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Eocene Cuttles

Hajar

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#1
Here is a pair of Eocene Belosaepia prongs from Belgium, the larger one being 17 mm long. For comparison with the modern I've added a photo of the pointy end of a modern cuttlebone off a local beach and a view of a Sepia couple with their flesh still on. I've still not seen any examples of these from the local Eocene rocks, but have my eyes open for them.
 

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OB

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#3
Nice one!
 

OB

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#5
Now, why indeed have cuttles disappeared/never appeared from/in the western hemisphere...
 

DWhatley

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#7
OB, I have often wondered about that too. I don't think we have nautilus either but why not?
 

Hajar

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#8
On a quick browse I collected these three quotes:

“There have only been two genera of coleoid cephalopods recovered from Oligocene aged sediments of North America; Oligorostra alabami Ciampaglio & Weaver, 2008 and Oligosella longi Ciampaglio & Weaver, 2008.” , from Weaver et al. (2010). These are thought to be spirulids and not belosaepiids.

“The oldest Sepiinae (Sepia and Archeosepia) occur in the Upper Eocene and Oligocene marls of the Budapest region (Sz6r6nyi, 1933; Wagner, 1938).” , from Hewitt & Pedley (1978).

“Everyone recognises that the older Cenozoic genus Belosaepia Voltz, 1830 is connected to Sepia Linnd, 1758 via Hungarosepia Doyle et al., 1994 ... from the Lutetian-Priabonian of Hungary” , from Hewitt & Jagt (1999).

So a sketched outline might be something like the following?: Late Eocene extinction of Belosaepia and Anomalosaepia in American seas; appearance of Sepia in the seas of Bohemian Europe via Hungarosepia and the opening North Atlantic proving an obstacle to migration of Sepia westwards.
 

DWhatley

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#9
TOO many rabbit trails :grin: I think I missed out on the expanding planet theory somewhere. Is the most current/accepted theory now that material moves between the riffs or is the expanding planet a partially accepted idea? I am just now learning that they teach putting a comma before the "and" in a list :old:
 

Hajar

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#10
Good fun. Those plate tectonic reconstructions are on a constant-volume Earth. New ocean crust forms at the spreading ridges (e.g. Mid-Atlantic Ridge) and elsewhere ocean crust is consumed as it descends into the mantle at subduction zones (deep sea trenches, e.g. off west coast of Chile). This is a good summary picture. As the Atlantic opens the Pacific shrinks due to subduction around the "Ring of Fire".

I think you could be right about the comma (though it was a crime to put a comma before the "and" when I was a kid) - one (North Carolinan) opinion says "If the items in the list are longer and more complicated, you should place a final comma before the conjunction." Then I looked at the BBC: "Make sure that you don't use a comma before the word and at the end of your list."!

Tomorrow I'm going to go out looking for Eocene cephalopods.
 

Hajar

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#11
and there's a good discussion of the history of the expanding Earth idea here. ".. since the recognition of plate tectonics in the 1970s, the scientific consensus has rejected any expansion of the Earth. Measurements suggest that, on very long timescales, the Earth is slowly shrinking, due to thermal contraction."
 

Architeuthoceras

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#12
Hajar;167874 said:
So a sketched outline might be something like the following?: Late Eocene extinction of Belosaepia and Anomalosaepia in American seas; appearance of Sepia in the seas of Bohemian Europe via Hungarosepia and the opening North Atlantic proving an obstacle to migration of Sepia westwards.
This may explain the Eastern side of NA, but why haven't they crossed the Pacific?
 

Hajar

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#13
Well, even in its present reduced state (see plate tectonic reconstructions here) that's a much larger ocean than the Atlantic.

So, what are the controls on cuttlefish distribution in the present? e.g. is there a lower bound of water temperature beneath which they don't thrive? Are they restricted to a certain band of water depths? Do they live in the open ocean or only in a belt around coastal waters (i.e. continental shelves)? Experts on modern cuttlefish please help!

This states that "Cuttlefish inhabit shallow tropical or temperate coastal waters, usually migrating to deeper water in winter. They are not usually found below 500m (1,640 ft)." If they are creatures of coastal waters and continental shelves and not open ocean animals then they would have a migration path along the Aleutians to take to reach the Americas and those are very cold waters.

I found this on a pygmy cuttlefish in Russian Pacific waters. "The Russian Maritime Province is by all means the northernmost outskirt of the species geographical range". The sea gets very cold north of here, and the Sea of Okhotsk freezes over in winter. If you look at the map of sea surface temperature shown here you can see that the 10-12 degree C band passes through the Sea of Japan; now look at the North Atlantic, that band of temperatures occurs much further north there, extending as far as Scotland (Sepia oficinalis territory), but not as far as Iceland.
 

DWhatley

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#15
It seems odd to me that we have both squid and octopuses but no cuttlefish or nautilus. I don't know much about squid but I am learning about octopuses. We have octopus species that drift in the plankton for a month or so (so these you would expect a wide range) as well as the species that are benthic from birth (would not roam far from home or be expected to traverse large bodies of water). If I understood right, there is evidence that they lived in this hemosphere at one time but became extinct but not so of the squid and octopuses (or possibly the squid and octopuses repopulated). Puzzling.

I was never taught the expanding earth theory (which seems a bit odd since my only exposure would have been in the 60's) so when I rabbit trailed you link I did not know if this was something new. I had recently read about the sea floor being far newer than we thought and that an exchange of mass was shown along the rifts. The only part that is different from what I remember being taught :old: is that scientists feel they have discovered where it goes and where it comes from which had been missing evidence.
 

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