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Shark Scales/skin?


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I am having trouble nailing down what exactly this fossil is and would appreciate some help. It is from the Phosphoria formation (270 ma), and was found on a horizon of low grade phosphate that was roughly 20x10 feet. The gentleman who found the fossil said it was covering the horizon and that there were 20-30 3 inch diameter tooth whorls as well! So this material is supposedly associated with helicoprion fossils.

The picture is the fossil as is, the guy that collected it POURED shellac over the entire surface :shake head:

The blue tinted 3d model is what I built today based on a surface scan of the rock.

post-5052-0-84985300-1363138644_thumb.jpg

post-5052-0-37372800-1363138677_thumb.jpg

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No bells ringing for me...

Did he show you evidence for the 'tooth whorls'?

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Hey, Jesse,

It does have some resemblance to shark skin with denticles in it.

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I see lots of 'wrinkles'...what do you see that could be denticles?

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Auspex, he showed me a small whorl that he said was collected in the same spot, and keeps telling me that he has a picture.

Rich, that was my initial impression (pun intended lol). The shellac is obscuring a lot of the fine details though.

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Did the rock need to be stabilized, or did he add the shellac just because? Assuming the rock is durable, couldn't the shellac be removed with lacquer thinner? I've rescued a few siderite nodules with the stuff.

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It is a loosely consolidated phosphatic limestone, I would be afraid to try removing the shellac. It is interesting preservation, most of the fossils from this formation are in concretions, a few are in matrix like this one, and a rare few are preserved as tightly compacted mud in the shape of tooth whorls.

He did have an early habit of shellacing every specimen he found. When we went down last week I took him a 20 year supply of butvar powder and forbade him from using anything else lol.

Edited by Jesse
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Hi Jesse,

It has a similar look to some Pennsylvannian denticles I have seen preserved in the Mecca and Logan Quarry shale of Indiana and Illinois.

Can you give us more information on the layer of mini tooth whorls??? Were they all collected and if so what happened to them.

Do you have any pictures you can post?

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Thanks Rob, I see the same thing, but a couple of members of my research group expressed doubt.

Sadly he only recovered the one whorl, the rest have long since been turned into round up :(

The way the mine works is they basically take a dozer blade and mount it so it is perpendicular to the ground then they scrape off large sections of the mine wall. The blade just happened to perfectly expose the layer they where in, similar to the specimen we tried and failed to save last year. The whorls were in loose matrix and couldn't easily be excavated, so he pulled out a chunk of the "scales" and one of the whorls and they scraped off the rest.

The rest of the pictures are on my work computer, I will share a few in the morning!

Here is a slightly less than good photo of the little whorl, and again with the shellac...

post-5052-0-15153700-1363146411_thumb.jpg

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Maybe a little judicious use of alcohol and a Q-tip could open a window just big enough for some microphotography?

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Fossildude19

Very interesting samples - too bad about the shellac. :(

Here are some cropped and retouched photos of the small whorl.

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and with colors reversed.

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There doesn't seem to be a ton of detail visible through the shellac.

Regards,

Edited by Fossildude19
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Fossildude19

And here's the "skin fossil" lightened up a bit.

post-2806-0-95482800-1363186072_thumb.jp

Regards,

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Thanks Tim!

Here is a close up of the finished 3d model with enhanced lighting. It is still hard to make out distinct scales...

post-5052-0-56254000-1363278571_thumb.jpg

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And because you have all been so helpful, here is a bonus bizarre Helicoprion! It is preserved in what is basically hard packed clay, and we have not been able to id it to a distinct species, very odd.

post-5052-0-74048200-1363279024_thumb.jpg

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^^ This is correct, except for the ugly part, they just have some character lol!

Auspex if you have been to an aquarium then you almost certainly have seen a holocephalan, usually a port jackson shark. They call them sharks, but they are chimeras just like the ratfish.

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Here is the finished 3d model of the above odd fossil.

post-5052-0-28187800-1363322840_thumb.jpg

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^^

Auspex if you have been to an aquarium then you almost certainly have seen a holocephalan, usually a port jackson shark. They call them sharks, but they are chimeras just like the ratfish.

The Port Jackson shark is in the genus Heterodontus, they are true sharks not holocephalans. I'm not sure if ratfish are ever displayed in aquariums, I've never seen one.

I don't see anything in this fossil that looks like a denticle to me. Have you ever found denticles associated with your Helicoprion fossils? I would be interested in seeing them.

Edited by Al Dente
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Hi,

Most of ratfishes live in the depth wathers. It certainly explains why we don't see them in aquariums. It would be as to have a cœlacanth ! They need a certain pressure of the water to live.*

Coco

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I have seen multiple artist renditions of the placement of the tooth whorl in the Helicoprion mouth over the years. Truthfully none looked very practical or workable to me. Does anyone have an artist rendition that reflects the current thinking of the tooth whorl placement in the Helicoprion mouth?

Marco Sr.

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...Does anyone have an artist rendition that reflects the current thinking of the tooth whorl placement in the Helicoprion mouth?

LINK

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Auspex

Thank you for the link. I totally missed that post. It is awesome that the positioning of the tooth whorl in the Helicoprion mouth has now been scientifically determined. The positioning is really bizarre though. Just shows the diversity that nature produces.

Marco Sr.

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The Port Jackson shark is in the genus Heterodontus, they are true sharks not holocephalans. I'm not sure if ratfish are ever displayed in aquariums, I've never seen one.

I don't see anything in this fossil that looks like a denticle to me. Have you ever found denticles associated with your Helicoprion fossils? I would be interested in seeing them.

I stand corrected, I could have sworn that I read somewhere that they were chimeras, but alas you are correct!

If you zoom in close on the model I built and fiddle with the light some not quite distinct shapes appear. If I squint I can convince myself that I see a few loose denticles, but not enough to be 100% sure. In truth I am having trouble seeing this as anything other than shark, maybe not Heliocprion, but maybe a cousin. I have never personally seen any in association with a whorl, but supposedly this sample was. I cannot verify this claim however. In one of the newer publications a researcher claims to have found denticles and upper jaw teeth in a Helico bearing concreation, but these were found after the concretion was dissolved in acid and without context they could have come from anywhere and anything.

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