tiniest jaw?

[debivort]

Found this in likely Oligocene sediments. V-shaped in cross-section, about 7 "teeth" per side, tapered to one end, 2mm long. A jaw? A tiny claw? A piece of fishy bone?
 

[hemipristis]

Interesting!  I’ll be curious to hear ideas.  Jawed worm?

[jpc]

In the first photo it looks hollow.  Crab claw?  

[old bones]

Your find reminds me of a Mantis Shrimp mandible. Here is one that I found in the Montbrook matrix.

 

[Al Dente]

4 minutes ago, old bones said:

Your find reminds me of a Mantis Shrimp mandible. Here is one that I found in the Montbrook matrix.

 

I was about to say the same thing. Here's a photo I found on the internet years ago of a recent mantis shrimp that matched one of my fossils. I don't remember what site posted this image.

 

 

[debivort]

Thanks everyone, I think you've solved it — a molar process of a stomatopod mandible.

 

Illustration in Kunze 1981 https://doi.org/10.1098/rstb.1981.0032

 

[digit]

Boy, you all beat me to it!

 

This is indeed a stomatopod (mantis shrimp) mandible fragment. Here is a good photo from the paper linked to below. The narrow section with the two serrated surfaces labeled (m) is called the "molar", (i) indicates the "incisor", and (bs) is for the "basal section". Whereas the majority of the exoskeleton of a stomatopod is composed of chitin (which being highly organic does not preserve well), the mandible is composed of fluorapatite (Ca₅(PO₄)₃F). The mouth parts must be more sturdy as they are subject to both more pressure and wear.

 

 

https://www.researchgate.net/publication/295898980_Calcium_phosphate_mineralization_is_widely_applied_in_crustacean_mandibles

 

Here are some additional images of stomatopod mandible fragments found while picking micro-matrix from the Montbrook site here in northern Florida.

 

 

 

 

The scale in the last image above is 0.5 mm so you can get an idea of the size of these little gems.

 

If you are finding mandible fragments, you may also come across fragments of the claws (dactyls). There are two main types of stomatopod dactyl--smashers (with rounded "hammers") and spearers (with sharply serrated "blades").

 

The smashers generally scurry around the bottom looking for their prey items (often molluscs and crustaceans). Larger smasher stomatopods can fire the hammer out at such a speed that it can stun and crack through the exoskeleton of their prey. Aquarists who make the mistake of adding one of these to their saltwater tanks have been known to lose a tank when the stomatopod punches through the glass (I've heard with the force of a .22 caliber bullet) emptying the tank. If you've seen one of these in a public aquarium, they generally use a bullet-proof glass.

 

The spearers generally hide in their burrows and wait for an unsuspecting fish to pass overhead. In a flash they dart out and extend their dactyls to spear their prey returning to the safety of their burrow often quicker than the eye can see. If you do an internet video search for the phrase "mantis shrimp feeding" you've be rewarded with many incredible videos of these amazing animals.

 

@Al Dente was the first to help me identify numerous fragments of spearer dactyls in the Montbrook (and Cookiecutter Creek) micro-matrix. We were also finding what I had dubbed "canoes" for lack of a better term. They were fragmentary and defied diagnosis till I finally found a better preserved and more complete fragment that gave away its identity. As with the mandible fragments, these are the other part of stomatopods that need to be much stronger than chitin can provide and are also mineralized with fluorapatite. Below are some images of the fragments of both types from Montbrook as well as a descriptive illustration indicating their location on the business end of the claws.

 

Cheers.

 

-Ken

 

 

 

 

 

 

 

 

[digit]

I have also found what I believe are the carpus (see image above) from the "smasher" type. These are not as common but must also be mineralized well enough to be preserved.

 

Would be greatly interested to see if you spot any of these other stomatopod bits while picking through your Oligocene matrix.

 

 

Cheers.

 

-Ken

 

 

[debivort]

Thanks for unpacking all of this @digit! I will definitely keep an eye out for spear, smasher and canoe pieces.

[digit]

I sort micro-fossils as I pick. I have general categories (shark teeth, fish teeth, fish spines, etc.) and I use a bead jar storage container (from Walmart arts, crafts & sewing area) to organize the different types. I unscrew the lids and set the little "gem jars" on top of them to raise them in their tray. To label the different sorting categories I write on little slips of paper that I curve into each jar. Though I've long since learned what the curious rounded shapes are, the label still reads "canoes" as it is still how I think of them. I do have other jars/labels for "stomatopod dactyl" fragments and "stomatopod mandible" fragments.

 

Also, be on the lookout for these little curiosities:

 

 

They stumped us for quite some time appearing like some sort of unusual fish tooth. Again, it took a more complete specimen to solve this mystery. They are the hardened tips (fluorapatite again) of alpheid (snapping/pistol shrimp).

 

 

 

 

There are all sort of unusual invertebrate bits that can be found while picking micro-matrix. Hold onto (and accumulate) any oddities that look to be biologic in origin.

 

 

Cheers.

 

-Ken

[Al Dente]

31 minutes ago, digit said:

Below are some images of the fragments of both types from Montbrook as well as a descriptive illustration indicating their location on the business end of the claws.

 

Nice photos. This photo just helped me identify little fragments I find in various aged deposits here in NC. I find short segments with an unusual pattern and small serrations that I've always assumed were some sort of fish fin spine. The end of this claw has the same pattern and serrations. I think I've incorrectly identified some on this forum as fish fin spines. The circled portion of your photo is what I've been finding, broken off from the rest of the claw.

 

 

[Al Dente]

17 minutes ago, digit said:

They stumped us for quite some time appearing like some sort of unusual fish tooth. Again, it took a more complete specimen to solve this mystery. They are the hardened tips (fluorapatite again) of alpheid (snapping/pistol shrimp).

 

I know of a paper where Oligocene claw tips were mis-identified as cuttlefish prongs.

[digit]

Glad I could repay the favor.

 

I also find a number of these highly fragmented but well preserved bits. I'm thinking they may be hardened edge pieces of possibly the merus or propus sections of these stomatopod claws. Just haven't found the more complete piece which will cinch this identification. Just need to keep picking more.....

 

 

Cheers.

 

-Ken

 

 

 

[Al Dente]

Here's one that I think is a mantis claw fragment that I mis-identified. https://www.thefossilforum.com/topic/114168-fossil-id/#comment-1261541

[digit]

6 minutes ago, Al Dente said:

 

I know of a paper where Oligocene claw tips were mis-identified as cuttlefish prongs.

The odd thing that throws people is that when chemically ablated/analyzed while doing SEM imagery, they pick up significant amounts of calcium, phosphorus and fluorine which generally leads folks away from the crustaceans as chitin is: (C₃₀H₅₀O₁₉N₄). For a while we had the "canoes" pegged as vomerine teeth of frogs! We tend to identify things based on our knowledge base--and sometimes that leads us merrily astray.

 

 

Cheers.

 

-Ken

[digit]

4 minutes ago, Al Dente said:

Here's one that I think is a mantis claw fragment that I mis-identified. https://www.thefossilforum.com/topic/114168-fossil-id/#comment-1261541

Indeed! Hard to see in my "grab shot" image that I posted above but if you blow it up you can just barely see the texturing on the surface toward the tip of the claw. I really do need to relocate that specimen and get better images. We just got an expensive new digital microscope at the museum and I'm itching to try it on some specimens.

 

Cheers.

 

-Ken

 

[debivort]

Hi @digit — my micosorting method is very similar. little gem jars for roughly 30 categories of items, with curved slips of paper as labels. I keep them open while sorting except for the jar for shark dermal denticles because I learned the hard way how unrecoverable the denticles are if they fall out of the jar. In the recent sorting effort I switched it up a bit, collecting everything "fossily" for a second round of sorting into jars to follow (except anything immediately remarkable as more precious or unusual, which I file away immediately). This saves the time of targeting each little bone fragment or wrasse pharyngeal tooth to its specific jar, and I think it will be efficient to sort the bulk fossil pile in to 30 sub piles which can be transferred to jars en masse. At least that's the theory for this round.

 

It's also a good approach given this thread — I will now have the search image of these shrimpy bits in mind as I go back through my pile of all fossily material.

Edited February 21 by debivort

[digit]

1 hour ago, debivort said:

Hi @digit — my micosorting method is very similar. little gem jars for roughly 30 categories of items, with curved slips of paper as labels.

Patent infringement!!!

 

Hah! I'd good to see that we've converged upon many of the same methods.

 

Ray dermals are usually a bit larger and are almost sneeze-proof in size. You are correct that most shark dermal denticles (a researcher friend calls these "shark dandruff" which is a term I'm adopted ) are super tiny. Other than those from Ginglymostoma which are a tad larger, most of my shark dandruff is found picking the size class of matrix caught by my 1/30" sifting screen so they are just under a millimeter in size. Think of how many of these denticles you'd need to cover a Great White Shark (or Whale Shark).

 

Here are some from Montbrook.

 

Cheers.

 

-Ken

 

   

 

   

 

   

 

[debivort]

With some guidance from @digit I've upgraded my imaging system. New pictures of this mandible molar process:

[Randyw]

Great picture! 

[digit]

8 hours ago, debivort said:

New pictures of this mandible molar process:

Beautiful!

 

 

Cheers.

 

-Ken

[ClearLake]

On 2/23/2024 at 10:21 PM, debivort said:

New pictures of this mandible molar process:

Wow!  Fantastic photo!!  Well done!