Mystery Shark's teeth

[kate_rose]

Hello,

 

These are also from our hunt in the Aquia formation of Charles Co. MD.  Sharks of the world didn't give me much insight.  The only species that I noticed where the enamel extends out on to the roots like this is the extinct goblin shark Anomotodon novus.  I definitely have some teeth from that species I think but these are substantially different.   These are larger, more robust and the have the cool extended enamel and bumps/cusplets on the shoulders of the labial side.  Any thoughts?? (ruler in mm and squares 1/4")

 

Kate

 

Edited May 25, 2019 by kate_rose

[Randyw]

I’m no expert on teeth. But they look a lot like sand tiger (carcharias taurus) to me

[kate_rose]

I am no expert either and I know C taurus is supposed to occur in that formation but according to the book the cusplets are supposed to be pointy.  I guess they could be worn off . . . but just based on the other teeth I have looked at the bumps seem intact to me.  Now that you mention it the teeth aren't very pointy anymore - maybe it is wear.  Thanks Randy.

 

[hemipristis]

If these are from the Paleocene Aquia Fm, they're too old to be Carcharias taurus but the tooth on the right does indeed have that standard, striated "sand tiger" look to it for sure, which over time is called Scapanorhynchus sp., Stroiatolamia striata, Striatolamia macrota or C. taurus, depending on the age.  In this case, it would be Striatolamia striata**.

 

Re: the tooth on the left, the concavity of the labial root base and more robust blade lend me to believe that it is Jaekelotodus robustus. I posted photos of French and  Belgian teeth of this species below.

 

I welcome others' thoughts of course.

 

 

**Despite insistence by some that there are identifiable morphological differences between these four species, the nuance is lost on me.  I honestly believe if you handed a 2 dozen of these teeth to collectors without provenance information, most would be unable to distinguish them, which makes me question the validity of the current nomenclature. I'm apparently not alone:

 

"The genus Striatolamia left a fossil record with teeth that can be easily confused with those from other genera. I find it particularly disconcerting to need to know the stratigraphic position before             tendering an opinion as to whether an anterior tooth might be Scapanorhynchus or Striatolamia, or at other times, Carcharias or Striatolamia. The experts may find the subtleties "obvious", but I've never achieved that comfort level".

 -- Jim Bourdon 1999 (Elasmo.com)

[Randyw]

You are correct. I should have used the older striata. I thought about robustus but I don’t have enough knowledge of the differences between them to make that call.... they just seemed a little small for that to me...

[Gizmo]

Try this. - https://www.fossilguy.com/sites/potomac/liv_col.htm

[kate_rose]

Hemi,

 

I am confused.

 

If the left one is Striatolomia striata then what are the these teeth with really clear striations (below - repeated from earlier post) that were collected at the same time.  Do shark's teeth change in structure as they age so the younger ones have the grooves and the older ones the smooth enamel?? The look really different to me . . .  I have some very worn pieces of teeth that I would tentatively identify as S. striata (collected at the same time) just based on the striations which remain even after the enamel is gone.  Despite the cusplets being worn off it seems odd that no grooves would remain on the tooth on the left if it is really striata.  Are you saying there is intermediate forms between the two in the same formation and I am just looking at the extremes?  I am not a good judge of wear on a tooth - are these teeth just really worn??

 

I am surprised that the one on the right is a different species because they look soo similar to me.  I figured the variation was just due to location in the mouth.  So teeth can look really the same in color and enamel texture and wear, be collected at the same time, and be totally different species?  Wow - tough field

 

I know I ask a lot of questions.  I am just trying to figure it out.

 

Thanks for you help,

 

Kate

 

P.S. Also is former Purse State Park - now Nanjemoy Wildlife Management Area (Charles Co, MD) Aquia formation?  From my reading I was pretty sure it was but just wanted to be sure.

 

  

 

 

 

   

Edited May 25, 2019 by kate_rose
further addressed posters previous statements

[kate_rose]

Ginko,  Thanks for the reference.  I have read all of fossil-guys material that is online about Potomac river fossils and most of his other stuff too.  I still have a lot of questions probably because I am a newbie.

 

Kate

[hemipristis]

5 hours ago, kate_rose said:

Hemi,

 

I am confused.

 

If the left one is Striatolomia striata then what are the these teeth with really clear striations (below - repeated from earlier post) that were collected at the same time.  Do shark's teeth change in structure as they age so the younger ones have the grooves and the older ones the smooth enamel?? The look really different to me . . .  I have some very worn pieces of teeth that I would tentatively identify as S. striata (collected at the same time) just based on the striations which remain even after the enamel is gone.  Despite the cusplets being worn off it seems odd that no grooves would remain on the tooth on the left if it is really striata.  Are you saying there is intermediate forms between the two in the same formation and I am just looking at the extremes?  I am not a good judge of wear on a tooth - are these teeth just really worn??

 

I am surprised that the one on the right is a different species because they look soo similar to me.  I figured the variation was just due to location in the mouth.  So teeth can look really the same in color and enamel texture and wear, be collected at the same time, and be totally different species?  Wow - tough field

 

I know I ask a lot of questions.  I am just trying to figure it out.

 

Thanks for you help,

 

Kate

 

P.S. Also is former Purse State Park - now Nanjemoy Wildlife Management Area (Charles Co, MD) Aquia formation?  From my reading I was pretty sure it was but just wanted to be sure.

Ah, Purse State Park.... many a fine fossil hunt. Love that place!  

 

I apologize, I may have confused you.  When I referred to the "left tooth", I was referring to the left tooth in your photo below (with both root lobes).  I believe it to be Jaekelotodus robustus.  No striations on this one.

 

The one on the right however is Striatolamia sp., same as the teeth you noted in your other post, but in this one, most of the striae have been worn away.

 

Shark teeth ID can be simple (Megalodons, tigers, Hemipristis), tricky (these teeth), or maddening (speciating the teeth from the genus Carcharhinus).  It takes a lot of reading, and many, many hours examining, re-examining, identifying, and re-identifying your teeth before you'll start to feel comfortable. I've been doing this for 20 years and I still have piles of teeth labelled ???? 

 

Best of luck, and always feel free to ask questions. There's an encyclopedia's worth of knowledge in this group.