Ammonite Anatomy

[Scylla]

soft tissue preservation of an ammonite without its shell!

 

https://www.newscientist.com/article/2265570-strange-fossil-is-the-first-to-show-an-ammonite-without-its-shell/

[DPS Ammonite]

35 minutes ago, Scylla said:

soft tissue preservation of an ammonite without its shell!

 

https://www.newscientist.com/article/2265570-strange-fossil-is-the-first-to-show-an-ammonite-without-its-shell/

Here is a better copy:

https://sjpp.springeropen.com/articles/10.1186/s13358-020-00215-7

 

 

 

[MrR]

Interesting article in the NYT about an ammonite fossil that mineralized outside its shell. I believe the NYT allows 10 articles to be read without a subscription. I don't think I would have recognized it for what it is. Enjoy.

 

Bare Ammonite

[LabRatKing]

I have oft wondered if some ammonites and ammonoids were more like these guys (Spirula) that the standard artists' interpretations based on nautiloids.

 

Sadly this fossil doesn't really clear that hypothesis up.

 

Recently it was found that many more of these extant guys actually swim in a vertical orientation as opposed to dorso-ventral horizontal orientation, as if hanging down from their internal shell, but I'll be darned if I can find the journal article I was reading it in now.

 

 

 

 

[Al Dente]

2 hours ago, LabRatKing said:

I have oft wondered if some ammonites and ammonoids were more like these guys (Spirula) that the standard artists' interpretations based on nautiloids.

 

Sadly this fossil doesn't really clear that hypothesis up.

 

Recently it was found that many more of these extant guys actually swim in a vertical orientation as opposed to dorso-ventral horizontal orientation, as if hanging down from their internal shell, but I'll be darned if I can find the journal article I was reading it in now.

 

Yes, they swim in a vertical orientation. The first one filmed in its natural habitat was just a few months ago and made some headlines. It swam tentacles pointing upward. This makes sense in terms of countershading. They have a light organ on their bottom so any animal looking up at it would see the light blending in with the surface light. Here's one of the posts about the new footage-https://www.sciencealert.com/first-ever-deep-sea-footage-of-a-ram-s-horn-squid-has-scientists-freaking-out

 

 

[RuMert]

Something like this. No hood, big funnel, round eyes, ten arms, lots of shell structures like limpets, different shell ornamentation (outer whorl is often smooth, especially with females) etc. I plan to summarize current ideas about ammos in a post here sometime

[Fossildude19]

TOPICS MERGED.   

 

@MrR

[LabRatKing]

3 hours ago, Al Dente said:

Yes, they swim in a vertical orientation. The first one filmed in its natural habitat was just a few months ago and made some headlines. It swam tentacles pointing upward. This makes sense in terms of countershading. They have a light organ on their bottom so any animal looking up at it would see the light blending in with the surface light. Here's one of the posts about the new footage-https://www.sciencealert.com/first-ever-deep-sea-footage-of-a-ram-s-horn-squid-has-scientists-freaking-out

 

 

Yup that’s the article I was trying to find! Was another around the same time that had totally transparent species with tightly could shell that oriented the face down too.

 

part of my pub time hypothesis is due to the protrusions on some ammonite fossils. Sure to an extent, knobs, protrusions and tubercles can increase lift and reduce drag (think shark skin and blue whale fins) but I wonder if those aren’t actually some sort of attachment point for soft tissues.

[Thomas.Dodson]

11 minutes ago, LabRatKing said:

Yup that’s the article I was trying to find! Was another around the same time that had totally transparent species with tightly could shell that oriented the face down too.

 

part of my pub time hypothesis is due to the protrusions on some ammonite fossils. Sure to an extent, knobs, protrusions and tubercles can increase lift and reduce drag (think shark skin and blue whale fins) but I wonder if those aren’t actually some sort of attachment point for soft tissues.

An interesting idea.

 

Ornamentation is so complex and variable and sexual dimorphism so common I've often wondered the precise extent ornamentation plays in lift/drag, sexual selection, mechanical use, protection, etc... Then there's also the issue of intraspecific variability within a sex and drastic ontogenetic changes in some species to shake things up. I'm reminded of a quote from a paper. "The ammonoid shell is a complex structure and any single interpretation of its function would be naive". That was from "Aspects of ammonite biology, biogeography, and biostratigraphy" (W J. Kennedy and W. A. Cobban 1976). PDF LINK

This conversation reminded me of it and to read it again. It's a pretty ambitious attempt to summarize and discuss what we know about ammonite biology as a whole. I'm not sure much has changed in the debates since it was published.

[LabRatKing]

1 minute ago, Thomas.Dodson said:

An interesting idea.

 

Ornamentation is so complex and variable and sexual dimorphism so common I've often wondered the precise extent ornamentation plays in lift/drag, sexual selection, mechanical use, protection, etc... Then there's also the issue of intraspecific variability within a sex and drastic ontogenetic changes in some species to shake things up. I'm reminded of a quote from a paper. "The ammonoid shell is a complex structure and any single interpretation of its function would be naive". That was from "Aspects of ammonite biology, biogeography, and biostratigraphy" (W J. Kennedy and W. A. Cobban 1976). PDF LINK

This conversation reminded me of it and to read it again. It's a pretty ambitious attempt to summarize and discuss what we know about ammonite biology as a whole. I'm not sure much has changed in the debates since it was published.

Hmmm...I have a laminar flow tank...perhaps we should all gather up some casts of pristine ammos and have a look at how water moves around them...