I Would Just Like To Say...

[Jesse]

That was hard to track down! I see what you are talking about now, and I think you have a reasonable hypothesis. That fossil is from a juvenile, at about 35 cm total skull length, and is before the tooth batteries began to curve. They would have almost certainly had a different feeding method as a juvenile living in the "shallows" than they would as an adult in the deep. If you look at some of the southern hemisphere porpoises they have a thin beak with teeth at the end for plucking food bits out of tight spots.

[VisionXray23]

That was hard to track down! I see what you are talking about now, and I think you have a reasonable hypothesis. That fossil is from a juvenile, at about 35 cm total skull length, and is before the tooth batteries began to curve. They would have almost certainly had a different feeding method as a juvenile living in the "shallows" than they would as an adult in the deep. If you look at some of the southern hemisphere porpoises they have a thin beak with teeth at the end for plucking food bits out of tight spots.

I think we naild it. Look at this! It's a skull of Dall's porpoise.

[Auspex]

...Look at this! It's a skull of Dall's porpoise.

Interesting!

The porpoise's teeth are peg-like, though, not cutting blades, so it might not be the best model for comparison as to use.

[Jesse]

Auspex, I would not expect adult edestids to feed in a manner similar to a dolphin. If any of them did I suspect it would be the juveniles, their tooth batteries appear to be nearly strait and their teeth aren't nearly as blade like as the adults. Once the tooth batteries began to curve this method would become less and less efficient.

This very hypothesis was published in 2009 by a Russian helicoprion researcher. He suggested that the adult would feed in this manner, with the tooth whorl being distally located on the end of a long lower jaw. This makes little sense for a helicoprion to feed with this method as even the smallest juveniles had a curved juvenile tooth arch.

[Nandomas]

http://www2.isu.edu/headlines/?p=4270

here we are ))

[Bullsnake]

http://www2.isu.edu/headlines/?p=4270

here we are ))

Thank you, Nando. I enjoyed reading that, and this whole thread has been fascinating.

[Jesse]

Thank you Nando!

[Bullsnake]

Thank you Nando!

Hi Jesse.

Earlier in this thread there was mention of the plate-like teeth in the palate. Are there pictures of these available?

[Joyce]

That is an awesome article! Those fossils are huge. Its head must be massive to encapsulate those enormous whorls. I love it!!!!

I too have enjoyed this thread.

Edited February 27, 2013 by Joyce

[Jesse]

Hi Jesse.

Earlier in this thread there was mention of the plate-like teeth in the palate. Are there pictures of these available?

These are still being tossed around. The fossil that was CT scanned for this paper is the only one that has them, and there aren't that many of them. Clearly this specimen was an anomaly in terms of preservation, but it only has about 6 of these tiny teeth preserved. We are not yet clear on their function, or placement, sadly.

[Scylla]

Very cool, I wonder if the teeth position has any bearing on Masiakasaurus.

[Still_human]

On 2/17/2013 at 12:32 AM, Jesse said:

Is this the X-ray you are talking about?

Wow, That’s awesome, I had no idea they found anything from Edwards other than teeth/tooth bar, but how can they tell anything from that? It looks solid black from that picture. I guess they probably scanned it from different angles though. Is that the only picture of skull?

EDIT:Nevermind, I found a more detailed version:)

[Still_human]

On 2/13/2013 at 9:21 PM, Jesse said:

And Sarcoprion, sadly this specimen was serial sectioned so there are no real photographs of it

What does serial sectioned mean?

[Still_human]

On 2/11/2013 at 9:49 PM, Jesse said:

It is kind of unclear where Helicoprion came from. They are the only chondrichthyans known that grow dentition in a complete spiral, but they have some closely related cousins. They are almost certainly related to Edestus, which predates the earliest helicos by about 20 million years. There is also some speculation that Helicoprion is closely related to both Sarcoprion and Ornithoprion, who both have a have volution whorl of teeth. A couple of other likely ancestors are Huanohelicoprion and Sinohelicoprion, these also predate saw jaw by around 20 million years. Finally, the closest likely relative is a very little know shark named Shaktauites, of which only 1 partial fossil has been found. This shark has an almost complete very open single whorl, was found in the same quarry as H. bessinowi, and is roughly 6-10 million years older.

All that said, yes there is circumstantial and as of yet unsubstantiated evidence that they followed a long line of evolution that dead ended with them!

Would you happen to have, or know a link to any diagrams/pictures of the shaktauites
fossil? I can’t find anything visual, and VERY little even written, about them.

[Still_human]

I just came across this picture while looking for the Edestus skull pictures, and was shocked, and thought you all might want to be shocked too. I’ve seen pictures of how large they were supposed to be, compared to a human, but this is a different aspect of the comparison, that I have NOT seen before, and that really gives me a different impression...and the chills! This is a jaw fragment found, and it’s to scale!