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Shark Denticles

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PA Fossil Finder    55
PA Fossil Finder

In a recent post about denticles (here), it was mentioned that most of the dermal denticles we find are usually from rays, and not sharks. Ray denticles are much larger than most shark denticles, especially the big sharp thorns common on some rays. I was determined to finally find a few nice shark denticles for my collection - I've already got plenty of ray denticles, but I had never found any from Cenozoic sharks (I have a few tiny Paleozoic denticles, but those are much different looking).

Shark Tooth Hill is a site near Bakersfield, California. It is Middle Miocene in age. I had some left over microfossil matrix that I had searched already. I'm glad I saved it! I poured out the silt and tiny pebbles from the bottom of the bag and put it into a small vial. I filled it with some water, shook it up, and poured out the finest silt and water. I repeated this process until only the sand and tiny grains of gravel were left at the bottom. I let it dry overnight, and today I searched a little under my microscope. I was surprised to find a few very small fish teeth (most were less than 1 mm long), and I also think I found my first shark denticles from this site!

post-10984-0-87031300-1458175232_thumb.jpg post-10984-0-41100500-1458175233_thumb.jpg post-10984-0-23147900-1458175234_thumb.jpg

I was experimenting with a cheap new digital microscope to get these photos - the camera on the microscope doesn't have the greatest resolution and can only seem to capture small images, so I combined four views of each denticle for these pictures.

Edited by PA Fossil Finder

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caldigger    456
caldigger

Glad you found some additional items.

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MarcoSr    602
MarcoSr

Really nice. It takes a lot of patience to search that really small fine matrix. But the placoid scales/ dermal denticles definitely make the effort worthwhile. Placoid scales can widely vary on individual sharks depending on where on the shark they are from. So very different looking scales can actually be from the same species of shark. Also different species of shark can have very similar scales. So identifying them is extremely challenging.

Marco Sr.

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PA Fossil Finder    55
PA Fossil Finder

Really nice. It takes a lot of patience to search that really small fine matrix. But the placoid scales/ dermal denticles definitely make the effort worthwhile. Placoid scales can widely vary on individual sharks depending on where on the shark they are from. So very different looking scales can actually be from the same species of shark. Also different species of shark can have very similar scales. So identifying them is extremely challenging.

Marco Sr.

Thanks. Yes, I know scales and denticles can be hard to pin down an ID for - I'm satisfied with just "shark denticle" for now.

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ynot    2,050
ynot

Those are some nice finds!!

I have to take a look at the matrix that I saved from what went through the window screen.

Tony

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PA Fossil Finder    55
PA Fossil Finder

I think I found another denticle, but I can't tell if it is from a shark or a ray. Based on the shape, I would say ray, but it's so much smaller than all the ray denticles I've seen and the star shape reminds me of bramble shark denticles.

post-10984-0-09703100-1458235238_thumb.jpg

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Al Dente    1,514
Al Dente

I think I found another denticle, but I can't tell if it is from a shark or a ray. Based on the shape, I would say ray, but it's so much smaller than all the ray denticles I've seen and the star shape reminds me of bramble shark denticles.

attachicon.gifDermal Denticle, Sharktooth Hill CA.jpg

There are some similarities with your denticle and some that occur on male Rhinobatos. Here is a picture of some Rhinobatos denticles. The ones labeled "G" look a little similar. Rhinobatos occurs in the STH fauna.

post-2301-0-86110300-1458304711_thumb.jpg post-2301-0-16333000-1458304682_thumb.jpg

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PA Fossil Finder    55
PA Fossil Finder

There are some similarities with your denticle and some that occur on male Rhinobatos. Here is a picture of some Rhinobatos denticles. The ones labeled "G" look a little similar. Rhinobatos occurs in the STH fauna.

attachicon.gifrhinobatosdrawing.jpg attachicon.gifrhinobatosdrawingmale.jpg

Yes, those denticles do look similar. Where did you find those illustrations? I've been looking for better ways to identify my denticles.

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Al Dente    1,514
Al Dente

Yes, those denticles do look similar. Where did you find those illustrations? I've been looking for better ways to identify my denticles.

These are from "Fishes of the Western North Atlantic" a multivolume set by Bigelow and Shroeder written in the 1950s. I only have two of the volumes, one dealing with sharks and another with rays. They had line drawings of the denticles and teeth of the sharks and started on the rays but after the first several species of rays they quit showing the denticles. Too bad.

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Herb    373
Herb

In a recent post about denticles (here), it was mentioned that most of the dermal denticles we find are usually from rays, and not sharks. Ray denticles are much larger than most shark denticles, especially the big sharp thorns common on some rays. I was determined to finally find a few nice shark denticles for my collection - I've already got plenty of ray denticles, but I had never found any from Cenozoic sharks (I have a few tiny Paleozoic denticles, but those are much different looking).

Shark Tooth Hill is a site near Bakersfield, California. It is Middle Miocene in age. I had some left over microfossil matrix that I had searched already. I'm glad I saved it! I poured out the silt and tiny pebbles from the bottom of the bag and put it into a small vial. I filled it with some water, shook it up, and poured out the finest silt and water. I repeated this process until only the sand and tiny grains of gravel were left at the bottom. I let it dry overnight, and today I searched a little under my microscope. I was surprised to find a few very small fish teeth (most were less than 1 mm long), and I also think I found my first shark denticles from this site!

attachicon.gifShark Denticle 1, Shark Tooth Hill CA.jpg attachicon.gifShark Denticle 2, Shark Tooth Hill CA.jpg attachicon.gifShark Denticle 3, Shark Tooth Hill CA.jpg

I was experimenting with a cheap new digital microscope to get these photos - the camera on the microscope doesn't have the greatest resolution and can only seem to capture small images, so I combined four views of each denticle for these pictures.

nice pics

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PA Fossil Finder    55
PA Fossil Finder

I found another nice shark denticle yesterday.

post-10984-0-03036500-1460059237_thumb.jpg

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old bones    146
old bones

These are great! You are getting quite a unique collection together. :)

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PA Fossil Finder    55
PA Fossil Finder

As I've already stated earlier in this thread, the shark denticles I found in the fine sand and silt from Sharktooth Hill are the first Cenozoic denticles I've collected. However, I do have some from older time periods. So, I thought I'd share some pictures of a few older shark denticles - here are a few from the Late Triassic.

post-10984-0-89211900-1460248957_thumb.jpg post-10984-0-99990300-1460248958_thumb.jpg post-10984-0-07058400-1460248960_thumb.jpg

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ynot    2,050
ynot

NICE!!!

Tony

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Mediospirifer    95
Mediospirifer

Very nice!!!

Makes me think I need to search through the finer fractions from the various sharktooth matrices I have. I've been busy with searching larger matrix, photographing and mounting conodonts, arranging and catalogging larger fossils in Riker boxes, and various work around the house and yard now that we have some warmer weather. I'll soon be adding soaking and washing micromatrix to my list of fossil-related things to do! And, of course, collecting more...

Where does all the time go? There's never enough of it!

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Coco    333
Coco

Hi,

I agree with you Mediospirifier, I militate for years to have 35-hour days instead of only 24 so much I am lacking time, but nobody wants to give them to me ! :)

Coco

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siteseer    399
siteseer

Just to be clear. When people say they collected Sharktooth Hill, they are referring to the bonebed that runs through the area and contains the fossils. There is an actual hill near Bakersfield called "Sharktooth Hill" and it was a rich site for these fossils but no one collects there as has been off-limits to hunting since at least 1970. The Sharktooth Hill Bonebed is within the sedimentary rock formation called the Round Mountain Silt. Back in the 30's, the formation was considered to be the Temblor Formation but it was later determined that name was only applicable to rocks exposed farther north. Some people (even a few geologists) have called it the Temblor even within the past ten years.

Adding confusion, there are at least three other shark-tooth bearing layers in the Bakersfield area. Sometimes, you see collectors refer to all of them as "Sharktooth Hill" but if you've seen the teeth from these layers, you notice the different mix of species and preservations.

Jess

Shark Tooth Hill is a site near Bakersfield, California. It is Middle Miocene in age.

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siteseer    399
siteseer

Al Dente,

I have a photocopy of the shark one and have referred to it numerous times. Anyone who really gets into shark teeth should have have it.

Jess

These are from "Fishes of the Western North Atlantic" a multivolume set by Bigelow and Shroeder written in the 1950s. I only have two of the volumes, one dealing with sharks and another with rays. They had line drawings of the denticles and teeth of the sharks and started on the rays but after the first several species of rays they quit showing the denticles. Too bad.

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PA Fossil Finder    55
PA Fossil Finder

Just to be clear. When people say they collected Sharktooth Hill, they are referring to the bonebed that runs through the area and contains the fossils. There is an actual hill near Bakersfield called "Sharktooth Hill" and it was a rich site for these fossils but no one collects there as has been off-limits to hunting since at least 1970. The Sharktooth Hill Bonebed is within the sedimentary rock formation called the Round Mountain Silt. Back in the 30's, the formation was considered to be the Temblor Formation but it was later determined that name was only applicable to rocks exposed farther north. Some people (even a few geologists) have called it the Temblor even within the past ten years.

Adding confusion, there are at least three other shark-tooth bearing layers in the Bakersfield area. Sometimes, you see collectors refer to all of them as "Sharktooth Hill" but if you've seen the teeth from these layers, you notice the different mix of species and preservations.

Jess

Yes, that's what I meant. Sorry if I caused any confusion!

So the Round Mountain Silt is it's own formation now? I thought it was a member of the Temblor Formation.

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siteseer    399
siteseer

The Round Mountain Silt has been its own formation for decades but even some paleontologists refer to publications older than a couple of detailed revisions/reviews (Addicott, 1970; Bartow and McDougall, 1984).

Jess

Addicott, W.O. 1970.

Miocene gastropods and biostratigraphy of the Kern River area, California. USGS Professional Paper 642. 174 p.

Bartow, J.A. and K.A. McDougall. 1984.

Tertiary stratigraphy of the southeastern San Joaquin Valley, California. USGS Bulletin 1529-J. 41 p.

Yes, that's what I meant. Sorry if I caused any confusion!

So the Round Mountain Silt is it's own formation now? I thought it was a member of the Temblor Formation.

Edited by siteseer

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