorphs reduced an arm pair to form those long sensory filaments, but this is a different arm pair to the tentacle conversion of the squid.
One strange feature of Vampyroteuthis is that in common with many of the ancient vampyromorphs it actually has two pairs of fins. The second pair of fins are grown in its juvenile stage but are absorbed back into the body as the creature grows, developing the second pair in its adult stage. So although in most photos you will find the animal with one pair showing, it actually has two, one pair being lost as it grows.
Most of the fossil 'squid' you will occasionally find for sale, most commonly German Jurassic specimens, are actually vampyromorphs, only very distantly related to modern squid. One of the earliest vampyromorphs known, Mastigophora brevipinnis from the mid Jurassic Oxford Clays displays the eight arms and two filament structure. Another fossil vampyromorph of about the same date is Trachyteuthis which also has two pairs of fins.
Interesting group, I can see why the Vampire Squid is frequently referred to as a living fossil! As for freshwater octopuses.....nah, afraid not. That's come up here before, I'll see if I can find the original thread for you.
Phil
a few tried but got suspended.......that was back in the dark ages of course!)
