Hemi Positions

[Shellseeker]

I tend to use fossil finds to generate questions to clarify things in my mind. Today - Snaggleteeth. Just before the rains came, I found the two teeth in Photo#1,

I Love finding hemis, especially pretty ones like these. I know the tooth on top is an upper.

Here is another photo from a couple of years back...

A lower and an upper..

Here is the first really nice tooth I found in 2009.

So the question -- Are the Hemis in this last photo and the lower one in the 1st photo both lowers? and the jaw position if possible -- left, center, right.

I figure that there are some Hemi experts out there.. SS

[Coco]

Hi,

I am looking at my recent Hemipristis elongatus jaw. Here is what I see on this species :

- it hasn't upper symphyseal tooth,

- upper parasymphyseales teeth are notched only on the outer sides,

- it has lower symphyseal tooth,

- this symphyseal tooth isn't notched.

In your hand, the big Hemipristis (H. serra if Miocene) is an upper and left tooth, the other one a lower left tooth.

Your marvelous dark tooth is probably the one just after the upper parasymphyseal tooth. But to see if it is a left or a right one, you have to do a pic on its natural position (root upward and photo done well face)

Coco

[Shellseeker]

Coco,

Thanks for the quick response. I located this a set of dentition at this website: http://www.fossilguy.com/gallery/vert/fish-shark/hemipristis/hemipristis.htm.

If you has a similar site you use, please share.

When you state , upper left or lower right I assume it is from the perspective of the shark. I am pleased to be able to place a tooth into a relatively appropriate position.

The dark tooth is the mystery. I found it when I had just started hunting in Arcadia Florida. It was so pretty and I thought I would find many more like it going forward. Well, in the last 5 years, I have found thousands of hemis, big and small, but not another that has the same combination of serrations on both side to the tip, and symmetrical rather than curved.

For those 5 years, I actually was unsure whether it was a very unusual upper or very unusual lower. I'll get a photo from straight on and post it. SS

[Coco]

When you state , upper left or lower right I assume it is from the perspective of the shark.

Sorry, I wasn't very explicit. I spoke by having the jaw of shark in front of me.

In your hand, the big Hemipristis (H. serra if Miocene) is an upper and left tooth, the other one a lower left tooth.

I mean that the big tooth is an upper tooth situated in the right part in the shark jaw, and that the other tooth is a lower one situated also in the right part of the jaw (to consider as if they teeth was yours in your mouth)...

Here is a pic :

Coco

[Shellseeker]

Coco,

A more recent photo, looking straight on -- I am still not sure if it is upper or lower, but must be close to center of the jaw-

[Coco]

Hi,

Oh yes ! Nice tooth !

You are right, it is an upper tooth, and I think this one follows the parasymphyseal one.

In recent Hemipristis elongatus, upper teeth are less curved than those of Hemipristis serra... Not always easy to compare !

Coco

[Al Dente]

Shellseeker makes the comment about the number of serrations on the unusual Hemipristis tooth he found. Serrations on Hemipristis teeth increase with increasing age of the shark that produces the teeth. Here is a picture I snipped out of a paper that shows this.

From: Chandler, Chiswell, Faulkner, 2006. Quantifying a possible Miocene Phyletic Change in Hemipristis (Chondrichthyes) Teeth. This paper can be downloaded free online.

Edited June 29, 2014 by Al Dente

[Al Dente]

As to the question of whether Shellseeker's tooth is an upper or a lower, it depends on the reference you use. There are some similar on elasmo.com that look like they are labeled as upper teeth. I've looked at similar teeth in my collection that I've always considered to be lowers based in the very large lingual bulge and the teeth appear to be very compressed in the mesial - distal direction. Here is a picture of some of mine that I think are lowers. Shellseeker's tooth does look a little more symmetrical than my teeth.

[Al Dente]

Here's one of the above teeth showing the large lingual bulge that I have assumed only occur on the lower teeth.

[Shellseeker]

Here's one of the above teeth showing the large lingual bulge that I have assumed only occur on the lower teeth.

For the same reasons you provide. I had always assumed that this was a middle-left jaw lower -- I have a collection of some of these that look like my tooth, but have greater curve and smaller/less serrations.

Now Coco illustrates that upper tooth just next to the parasymphyseal of h. elongatus which also looks very similar.

All I can say is that whatever you identify the lower left and lower right teeth in your post #8 should also be the identifiacation of my tooth. To me your lower left and my tooth are mirror images. SS

[Coco]

Here's one of the above teeth showing the large lingual bulge that I have assumed only occur on the lower teeth.

On recent Hemipristis elongatus, it exists a large lingual bulge also on upper teeth situated near the symphyse.

Coco

[Al Dente]

On recent Hemipristis elongatus, it exists a large lingual bulge also on upper teeth situated near the symphyse.

Coco

Thanks Coco.