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Fish fragment? Lower Jurassic, Whitby, England.


TqB

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DSC_0366.thumb.JPG.c549016247a322e13126db664a869597.JPG 

 

I love the crab claw or urchin possibility but my eye keeps going back to this spiral like thing. Does not seem like it would be a projection from these possibilities.

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Maybe foramenifera? :shrug:

This piece is definitely a headscratcher. :headscratch:

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Thank you all so much for the replies - they've all made me think! Thanks especially to @ynot for marking up all the dimples!

 

One thing to consider is that there was practically no bottom fauna at the time - too anoxic - so gastropods, echinoids and benthonic arthropods just don't occur.

The fauna is pretty much all nektonic - reptiles, fish, coleoids, ammonites.

 

I'm still favouring fish ( @GeschWhat Lori - would love it to be a bit of odd coleoid or nudibranch but the shape doesn't match anything I can think of!)

 

I've taken some more photos, under water this time which is revealing.

 

I think this shows that:

 

1)  It is a definite, single structure - I'm sure it's not a coprolite or tar. See the regular, denticulate/knobbly protrusions along much of the margin.

 

2)  I'm pretty sure the white things are part of the structure and that most of the dimples, even the small ones, represent missing inclusions of similar form and size.

The specimen is worn and the smallest dimples are just the bottoms of much larger ones . (This is clearer under a microscope than in the photos I'm afraid.)

 

3)  @minnbuckeye - the apparent spiral is really just a dimpled, grooved surface, like an asymmetrical heart. See last photo below (as close as I can get with my camera, it's only 1mm across).

 

IMG_3107.thumb.jpg.59996bbe52a36ab603bc4525f1e62f2f.jpg

 

Closeup of the denticulated/knobbly margin:

IMG_3110.thumb.jpg.8005875d05a44f5ef5e4a9b35649253a.jpg

 

Showing dimples worn to various depths. I think all these were occupied by the white spheroids:

5b47480c1e785_IMG_31132.thumb.jpg.f7950097b89bdf43c2adeb557bf343b0.jpg

 

Showing that this bit isn't actually a spiral. (1mm diam)

IMG_3113.jpg.6008d4223f29274d1940f12c55a906c4.jpg

 

 

     

 

Tarquin

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Really looks like crustacean.....? Maybe carried in by scavanger/predator from more oxic area...

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20180712_101042.jpg.a275153ba20258e204e3548bcb606b30.jpg

 

These bumps scream crab/loster claw to me. Even though certain arthropods didn't exist on the ocean floor at the time doesn't mean it couldn't have been eaten from somewhere else and regurgitated there. 

~Charlie~

"There are those that look at things the way they are, and ask why.....i dream of things that never were, and ask why not?" ~RFK
->Get your Mosasaur print
->How to spot a fake Trilobite
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1 hour ago, westcoast said:

Really looks like crustacean.....? Maybe carried in by scavanger/predator from more oxic area...

 

2 minutes ago, ynot said:

I agree.

 

2 minutes ago, ynot said:

I agree.

 

Thanks - I'm certainly prepared to be persuaded of this. :) But what about the little white beads which are definitely part of it?

Tarquin

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13 minutes ago, TqB said:

 

 

 

Thanks - I'm certainly prepared to be persuaded of this. :) But what about the little white beads which are definitely part of it?

Do a Google (or other) search for Kaiparowits crustacean cuticle image. I think if you find the same figure h you will see a similarity, even if yours is a lot more eroded or worn..

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Tanaidean decapoda are known from the Swiss Opalinuston,which is somewhat of a "black shale"

(dysoxic to anoxic claystone,perhaps)

edir:seasonal anoxia.

 

 

 

 

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29 minutes ago, westcoast said:

Do a Google (or other) search for Kaiparowits crustacean cuticle image. I think if you find the same figure h you will see a similarity, even if yours is a lot more eroded or worn..

Thank you, there is certainly a similarity.

I haven't seen anything like it in other Lower Jurassic arthropods from the area (lobsters are quite common in nodules above and below the Jet Rock) so it would be something unusual. :)

Tarquin

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1 hour ago, TqB said:

 

 

 

Thanks - I'm certainly prepared to be persuaded of this. :) But what about the little white beads which are definitely part of it?

Possible Gastroliths as @doushantuo suggests. A crab eating fish that swallows rocks to help it break the shell apart. Then regurgitates the shell after the soft tissue is broken down. Just a fun guess. 

~Charlie~

"There are those that look at things the way they are, and ask why.....i dream of things that never were, and ask why not?" ~RFK
->Get your Mosasaur print
->How to spot a fake Trilobite
->How to identify a CONCRETION from a DINOSAUR EGG

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I think I'll move over to the decapod camp. I can now easily see that as a squashed claw missing the dactyl. 

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UPDATE :)

 

I've just tested the hardness of the white spheroids (under a microscope) and it comes out as 5 (scratches fluorite, scratched by quartz, apatite and the spheroid just burnish each other).

(Should have done this first of course.:blush:)

Also, there's no acid fizzing.

 

So it's presumably apatite bone/tooth material, not calcite. (The black material is softer though, about the same as calcite).

 

Over on a Facebook page (Yorkshire Fossil Hunters), Dapedium (ganoid fish) head armour is the preferred suspect. Arthropod was the second contender but the chemistry seems to rule that out.

Tarquin

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Here is part of a mashed up Dapedium that I have from the Lower Lias of Lyme Regis. I hadn't realised before that the tubercles are quite discreet, hard enamelled elements within softer bone face plates. I tested the hardnesses here too and they're the same as the specimen in the thread.

Different colour preservation but I think it's convincing.

 

IMG_3116.thumb.jpg.e2298c75a5d5f3bffc5f1606eeb87ae5.jpgIMG_3117.thumb.jpg.f8cca77c7fdf62c756b3b52ccf384e43.jpgIMG_3115.thumb.jpg.bb340e82a23985694cc5ad752675f5fe.jpg

 

Tarquin

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I would call the margin here 'variably amorphous' (as oxymoronic as that may sound).

~~.jpg

 

Rather chaotic for a hard organic material, no?

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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8 hours ago, TqB said:

One thing to consider is that there was practically no bottom fauna at the time - too anoxic - so gastropods, echinoids and benthonic arthropods just don't occur.

I wouldn't totally rule out a hydrocarbon seep of some kind. There are many creatures that form micro communities in this type of environment. Whatever these white objects are could rely on chemosynthesis. Back in April or May, I got hooked watching live streaming from the NOAA's Okeanos Explorer. They were exploring mud volcanos? in deep portions of the Gulf of Mexico. For the most part, the areas were devoid of life (aside from the occasional nudibranch). However, there were scattered hydrocarbon seeps teaming with life, though most very small. Here is an article describing the kind of life found in such environments. I remember seeing abandoned areas where life had dyed off or moved, but haven't found anything on that yet and I can't remember what those areas looked like. There are numerous other articles on seeps on this site as well. 

 

https://oceanexplorer.noaa.gov/explorations/06mexico/background/hardgrounds/hardgrounds.html

 

 

 

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Just a thought on some of the suggestions that I would like logically argued out even if for my own benefit as I do not have a clue what the object is.

The specimen is distorted with several areas having overlapped other sections.

Some areas are close to, as in life as I assume there was once some curvature in the surface. 

 

Crustacean - would not the hole exoskeleton be made of the same material and thus fossilise the same colour and density.

Fish external - same material with scales and head armour.

Fish teeth - the dimple size indicates that the crushing teeth would vary in size from row to row.

Isolated seep blob with secondary objects on - blob spacing too uniform and only on object.

 

Echinoid - the photo I used earlier would fossilise the same throughout but may be viable if the specimen had spines that were made from a different material than that of the body but unsure.

 

Skin with dermals may be best and the edge of interest be interpreted as margin near the mouth.

 

Mike

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13 hours ago, Auspex said:

I would call the margin here 'variably amorphous' (as oxymoronic as that may sound).

 

Rather chaotic for a hard organic material, no?

 

12 hours ago, Mike from North Queensland said:

Just a thought on some of the suggestions that I would like logically argued out even if for my own benefit as I do not have a clue what the object is.

The specimen is distorted with several areas having overlapped other sections.

Some areas are close to, as in life as I assume there was once some curvature in the surface. 

 

Crustacean - would not the hole exoskeleton be made of the same material and thus fossilise the same colour and density.

Fish external - same material with scales and head armour.

Fish teeth - the dimple size indicates that the crushing teeth would vary in size from row to row.

Isolated seep blob with secondary objects on - blob spacing too uniform and only on object.

 

Echinoid - the photo I used earlier would fossilise the same throughout but may be viable if the specimen had spines that were made from a different material than that of the body but unsure.

 

Skin with dermals may be best and the edge of interest be interpreted as margin near the mouth.

 

Mike

 

The consensus from some local very experienced collectors and palaeontologists that I've now talked to is that this is a weathered Dapedium (or similar) jaw, probably dentary, maybe in lingual view - it's very worn through anyway.

(The collectors with most experience of these beds suggested this immediately.)

 

The key to this specimen lies in the construction of Dapedium head armour (and some related fish I think but I'm not an expert):

Part of the diagnosis for the genus is, "cheek and lateral side of lower jaw heavily ornamented by ganoine tubercles and ridges" - i.e. hard,glassy apatite in softer bone.

 

@Mike from North Queensland - so "bone with ganoine tubercles" rather than "skin with dermals", and near the mouth looks just right. :)

 

@Auspex - the chaotic edges would be caused by the very lumpy architecture of this material, combined with weathering and matrix fill - see, for example, photo 4 below.

 

As I showed above, here are some ganoine tubercles on a piece of Dapedium head plate with different preservation, from another location:

IMG_3120.thumb.jpg.62db7367dea927235176c3f032cd3084.jpg


 

?Dentary from a Dapedium to show the orientation. This one is ridged rather than tuberculated (this varies according to species):

5b48712040539_ScreenShot2018-07-13at09_57_19.jpg.032146a74f2cc0e463bc2634654dc9c4.jpg

 

My specimen in similar orientation, if it's the same bone (possibly lingual, very weathered anyway). The white pieces hardness test as 5, consistent with "glassy apatite" ganoine tubercles.

IMG_3107.thumb.jpg.69a0c19ef72f1f4ab3a77c4eb3636400.jpg

 

Another ridged (with some tubercles) species (a cast in my collection):

IMG_3118.thumb.jpg.30ec1794f1d5ebf37af2d7961e9806f1.jpgIMG_3119.thumb.jpg.b86e8bc8be92d3b548f03ee374d5bbee.jpg

 

 

Tarquin

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Excellent discussion!

The subject is so obscure that resolution hinged on deep knowledge of the site, by experienced local collectors.

I love it when the magic works!

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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the fossil seems to be outlined "stylolitically" as well,at least partly.

Tarq, fig 7b from the Palaios article I posted clearly show spheroidal cuticular fragments

 

 

 

 

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2 hours ago, Auspex said:

Excellent discussion!

The subject is so obscure that resolution hinged on deep knowledge of the site, by experienced local collectors.

I love it when the magic works!

Thanks to all who have contributed!  

I have learned a lot from this. The byways are just as interesting as the main thread. :) 

 

2 hours ago, doushantuo said:

the fossil seems to be outlined "stylolitically" as well,at least partly.

Tarq, fig 7b from the Palaios article I posted clearly show spheroidal cuticular fragments

 

I think it's oxidised pyrite veins - there's a lot of pyrite in the formation. It could well be stylolitic solution and migration.

Yes, the spheroids look similar and may have a comparable strengthening function. I gather they're calcitic while the fish ones are shiny apatite.

Tarquin

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The fossil seems to be surrounded by small-scale polygonal faults ,outlined by (Possibly) larger grainsizes?

Thanks to everyone for rekindling an old fascination with the Jurassic of Yorkshire.:P

Still very, very fond of my (way too little) collection of the PYGS

 

 

 

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7 minutes ago, doushantuo said:

The fossil seems to be surrounded by small-scale polygonal faults ,outlined by (Possibly) larger grainsizes?

Thanks to everyone for rekindling an old fascination with the Jurassic of Yorkshire.:P

 

I think they're relatively recent desiccation cracks filled with pyritic sulfate crystals.

Yorkshire geology rocks. :P

Tarquin

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