Very odd little jaw

[Lone Hunter]

Yesterday took Rockwood out to Grapevine lake to explore the Woodbine, we went on treacherous hike below spillway that may or may not have been restricted area.  Spotted this in place where sun could have bleached it, didn't know what it was without glasses so stuck it in my pocket for not so safe keeping.  Didn't make it back in one peice and it's driving me nuts trying to figure out what it came from or if it's fossil or not. I put the peices in order in one picture, the little strip of teeth goes middle. 

[Carl]

It's a crab claw rather than a jaw. Nice find!

[caterpillar]

+1 for crab

[pachy-pleuro-whatnot-odon]

Yup, crab. If there are no extant crustaceans in the area (which, other than potentially river lobsters I shouldn't think so), then this is definitely a fossil and a very nice find!

[Lone Hunter]

Well I'll be, those sure looked like little teeth.  How cool if this is fossil!   But not cool that I think I left some behind, I can't see details good and I'm pretty sure there was a little pile of white things,  I reached down and grabbed peice and my first thought was it felt like crawdad claw that I see around ponds so I left the other pieces. Then changed my mind after putting on glasses.  Had it right blind. Thanks everyone!

[pachy-pleuro-whatnot-odon]

3 minutes ago, Lone Hunter said:

my first thought was it felt like crawdad claw that I see around ponds

 

Just goes to show first instincts are often right

 

Anyway, the fact that the specimen is hollow rather than filled in with sediment, and you do seem to find them around the area would suggest that this is more than likely also a recent specimen rather than a fossil...

[Lone Hunter]

I find them in Eagle Ford and there's usually a lot of parts strewn around ponds where I've caught them and birds feast on them.  That was only one I saw in Woodbine which is why I spotted it, very few white things. Crawdads I catch don't have claws like that either.  Maybe someone more familiar with Grapevine area can figure it out. 

Edited March 21, 2022 by Lone Hunter

[Rockwood]

Out of habit I kept a close eye on the tides there.  None. The place is peppered with parks though. Could snow crabs have been in one of those picknick baskets ?

 

[ClearLake]

35 minutes ago, Rockwood said:

Out of habit I kept a close eye on the tides there

You're in the south now, you don't need any tides to bring in these little critters.    They live in the fresh water streams, lakes and nearby mud not to mention are often eaten out of large boiling pots.  A quick search and I picked one species out of dozens that live in Texas that has the little bumps along the claw.  I'm sure with some diligent searching, one could find a better match.  Or maybe it is leftovers from some picnic of a more marine creature.   If it is truly out of the formation, I'm not familiar with the range of possibilities (seems unlikely given it is hollow, but...)

 

[daves64]

Lets not forget what looks to be beekite on them as well.

[Rockwood]

Come to think of it, I did see one in the river that I was a bit relieved when it backed off first. 

[JohnJ]

I wouldn't worry too much about the breakage.  I think it is definitely a modern, sun bleached crawdad claw.  

[Rockwood]

Are their shells like crabs in that they are composed of both chitin and calcite, making this remnant primarily the calcite component ?

[JohnJ]

From the photos, I see nothing suggesting calcite.  As @ClearLake mentioned, an image search for "crawdad species in Texas" will show photos that match large adult specimens. 

 

These are mostly thick walled parts of the animal.

[pachy-pleuro-whatnot-odon]

1 hour ago, Rockwood said:

Are their shells like crabs in that they are composed of both chitin and calcite, making this remnant primarily the calcite component ?

 

While crustacean exoskeleton are indeed composed of mineralised chitin, the exact mineral component that helps harden the shell seems to vary. Compare this statement from Boßelmann et al. (2007)

 

Quote

The exoskeletons of the American lobster Homarus americanus and of the edible crab Cancer pagurus were analysed with structural and chemical methods. The exoskeletons consist of crystalline magnesian calcite in the form of nanocrystals (domain size about 20 nm), amorphous calcium phosphate (ACP), and α-chitin.

 

with statements like the below:

 

Quote

Crustaceans have a hard, durable exoskeleton composed of chitin, usually hardened with calcium carbonate, which varies in rigidity between taxa and between life-history stages.

(source)

 

or:

 

Quote

The same Bouligand structure is also characteristic of collagen networks in compact bone, cellulose fibers in plant cell walls and other fibrous materials [12]. In crab exoskeletons, the minerals are in the form of calcite or amorphous calcium carbonate, deposited within the chitin–protein matrix [11,13–16].

(Source: Chen, Lin, McKittrick and Meyers [2008], p. 588)

 

So it seems that while it is true that calcium carbonate and chitin form the primary components of crustacean exoskeletons and calcite is a form of calcium carbonate, the reverse is not immediately true in that not all exoskeletal calcium carbonate is indeed calcite.

[ClearLake]

I should have put in my post from the other day with the crawfish picture the website from which it came.  I found it here: State of Texas (invertebratezoology.org)

 

That site is quite nice as it lists all the crawfish species found in Texas and has pictures of most of them.  If you wanted to try and identify your specimen @Lone Hunter, that might be a good place to start to see if there is something that matches.  Or maybe we have a hit some sort of TMI level. 

[Lone Hunter]

I suppose what I'm wondering is how to tell if it's crayfish, lobster, or crab. The thing about crayfish is if they are present in surrounding water sources you usually see their remains everywhere, the absence of this in area we were hunting seemed strange.