Ordovician Coiled Nautiloid

**Architeuthoceras** · Nov 21, '04, 11:06pm

Found this the other day. Quite remarkable preservation for something almost 500my old. All the shell is missing, an external mold on the left shows how the shell had small ribs or undulations, and the growth lines are visible. The siphuncle, or at least an internal mold of the siphuncle is seen near the top of the photo. Some of the internal molds of the chambers have been silicified and show how closely spaced the septa were. There is also a gastropod internal and external mold just above the nautiloid.

**cthulhu77** · Nov 22, '04, 4:28am

Awe inspiring...simply beautiful.

**Phil** · Nov 22, '04, 8:46am

That's fantastic Kevin.

Any idea what sort of nautiloid it is?

**Architeuthoceras** · Nov 22, '04, 1:15pm

Not near as nice as a chunnel nautiloid is it :( Probably Aphetoceras like the other one, but it may be just a partially coiled form, too bad it isnt all there.

**Phil** · Nov 22, '04, 9:04pm

Maybe not as nice, maybe, but it is five times older....

If anyone is wondering what Aphetoceras looked like, here's a little image. I believe that this type of shell is known as a gyrocone (?).

**Jean** · Nov 22, '04, 9:27pm

looks a bit like Spirula

J

**spartacus** · Dec 13, '04, 12:46pm

sorry I'm late big Kev, was unavailable at the time of posting & still catching up.
that's pretty special considering what the remains could have gone through after 500my wow

not quite so impressive but similar was a pair of [/i]Cardioceras chalcedonicumsssss (possibly) I found in a nodule in the UK. A bit fragged, but like Steve Austin, I will rebuild them (on a tighter budget)
when i started getting all the bits together it was amazing what I found I had considering it was up to 160myo. having read up & been educated by you guys on what's what it was pukkal to see how our curly friends were really put together other than by a diagram

hats off
I will post as soon as I find their box, now where'd I put 'em ?

Keef

**Architeuthoceras** · Jan 24, '05, 3:12pm

I just attached a larger photo for a little more detail on the first post. And added this photo from another thread.

With the whorl and spiral expansion rates on this I am quite sure it is an Aphetoceras sp. This means it was the first nautiloid that coiled more than 1.25 whorls, and makes it the first member of the Order Tarphyceratida, the ancestral order of all coiled nautiloids*. Those that didnt coil more than 1.25 whorls, and have the large, ventral siphuncle, and close spaced septa, are left in the order Ellesmeroceratida, the order all the other forms of cephalopoda sprang from.
It is amazing what you can learn when you go to the library instead of the desert.

* this depends on who's classification you are reading.

**Phil** · Jan 25, '05, 6:02pm

Thanks Kevin, a lovely and interesting find. Is this a rare specimen, the first such you have found?

(By the way, I've restored the line drawing above for everyone to see a reconstruction of the shell form)

**Architeuthoceras** · Jan 25, '05, 11:12pm

These two are the only ones I would confidently refer to Aphetoceras. there are a few external molds in the same horizon that have the same ornamentation, but I cant be sure they are the same genus.

This small impression maybe an external mold?? compare it with the external mold (lower left) on the first attachment.

**Architeuthoceras** · Nov 25, '05, 11:36pm

I dont know what to think about this fossil

With no septa or siphuncle showing it may not even be a cephalopod, but it has the same shape as the Aphetoceras found in the same beds. About the best I found today anyway.

**Phil** · Nov 28, '05, 2:27pm

Very nice find indeed Kevin.

If it is not a ceph, and surely with that shape it must be, what else could it just possibly be do you think?

I wish I could find cephs that old. Mine are just playful young pups in comparison.

**Architeuthoceras** · Nov 28, '05, 3:04pm

It is probably an internal mold (or a fossil of an internal mold) of the gastropod Maclurites.
I didnt think gastropods had loose coils, but it may just be that the part exposed makes it look loose coiled.

I wonder why it's pink?

Thanks for another wave to surf Phil