What did Petrodus sharks look like? (Are they known only from denticles?)

[Gramps]

All,

I have been finding a few dermal denticles in Northeast Oklahoma Pennsylvanian shales. Based on published reports and images from our area, I believe these are Petrodus. I’ve attached an image of two denticles I found yesterday.

I’ve been looking for images of the entire shark because I’m curious about the animal’s overall appearance; however, I’m only finding images of the denticles. Do scientists know what these sharks looked like, and if so, does anyone know of resources containing overall images?

Best wishes.

[fossilsonwheels]

I believe Petrodus is a taxon based only on denticles. I personally have not seen any other material assigned to it and couldn’t locate any publications describing other remains. 

 

Some of our knowledgeable members may have information on the subject that I do not though. 

[Tidgy's Dad]

As these denticles are very rarely found amongst other sharks digestive remains, it is assumed by some that the shark was either very large or indigestible. 

[Gramps]

Thank you, Fossilsonwheels and Tidgy's Dad for your help.

Best wishes.

[connorp]

I've attached an interesting paper on Petrodus. It describes what was interpreted as a patch of shagreen containing both Listracanthus and Petrodus denticles. I don't know if anything new has been learned about Petrodus since the paper's publication. There have been two associations of Listracanthus denticles posted on the forum in the past couple years that may be sections of the Listracanthus animal, but I haven't heard anything about them in a while.

Affinities of the Chondrichthyan organ-genera Listracanthus and Petrodus.pdf

[Gramps]

Thanks, Connorp. The article is very interesting, with lots of intriguing citations. The newer "cited by" references in Google Scholar also look to hold some interesting info. This line of publications promises provide plenty of good reading as we head into the long winter evenings.

Best wishes.

[LanceH]

I looked into this and the old ones favor denticles found in the throat/gill area of a living ray or shark I forget.  Same shape at least. 

[jdp]

On 10/23/2020 at 4:21 PM, connorp said:

I've attached an interesting paper on Petrodus. It describes what was interpreted as a patch of shagreen containing both Listracanthus and Petrodus denticles. I don't know if anything new has been learned about Petrodus since the paper's publication. There have been two associations of Listracanthus denticles posted on the forum in the past couple years that may be sections of the Listracanthus animal, but I haven't heard anything about them in a while.

Affinities of the Chondrichthyan organ-genera Listracanthus and Petrodus.pdf

 

Back in 2001, Dick Lund & co (I was part of that team) collected the tail end of this fish, from around the pelvic fins to the tip of the tail. What I can say is it's a relatively robust fish with a broad heterocercal tail, no fin spine on the second dorsal fin (so not ctenacanth or hybodont), and a thick covering of Petrodus scales. I remember seeing a few Listracanthus scales on the dorsal side but it's been 20 years since I last saw it. It's a large shark...it probably reached at least 2-3 meters long extrapolating from what we collected if I'm remembering right.