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Eocene Potomac River Myliobatis Stingray Plate


shark57

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BusyEagle and I ventured out to the Potomac River Miocene/Eocene cliffs today to take advantage of the warm weather. Shortly after arriving the rains came down and drenched us. We toughed it out for a while, and just before turning back I spotted this in the cliff (sorry about the blurriness of this pic).

post-12754-0-94077200-1387773924_thumb.jpg

Here is what it looks like after partial prep:

post-12754-0-19850700-1387774007_thumb.jpg

Seven rows with two rows of side teeth, about 1.5 inches long. I will probably take it out of the matrix to expose the other side. This is my first ray plate from this bed in 25 years of collecting.

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Hi,

Oh ! FOTM ?

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...

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Gary

Really nice plate. Myliobatis have seven dental files in each jaw (3 lateral, 1 medial, 3 lateral). It is odd with the great preservation of your plate that it has 5 files (2 lateral, 1 medial, 2 lateral). I've found several really nice Aetobatis plates and one nice Myliobatis plate smaller than yours from there. I've found lots of Aetobatis individual teeth over the years but far fewer Myliobatis individual teeth. So I think that Myliobatis is not as common as Aetobatis there.

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

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Excellent plate. Show us some pictures after you expose the back side of it.

Bulldozers and dirt Bulldozers and dirt
behind the trailer, my desert
Them red clay piles are heaven on earth
I get my rocks off, bulldozers and dirt

Patterson Hood; Drive-By Truckers

 

image.png.0c956e87cee523facebb6947cb34e842.png May 2016  MOTM.png.61350469b02f439fd4d5d77c2c69da85.png.a47e14d65deb3f8b242019b3a81d8160.png.b42a25e3438348310ba19ce6852f50c1.png May 2012 IPFOTM5.png.fb4f2a268e315c58c5980ed865b39e1f.png.1721b8912c45105152ac70b0ae8303c3.png.2b6263683ee32421d97e7fa481bd418a.pngAug 2013, May 2016, Apr 2020 VFOTM.png.f1b09c78bf88298b009b0da14ef44cf0.png.af5065d0585e85f4accd8b291bf0cc2e.png.72a83362710033c9bdc8510be7454b66.png.9171036128e7f95de57b6a0f03c491da.png Oct 2022

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Gary

Really nice plate. Myliobatis have seven dental files in each jaw (3 lateral, 1 medial, 3 lateral). It is odd with the great preservation of your plate that it has 5 files (2 lateral, 1 medial, 2 lateral).

Marco Sr.

Marco, Jim Bourdon on Elasmo states that several Myliobatis species have "at least two per side" when talking about lateral files. Apparently they don't always have three.

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Marco, Jim Bourdon on Elasmo states that several Myliobatis species have "at least two per side" when talking about lateral files. Apparently they don't always have three.

Cappetta states 7 dental files with 3 lateral files per side as a feature of Myliobatis. I had always thought 3 lateral files on each side so I would really like to understand what Jim Bourdon means by his comment. The use of the terms "several" and "at least" have me confused. From what Cappetta has stated I would at least expect the "several" to be "all". When I find Myliobatis plates they vary from no lateral files to three (even in situ) but I always assumed the variation was do to damage as the lateral teeth are easy to break off of the plates. I'm curious if there are any modern Myliobatis species that do not have 3 lateral files on each side. For me that would be a good test of three versus less.

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

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I normally use Cappetta as a baseline for what I believe on fossil sharks and rays. If I read something or see something (from personal collecting) that is convincing and different, I then move from that baseline. Cappetta does state 7 dental files for Myliobatis for both the upper and lower jaws without noting exceptions in his latest 2012 book. Gary just pointed out to me a modern Myliobatis Californica plate on elasmo.com that has 8 files, 3 lateral files on one side, a medial file, and then 4 lateral files on the other side, for a total of 8 files. When I see something like this I can then say that a fossil Myliobatis might have more than 7 files. When I see an in situ specimen in great condition like Gary's with only 5 files, then I do start to question 7 files again and start to think that complete fossil Myliobatis plates could have less than 7 files. Can anyone point to pictures of a modern Myliobatis complete plate that has less than 7 files? Seeing complete modern plates with less than 7 files would convince me that complete fossil Myliobatis plates could have less than 7 files.

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

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Marco Sr.,

That is another thing you can ask Bruce Welton about. In the article he co-wrote with Zinmeister on Eocene sharks/rays of Antarctica he mentioned looking at numerous specimens of the California bat ray (the result of a fishing derby). He might have some extra info on the variation he saw.

Jess

Can anyone point to pictures of a modern Myliobatis complete plate that has less than 7 files? Seeing complete modern plates with less than 7 files would convince me that complete fossil Myliobatis plates could have less than 7 files.

Marco Sr.

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Shark57,

That's a great piece. There's a part of me that thinks you should leave in matrix or at least try to prep it into a plate that has both sides exposed with matrix around it but I also understand wanting to take it out too.

I have some loose ray plates but only a couple of them still in matrix.

Jess

BusyEagle and I ventured out to the Potomac River Miocene/Eocene cliffs today to take advantage of the warm weather. Shortly after arriving the rains came down and drenched us. We toughed it out for a while, and just before turning back I spotted this in the cliff (sorry about the blurriness of this pic).

attachicon.gifeocene ray plate 12-22-13.JPG

Here is what it looks like after partial prep:

attachicon.gif100_4196.JPG

Seven rows with two rows of side teeth, about 1.5 inches long. I will probably take it out of the matrix to expose the other side. This is my first ray plate from this bed in 25 years of collecting.

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Marco Sr.,

That is another thing you can ask Bruce Welton about. In the article he co-wrote with Zinmeister on Eocene sharks/rays of Antarctica he mentioned looking at numerous specimens of the California bat ray (the result of a fishing derby). He might have some extra info on the variation he saw.

Jess

Jess

Thank you. I have been corresponding with Bruce about Cetorhinus and will definitely ask him about his observations on the dentition of the California bat ray. I really believe that to understand fossil shark and ray dentitions you need to study the modern ones. Now that I'm semi-retired I've thought about hanging out at the docks to see the dentitions of the sharks and rays that the fishermen are bringing in versus trying to buy jaws. I'm sometimes perceived as a little weird when it comes to fossils, but hanging at the docks may definitely solidify that persona.

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

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Shark57,

That's a great piece. There's a part of me that thinks you should leave in matrix or at least try to prep it into a plate that has both sides exposed with matrix around it but I also understand wanting to take it out too.

I have some loose ray plates but only a couple of them still in matrix.

Jess

If the other side was the side that was exposed, I would leave it in matrix. I am hoping it has beautiful, black shiny enamel on it.

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Hi,

In recent jaws, I just have Myliobatis freminvillis, and it has 7 files on the upper and on the lower jaws...

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

 

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Hi,

In recent jaws, I just have Myliobatis freminvillis, and it has 7 files on the upper and on the lower jaws...

Coco

Coco

Thank you for the input. That matches what Cappetta says about 7 files for Myliobatis. Have you seen any Myliobatis with more files or less files than 7?

I've seen other posts where you show some of your modern shark and ray jaws. Really impressive. How do you obtain your jaws?

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

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Marco, more evidence of variable lateral files, this is from Elasmo in describing the myliobatid Pteromylaeus:

"Hovestadt-Euler and Hovestadt (pers com. 2007) note that in the extant genus, the lateral file-count is variable and the diagnostic characteristic of the genus is the elongated medial tooth and the presence of one or more lateral files. At Lee Creek, otherwise similar toothplates have been found with one (fig. 5), two (fig. 6) and three (fig. 4a; left, termino-lateral positions missing) lateral files -- tending to validate their observations with the Recent taxon."

What does Capetta say about the lateral files for this genus?

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Marco, more evidence of variable lateral files, this is from Elasmo in describing the myliobatid Pteromylaeus:

"Hovestadt-Euler and Hovestadt (pers com. 2007) note that in the extant genus, the lateral file-count is variable and the diagnostic characteristic of the genus is the elongated medial tooth and the presence of one or more lateral files. At Lee Creek, otherwise similar toothplates have been found with one (fig. 5), two (fig. 6) and three (fig. 4a; left, termino-lateral positions missing) lateral files -- tending to validate their observations with the Recent taxon."

What does Capetta say about the lateral files for this genus?

Gary

Cappetta states that "the dentition is very close to the dentition of the genus Myliobatis" He then describes "the main differences that can be observed at the level of the lower dental plate" which all deal with the tooth morphology. He ends by saying that the genus is more common and more widespread as a fossil than currently estimated. He doesn't specifically comment on the number of files. He shows the upper and lower jaws of a recent Pteromylaeus bovina which both have 7 files. So Cappetta doesn't acknowledge the lateral file-count variability in his description of the genus. If the file variability of Pteromylaeus is seen in the extant genus, that is pretty good evidence to me that it could also apply to the fossil genus of Pteromylaeus.

Also in his discussion of the Family Myliobatidae which proceeds the genus descriptions he states "the dental plates consist in one to seven dental files" So the recent plate of Myliobatis Californica shown on elasmo.com that has 8 files would also not fit with what he is saying. It is really starting to look like he isn't aware of some of the file variability or doesn't recognize it for some reason.

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

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Hi,

Have you seen any Myliobatis with more files or less files than 7?

I rarely saw Myliobatis jaws because I think that they don't live on the European coast, I can't thus answer you.

I've seen other posts where you show some of your modern shark and ray jaws. Really impressive. How do you obtain your jaws?

I didn't finish this "inventory" of my collection, because I didn't continue to make pics. It would be a good resolution for 2014 !

I obtained the majority of my jaws on a known site of bids. For the french species, I obtained them from my fishmonger who fetches his fishes in the auction, he thus has them integers. I was so able to get back the bodies of skates of the snout in the tail, to measure them and to know if they were males or females for the greater part. I prepared myself these jaws.

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

 

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Gary

Cappetta states that "the dentition is very close to the dentition of the genus Myliobatis" He then describes "the main differences that can be observed at the level of the lower dental plate" which all deal with the tooth morphology. He ends by saying that the genus is more common and more widespread as a fossil than currently estimated. He doesn't specifically comment on the number of files. He shows the upper and lower jaws of a recent Pteromylaeus bovina which both have 7 files. So Cappetta doesn't acknowledge the lateral file-count variability in his description of the genus. If the file variability of Pteromylaeus is seen in the extant genus, that is pretty good evidence to me that it could also apply to the fossil genus of Pteromylaeus.

Also in his discussion of the Family Myliobatidae which proceeds the genus descriptions he states "the dental plates consist in one to seven dental files" So the recent plate of Myliobatis Californica shown on elasmo.com that has 8 files would also not fit with what he is saying. It is really starting to look like he isn't aware of some of the file variability or doesn't recognize it for some reason.

Marco Sr.

Dear All,

just for your information concerning this topic : Hovestadt D.C. & Hovestadt-Euler M., 2013, Generic assessment and reallocation of Cenozoic Myliobatins based on new information of tooth, tooth plate and caudal spine morphology of extant taxa. ISSN: 1377-4654 .

I am sure that you will find the answer to your question.

Sincerely

http://www.palaeontos.be/24/det24.htm

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Dear All,

just for your information concerning this topic : Hovestadt D.C. & Hovestadt-Euler M., 2013, Generic assessment and reallocation of Cenozoic Myliobatins based on new information of tooth, tooth plate and caudal spine morphology of extant taxa. ISSN: 1377-4654 .

I am sure that you will find the answer to your question.

Sincerely

http://www.palaeontos.be/24/det24.htm

Thank you so much for the link. I really had the wrong idea about Myliobatis plates. After seeing some of the Myliobatis plates with two medial files or five lateral files on one side or plates where the files changed in the middle or where there wasn't a traditional medial file, I now understand that the 7 file description for Myliobatis is definitely not accurate at all, at least in some cases.

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

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