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Shark And Ray Dermal Thorns


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The recent posts on dermal denticles have made me want to post some photos of denticles that are in my collection. I've been photographing these for the past few years. Most dermal denticles are too small for me to attempt to adequately photograph so I only photograph the larger denticles that are sometimes called "Thorns". I'll start with the modern ones.

Recent

Male clearnose skates (Raja eglanteria) are covered with a variety of thorns. Here's a few from a single individual:

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And here are detailed images of some of the thorns. I've toasted these in the oven to darken them. I have problems photographing bright white objects through my microscope.

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Dasyatis sabina are the most common stringray that I catch. They have a row of denticles down their back and some have star shaped denticles on the head.

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Here's a cluster of denticles from between the eyes.

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Here's a patch of skin from a Rhinobatos (guitarfish):

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And a patch of skin from an angel shark Squatina dumeril:

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Pliocene

The huge denticles from Dasyatis centroura are found from Pliocene sediments. I haven't included these large "bucklers", just smaller thorns. I haven't found many in the Pliocene, mostly from lack of screening of this material. Here are a couple.

The first one is most likely from a skate:

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Miocene

Pungo River Formation - NC

All these Pungo River denticles are from the black phosphatic sands that I carried out of the Lee Creek Mine in buckets. The thorns are usually in good condition when collected this way. Material from the reject piles is heavily abraded and the thorns are usually broken if they survive at all.

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Miocene

Round Mountain Silt - California

I haven't had much opportunity to collect from the Round Mountain Silt but it is loaded with denticles. I still have a lot of types to photograph but here are a few that I've already completed.

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This last one is very similar to Oligocene denticles from NC that have been identified as Squatina

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Beautiful photos... and very nice little collection.

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Oligocene

The River Bend Formation in North Carolina produces a variety of tiny denticles but this type is the only one I would call a thorn. These are fairly numerous and a publication on the fauna by Gerard Case identifies these as Squatina denticles.

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Eocene

Nothing. I collect the Eocene Castle Hayne on a regular basis and have never found a denticle larger than a millimeter. My guess is the warm temperatures didn't favor the skates. There are not many Dasyatis remains found. The "Eagle rays" were plentiful but they probably didn't have much in the way of denticles.

Paleocene

Not much besides some blocky types that I have yet to photograph. I don't collect much in the Paleocene but will continue looking.

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Cretaceous

I haven't photographed much of my Cretaceous collection. Most of my Cretaceous sites are from reworked deposits so delicate denticles might be destroyed. Here are a few of the more common types. The first is a common "blocky" type denticle. I've seen similar in the Paleocene of Maryland.

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This type might be a rostral tooth from a Ptychotrygon. I'll call it a denticle for now.

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These are interesting. At least one author has called these fish teeth. Others have correctly identified them as denticles. These are very common in some deposits.

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I still have a lot to photograph and may add more over the next year or two.

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Harry Pristis

Excellent microscope photography! You must have the patience of Job, Al Dente!

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sixgill pete

Great post Eric. I have a few denticles from some of the same locations. Now, I have something to compare them too.

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WOW these photos are great and the collection is well what can I say . This is the way we all should do our fossils for all to see, if only I could. THANKS George

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It is a nice subject Al Dente ! I have to do pics of mine (recent)...

Coco

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Eocene

Nothing. I collect the Eocene Castle Hayne on a regular basis and have never found a denticle larger than a millimeter. My guess is the warm temperatures didn't favor the skates. There are not many Dasyatis remains found. The "Eagle rays" were plentiful but they probably didn't have much in the way of denticles.

Paleocene

Not much besides some blocky types that I have yet to photograph. I don't collect much in the Paleocene but will continue looking.

Eric

Great post!!!! I have trouble also taking pictures of white objects through my microscope even on black backgrounds. That one denticle does look like what a number of authors are calling a Ptychotrygon rostral tooth.

I have a large number of Eocene denticles from VA and some from the UK. I also have a number of denticles from the Paleocene of MD. Unfortunately I need to take pictures of them.

Marco Sr.

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Marco-

Your Eocene specimen looks like ones I find in the Oligocene River Bend Formation. A similar one was published from the Chandler Bridge Formation - "Late Oligocene sharks and rays from the Chandler Bridge Formation, Dorchester County, SC, USA". In that paper they call it a Cetorhinus denticle. Pictures of modern Cetorhinus denticles that I have seen don't look much like this. They do mention Squatina as a possibility and I think that is a good comparison. Here is my modern Squatina skin with your denticle superimposed along with the Chandler Bridge denticle.

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Marco-

Your Eocene specimen looks like ones I find in the Oligocene River Bend Formation. A similar one was published from the Chandler Bridge Formation - "Late Oligocene sharks and rays from the Chandler Bridge Formation, Dorchester County, SC, USA". In that paper they call it a Cetorhinus denticle. Pictures of modern Cetorhinus denticles that I have seen don't look much like this. They do mention Squatina as a possibility and I think that is a good comparison. Here is my modern Squatina skin with your denticle superimposed along with the Chandler Bridge denticle.

attachicon.gifSquatina comparison.jpg

Eric

Definitely looks like a match. This specimen came from matrix that I got from Larry Martin from the Orangeburg Formation in the LaFarge Quarry. This is the same matrix in which I found a good number of Pristiophorus oral teeth. According to Larry "The matrix I sent was not from the quarry proper, it was from a sink hole, a solution hole, on the east quarry wall & it didn't go down to the quarry bottom."

Marco Sr.

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  • 7 years later...

Hey everyone. I was wondering if anyone had any idea on what species this dermal denticle could be from? From Hell Creek Formation. For scale, the diameter of the pencil lead is 700 microns

Photo on 10-7-21 at 2.21 PM.jpg

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Fossildude19

Cropped and brightened:

 

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4 hours ago, JackS said:

Hey everyone. I was wondering if anyone had any idea on what species this dermal denticle could be from? From Hell Creek Formation. For scale, the diameter of the pencil lead is 700 microns


It looks more like a sawfish rostral tooth than a dermal denticle. I think Ischyrhiza avonicola has been found in the Hell Creek.

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1 hour ago, Al Dente said:


It looks more like a sawfish rostral tooth than a dermal denticle. I think Ischyrhiza avonicola has been found in the Hell Creek.

Amazing. Thanks for the help

 

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I thought it might be a Ptychotrygon rostral spine but don't know of a report of the genus from the Hell Creek Formation.  It wouldn't be impossible but it would seem more likely that it is a small I. avonicola spine.

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