Jump to content

PA Fossil Finder

Recommended Posts

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.

Stephen

Link to comment
Share on other sites

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.

"Any day that you can fossil hunt is a great day."

My family fossil website     Some Of My Shark, Ray, Fish And Other Micros     My Extant Shark Jaw Collection

image.png.9a941d70fb26446297dbc9dae7bae7ed.png image.png.41c8380882dac648c6131b5bc1377249.png

Link to comment
Share on other sites

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.

Stephen

Link to comment
Share on other sites

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

Stephen

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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.

Stephen

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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

"Absence of evidence is not evidence of absence"_ Carl Sagen

No trees were killed in this posting......however, many innocent electrons were diverted from where they originally intended to go.

" I think, therefore I collect fossils." _ Me

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth."__S. Holmes

"can't we all just get along?" Jack Nicholson from Mars Attacks

Link to comment
Share on other sites

  • 3 weeks later...

I found another nice shark denticle yesterday.

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

Stephen

Link to comment
Share on other sites

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

Stephen

Link to comment
Share on other sites

  • 3 weeks later...

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!

Link to comment
Share on other sites

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

----------------------
OUTIL POUR MESURER VOS FOSSILES : ici

Ma bibliothèque PDF 1 (Poissons et sélaciens récents & fossiles) : ici
Ma bibliothèque PDF 2 (Animaux vivants - sans poissons ni sélaciens) : ici
Mâchoires sélaciennes récentes : ici
Hétérodontiques et sélaciens : ici
Oeufs sélaciens récents : ici
Otolithes de poissons récents ! ici

Un Greg...

Badges-IPFOTH.jpg.f4a8635cda47a3cc506743a8aabce700.jpg Badges-MOTM.jpg.461001e1a9db5dc29ca1c07a041a1a86.jpg

 

Link to comment
Share on other sites

  • 1 month later...

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Stephen

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

  • 2 months later...

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...