Ammonite Fish

[Ptychodus04]

My father passed away a few years ago, and I got the vast majority of his fossil collection. My mom kept a few bits of broken ammonite to use as yard decorations. One was a living chamber from a large Metoicoceras with shell preserved. This came from the upper Britton Formation (Sciponoceras gracile zone), Eagle Ford Group, Late Cenomanian of Carrollton, TX. He had collected this piece in the late 80's-early 90's and it bounced around in a box moving several times across the country before it came back to Texas to sit for nearly a decade without being looked at.

One side of the living chamber is crushed in, so my mom set it in the garden "good" side up. Fast forward about a year. The Texas sun and weather had done it's worst on the shell. I glanced at the fossil and saw something weird shining through. So, I rescued it from the garden and cleaned off all the powdery shell material. Ten minutes with the ARO, and voila... I give you the fish within an ammonite. The question is... Did the fish swim into the shell after the ammonite died, or are we looking at preserved stomach contents?

[John K]

from what I know, an ammonite's shell contained mostly gas-filled chambers, used as bouancy; only the first chamber contained the actual body of the animal (not to say the rest of the shell wasn't part of the animals body, but you get my point I hope...); so I think the fish swam in post-mortum. Very cool fossil

[fossilized6s]

Ha, that is was one the coolest associated fossils i have ever seen!

My guess is that it set up residence there. But you would figure the sections of the internal chambers would prevent it from going so far in. Also, i would guess that there would be other sea floor sediments found with it. Honestly, i haven't a clue....

But very cool. Thanks for posting this.

[Ptychodus04]

Only the living chamber of the ammonite was preserved. The septum visible in the photo (near the fish's head) is the beginning of the first chamber. None of the phragmacone was recovered. This is a common preservation in the Britton Formation. Only the living chamber fills with sediment and the phragmacone gets crushed on the larger ammonites. My personal thought is that the fish swam in post mortem, but it's in the right place to be stomach contents...

[fossilized6s]

You got to figure that the fish would be pretty mangled and diced if it was eaten though. Idk

Edited September 25, 2014 by fossilized6s

[Fossildude19]

I'm thinking post mortem fish swimming in.

They liked to hide inside stuff.

Gotta say, that is one of the cooler fossils I have seen, though.

Regards,

[Foshunter]

That is just awesome to find something like that, gotta be an extremely rare occurance. Thanks for sharing, like alot----Tom

[Xiphactinus]

Awesome fossil! Kind of reminds me of the Inoceremus clams in the Niobrara Chalk that are sometimes found with fish inside them.

[Ptychodus04]

Thanks all. I agree that the fish probably found himself a new home in the vacated ammonite shell. You would expect ammonite stomach contents to look more like a fritter than a kipper after running through their beak!

[tmaier]

"Blenny" and "goby" are the common name of extant fish that inhabit old shells and crevices.

http://en.wikipedia.org/wiki/Blennioidei

http://www.google.com/images?hl=en&q=blenny&gbv=1&sa=X&oi=image_result_group&ei=lUskVPDlO46WyASW_4DoCA&ved=0CCEQsAQ

http://en.wikipedia.org/wiki/Goby

http://www.google.com/images?q=goby&hl=en&gbv=1&sa=X&oi=image_result_group&ei=LE0kVLC6BMGkyATX1ID4Ag&ved=0CC4QsAQ

I snorkle and dive, and if you hang still over a pile of old shells or reef, the blennies and gobies peek out of their homes to watch you.

[Auspex]

What a wonderful piece!

I doubt that ammonites swallowed fish whole, so a fish sheltering, or a dead fish conveniently washing in, is a more likely scenario.

[BobWill]

. None of the phragmacone was recovered. This is a common preservation in the Britton Formation. Only the living chamber fills with sediment and the phragmacone gets crushed on the larger ammonites....

I find this intriguing considering it's the other way around in most formations where I collect. I once asked if that was due to predation since an ammonite eater would probably crush the body chamber to get to the meat and was told it was more likely due to the phragmacone having the extra support of the septa which are absent in the body chamber which was therefore more likely to be crushed. That made sense to me but I am having trouble coming up with a reason for the preservation you are finding in the Britton. The only thing I can imagine is that the outer shell is built more thickly with maturity and maybe the body deteriorates and fills in with sediment more quickly in the Britton. Any ideas out there?

[Uncle Siphuncle]

Ammonite fish are COOL! I've only found one...Fort Worth Fm...Mortoniceras vs. Osmeroides...looks like the Mort came out on top.

[MB]

Try to find some idea in:

Late Cretaceous fish cans: Fish preserved in ammonite body chambers from platy limestones in northeastern Mexico

Christina Ifrim

Torrey Nyborg

Josep A Moreno-Bedmar

Francisco J Vega

Hector Porras-Múzquiz

[Ludwigia]

Hi Kris,

What a great discovery! You don't find something like that every day, although good ol' Dan manages to come up with at least one of just about everything.

[Ludwigia]

I find this intriguing considering it's the other way around in most formations where I collect. I once asked if that was due to predation since an ammonite eater would probably crush the body chamber to get to the meat and was told it was more likely due to the phragmacone having the extra support of the septa which are absent in the body chamber which was therefore more likely to be crushed. That made sense to me but I am having trouble coming up with a reason for the preservation you are finding in the Britton. The only thing I can imagine is that the outer shell is built more thickly with maturity and maybe the body deteriorates and fills in with sediment more quickly in the Britton. Any ideas out there?

Ammonites with flatly pressed phragmocones and 3D body chambers are quite a common occurrence in the Pliensbachian layers at the clay pit in Buttenheim, Bavaria. I think you are on the right track with your assumption. When the phragmocone is sealed, then the chambers are of course hollow and it doesn't take long before the sediment crushes them, whereas the body chamber generally fills up quite quickly. But you could then ask why does it often happen the other way around? I think that the speed of sedimentation is a factor here. If the phragmocone is filled as well as the body chamber, then it also has the added advantage of the support of the septal walls, whereas the body chamber does not and can't hold up to the increased pressure.

[Ptychodus04]

I agree that we are looking at a product of rapid sedimentation. There's evidence of rapid deposition as well as water currents. In the lower Britton, all fossils that I have collected that are around 12 inches or larger are oriented pointing east-west.

[Ptychodus04]

BTW, leave it to Dan to pull that out of his hat! If you rotate the specimen 180 degrees, then the fish came out on top! LOL.

Nice find.

[James_S]

Wow, it's absolutely amazing. Seriously, congratulations. You must have a very good eye to catch a glimpse of the fish while the fossil was just a garden ornament!

[Uncle Siphuncle]

Here is my ammonite-shark...Escondido Fm, Sphenodiscus ammo and not sure of shark vert genus (Squalicorax, Serratolamna, etc.). Verts too fragile to prep further.

[Ptychodus04]

Ok, you officially make me sick! LOL!!!

[Uncle Siphuncle]

Crab appendages in that slab as well as some Turritella on the back side. Escondido bouillabaisse on a slab!

[Ptychodus04]

Awesome!

[bone2stone]

Ain't it the truth.

Jess B.

[Mike from North Queensland]

It is interesting to see sea animals go inside ammonite shells only to die and be preserved in the sediment infill and then be exposed when the actual shell is lost. Attached is an example I picked up for an aquarium rock only to notice after a week in the tank.

Mike