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presentation of understanding shark tooth features for identification


fossilnut

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I volunteer at a natural history society. i was asked to do a zoom talk for a general audience on identifying fossil shark teeth. As I looked at a few online shark tooth identification Guides, what struck me was the number of scientific words or descriptive terms that a person would need to understand to use a Guide. It would be discouraging to have to stop and look up each term. So I tried to find a site where all the words or terms were explained with words and pictures that would be clear. I did not find one. Can any of you point me to one?

I had never tried on my own to id shark teeth. I relied on others. So I approached this as a newbee. I put together a power point program showing pictures (53) of shark teeth crown and root features, pictures showing the labial and lingual sides, serrations, cusps, cutting edge directions-mesial & distal and changes in teeth based on their tooth position. For fun, pictures of pathological teeth are shown.

All comments, suggestions would be appreciated. thanks for reading

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Have you looked HERE?

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Thanks Fossildude19. Yes I did see that site. It had the one picture at the start but there were no pictures to go with the many glossary word definitions which left me unclear as to the meaning. For example: Directional terms  Labial (from the front) Lingual (from the back) I pick up a tooth but how do I know what is the front or back? For me, I need a visual-a picture. No mention of flatter or more convex shape etc.

This is a discussion with myself as to how to help a person begin to understand these terms. What importance in life did they have? Protect the tongue from being cut? Shape of tooth as it relates to type of prey? So the talk tries to bring in (as best I understand) what the features do for the living creature. Not just a dull recital of definition.

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Not sure if this is accurate or not and its a little confusing but it has a whole lot of termsShark teeth terminology, anterolateral part of the upper left tooth [17]. |  Download Scientific Diagram

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Thanks Top Trilo. And I thought the Halloween Horrors were over. I did not see that one! Wow that is busy and requires a whole lot of concentration to grasp. Not sure what the difference is between crown and blade-if any?

I recognize it is easy to criticize but to do a clear, understandable and "simple" is very hard. A picture without a verbal explanation is as bad as a verbal explanation without a picture-for me.

As you can tell, I am still trying to figure out how to put together as clear a presentation to a newbee or an oldbee like me that makes sense and is enjoyable and holds the viewers attention.

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I haven't been able to find what your looking for. If I understood right you need the terms and how the shape of the tooth corresponds with the sharks behavior and traits right.

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The problem is there is no standard set of terms.  There can be three terms that people (whether professional or amateur) use for the same tooth character, a "character" being a particular feature like a cusplet or a foramen.  This just happens to be a day when I can't go into detail and explain everything but here are some notes:

 

It starts with general terms.  A shark tooth has a crown and a root.  The crown is coated with an enamel-like substance that is called "enameloid."  After that it gets complicated because you're going to get a different set of terms applicable to different teeth and it can change from the anteriors (the teeth at the front of the jaw) to the posteriors (the teeth at the back).  Not all teeth of the various (and numerous) genera have a central foramen.  Some have more than one.  The plural of foramen is "foramina."  Not all teeth have cusplets.  Sometimes the serrations seem to grade into larger serrations that someone else might call a cusplet.  Not all teeth have a neck which is usually called a bourlette when it's larger on larger teeth.  The vast majority of shark teeth are under an inch long so a 1-inch tooth would be considered large unless it's from a genus with clearly larger adult teeth.

 

That chart given above is a little busy.  The term "transverse ridge" refers to raised segments of enameloid.  They are usually called "folds" but can be called simply ridges  When present, they tend to be short as in the figure.  They also tend to be on one side or "face" of the tooth.

 

The crown is generally one unit and that's the cusp but it can have smaller ones too and those are cusplets (aka lateral cusplets).  The cusp is often called the "main cusp" when there are cusplets.  When the crown extends to the sides to the ends of the root lobes the part of the crown that comes off that curve and is roughly horizontal or sloping is called the "blade," or more commonly, the "heel."  This is a direct translation of what it's called in French.  Some tooth terms are translations from French terms because many early paleontologists were French.  The study of shark teeth basically began in the very late 19th century and early 20th century.  The "heel" is also called the "shoulder."

 

The crown foot is really just the boundary between the crown and the root.  It's sort of left as a general area in the figure.

 

The cutting edges are mesial and distal.  The mesial edge is the leading edge.  If the tooth were in the jaw, it would be the edge on the side toward the front of the jaw.  You can generally distinguish mesial and distal edges because teeth often lean one way.  It's not as easy when they are straight.

 

I have to go now but will try to get back to this.  Maybe another shark tooth collector an fill in. 

 

Jess

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I really appreciate your detailed response. I am learning a lot. One unfamiliar area for me is the foramen/foramina. If I understand correctly, these have to do with blood supply and feeding for the tooth which are obviousl y very important. This is not something that I have heard other experienced collectors talk about. Also I never heard about transverse ridges. What purpose did they serve? While the use of different terms is true, I am going to try and keep it simple but maybe just mention that fact without spending time on it unless questions come up asking about a different word.

I would be very thankful if you could continue on with your very informative thoughts. Thank you for sharing your knowledge.

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hello fossilnut!

The LC Vol III page 79 has a page of diagrams as well.

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17 hours ago, fossilnut said:

Thanks Fossildude19. Yes I did see that site. It had the one picture at the start but there were no pictures to go with the many glossary word definitions which left me unclear as to the meaning. For example: Directional terms  Labial (from the front) Lingual (from the back) I pick up a tooth but how do I know what is the front or back? For me, I need a visual-a picture. No mention of flatter or more convex shape etc.

For labial and lingual, I used to explain to LC visitors the terms labial (from labia, or lips, to it's the outer side of the tooth) and lingual (from lingua or tongue, the inner side of the tooth), and to think about it as if one were taking the wedge-shape of a tooth and cutting vertically downward into a piece of meat.  As the tooth pierces the meat, the wedge-shape of the lingual (inner) side directs the cleaved portion of the meat inwards, into the mouth.  

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13 hours ago, fossilnut said:

I really appreciate your detailed response. I am learning a lot. One unfamiliar area for me is the foramen/foramina. If I understand correctly, these have to do with blood supply and feeding for the tooth which are obviousl y very important. This is not something that I have heard other experienced collectors talk about. Also I never heard about transverse ridges. What purpose did they serve? While the use of different terms is true, I am going to try and keep it simple but maybe just mention that fact without spending time on it unless questions come up asking about a different word.

I would be very thankful if you could continue on with your very informative thoughts. Thank you for sharing your knowledge.

 

 

Yes, the foramina are the openings for tiny blood vessels.  in many fossil teeth these are obscured because they are often filled in by fine sediment or they are eroded and/or covered by matrix.  Sometimes, you find a well-mineralized tooth with the root intact and the foramina are better observed. 

 

The ridges (=folds) are seen in only some sharks.  I'm not sure they have a purpose and may be vestigial.  They might have had a purpose in an ancestor.   They are already short  in the Middle Cretaceous genus, Cretodus and are still short in a modern one, Galeorhinus (which appeared during the Cretaceous).  The ridges are longer in some catsharks (Family Scyliorhinidae).  They might help reinforce the base of the crown from lateral stresses.  They might be considered vestigial in some genera - something once useful in an ancestor but more or less ornamental in a descendant.  I'm not sure I've ever heard anyone talk about their possible function. 

 

Jess

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@hemipristis

4 hours ago, hemipristis said:

 As the tooth pierces the meat, the wedge-shape of the lingual (inner) side directs the cleaved portion of the meat inwards, into the mouth.  

This is very useful. Gives a good "visual" to make clear its functional purpose for the living animal.  Sorry, I don't understand your reference to LC. Please explain. Thanks for your information.

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@sharkdoctorPurdy's focus on understanding the tooth's position blew me away. That level of understanding would require extensive experience with many teeth from the same species. Could you help me with two items. I already had attempted to explain the  importance of tooth position and how one would come to understand and determine that for an individual tooth. "This information would come from the rare finding of associated fossil teeth arrangement and from modern shark jaws from similar species of sharks." Is this accurate?

The 2nd question, Purdy talks about "the attitude of the crown". Under his definitions, the only definition is "the apical portion of the crown is curved-recurved." Is this what "attitude" means or is there a larger definition?

Actually I have a third question re Pathological teeth. Purdy's definition is that the tooth germ is damaged by a foreign piece of prey eaten such as a string ray barb or marine catfish spine. Can faulty gene replication also result in tooth pathology? I have seen pictures of pathological meg teeth. IMO. It is unlikely that they would be eating sting rays or catfish. Certainly damage could occur from other prey ingestion.

I would be very grateful for your help. Appreciate your wishes for a good talk. I have invested a lot of time in trying to find and use pictures as well as descriptive explanations in every day language to explain the technical terminology. As important to try and link it all to the living animal.

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Hi,

 

Some sharks occasionally feed on rays, we have already seen photos of current shark jaws damaged by the sting of a ray left in, which can cause pathological teeth.

About the shape of the teeth in a shark or ray jaw, look in my signature, I made a topic on heterodontics ;)
 
Coco
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@fossilnut 

Question 1: Shimada, K. (2005). Types of tooth sets in the fossil record of sharks, and comments on reconstructing dentitions of extinct sharks. Journal of Fossil Research, 38(2), 141-145.

Available here: http://www.kasekiken.jp/kaishi/kaishi_38(2)/kasekiken_38(2)_141-145.pdf

 

Question 2: Sorry, I have no clue on this one. I suspect some of our resident shark experts might have an idea on this.

 

Question 3: Elasmo.com has a section on pathologies that covers this topic in some detail: http://www.elasmo.com/refs/terms/patho.html

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@sharkdoctorAgain my thanks for your references. Shimada certainly shows how difficult a process it is to develop a tooth set and the need to clearly set forth how it was put together. I hope someone will speak to Purdy's use of the term "attitude".

I have a date of 12/02 for the presentation. Now I only need to be able to tackle and succeed in the computer processes to deliver it.

I appreciate everyone's responses. They were all very helpful to me. Thanks Be safe and stay Well. Tom

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Good luck with your presentation! If you are willing to share, it could make an interesting resource for others that do outreach on the forum?

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