Hermit Crabs in Ammonite Shells

[Architeuthoceras]

http://satori.geociencias.unam.mx/23-3/(13)Jagt.pdf

Posted on another fossil forum by one of our members, hope he dont mind my cross post.

 

[Tintenfisch]

 

[cuttlegirl]

How cool is that? It was a pretty small ammonite though, looks like 2 inches or less. Thanks for the link.

 

[monty]

I'd say "way, way, cool!" is how cool that is... I didn't recognize the authors' names as TONMOers, or was it a TONMOer who just reposted, not authored? Or am I just clueless? or is it the mysterious "Um..." who hides his name from the uninitiated?

 

[Phil]

Just a quickie - have a look at this:

http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Crustacea/fossils.html

 

[cuttlegirl]

Just a quickie - have a look at this:

http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Crustacea/fossils.html

Wow, thanks for the link Phil. What amazes me is how well the hermit crab claw fits in the aperture of the ammonite, I wonder when they made the switch to gastropods? I guess it's a good thing they did, seeing as there aren't many empty ammonite shells around today .

 

[hallucigenia]

Wow.
...Holy crap, that's really awesome! Hermit crabs have been using gastropods since at least somewhere in the Cretaceous, I know that -- I suppose that, as cuttlegirl points out, that's a good thing. I don't think I remember any earlier than that. Don't know how much of a transition it is, though. I think I'll look into that; I'll edit this if I find anything interesting.

 

[main_board]

Very, very cool!

 

[AndyS]

He (I ) does of course not mind (I still read this forum allthough this part of it has gone a little quiet recently), but I insist to be quoted completely since there is more of it :

http://www.discussfossils.com/display_topic_threads.asp?ForumID=13&TopicID=1130&PagePosition=1

All the best,

AndyS

 

[Phil]

That's an interesting point cuttlegirl. I wonder if hermits switched from ammonites to gastropods or whether they used both kind of shells throughout their evolutionary history. I have always thought they were opportunists using whichever shells for shelter that came along, but maybe they are species specific in their choice of shells? I really don't know. I'm sure a decaying ammonite would have made a good meal for such a roving scavenger.

 

[cuttlegirl]

How big is that ammonite Phil? Can you show me in double decker bus lengths???

I wonder if the abdomen is shaped differently in those hermit crabs that inhabited ammonites? Living hermits that inhabit gastropods have an coiled abdomen that coils to allow it to "hang on" to the shell (along with some specialized appendages). There are some hermit crabs that inhabit sponges and worm tubes and even a species that inhabits Scaphopods (Orthopagurus minimus). That species has a straight abdomen.

http://www.public.coe.edu/departments/Biology/hermit.html

 

[cuttlegirl]

More questions... Since an ammonite shell had chambers, would an ammonite shell be lighter than a gastropod shell of the same size? It seems that an ammonite shell would cost less energy to haul around and still provide protection for the hermit crab.

Do any animals inhabit empty Nautilus shells today? Or do they float? Did ammonite shells float after the animal died? If so, then how did a hermit crab inhabit it?

 

[Brock Fluharty]

But it would seem that since it has chambers, it would be more easily broken open, depending on what they were made of, and how old the ammonite was.

 

[cuttlegirl]

But it would seem that since it has chambers, it would be more easily broken open, depending on what they were made of, and how old the ammonite was.

Well I am not sure of the thickness of ammonite shells, but Nautilus shells are relatively strong - not as strong as most gastropods, and if only one chamber was broken, it wouldn't affect the last chamber that the hermit crab was living in. The chambers would kind of act as buttresses to strengthen the shell.

 

[cuttlegirl]

Well, I figured out the answer as to whether Nautilus shells float - they do and surprisingly (at least to me ) in the same position as when inhabited by the animal. You could float one in your fish tank and it would be as about as exciting as having a real live Nautilus! and most people would never know the difference.