Posterior Cretalamna Or Otodus Or . . .

[jbstedman]

I am having a hard time figuring out a good way to distinguish posterior Cretalamna appendiculata from Otodus obliquus teeth.

How would you ID this tooth?

Cretalamna or Otodus or something else? (I hope not "something else" since I thought I was starting to learn a bit about this process.)

I've assumed size would be a good marker (big = Otodus), but with an isolated tooth, it's hard to know if you're dealing with an adult Cretalamna or a juvenile Otodus. I see U shaped roots in both genera of sharks, as well as smooth crowns, broad triangular cusplets, an absence of a nutrient groove, . . . .

[PaleoRon]

I would say Otodus. The Cretolamna I have found along the Potomac are pretty distinctive and very few of them have been even close in appearence to the Otodus I found in the same locations.

[jbstedman]

I would say Otodus. The Cretolamna I have found along the Potomac are pretty distinctive and very few of them have been even close in appearence to the Otodus I found in the same locations.

What sets the Cretalamna apart?

The pictures on elasmo.com suggest some basic similarity when you look at lateral and posterior teeth.

Edit: Sorry, I didn't realize that the second picture (below) was posted. I thought I had deleted it. Anyway, I believe the one below is a Cretalamna appendiculata. It's from a Cretaceous site in Maryland. (Excuse the number in the picture -- it's for my database.) It does look something like the first picture I posted.

[hybodus]

jbstedman, good question, and I would love to see someone post a reasonable descriptive overview of distinguishing characteristics... The reality is that US Paleogene Otodus and Cretalamna teeth share VERY similar tooth designs, and are even more difficult to tell apart in smaller teeth.

I also have a bucket of teeth from the Potomac where quite frankly many of them could go either way - perhaps my eye is just not experienced enough. I would say that the first specimen you posted looks more like an Otodus - and the only reason I say that is that it fits my view of a classic Otodus shape - I do not base this view on any definitive characteristics other than having stared at a whole bunch of them, and going cross eyed in the process...

[Harry Pristis]

jbstedman, good question, and I would love to see someone post a reasonable descriptive overview of distinguishing characteristics... The reality is that US Paleogene Otodus and Cretalamna teeth share VERY similar tooth designs, and are even more difficult to tell apart in smaller teeth.

I also have a bucket of teeth from the Potomac where quite frankly many of them could go either way - perhaps my eye is just not experienced enough. I would say that the first specimen you posted looks more like an Otodus - and the only reason I say that is that it fits my view of a classic Otodus shape - I do not base this view on any definitive characteristics other than having stared at a whole bunch of them, and going cross eyed in the process...

That IS a good question. I don't have any Potomac River teeth, but I do wonder about these same sharks from Morocco.

Which shark(s) are these?

[jbstedman]

jbstedman, good question, and I would love to see someone post a reasonable descriptive overview of distinguishing characteristics... The reality is that US Paleogene Otodus and Cretalamna teeth share VERY similar tooth designs, and are even more difficult to tell apart in smaller teeth.

I also have a bucket of teeth from the Potomac where quite frankly many of them could go either way - perhaps my eye is just not experienced enough. I would say that the first specimen you posted looks more like an Otodus - and the only reason I say that is that it fits my view of a classic Otodus shape - I do not base this view on any definitive characteristics other than having stared at a whole bunch of them, and going cross eyed in the process...

Yes, life's certainly easier if the teeth are bigger.

I guess the confusion over these teeth is natural. I've looked at Kent's Fossil Sharks of the Chesapeake Bay Region. He concludes that Otodus obliquus came from Cretalamna appendiculata and suggests the distinctions between the two are minor. The two he mentions are the lingual protuberance (apparently, in C. appendiculata, the protuberance is not as clearly "demarcated" from the rest of the root) and nutrient pores (loose cluster in C. appendiculata and horizontally dispersed in O. obliquus). Not sure what the first distinction really looks like. As to the second, with river worn teeth, not always easy to map the pores.

[jbstedman]

That IS a good question. I don't have any Potomac River teeth, but I do wonder about these same sharks from Morocco.

Which shark(s) are these?

Based on Kent, would the middle tooth be Otodus and the others likely Cretalamna? The protuberance is certainly more prominent and distinguishable from the rest of the root in that middle tooth. Is that what he had in mind?

Harry, are there obvious nutrient pores in these specimens?

[Harry Pristis]

Based on Kent, would the middle tooth be Otodus and the others likely Cretalamna? The protuberance is certainly more prominent and distinguishable from the rest of the root in that middle tooth. Is that what he had in mind?

Harry, are there obvious nutrient pores in these specimens?

Well, here's what I know, Jim. All three of these teeth were in one box in my drawer labelled "Cretalamna appendiculata." In selecting a few to photograph, I noticed the different root shape of "B" . . . with lines more "boxy" than flowing.

The root shape of "A" and "C" most resemble one-another; but, I have large teeth in my drawer labelled "Otodus obliquus" which are not unlike the boxy-rooted "B" tooth.

Here's a larger Otodus with a root more like "A" and "C".

Under magnification, I detect a single, tiny nutrient pore in the "B" and in the "C" teeth. I can find no nutrient pores on "A" tooth, though such a tiny pore could be obscured in the roughened root surface.

I seem to recall someone arguing in another thread months ago that there were NO small Otodus teeth from the Khouribga phosphate, ascribing that peculiarity to the habitat of that embayment. Instead, it may be that the small Otodus teeth are not reliably (or easily, at least) distinguished from the adult Cretalamna teeth. So, any apparent dearth of small Otodus teeth simply may be an artifact of our difficulty in distinguishing between the two (as implied in Kent's observation).

Just when I thought I had a handle on these Eocene teeth!!!

[Northern Sharks]

I'd love to say there's an easy tell that you all are missing, but I'm in the same boat as everyone else.

[hybodus]

Well, here's what I know, Jim. All three of these teeth were in one box in my drawer labelled "Cretalamna appendiculata." In selecting a few to photograph, I noticed the different root shape of "B" . . . with lines more "boxy" than flowing.

The root shape of "A" and "C" most resemble one-another; but, I have large teeth in my drawer labelled "Otodus obliquus" which are not unlike the boxy-rooted "B" tooth.

Here's a larger Otodus with a root more like "A" and "C".

Under magnification, I detect a single, tiny nutrient pore in the "B" and in the "C" teeth. I can find no nutrient pores on "A" tooth, though such a tiny pore could be obscured in the roughened root surface.

I seem to recall someone arguing in another thread months ago that there were NO small Otodus teeth from the Khouribga phosphate, ascribing that peculiarity to the habitat of that embayment. It may be that the small Otodus teeth are not reliably (or easily, at least) distinguished from the adult Cretalamna teeth. So, any apparent dearth of small Otodus teeth simply may be an artifact of our difficulty in distinguishing between the two (as implied in Kent's observation).

Just when I thought I had a handle on these Eocene teeth!!!

Well said Harry - the Cretalamna/Otodus id's are so tough in Paleogene teeth... I agree in that I use the "boxy" root as a general characteristic, especially so in lateral teeth, but the line seems to be even more blurry with anterior teeth... and in all of my references, the nutrient pore count varies widely between the two genera...

[Harry Pristis]

I'd love to say there's an easy tell that you all are missing, but I'm in the same boat as everyone else.

Darn! I was hoping you had an answer for us, NS. That leaves it up to PaleoRon.

PaleoRon Posted Yesterday, 07:13 PM

I would say Otodus. The Cretolamna I have found along the Potomac are pretty distinctive and very few of them have been even close in appearence to the Otodus I found in the same locations.

Do you have images of Potomac teeth that illustrate the differences? How about it, Ron -- can you sort this out for us?

[tracer]

i have a question related to this. to me, the binomial system attempts to parse what at times can't be. everyone seems to speak of how hard it is at times to identify shark teeth, as if the problem is with the teeth, rather than the classification construct. is there a point at which on this kind of thing you decide that the boundary between species (as defined by humans) is too indistinct and teeth which show characteristics within a certain range should be considered unclassifiable "transition" teeth? or maybe, like spacetime, there needs to be a dimension or two added to physical characteristics to further differentiate specimens.

(i'm a little "out there" this evening)

[jbstedman]

i have a question related to this. to me, the binomial system attempts to parse what at times can't be. everyone seems to speak of how hard it is at times to identify shark teeth, as if the problem is with the teeth, rather than the classification construct. is there a point at which on this kind of thing you decide that the boundary between species (as defined by humans) is too indistinct and teeth which show characteristics within a certain range should be considered unclassifiable "transition" teeth? or maybe, like spacetime, there needs to be a dimension or two added to physical characteristics to further differentiate specimens.

(i'm a little "out there" this evening)

No, you're not out there. I agree with the point you're making. Still, it's frustrating when that "transition bucket" gets so full.

And in this instance I'm unsure at a higher level (the genus) than usual.

[tracer]

we humans seem very unhappy with "fuzziness" in our worldviews, but i think we sometimes obfuscate through attempting to force clarity. i personally prefer to have many fuzzy perceptions than to have my own sharp drawings of what i couldn't clearly see. but i do get tired of trying to understand certain things and give up occasionally, at least temporarily.

[hybodus]

Tracer - not as out there as you think... and I agree! So, as you well know, the fossil record as far as extinct sharks goes is pretty poor - LOTS of teeth, and some occasional skeletal remains - and luckily, a very occassional articulated skeleton or so... but nothing that can be compared to the fossil skeletal record of extinct animals with bones.

So ok... it sucks to have cartilage - and some isolated shark teeth can be pretty diagnostic if you are able to reference one of those few articulated specimens, or a fair fossilized portion of jaw with teeth, or even an associated tooth set - but not a whole lot of them exist.

Below is an example of Hybodus basanus - a skull, with preserved teeth - I can certainly understand the Hybodont naming due to many Hybodont remains with well defined characteristics that match this skull and teeth - I have several of these, and I can pretty much get down to species level for a bunch of Hybodont sharks, but for the vast majority of them, the ID is based on a reference to a fossil horizon that someone smarter than I found some teeth and gave them a name - the number of genera and species is pretty mind boggling in the shark fossil record. I think we have more dang extinct sharks than any other type of organism... seems pretty funny to me...

Extinct fossil sharks do seem to be the poster child for what the _)(*(^^%^! And MANY genera have been named solely on the basis of isolated teeth, fin spines or dermal denticles. Some of them are very funny. I personally like the Listracanthus and Petrodus dermal denticle issue: ok, so we have these fossils which are restricted to the Paleozoic, and found in many places, often associated with shark remains, but a fossil shark has never been found with deffinitive Listracanthus or Petrodus like denticles - so how in the world can we give a name to something that we say is a shark when we have no idea? Zangerl (1981) dedicates a good amount of discussion to the topic and contends that based on known remains, Petrodus was likely a large animal covered only with petrodi, and possibly come from Carcharopis, a Paleozoic shark with teeth similar to Edestus. He further elaborates that Listracanthus is likely a shark with a dermal skeleton consisting of large numbers of both listracanthi and petrodi.... ok....so I do not get it.... Listracanthus and Petrodus dermal denticles below:

Wow - quite a ramble for me - the short of it is we have a few associated tooth sets for both Otodus and Cretalamna, and very little skeletal material - And again, folks seem to be able to create great taxonomic designations based on tooth design alone - not everyone buys into the Cretalamna - Otodus lineage, but hey, they are cool teeth!

[hybodus]

Sorry about the post folks - working late on a project for work and way too much caffeine in my system right now

[Auspex]

Among the fossil elasmobranches, a lot of form taxons based on teeth have been erected. Not much else one can do when associated remains are so rare, and comparison to modern teeth will only get you so far.

[jbstedman]

I find it very hard to throw in the towel. Our drive to categorize is innate and it is frustrating not to be able to do so. And there is my certainty that the experienced amateurs and the professionals know much more than than I do about this. So, when I don't see the distinctions that they apparently do, I assume I'm the one not seeing something. (That is, until a new paper emerges in the literature that reworks the categorization construct and groups certain teeth very differently in an effort to make more sense.)

Interestingly, Jim Bourdon (elasmo.com) looked to others to distinguish the specific genera we've been dealing with here:

"In the Paleogene, very similar tooth-designs are ascribed to both Otodus and Cretalamna based largely on differences of root shape. The below specimens have been ascribed to Cretalamana by those more experienced than myself."

Finally, Hybodus writes: " I think we have more dang extinct sharks than any other type of organism... seems pretty funny to me..."

That's a fascinating observation and makes sense given what is typically used to classify fossil sharks. Have others made the same observation?

[hybodus]

For fossil sharks, the further back in time you go the more obvious it becomes. I love looking at the taxonomic history of the Paleozoic sharks.

Within the order Cladoselachida, more than seventy nominal species have been assigned to Cladodus since the erecting of Cladodus mirabilis AGASSIZ 1843. Some of this has been somewhat sorted out, but the reality is that the vast majority of remains currently attributed to the Cladoselachida are based on isolated teeth (there are several described neurocrania from The Devonian of Germany, as well as well preserved body fossils from the Devonian Cleveland Shale of Ohio).

Due to lack of skeletal material, many early shark workers (and many today still do it) erect new genera based on teeth. Sticking to the Cladodus example(Eastman, 1907) in Devonic Fishes of the New York Formations, provides a tooth description from Smith Woodward; Every tooth has a principal cusp with variable smaller lateral cusps, and the broad base of each is overlapped by its successor behind. Zangrel (1981) defines cladodont teeth as possessing an elongated crown and small base in simplest form. Sounds like a description that fits quite a few sharks, so it’s no surprise that so many assignments have been made to this order over the past 160 years.

[tracer]

"Our drive to categorize is innate and it is frustrating not to be able to do so."

very, very true. but unfortunately that drive frequently leads to artificial knowledge created by stretching to cover gaps, or shoe-horning complexities into generalities. i'd bet there wouldn't be nearly the number of species of critters currently recognized if for the past 100 years there had been any meaningful sanction or penalty associated with erroneously creating a species name.

when you're a layperson such as myself and examining the "big picture" macro concepts, you look at things like the definition of a species and see that it means the critters could get together and enjoy the huge benefit of having children, and their children could do the same. ("children" is a generic term that i just defined. i'm learning that i can do that.)

so anyway, then there's all these fossil species that nobody ever saw do the whoop whoop. (anson, can i say that?). then somebody finds a denticle and it's off to the races.

i don't know. the other day i was looking online at stuff about horse evolution, and i found this little chart showing the top squiggles on teeth (sorry for the technical language) and saying that if the squiggles vary by these little amounts, you can tell that it's from a zebra, or a horse, or an ash (-h+s). so i'm looking at this, and noting the relatively slight variations and thinking about all the variations that could fall in between. and i just keep asking myself, self - this is like reading tea leaves. where do i find in these squiggles whether these beasties could get together and fruitfully do the whoop whoop?

it's just all falling apart for me, conceptually. i mean, i've also see those scary embryo pictures where all the different critters look the same. what if we all ought to have multiple classifications at various stages of our development, based primarily on our temperaments? nah, that wouldn't work, because then i'd probably be a different species every day...

[Fat Boy]

I think that I remember reading somewhere that Otodus teeth, especially the larger ones and the anterior ones, have a bourlette and C. appendiculata doesn't. Also, the cusplets on the anterior teeth of C. appendiculata are much larger in proportion to the main cusp. However, I also remember reading that in the smaller posterior Otodus teeth, the bourlette is either very small or absent. In addition to possible identifying characteristics mentioned above, these might also help in the distinction. I'll try to find where I read that and see if it's reliable. Off the top of my head I can't remember. That said, it's quite possible that the source was incorrect as well, so please take this with a grain of salt!

These same types of identification issues also plague me when trying to identify sand tiger like teeth.

[PaleoRon]

I finally found my Paleocene teeth and I put some of them together for comparison. Some teeth have characteristics of both species but they are in the minority. The four in the upper left could go either way, the first two are a bit large for Cretolamna, but as you can see most of the others are VERY distinctive. There is a lot of variability in the small Otodus teeth at this site. Many of the small Otodus don't look much like larger adult teeth (which are exceptionally rare at the site) but after looking at hundreds of teeth you start to see that there is a pattern of gradation. There are a few species of extant sharks that have dentitions that also differ markedly from juvenile specimens to adults. Many of the juvenile great white jaws I have seen are full of narrow teeth with small side cusps suited for feeding on fish, while the adult teeth are robust triangular shearing teeth without cusps. If you only had small juvenile teeth and large adult teeth it would appear that you had two different species instead of one that goes through a distinct change in tooth morphology. The Cretolamna teeth are rare compared to the Otodus along the Potomac and there doesn't seem to be a lot of variation in the specimens that I have seen. Most of the teeth have a squarish root with cusps that look oversized but there are some with cusps more in proportion to the size of the tooth. There doesn't seen to be as much difference in the posterior teeth as you see in Otodus and the most curved posterior Cretolamna tooth I have seen so far had a blade that was only slightly inclined. I have probably seen less than two hundred of these teeth, compared with a couple thousand Otodus from the Potomac, so I may not be getting the full picture but these are my observations.

[PaleoRon]

Here's a pic of the Cretolamna "sitting up".

[Bill]

What sets the Cretalamna apart?

The pictures on elasmo.com suggest some basic similarity when you look at lateral and posterior teeth.

Edit: Sorry, I didn't realize that the second picture (below) was posted. I thought I had deleted it. Anyway, I believe the one below is a Cretalamna appendiculata. It's from a Cretaceous site in Maryland. (Excuse the number in the picture -- it's for my database.) It does look something like the first picture I posted.

Hi JB,

I don't know where the above (your second pic') was collected, is Maryland on the Western Atlantic or Gulf Coast to Texas? and it has double cusplets. Jim Bourdon at Elasmo states-

"Less common than C. appendiculata, C. maroccana are knopwn from Late Cretaceous sediments of the Western Atlantic and Gulf Coast to Texas. They are identifiable by their dual lateral cusplets and weakly concave basal root margin.

[mommabetts]

Hi JB,

I don't know where the above (your second pic') was collected, is Maryland on the Western Atlantic or Gulf Coast to Texas? and it has double cusplets. Jim Bourdon at Elasmo states-

"Less common than C. appendiculata, C. maroccana are knopwn from Late Cretaceous sediments of the Western Atlantic and Gulf Coast to Texas. They are identifiable by their dual lateral cusplets and weakly concave basal root margin.

Maryland is on the North east coast.