Malacology - H.G. Wells Style

John,

Thanks for the info about the Rhizocephalan. I know one shouldn’t be emotive about behaviour patterns but what a horrific creature! Hadn’t heard of that one before; much to my regret I read about it whilst eating a prawn sandwich. Bad idea.

Going back to the origins of the mollusca there have been a few interesting finds in recent years, notably a strange beast known as Kimberella that was described about five years ago and was discovered at the White Sea in the Arctic circle on the north coast of Russia and dates to about 550mya. This places it almost immediately before the Cambrian ‘explosion’ that gave rise to modern bauplans in a remarkably short space of time. (hotly debated, most estimates say about twenty million years). Kimberella is interesting as it is difficult to interpret but is thought to be an early mollusc. Physically it looks like a jellyfish without the tentacles but has bilateral symmetry and a tough (non-mineralised) but flexible shell. Some fossils apparently display a mollusc type foot and although no radula has yet been found associated with this animal, as far as I know, not all mollusc fossils do.

Trace marks and scrape marks in some late Precambrian sediments may well have been caused by a creature such as this or even its ancestor. Trace marks date from 565mya or even earlier so there must have been some ancestral creature that lived in a mollusc fashion scraping up algae at this even earlier date possibly as far back as 620mya.

Other early (probable) molluscs are evident in the Tommotian faunas from Siberia (about 530mya) which largely consists of many tiny shells, many of which resemble monoplacophora. There are many varieties of cone, spiral, horn-shape and tube evident though whether or not they were molluscs depends on how a mollusc is defined, I suppose. Try doing Google searches under Tommotia, Yochelcionella or Latouchella if interested. Following this is the sudden evolution of modern body plans during the Cambrian ‘explosion’ including the arthropods and although probable molluscs were evident (re: Wiwaxia above) the relationships of these creatures to each other animal groups has been the source of much debate and study recently. All very complex.

I still have not discovered a cephalopod earlier in date to Plectronoceras (Upper Cambrian). I attach a copy of its anatomy here. I had to copy it from a text book to avoid copyright problems duplicating it here. It is quite probable that Plectronoceras evolved from something very similar to Latouchella as they do look similar (from drawings in textbooks, that is!)

On a different note, I think that 10m long Nautiloid was called Cameroceras. Must look that one up.

Phil

(PS If I have made any mistakes above I apologise. I have never actually studied zoology or palaeontology and am working out of a few books at home. All very interesting, isn’t it!)
 
Phil,

HA HA HA HA!! :lol: Well, if it makes you feel any better, the favorite host of Rhizos seems to the "dungees" (Dungones Crab(sp?)) Cancer magister here.

Yeah, the Rhizocephalan is a +100 on the freaky scale... but nontheless a miraculous lifeform. Just a testament to the power of life and its many forms. How hardy life on Earth can be!

Thanks for the info and the pic... I'm going to find some more information, now that I have some (scientific names).

Sushi and Sake,

John
 
Steve,

I can't find a specific reference to the 9 meter (30 ft) Endocerid, but almost any book on fossil cephalopods quotes that number. Even Teichert (1964, Treatise on Invertebrate Paleontology, Pt K, Mollusca 3,) mentions The 9 to 10 meter number only in the introduction to a couple of chapters. Manger, Meeks, and Stephan, 1999, Pathologic Gigantism in Middle Carboniferous Cephalopods, Southern Midcontinent, United States, in: Advancing Research on Living and Fossil Cephalopods, edited by Oloriz and Rodriquez-Tovar, Kluwer Academic/Plenum Publishers, have a nice summary of giant fossil and extant cephalopods with many specific references (but they only refer to Teichert for the 9 meter Endocerid). The longest Endocerid I have found is only 450mm. You can see a picture of an Endocerid on my web site

http://ammonoid.topcities.com/whiterock.htm

:nautilus:
 
Perhaps someone a little more familiar with the web/with ammonites could compile a list of ammonite or ammonite-related sites. :smile:
 
I was doing a little pleasure reading yesterday. My old invert zoology book Invertebrates by Brusca and Brusca has several branches of possible molluscan phylogeny, but nothing concrete. The funny thing is I have the feeling that there's a lot more to the origin of the cephs than ammonites and belemites, but I'm not sure what that may be.

Evolution: The itch you just can't scratch without a little spectacled beagle and a Way-Back machine...

Still though... Does there seem to be any indication of punctuated equilibrium along the cephalopod line? Any quantum leaps in ceph evolution over the last few hundred million years?

Sushi, Sake, and Pocky

John
 
I think phyletic gradualism in ammonoids is what makes them such good index fossils. Except for "punctuated" radiations after major extinction events, the ammonoid line is fairly smooth from their appearance in the Late Silurian?/Early Devonian, until their disappearance at the end of the Cretaceous.

Coleoids (with hard parts) appear in the Early Carboniferous. Could a cephalopod without recognizable or unfossilizable hard parts or without hardparts at all have evolved at the same time? Or even before? The great diversity of living cephalopods makes me think......

Where is that Wayback Machine?

:nautilus:
 
Maybe this is a weird question, but why aren't there any freshwater cephalopods? I mean, considering that others molluscs managed to colonize freshwater and land, it stands to reason that at least a FEW species of ceph might have tried... Any thoughts?

Sushi and Sake, and the occasional glass of Kirin Rose Life Milk Tea,

John
 
Heads up!

Starting July 8, "The Future is Wild" will be shown on Animal Planet as a new weekly series featuring all new weirdies from the far future! All hail the molluscan overlords! Who'll be making pearls NOW?!?!?

Sushi and Sake, but hold the Tako-Yaki

John
 
All,

Well, I'll be a monkey's nephew...

Just learned that H.G.Wells was a pupil of Thomas Huxley's. A nifty biographical detail, isn't it?

Clem
 
Are we talking Huxley as in Darwin's Bulldog? The man who destroyed Richard Owen?

Who wouldn't have loved to present in the great debate between Huxley and Bishop Wilberforce, IMHO the first and greatest direct clash between religious doctrine and emerging evolutionary theory. Oh, to be a fly on the wall (in a top hat).

Didn't know that!

Phil, (not at all in a pretentious mood).
 
Phil said:
Are we talking Huxley as in Darwin's Bulldog? The man who destroyed Richard Owen?

The very one.

The authors of the recent book "The Mistaken Extinction" had a little fun with poor Owen, presenting his own personal evolution in photographs: from strapping young man to hollow-eyed wretch. A wicked "in" joke, but payback's a-

:wink:

Clem
 
Sounds great, I'll have a look out for that one.

Was it written by Gideon Mantell's great-great-grandson by any chance? Just desserts, methinks! :twisted:
 

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