Some Questions About Cow Shark Species And Localities Where They Are Found.

[whowat13]

I recently acquired a small "lot" of cow shark teeth from Sacaco, Peru.

In the lot was 1 cow shark tooth that measures about 1.6 inches from front to back, and was wondering if there was any occurrence known of teeth from the giant cow shark Notidanidon loozi being found there.

Also, in the same lot, there were two cow shark teeth (these may be partials, but are from the leading edge of the tooth) that bear a very strong resemblance to a cow shark species that as far as I know is only found in Bakersfield, CA... Hexanchus andersoni. I would also like an opinion on any occurrence of this species in Sacaco, Peru.

I can not take pictures at the moment (my camera is packed for a trip I am going on tomorrow).

If anyone can either prove or deny whether these species are found there or not, I would love to hear what you think on the topic.

I may be able to take pictures later (when I reach my destination). If I can, I will post them in the ID section tomorrow evening.

Thank you all in advance...

-Bill H.

[siteseer]

Notidanodon is a shark known only from the Early Cretaceous to Late Paleocene so it would not be found at Sacaco. I think the oldest teeth in that area are Mid-late Miocene but most of the fossils from there are Early Pliocene in age.

Hexanchus andersoni is so far known confidently only from the Sharktooth Hill Bonebed. It's possible that its paleogeographic and chronologic ranges could be extended in the future (sites slightly younger in Orange County, CA) but the STH Bonebed is the only layer in the general region where Hexanchus of any age is somewhat common. I usually find at least one half/near-complete Hexanchus tooth when collecting that bonebed (though you can strike out too).

The cow shark from Sacaco has been identified as Hexanchus griseus (still alive today - the bluntnose sixgill shark) or Hexanchus cf. griseus (a taxon that compares favorably to griseus but may be just a close relative if not its immediate ancestor). Part of what would separate andersoni from griseus would be the size. A 1.6 inch andersoni would be unusually large but right in the zone for griseus.

You can get some variation in the teeth - finer serrations along the front (mesial) edge or the serrations can be enlarged to the point of looking more like the cusps that follow.

Hexanchus hasn't changed a lot since the Jurassic. It stayed out of the way of most other sharks inhabiting deepwater and it appears to have stayed small until sometime in the Oligocene when it started getting larger (perhaps a 4- 6 foot shark before then but reaching 10-15 feet by the Middle Miocene). Today, H. griseus can surpass 20 feet rivaling the largest known great whites.

I recently acquired a small "lot" of cow shark teeth from Sacaco, Peru.

In the lot was 1 cow shark tooth that measures about 1.6 inches from front to back, and was wondering if there was any occurrence known of teeth from the giant cow shark Notidanidon loozi being found there.

Also, in the same lot, there were two cow shark teeth (these may be partials, but are from the leading edge of the tooth) that bear a very strong resemblance to a cow shark species that as far as I know is only found in Bakersfield, CA... Hexanchus andersoni. I would also like an opinion on any occurrence of this species in Sacaco, Peru.

I can not take pictures at the moment (my camera is packed for a trip I am going on tomorrow).

If anyone can either prove or deny whether these species are found there or not, I would love to hear what you think on the topic.

I may be able to take pictures later (when I reach my destination). If I can, I will post them in the ID section tomorrow evening.

Thank you all in advance...

-Bill H.