Hexanchus from Chile

[Max-fossils]

Hi all,

 

I have here a six-gill cow shark tooth (Hexanchus) from the Atacama desert.

I do have a few questions about it:

• What is the species name?
• What position in the jaw is it?
• Exactly how old is it? (I'd like this to be as precise as possible; if you could tell me the precise stage it would be perfect!)

Thanks for the help!

 

Max

 

[Troodon]

Looks like an upper Hexanchus gigas  most likely from the Bahia Inglesa Formation, Miocene/Pliocene (4-6 mya)

[Max-fossils]

34 minutes ago, Troodon said:

Looks like an upper Hexanchus gigas  most likely from the Bahia Inglesa Formation, Miocene/Pliocene (4-6 mya)

Alright, thanks for the info!

Do you perhaps know the exact position?

[Max-fossils]

38 minutes ago, Troodon said:

Looks like an upper Hexanchus gigas  most likely from the Bahia Inglesa Formation, Miocene/Pliocene (4-6 mya)

Here is a jaw that I found online, apparently from a fellow TFF member.

I can't find any tooth though that looks very similar to mine...

 

[Troodon]

Your tooth is missing one cusp which makes comparisons more difficult.  I believe what your looking at is an artifical tooth set that someone put together but not associated.  There is lots of jaw to jaw variation including ontogenenetic and sexual dimorphism changes that will affect the shape of the tooth.  For example, males tend to have a higher primary cusp like your tooth.   One can argue positions but I still think it's an H gigas.  The one I circled is closest to yours

 

[caldigger]

Wow I picked the exact one out of the line up for the comparison. Unfortunately, I am quite old school when it comes to computers and don't know how to do drawing on pictures like that.  The latter cusp is broken off the tooth, which makes it look like a different one.

You however have the full root on yours which is often broken.  Is this a self found piece?

[siteseer]

As Troodon noted, the Bahia Inglesa Formation spans the Late Miocene and Pliocene.  A search on the web comes up with it ranging to 10 million years old.  In one publication (Suarez, 2015) the cowshark listed from the Late Miocene part and the Pliocene part is Hexanchus sp.  Troodon calls it H. gigas and that has been the name traditionally given to fossil Hexanchus teeth that resemble modern H. griseus teeth.  Some researchers think it is close enough to call them H. griseus teeth (see Purdy et al., 2001).

 

Since Hexanchus is known from both the Late Miocene and Pliocene and you don't know exactly where it was collected, the age will always be in question.

 

 

Purdy, R.W., V.P. Schneider, S.P. Applegate, J.H. McLellan, R.L. Meyer, & B.H. Slaughter. 2001.

The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. Smithsonian Contributions to Paleobiology, 90, 71–202.

 

Suarez, M.E.  2015.

Tiborones, rayas y quimeras (Chondrichthyes) fosiles de Chile.  Publicacion Ocasional del Museo Nacional de Historia Natural, Chile.  63: 17-33.

 

 

[Max-fossils]

17 hours ago, Troodon said:

Your tooth is missing one cusp which makes comparisons more difficult.  I believe what your looking at is an artifical tooth set that someone put together but not associated.  There is lots of jaw to jaw variation including ontogenenetic and sexual dimorphism changes that will affect the shape of the tooth.  For example, males tend to have a higher primary cusp like your tooth.   One can argue positions but I still think it's an H gigas.  The one I circled is closest to yours

Ok, thank you!

I do see indeed now that one cusp is missing.

But I don't think that this tooth is reconstructed though; what makes you say this?

[Max-fossils]

15 hours ago, caldigger said:

Wow I picked the exact one out of the line up for the comparison. Unfortunately, I am quite old school when it comes to computers and don't know how to do drawing on pictures like that.  The latter cusp is broken off the tooth, which makes it look like a different one.

You however have the full root on yours which is often broken.  Is this a self found piece?

Alright, thanks!

No, I didn't find the tooth myself, but I bought it from a friend of mine, who had it since quite some time in his collection.

 

Btw, if you want to circle/draw (or simply edit) a photo, I am sure that there is a program on your computer to do that. I use the Photos app on my Windows 10 laptop, with the draw option. Paint (on most Windows) is also a good app. What kind of computer do you have?

[Max-fossils]

14 hours ago, siteseer said:

As Troodon noted, the Bahia Inglesa Formation spans the Late Miocene and Pliocene.  A search on the web comes up with it ranging to 10 million years old.  In one publication (Suarez, 2015) the cowshark listed from the Late Miocene part and the Pliocene part is Hexanchus sp.  Troodon calls it H. gigas and that has been the name traditionally given to fossil Hexanchus teeth that resemble modern H. griseus teeth.  Some researchers think it is close enough to call them H. griseus teeth (see Purdy et al., 2001).

 

Since Hexanchus is known from both the Late Miocene and Pliocene and you don't know exactly where it was collected, the age will always be in question.

 

 

Purdy, R.W., V.P. Schneider, S.P. Applegate, J.H. McLellan, R.L. Meyer, & B.H. Slaughter. 2001.

The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. Smithsonian Contributions to Paleobiology, 90, 71–202.

 

Suarez, M.E.  2015.

Tiborones, rayas y quimeras (Chondrichthyes) fosiles de Chile.  Publicacion Ocasional del Museo Nacional de Historia Natural, Chile.  63: 17-33.

 

 

OK, thank you for all this useful info! I'll put it down as Miocene-Pliocene.

[Troodon]

I do 90 % of my input with an android tablet and there are lots of apps to modify photos

[Max-fossils]

Just now, Troodon said:

I do 90 % of my input with an android tablet and there are lots of apps to modify photos

Android tablets work just fine too.

As well as a good smartphone (iPhone 6 for me) will do the job.