Shark Teeth Identification

[Guest N.AL.hunter]

OK, so I have all these teeth I want to identify. After looking at several of the postings on here about shark teeth, is what I am seeing the truth... that two identical teeth can be called two different things based on their ages alone? Simply because one is from the Eocene and the other is from the Cretaceous or the Miocene, they are classified as different species based only on their ages. Or is this wrong and I am not reading carefully enough? Just wanting to find out.

[Gatorman]

Well if you have a tooth from the Eocene that looks nearly identical as one from the Cretaceous then likely they are along the same lineage. Probably the same genus but not the same species, shark tooth taxonomy seems to favor any variance to be a new species, i sometimes think they only do this to cause confusion.

[Harry Pristis]

OK, so I have all these teeth I want to identify. After looking at several of the postings on here about shark teeth, is what I am seeing the truth... that two identical teeth can be called two different things based on their ages alone? Simply because one is from the Eocene and the other is from the Cretaceous or the Miocene, they are classified as different species based only on their ages. Or is this wrong and I am not reading carefully enough? Just wanting to find out.

That sounds anomalous, NALh -- give us an example of what's troubling you.

For the sake of argument (the formal sort), I think that it's more accurate to say that teeth may be "similar" rather than "identical."

[jbstedman]

Though many others on the Forum are better able to respond to your question, let me make a fool of myself and take a stab at an answer (incomplete though it will be). The geologic age is not the defining criterion for identifying shark species, though it's often critical. The age of the formation from which teeth come is clearly important in helping to narrow the range of genera and species that might apply to any particular tooth -- some sharks are known only from certain time intervals. For example, I am not going to find Hemipristis serra in a Cretaceous site. If it's the same shark species in one time interval and in a succeeding one, it's the same shark species. There are many examples of shark species that cross different time intervals. For example, in my neck of the woods (Chesapeake Bay), Cretolamna appendiculata can be found in the late Cretaceous period and in the Paleocene and Eocene epochs. Some geologic boundaries are more important in this process than others. Most of the fossil species you can find in Cretaceous sites in the Chesapeake Bay area didn't make it into the Tertiary period (the K-T Boundary), though C. appendiculata does cross that boundary.

[Guest N.AL.hunter]

To clarify my comments: Usually when someone sends in their picture of a shark tooth to the forum for identification help, another member will say something along the lines of, "well if it was found in a cretaceous formation it might be 'X y', but if it was found in an eocene formation it is most likely 'X z'. So to me, if the tooth cannot be identified without the aid of knowing the formation it came from, then it must be the same as the earliest type found. If you can't tell the difference between 'X y' and 'X z' based on physical differences, then all teeth like that should be called by the oldest one, 'X y'.

Again, let me say I am just trying to find out some info before I start trying the monumental task of identifying my specimens. I have never formally identified my finds except for my Xaphactinus fossil, and I have thousands to ID. Because to me, if I have two teeth that look the same, they are the same regardless of where they were found.

[Auspex]

Don't pull your hair out; it won't help. A lot of fossil sharks are known primarily from their teeth, being (practically speaking) the only durable remains. Not a lot to go on, especially when you throw in convergant evolution (similarities in tooth morphology between not-too-closely related species). When a gap of 10 million years exists in the fossil record between two similar teeth, it's not a stretch to call them different species. I definitely feel your pain (I study fossil birds, which leave an even muddier taxonomy).

[PaleoRon]

Some types of teeth are very hard to ID unless you know the age of the teeth. Sand shark type teeth can sometimes be very difficult to correctly identify without knowing where they are from and how old they are. There are many species from the Cretaceous to recent that look very similar.

One well known lineage of sharks that is named based on age is Carcharocles. In the latest Eocene they are C. auriculatis but in the earliest Oligocene they are C. angustidens. The latest auriculatis and earliest angustidens look the same, but since they are from two different time periods they have different names. It happens again at the Oligocene - Miocene divide when C. angustidens becomes C. chubutensis. Same tooth morphology + different time period = new name.

C. chubutensis becomes even more interesting when you see an associated set of teeth that shows chubutensis type teeth, with cusps, toward the rear of the jaw and megalodon type teeth, without cusps, toward the front of the jaw.

Here's a link to an excellent reference on Cretaceous shark teeth.

http://www.texassharks.org/

[Harry Pristis]

To clarify my comments: Usually when someone sends in their picture of a shark tooth to the forum for identification help, another member will say something along the lines of, "well if it was found in a cretaceous formation it might be 'X y', but if it was found in an eocene formation it is most likely 'X z'. So to me, if the tooth cannot be identified without the aid of knowing the formation it came from, then it must be the same as the earliest type found. If you can't tell the difference between 'X y' and 'X z' based on physical differences, then all teeth like that should be called by the oldest one, 'X y'.

Again, let me say I am just trying to find out some info before I start trying the monumental task of identifying my specimens. I have never formally identified my finds except for my Xaphactinus fossil, and I have thousands to ID. Because to me, if I have two teeth that look the same, they are the same regardless of where they were found.

There are many reasons why systematically collecting (versus trophy collecting) of shark teeth is more complex and frustrating than collecting say postage stamps.

For one thing, variation is the overarching factor. Every shark is genetically distinct from every other shark, just as your fingerprints are different from mine -- all controlled by unique dna code.

There are positional differences in teeth from the same individual.

There are ontological differences in teeth from the same individual.

There is genetic drift within species.

There is convergent evolution between different species (as mentioned by Auspex).

There are environmental differences induced by injury or disease or food resources .

Further, there are biochrons, mostly marked by extinction events in earth's history, which may or may not be important in identifying a species.

Biochrons are chunks of earth's history when surviving taxa expand into new (or newly-vacant) niches. These older taxa in new niches may become new species, which thrive until some new catastrophe marks the end of their time. Indeed, a biochron is marked by the first and last appearances of various species.

Some species are not limited to one biochron, and survive into another (Carcharocles megalodon, a Miocene form, survived into the Pliocene, for example). Nonetheless, it is usually useful to know the geological age of any specimen to identify it reliably.

As much fun as we have here on this forum trying to identify fossils from (often) inadequate images, there is no substitute for equipping yourself with authoritative literature -- books and Internet resources such as elasmo.com. There have been any number of references to books that deal with shark teeth, so I won't repeat them here.

So, spend the time it takes. Immerse yourself in the literature and go through various sorts of your teeth. After a while, you'll start to recognize the subtle differences upon which taxonomists depend for their reputation and livelihood!

----------Harry Pristis

[Auspex]

Well said, Harry! As concise a discription of the challenges in fossil ID as I have ever read.

[Hogtownfossil]

Really, don't sweat it, nomenclature in paleontology is as prone to change as the price of oil. Every new paper or book I read changes some genus/species designation based on certain evidence the author finds important. Assigning a name to a fossil is not permanent, just a way to link that fossil to similar ones, good for us amateurs trying to organize our collection into some kind of order. All you can do is go by what the majority of collectors tend to agree to at the time, if you are lucky you can find some reference specific to your collecting locale/formation, if not you have to make do with studies of similar locales/eras/formations. Something new is always turning up fossilwise, so maybe you can be the first one on your block to have a new species named. If you don't even try to organize and identify your finds then you could be missing out on some important discoveries.

Personally in my collection I use a lot of "?", "cf." (conforms to), "aff." (has some affinities to), and just plain old "sp." in the identifications, just to remind myself nothing is really certain. Like the recent "Paragaleus/C.sealei/C.signatus" thread, whichever designation you use you can convey a good idea of what the teeth are like without having to do a long description and detailed pictures. It's just a convenient thing to do, and it makes for some spirited discussion too.

No big deal if you blow the ID, it will all work out in the end.

[non-remanié]

We also have to remember that sharks' teeth are just about the most scientifically worthless of any fossils. Besides looking at the bigger picture, for instance tracing lineages, and perhaps getting some scant clues about feeding habits, they do nothing more than look pretty darn cool! FLAME ON!

[Auspex]

Point taken, but surely you aren't uttering those ageless (and ultimately embarassing) words og science; "There's nothing more to be learned"?

[non-remanié]

Point taken, but surely you aren't uttering those ageless (and ultimately embarassing) words og science; "There's nothing more to be learned"?

Of course not!! I am just saying that they aren't generally very valuable scientifically so you should let me have them all! :>

[Auspex]

Of course not!! I am just saying that they aren't generally very valuable scientifically so you should let me have them all! :>

Sure. They're in the mail. Let me know when you get them.

[Guest N.AL.hunter]

Thank to everyone for the responses. It is as I thought then for some teeth. Looks like my cataloging job has gotten harder.

[jbstedman]

I was checking out dogfish sharks (Squalidae) on elasmo.com and found a comment by Jim Bourdon which is relevant for this thread.

He offers what I take to be a general statement against paleontologists separating similar teeth into different species just because they come from different periods (N.Al.Hunter's original concern). Bourdon notes the apparent stability of Squalidae species over time, and then he writes: “There would appear to be no valid reason (if there ever is) to use time as a relevant factor when determining a tooth’s identification. For example, Squalus teeth from the Middle Atlantic’s Oligocene, Miocene and Pliocene which compare well with S. acanthias are more likely to be from that species than some paleontological species erected on an ad hoc basis.”

[Guest N.AL.hunter]

jbstedman,

Thanks for this find. Now I know I am not the only one who thinks that age should not be a determining factor. For my collection, if it looks the same, it will be called by the oldest name I can find. Right or wrong. At least they will be identified somehow, since now they are just called "shark tooth, location".

[jbstedman]

jbstedman,

Thanks for this find. Now I know I am not the only one who thinks that age should not be a determining factor. For my collection, if it looks the same, it will be called by the oldest name I can find. Right or wrong. At least they will be identified somehow, since now they are just called "shark tooth, location".

N.AL.hunter:

Of course, as some responses in this thread suggest, there may be subtle differences between otherwise similar teeth that do warrant designation as different species.

jb

[siteseer]

Really, don't sweat it, nomenclature in paleontology is as prone to change as the price of oil. Every new paper or book I read changes some genus/species designation based on certain evidence the author finds important. Assigning a name to a fossil is not permanent, just a way to link that fossil to similar ones, good for us amateurs trying to organize our collection into some kind of order. All you can do is go by what the majority of collectors tend to agree to at the time, if you are lucky you can find some reference specific to your collecting locale/formation, if not you have to make do with studies of similar locales/eras/formations. Something new is always turning up fossilwise, so maybe you can be the first one on your block to have a new species named. If you don't even try to organize and identify your finds then you could be missing out on some important discoveries.

Personally in my collection I use a lot of "?", "cf." (conforms to), "aff." (has some affinities to), and just plain old "sp." in the identifications, just to remind myself nothing is really certain. Like the recent "Paragaleus/C.sealei/C.signatus" thread, whichever designation you use you can convey a good idea of what the teeth are like without having to do a long description and detailed pictures. It's just a convenient thing to do, and it makes for some spirited discussion too.

No big deal if you blow the ID, it will all work out in the end.

This brings up the point that virtually none of the modern species were described on the basis, even in part, of their teeth, while most fossil species are based solely on teeth. There is a cautionary tale within an article reviewing Eocene teeth from Antarctica (Welton and Zinmeister, 1980). A sample of over 300 dentitions of the California bat ray (Myliobatis californicus) was acquired as the result of a fishing competition. While all the dentitions certainly belonged to the same species, a wide range of variation in several characters was observed - wide enough that had the tooth plates been found as fossils, they would have been referred by some authors to more than one species (perhaps several with a new species proposed as well).

Building a collection of references is essential to gaining an understanding your collection. I am lucky to live not far from a USGS library and a couple of excellent university science libraries and have taken full advantage of their photocopiers as some of the original works are elusive or just plain expensive. I have been fortunate to have met a few researchers who are true experts (Bruce Welton, David Ward, Gordon Hubbell) and their comments on certain teeth/taxa have been very valuable to me. They helped me fill in the blanks - gaps in the literature that you will recognize as you learn more about sharks, their official descriptions, and subsequent comments on those descriptions. At some point one of us should start a topic on what would be considered must-have publications for a shark tooth collector library. Of course, if someone focused on a particular layer or sequence of layers (Lee Creek, Bone Valley, Moroccan phosphates, etc.), there would be another batch of references per area. These days, a lot of stuff is now online and a lot easier to find. At some point you may find yourself thinking about writing your own article or book on an aspect of fossil shark research that has been largely ignored.

[eddie]

OK, so I have all these teeth I want to identify. After looking at several of the postings on here about shark teeth, is what I am seeing the truth... that two identical teeth can be called two different things based on their ages alone? Simply because one is from the Eocene and the other is from the Cretaceous or the Miocene, they are classified as different species based only on their ages. Or is this wrong and I am not reading carefully enough? Just wanting to find out.

Great topic. Keep in mind, human ego plays just as much of a part as anything else in naming species. This alone causes confusion. Taxonomy is not an exact science, even with extant species. With fossil shark teeth, species along the same evolutionary line are often are defined by geologic time period in which they were found, which, imo, makes it even more confusing and arbitrary. Am I a different species than my great grandfather?

Personally, I wish the names themselves would indicate the time period rather than someone's name or some catchy latin term, that would be more straightforward. For example, "Carcharocles angustidens" should be "Carchorocles oligocenus", "C. chubutensis" should be "C. miocenus", etc.

As others have said, don't sweat it too much!

Thanks,

Ed

[siteseer]

Great topic. Keep in mind, human ego plays just as much of a part as anything else in naming species. This alone causes confusion. Taxonomy is not an exact science, even with extant species. With fossil shark teeth, species along the same evolutionary line are often are defined by geologic time period in which they were found, which, imo, makes it even more confusing and arbitrary. Am I a different species than my great grandfather?

Personally, I wish the names themselves would indicate the time period rather than someone's name or some catchy latin term, that would be more straightforward. For example, "Carcharocles angustidens" should be "Carchorocles oligocenus", "C. chubutensis" should be "C. miocenus", etc.

As others have said, don't sweat it too much!

Thanks,

Ed

A few sharks and rays are named that way (ex. Woellsteinia oligocaena, Megascyliorhinus miocaenicus). The problem with name indicating the time unit is that some genera contain multiple species living within the same time unit. The genera and species should be descriptive. You could give a shark a name to note the age or stage within a time unit but that would be misleading if the species lived across more than one age/stage.

I do understand naming a taxon to honor someone who has contributed to the field with little/no recognition. Someone should name the next new pinniped or shark after Bob Ernst, even if posthumously, in appreciation for all the specimens he dug and donated.