What is this?!

[Lulu88]

Hey guys and girls.

I’m so sorry if this is a common thing, I don’t hit the beaches often. 
 

but I just couldn’t wrap my head around what this is. 
first I assumed coral, then thought maybe the inner part of a sea snail shell? 

sorry for sounding silly. Just curious and it’s late and this seems to be the only thing I can focus on, hahaha 

[Lulu88]

[Lulu88]

[Lulu88]

[jcbshark]

Looks like the inner whorl of a shell to me 

[Fossildude19]

I agree - inner whorl of a large gastropod shell. 

[IsaacTheFossilMan]

Inner whorl of gastropod.

[caterpillar]

[jpc]

yup

[Harry Pristis]

A columella.  Native Americans along the Florida coast made tools from these shell parts.  You must find evidence of human alteration to call it a tool.

 

[IsaacTheFossilMan]

On 2/16/2021 at 7:22 AM, caterpillar said:

Isn't it from the top part? 

[Thomas.Dodson]

1 hour ago, IsaacTheFossilMan said:

Isn't it from the top part? 

No. This is part of the lower columnella as others have mentioned. Folds (also called plaits) occur closer the aperture and disappear/become a part of the whorls as you go into the spire. Of course there's a lot of variation in the size and shape columnellar folds (some gastropods have none, others change the number of them through ontogeny) but they all seem to follow this rule. It can be very annoying having to prepare the folds to expose diagnostic characteristics in some small gastropod species but that's another story...

 

Maybe this picture will help visualize it more. This is a Caricella pyruloides (Eocene, Georgia) with the outer lip gone exposing the unworn folds in the body whorl. It gives you another example of unworn folds.

 

[Lulu88]

So awesome, thank you guys and girls!

 

[IsaacTheFossilMan]

20 hours ago, Thomas.Dodson said:

No. This is part of the lower columnella as others have mentioned. Folds (also called plaits) occur closer the aperture and disappear/become a part of the whorls as you go into the spire. Of course there's a lot of variation in the size and shape columnellar folds (some gastropods have none, others change the number of them through ontogeny) but they all seem to follow this rule. It can be very annoying having to prepare the folds to expose diagnostic characteristics in some small gastropod species but that's another story...

 

Maybe this picture will help visualize it more. This is a Caricella pyruloides (Eocene, Georgia) with the outer lip gone exposing the unworn folds in the body whorl. It gives you another example of unworn folds.

 

Ahhhh, thank you! Maybe I should just stick to Brachiopods

[Harry Pristis]

I think Isaac and Thomas are each partially correct.  The columella starts on the big whelks where the shell starts to spiral and expand.  The lowest part of the shell is not spiral; it is hollow and called the siphon or siphon canal in the illustration.  Thomas' Caricela is interesting, but it is not the best illustration of this morphology. 

I have a queen conch sawn in half longitudinally somewhere in storage which may be a better illustration.  I'll try to find it. 

 

 

[Thomas.Dodson]

1 hour ago, Harry Pristis said:

I think Isaac and Thomas are each partially correct.  The columella starts on the big whelks where the shell starts to spiral and expand.  The lowest part of the shell is not spiral; it is hollow and called the siphon or siphon canal in the illustration.  Thomas' Caricela is interesting, but it is not the best illustration of this morphology. 

I have a queen conch sawn in half longitudinally somewhere in storage which may be a better illustration.  I'll try to find it. 

 

 

Yes, the siphonal canal of the shell is an extension of the aperture, not the columnella. If it wasn't clear the Caricella was just an example of columnellar folds to identify columnellas, not the siphonal canal. Here's a complete Caricella pyruloides with the intact outer whorl and siphonal canal that Herb posted in the forum gallery. 

I also found this cool X-ray on Wikipedia that illustrates the columnella very well. Note the more dense columnella and also how it expands to the whorls as it goes into the spire in contrast to simple folds that occur near the aperture. This is the point I was trying to make.

[Harry Pristis]

28 minutes ago, Thomas.Dodson said:

Yes, the siphonal canal of the shell is an extension of the aperture, not the columnella. If it wasn't clear the Caricella was just an example of columnellar folds to identify columnellas, not the siphonal canal. Here's a complete Caricella pyruloides with the intact outer whorl and siphonal canal that Herb posted in the forum gallery. 

I also found this cool X-ray on Wikipedia that illustrates the columnella very well. Note the more dense columnella and also how it expands to the whorls as it goes into the spire in contrast to simple folds that occur near the aperture. This is the point I was trying to make.

 

 

Thank you Thomas.  Allow me to point out that there is no "n" in columella.

 

[Thomas.Dodson]

12 minutes ago, Harry Pristis said:

 

Thank you Thomas.  Allow me to point out that there is no "n" in columella.

 

Woops. Thanks for pointing that out.

[IsaacTheFossilMan]

Ah, so it's the middle part?

[Thomas.Dodson]

45 minutes ago, IsaacTheFossilMan said:

Ah, so it's the middle part?

It depends on the species. In some whelks for example the siphonal canal is so long that the aperture and thus base of the columella fall in the "middle". In a lot of species the siphonal canal is shorter or absent so the base of the columella is proportionally "lower". I hope that makes sense.

[IsaacTheFossilMan]

4 minutes ago, Thomas.Dodson said:

It depends on the species. In some whelks for example the siphonal canal is so long that the aperture and thus base of the columella fall in the "middle". In a lot of species the siphonal canal is shorter or absent so the base of the columella is proportionally "lower". I hope that makes sense.

Right, that makes sense. I'm not too familiar with gastropods, apologies!

[Thomas.Dodson]

1 minute ago, IsaacTheFossilMan said:

Right, that makes sense. I'm not too familiar with gastropods, apologies!

No apologies necessary. this is a place of learning and questions are one of the best ways to learn.