Alopias Grandis -Giant Thresher-Correct Age?

[fossiljunkie]

Just a verification from anyone that can confirm the correct age of the giant thresher. Want to make sure i am up to date. In Joe Cocke's book "fossil shark teeth of the world" it states the giant thresher as miocene but i heard it's probably oligocene. Can anyone tell me if it is now believed to be oligocene? thanks.

[Auspex]

All mine came from Miocene deposits, with no Oligocene present.

Doesn't mean the shark wasn't present in the Olig., though.

[siteseer]

Alopias grandis is known with certainty only from Early Miocene layers (eastern coast of North America and Europe). In Joe Cocke's book, sites are listed as Cooper River and southern Florida. I don't know the southern FL site but the Cooper River cuts through multiple layers of Oligocene-Pleistocene age so the age is always questionable unless you can get a tooth in matrix.

A. grandis seems to disappear by the Middle Miocene but that's when you see the serrated form. I believe the serrated form was rarer in its time than grandis was in its day.

If it were from the Oligocene, we might expect to find it in a shark-rich formation like the Chandler Bridge - not reported in a recent review of the sharks and rays of it (Cicimurri and Knight, 2009). In my own experience, I have not seen one from the Chandler Bridge though I have seen rare teeth of the vulpinus morphology (broad-based crown) that are clearly larger than average - perhaps an ancestor of grandis or just unusually-large vulpinus (or both?). An average vulpinus generally ranges is in the 10-16mm width but the rare form clears 20mm. If any longtime Chandler Bridge collectors, like Angus Stydens, can add anything to this, please ring in.

Just a verification from anyone that can confirm the correct age of the giant thresher. Want to make sure i am up to date. In Joe Cocke's book "fossil shark teeth of the world" it states the giant thresher as miocene but i heard it's probably oligocene. Can anyone tell me if it is now believed to be oligocene? thanks.

[fossiljunkie]

siteseer,

thank you very much that was very helpful. i am thinking, as you have stated that it is early miocene only, unless someone has found otherwise.thanks again.

Edited July 25, 2010 by fossiljunkie

[Angus Stydens]

Henri Cappetta lists alopias grandis from the oligocene of Belgium. Here is a link to that paper: http://www.paleoglot.org/files/Capetta_70.doc

If when you say alopias grandis you are referring to the very large alopias described on elasmo.com, I can say with certainty that I have never seen one come directly out of the Oligocene in S.C., and that is after many, many years collecting in the Chandler Bridge and Ashley formations. I have only seen them reworked in lag deposits, so there is no telling what age they may actually be. They could be from a Miocene layer that was completely re-worked and is no longer present.. who knows?

I have to agree with siteseer, there is a large alopias rarely found in the Chandler Bridge that looks very vulpinus-like, but a good bit larger. They are very interesting teeth and I would really like to see someone do more research on them. In my opinion, they are about the rarest tooth you will find in the Chandler Bridge formation.