Donation: Megactenopetalus sp. Chimaera tooth!

[TNCollector]

Hello everyone,

 

This post is really late, but better late than never right!

 

Several months ago, I posted a tooth that I found in Late Mississippian Pennington Formation in East Tennessee in the Fossil ID section, whereupon I was referred to some experts in the UK. After a conversation with two experts about the tooth I had found, it was identified as a Megactenopetalus sp. tooth, an extremely rare and unique chimaeraform from the Carboniferous and Permian shallow seas. This type of tooth is not only remarkable because of its rarity, but also because it fills a niche in the chondricthyan family tree that few other genera fit into. It is a petalodontid...with dentine tubule structures. For those who are familiar with Paleozoic shark teeth, the bradyodonts are known for these features, often appearing on "crusher" teeth as small little dots on the surface of the teeth. The petalodonts on the other hand, are almost exclusively smooth, without exposed dentine tubules. One of the exceptions to this is the Megactenopetalus, which sports a pallet of petalodont-shaped, but bradyodont-textured teeth.

 

Also, this tooth is most likely the earliest occurence of this genera. The majority of the teeth found are from the Permian, with a few exceptions coming from the Pennsylvanian. This tooth was found in a slab of tan mudstone, which eroded from near the top of the Pennington Formation, very near the base of the Pennsylvanian contact of the Raccoon Mountain Formation. It was found near a marine Psephodus sp. tooth, and also a branch of terrestrial Lepidonendron root, indicating to me that this animal likely inhabited a subtidal lagoon setting, which is also further supported by several professional studies that have been performed on the Pennington Formation.

 

Shortly after posting it here on TFF, a member here (Carl) who works at the American Museum of Natural History expressed the museum's interest in acquiring this tooth. I then filled out the paperwork, packed it up carefully, and shipped it to its new home at AMNH! I must say, I was sad to see it leave my collection, but I thing it went to a great home and will be studied sometime in the future.

 

It is now classified as AMNH FF 21096!

 

Some information and photos of the tooth prior to donation.

 

Megactenopetalus sp. crown and root

Late Mississippian (Early Carboniferous)

Pennington Formation

East Tennessee, USA

2016

Roughly 1cm per crown

 

 

[JohnJ]

Congratulations on your donation, Jim.     You should post this specimen in the Partner's Gallery with a link back to this topic. 

 

@Carl has received several new tooth specimens for the AMNH in recent years.  Let's hope some great papers are in the works.   

 

 

[sixgill pete]

Way to go Jim!!!!

[Ludwigia]

Good work!

[old bones]

Fabulous! Congratulations on finding something worthy of donation, and giving a such a good home.  

[TNCollector]

Thanks everyone for the kind words! I hope that it will make it into a paper someday. I made a post in the gallery with a link to this post.

[Darktooth]

Congratulations on such a rare find!

[Fossildude19]

Well done, Jim!  

Congratulations!

Regards,

[Vieira]

Congratulations on your donation.

 

 

[Carl]

Thanks again, Jim!!!!

[TNCollector]

Thank you!

[JimB88]

just noticed this! Congrats Jim!

[Dsailor]

That is really great. I hope somewhere along the line someone said to you in an Indiana Jones voice "that belongs in a museum"

[deutscheben]

Wow, congratulations and thanks for the fascinating explanation!

[TNCollector]

22 hours ago, deutscheben said:

Wow, congratulations and thanks for the fascinating explanation!

 

On 2/6/2017 at 8:30 PM, Dsailor said:

That is really great. I hope somewhere along the line someone said to you in an Indiana Jones voice "that belongs in a museum"

 

On 2/5/2017 at 10:05 AM, JimB88 said:

just noticed this! Congrats Jim!

 

Thank you all! I hope to make some more interesting discoveries in the near future

[Archie]

What a fantastic tooth! Congratulations on your donation

 

[clastic2805]

As the author of a paper on Megactenopetalus, having handled most of the existing specimens, I have to say that I very much doubt that your specimen fits that species.  Having said that, I suspect it is a different, and probably new, species if not a new genus.

[siteseer]

On 8/10/2019 at 3:18 PM, clastic2805 said:

As the author of a paper on Megactenopetalus, having handled most of the existing specimens, I have to say that I very much doubt that your specimen fits that species.  Having said that, I suspect it is a different, and probably new, species if not a new genus.

 

 

I am very inexperienced with the genus with most of what I know limited to what was written about it in Chondrichthyes I (Zangerl, 1981) but I see what you're saying.  Back in the 80's Megactenopetalus was known from very few specimens from very few localities but the teeth were especially distinctive due to their size, 2-4 inches wide, which is gigantic for a Paleozoic chondrichthyan (and really one of any age).  The teeth shown do resemble a proposed lower tooth but are much smaller.  Wow, I had no idea that there has been more research done on the genus with a string of specimens extending well into the Carboniferous.

 

@fossilselachian and I knew a collector who was looking for teeth of this animal in the Middle Permian of Arizona.  He considered it a Holy Grail of sorts.  I don't know if he found one.

 

The Museum of Northern Arizona had at least one tooth on display for several years.

[clastic2805]

The tooth illustrated in nearly every paper on Megactenopetalus is one I prepared and restored.  My main tooth was only aboult half there, and the tooth shows the restored parts. It was in a block of limestone and I prepared it by using acetic acid.  There was enough present of the one side to allow me to restore the entire tooth.  I had the large piece and a fragment to work with, plus the tooth published by Lorie Rose David. 

 

It is noteworthy that the tooth's curve is more than 180 degrees, making it hard to image how this shark might have replaced teeth.  The new teeth would have been either too tight a curve, or too wide a curve to match the old tooth.  One feels that there was a single tooth top and bottom, and that this tooth was retained throughout life. Juvenile teeth would have ben a problem as well.

 

This curve was so tight that it's hard to see how the upper and lower teeth came together.  This is why I suggested that the shark might have been a coral grazer, like a modern parrot fish.

 

Tell your friend to keep looking.  It would be great to see an entirely intact tooth, top or bottom. These critters must have been very rare in life.