Mystery Specimen

[Carl]

There are 2 very disparate ideas proposed for this specimen from the Late Cretaceous marine sediments of New Jersey. I will keep them hidden for now because I don't want to taint anyone's ideas. I am looking only for justifiable suggestions, not wild guesses. Please only make suggestions that can be backed up, demonstrated as likely, or fleshed-out logically.

 

[Fossildude19]

Could this be a shrimp or crab claw/dactyl?

[DPS Ammonite]

What is it made of? Phosphate? Carbonate? What is the filling made of? It looks cancellous and sometimes granular. Give us a better phot of

the filling.

Edited December 12, 2023 by DPS Ammonite

[Sagebrush Steve]

25 minutes ago, Fossildude19 said:

Could this be a shrimp or crab claw/dactyl?

Looks just like the ones I get at the annual crab feed at my wife’s high school. 🙂

[sixgill pete]

The groove in the back side makes me think of a Cretaceous fish or shark dorsal spine

Edited December 12, 2023 by sixgill pete

[Coco]

1 hour ago, sixgill pete said:

The groove in the back side makes me think of a Cretaceous fish or shark dorsal spine

The groove in the middle photo also reminds me of a shark spine.

 

You can see the shadow of the hollow in my photo of a recent specimen.

 

Coco

Edited December 12, 2023 by Coco

[patelinho7]

Very good discussion here! First thing that came to mind for me was crustacean claw as well. 

[RJB]

My first thought was dactyl but after seeing coco's post, I'm not so sure.  Something fishy about the face of that.  Both the claws of shrimp and crab thats Ive seen and prepped dont have that flattened, even indented area? 

 

RB

[Carl]

19 hours ago, Fossildude19 said:

Could this be a shrimp or crab claw/dactyl?

I've personally never seen one with a flat ?occlusal surface. Do you know of any?

[Carl]

18 hours ago, DPS Ammonite said:

What is it made of? Phosphate? Carbonate? What is the filling made of? It looks cancellous and sometimes granular. Give us a better phot of

the filling.

I can't provide more photos as the specimen is in someone else's care, but I can say that it seems to be phosphatic and what's inside is most likely sandy matrix.

[sixgill pete]

If I can find my specimen I have a Cretaceous spine that looks very similar that was I.D.'d as shark, possibly Meristodonoides.

[Coco]

Hi,

 

I have forgotten to tell you that my shark spines are hollow.

 

Coco

[Carl]

OK. Now that I have some responses, I will tell you my thoughts. When this was first showed to me, I also figured it was shark dorsal fin spine. They are very rare, but well-known from these beds. However, they tend to be ornamented and the unornamented ones are thicker-walled that this one. It made me wonder if this could be the tip of a beak. It's a stretch but there were pterosaurs and likely birds in this area. Can any one confirm or deny that idea or suggest anyone who could?

[Rockwood]

@Auspex might be one. 

[jpc]

Carl, hard to say from the pix, but is it actually bilaterally symmetrical.  It would need to be so for a beak (unless it is from a crossbill, which it is not).  

[DPS Ammonite]

Any tests to see if it is bone vs cartilage vs keratin?

 

I wonder if this could be the keratin part of a claw sheath. I suppose that Cretaceous birds had claws.

 

See modern cat claw sheath below.

 

 

Edited December 15, 2023 by DPS Ammonite

[Carl]

15 hours ago, jpc said:

Carl, hard to say from the pix, but is it actually bilaterally symmetrical.  It would need to be so for a beak (unless it is from a crossbill, which it is not).  

As symmetrical as possible I suppose, but that would apply for beaks as well as fin spines.

[Carl]

14 hours ago, DPS Ammonite said:

Any tests to see if it is bone vs cartilage vs keratin?

 

I wonder if this could be the keratin part of a claw sheath. I suppose that Cretaceous birds had claws.

 

See modern cat claw sheath below.

 

 

I can't see any way for keratin to have survived in this depositional environment.

[Mahnmut]

Hi,

If it was a rhamphoteca- the ceratinous sheath of a beak-  I would not expect a preservation mode so similar to bones from the same deposits.

Same applies to claw sheaths, which are typically more curved.

No conclusive argument of course, but in my eyes these points tilt the probability heavily towards the shark spine.

Best regards,

J

[Carl]

On 12/15/2023 at 4:17 PM, Mahnmut said:

Hi,

If it was a rhamphoteca- the ceratinous sheath of a beak-  I would not expect a preservation mode so similar to bones from the same deposits.

Same applies to claw sheaths, which are typically more curved.

No conclusive argument of course, but in my eyes these points tilt the probability heavily towards the shark spine.

Best regards,

J

It's definitely not keratinous so I never thought it was a rhamphotheca. If it is a beak, it's the bony part.