A question about Cosmopolitodus (Isurus) planus

[ynot]

Hey Hi Everybody,

I was just wondering how large the teeth of Cosmopolitodus (Isurus) planus get?

If You have one that You think is in the top end size of these teeth, please post pictures here.

Thanks,

Tony

[Northern Sharks]

I can't say an exact measurement, but 2" is the magic number. The further you go over that, the rarer the teeth.

[ynot]

I can't say an exact measurement, but 2" is the magic number. The further you go over that, the rarer the teeth.

Thanks-- do You have any pictures of 2 inch plus teeth?

[Northern Sharks]

This is my largest

[ynot]

This is my largest

Nice-- thanks for posting it here!

Tony

[siteseer]

Tony,

Northern answered it. I have two teeth at 2 inches but once saw one that was at least 2 3/8." It was one of those deeply hooked teeth too.

If you haven't checked out Northern's shark tooth gallery, you should because it's a great show.

Jess

Nice-- thanks for posting it here!

Tony

[ArrowHead]

Hi - I have collected hundreds of planus from Sharktooth Hill and my largest personal find to date is 2.1" I did recently acquire a planus from an old collection that measures a hair over 2.5". This is the largest to date that I have seen in any collection. Photo attached.

[ynot]

5 minutes ago, ArrowHead said:

Hi - I have collected hundreds of planus from Sharktooth Hill and my largest personal find to date is 2.1" I did recently acquire a planus from an old collection that measures a hair over 2.5". This is the largest to date that I have seen in any collection. Photo attached.

WOW!!!

That is a monster!

 

Thanks for sharing it!

[Darktooth]

That's a beauty!

[siteseer]

On 3/20/2017 at 5:37 PM, ArrowHead said:

Hi - I have collected hundreds of planus from Sharktooth Hill and my largest personal find to date is 2.1" I did recently acquire a planus from an old collection that measures a hair over 2.5". This is the largest to date that I have seen in any collection. Photo attached.

 

 

That's a Carcharodon hastalis.  Carcharodon planus has more rounded root lobes than that.  A side view of that tooth would likely show a greater labiolingual thickness than you would see in planis.

 

I think planus is related to Carcharodon hastalis to the point that it descended from it directly sometime in the Early to Early-Middle Miocene.  There are intriguing isolated teeth that indicate this but I can't say I have definitive evidence.

 

 

 

 

 

 

 

 

 

[ArrowHead]

This particular tooth is middle Miocene so should be later than any hastalis/planus divergence.  The root does have some characteristics of C. hastalis, however having collected many hundreds of Sharktooth Hill hastalis, up to 3", I have never seen a hastalis crown deeply "hooked" like this. The crown on this tooth is also more compressed, while hastalis in this size range typically are very thick in cross section. An argument could be made that this is a pathological variant of C. hastalis, rather than C. planus.  With a sample size of one however it is hard to confirm whether the root of this "planus" is abnormal or the crown of this "hastalis" is abnormal. Either truth seems to point to a pretty unique tooth. It would be helpful to know if there are any other examples of large "hooked" hastalis from the fossil record, particularly from the Round Mountain formation.

[ynot]

2 hours ago, ArrowHead said:

This particular tooth is middle Miocene so should be later than any hastalis/planus divergence.  The root does have some characteristics of C. hastalis, however having collected many hundreds of Sharktooth Hill hastalis, up to 3", I have never seen a hastalis crown deeply "hooked" like this. The crown on this tooth is also more compressed, while hastalis in this size range typically are very thick in cross section. An argument could be made that this is a pathological variant of C. hastalis, rather than C. planus.  With a sample size of one however it is hard to confirm whether the root of this "planus" is abnormal or the crown of this "hastalis" is abnormal. Either truth seems to point to a pretty unique tooth. It would be helpful to know if there are any other examples of large "hooked" hastalis from the fossil record, particularly from the Round Mountain formation.

Can You post pictures of this tooth from the labial and side views?

Thanks,

Tony

[ArrowHead]

Hey Tony - I took the attached photos last night to add to the thread showing the lingual and labial views. I included several planus in the 2" range and several hastalis in the 2 1/2" range, all from Sharktooth Hill, for additional comparison. I didn't think to take side views but can do that as well.

 

Rusty

[ynot]

I would like to say "Thank You all" for responding to this thread!!!

 

 

Here are the 2 largest that I have...

[siteseer]

On 3/22/2017 at 0:35 PM, ArrowHead said:

This particular tooth is middle Miocene so should be later than any hastalis/planus divergence.  The root does have some characteristics of C. hastalis, however having collected many hundreds of Sharktooth Hill hastalis, up to 3", I have never seen a hastalis crown deeply "hooked" like this. The crown on this tooth is also more compressed, while hastalis in this size range typically are very thick in cross section. An argument could be made that this is a pathological variant of C. hastalis, rather than C. planus.  With a sample size of one however it is hard to confirm whether the root of this "planus" is abnormal or the crown of this "hastalis" is abnormal. Either truth seems to point to a pretty unique tooth. It would be helpful to know if there are any other examples of large "hooked" hastalis from the fossil record, particularly from the Round Mountain formation.

 

 

Hi Arrowhead,

 

It sounds like you know your stuff.  I'm away on business but will be home this week and will have to look at some of my teeth and get back to you.  Your photo with the tooth and the same-size hastalis and large planus is good evidence indicating that your tooth is a planus.  It isn't as broad as hastalis tends to be.  However, the root still looks more hastalis and what I've learned over the years is that root characters are at least as important as crown characters in identifying teeth though perhaps more with respect to jaw position.

 

It sounds like you have done more collecting than me too.  I know how hard that work often is.  Digging in July is brutal by about 1130 and it's cold in December.

 

Anyway, the only other thing to consider is that your tooth could be from a very old hastalis individual the teeth of which did not reach a size to match the age of the animal.  Though, I have to admit, even in that case, only in planus do you see the clearly-hooked teeth.  I have a tooth which a jeweler was going to make a necklace out of but I recognized it as oddball because it was a lateral and deeply-hooked.  It has a hole drilled in it but I bought it.  As I recall, that tooth has an irregular root (no rounded lobes) but I'll have to check when I get home.

 

It's an interesting tooth in any case.  It would be easily the largest planus I've ever seen or heard of.

 

Jess

[sagacious]

The 2.5"+ tooth looks very much like C hastalis to me.  The root looks like that of a first upper anterior hastalis.  I have a few C hubbelli teeth that have a similar hooked shape, so it's possible for hastalis/hubbelli teeth to be hooked in rare instances.

 

Seemingly, the options are that either it's a C hastalis tooth with an unusually hooked crown, or it's a C planus tooth with both an exceptionally large crown and an unusually hastalis-like root, which seems somewhat less likely.

 

Certainly it's an amazing tooth, as are the beautiful C planus teeth posted by ynot.

 

[doushantuo]

isu

 

"Remarks: The systematics of makos (genus Isurus) was formerly chaotic, with a few regional species recognized on growth changes within a single species, Isurus oxyrinchus (Garman, 1913; Fowler, 1941; Bigelow and Schroeder, 1948; Smith, 1957)."

warning:contains line drawings of dentitions 

[doushantuo]

hook,nolineorsinker

[ArrowHead]

Sorry for the delay on getting the side views posted.  I got distracted by a big C. hastalis lower I found this past weekend, but I did get that one posted to the general discussion this afternoon. I'll get back on a good comparison photo giving side views tomorrow. 

[ArrowHead]

I had this great idea that I would take a side view photo of the big hooked "planus/hastalis" sandwiched between a similar sized hastalis and a large planus. The thought was we could get some clues by comparing the labial/lingual thickness of the three.  All went well until I tried to pick a typical planus to include in the photo. Working from about a dozen planus in the 1.5" - 1.75" range I was currently cleaning up from this past weekend's dig, I found that there are two pretty distinct root forms in this small group of planus teeth 1) the classic deeply "U"d Mickey Mouse rounded lobes and 2) a shallow "U" with more squared lobes typically associated with hastalis and the square lobed roots are significantly lab/ling thicker. I think I've confused things even more - either the hooked "planus" tooth has two root forms that would most likely be determined by tooth position  OR "hastalis" has a much higher frequency of deeply curved teeth than previously thought (in this case about a third of the teeth out of the dozen). Agassiz has some explaining to do here....

 

Top row - side views

Middle Row - square lobes

Bottom Row - rounded lobes

 

Maybe look at your collections and see if there are similar differences in your "planus" teeth.

 

[Troodon]

I think the difference in root shape is where he tooth is located in the jaw.  Those box shaped ones are lateral while the others are anterior teeth.

[ArrowHead]

That seems reasonable and would argue that the large 2.5" hooked tooth I showed earlier in the post is a large lateral C. planus. Others have argued however that those squared off roots indicate that tooth is an abnormal C. hastalis.  It may seem like splitting hairs, but Tony's original question in the post was "how large do planus get". 2.5" would likely place this tooth in question at the planus upper boundary so it would be rewarding to help define that boundary. Probably no way to really settle the issue though - fossil taxonomy is never simple. 

[ynot]

On 3/20/2017 at 2:37 PM, ArrowHead said:

Hi - I have collected hundreds of planus from Sharktooth Hill and my largest personal find to date is 2.1" I did recently acquire a planus from an old collection that measures a hair over 2.5". This is the largest to date that I have seen in any collection. Photo attached.

I think this is a C. planus.

I see the curve as a continual bend, whereas the bent C. hastalis teeth, that I have seen ided here on TFF, have a straighter edge that has a bend in it.

 

[sagacious]

On ‎3‎/‎30‎/‎2017 at 6:01 PM, ArrowHead said:

That seems reasonable and would argue that the large 2.5" hooked tooth I showed earlier in the post is a large lateral C. planus. Others have argued however that those squared off roots indicate that tooth is an abnormal C. hastalis.  It may seem like splitting hairs, but Tony's original question in the post was "how large do planus get". 2.5" would likely place this tooth in question at the planus upper boundary so it would be rewarding to help define that boundary. Probably no way to really settle the issue though - fossil taxonomy is never simple. 

 

If this is indeed a C planus tooth, then based on the root lobes, it's almost certainly a first upper anterior, and not a lateral tooth.  Were it actually a 2.5" lateral tooth -- lateral Carcharodon/Cosmopolitodus/Isurus teeth generally being smaller in crown height than anterior teeth -- then one would have to explain the absence of 3"+ anterior planus teeth.  Also, this tooth doesn't show the degree of distal directedness of a typical C planus lateral tooth, with upper laterals generally being more deeply 'hooked' than upper anterior teeth.  I could accept this tooth as either a C hastalis or planus first upper anterior, but not a lateral from either.  That part at least, seems uncontroversial.

 

Regarding the root lobes: The mesial root lobe on the 2.5" tooth is visibly much smaller than the distal lobe. This argues persuasively that it's a first upper anterior tooth, and not a lateral tooth.  The mesial lobe, being somewhat crowded up next to the symphysis, is often reduced in size as compared to the distal lobe on that tooth.  Lateral teeth generally have root lobes much more symmetrical in size.

 

While I have C hastalis teeth with curved crowns, and a quick double-check on Elasmo "... does note that distally curved xiphodon [hastalis] teeth are relatively common", the above 2.5" tooth does look very much like the first upper anterior tooth in the Cosmopolitodus planus dentition on that website.

 

I think it's easy to get distracted by the round or square root lobe paradigms. As noted above, even a small selection of C planus teeth will show both shapes for the same tooth positions.  One can see the same in, probably, any decent selection of Carcharodon sp teeth.  That's the 'noise' that makes tooth position assignment sometimes very difficult, and it's the reason one often hears the advice that the more teeth one can see and handle, the better.

[siteseer]

5 hours ago, sagacious said:

 

If this is indeed a C planus tooth, then based on the root lobes, it's almost certainly a first upper anterior, and not a lateral tooth.  Were it actually a 2.5" lateral tooth -- lateral Carcharodon/Cosmopolitodus/Isurus teeth generally being smaller in crown height than anterior teeth -- then one would have to explain the absence of 3"+ anterior planus teeth.  Also, this tooth doesn't show the degree of distal directedness of a typical C planus lateral tooth, with upper laterals generally being more deeply 'hooked' than upper anterior teeth.  I could accept this tooth as either a C hastalis or planus first upper anterior, but not a lateral from either.  That part at least, seems uncontroversial.

 

Regarding the root lobes: The mesial root lobe on the 2.5" tooth is visibly much smaller than the distal lobe. This argues persuasively that it's a first upper anterior tooth, and not a lateral tooth.  The mesial lobe, being somewhat crowded up next to the symphysis, is often reduced in size as compared to the distal lobe on that tooth.  Lateral teeth generally have root lobes much more symmetrical in size.

 

While I have C hastalis teeth with curved crowns, and a quick double-check on Elasmo "... does note that distally curved xiphodon [hastalis] teeth are relatively common", the above 2.5" tooth does look very much like the first upper anterior tooth in the Cosmopolitodus planus dentition on that website.

 

I think it's easy to get distracted by the round or square root lobe paradigms. As noted above, even a small selection of C planus teeth will show both shapes for the same tooth positions.  One can see the same in, probably, any decent selection of Carcharodon sp teeth.  That's the 'noise' that makes tooth position assignment sometimes very difficult, and it's the reason one often hears the advice that the more teeth one can see and handle, the better.

 

Hi Sagacious,

 

I came to the same conclusion although I don't have any hastalis teeth that are curved like Arrowhead's.  My angle is also that the tooth in question is far enough beyond the realistic size range for the species based on all the teeth I've seen (my collection, friends' collections including Bob Ernst), that I considered it highly unlikely to belong to that species.  Two inch teeth are rare enough.  I have seen one teeth pushing 2 1/4 inches but 2 1/2 inches would be that extra level of magnitude of rarity like a 7 1/2-inch megalodon in my opinion.  We still can't say it's impossible to find one but I don't see that tooth as a candidate.

 

Right, it can't be a lateral because it's too big.  It begs for anterior teeth over three inches.  We could say, "Well, then it's an anterior."  The first anterior of planus does seem to be the largest tooth in the jaw so a 2 1/2" second anterior indicates an even larger giant specimen in the same individual.  The few 2-inch planus teeth I have appear to be first upper anteriors.  They are tall teeth relative to their width with the shallowest curve to them relative to other teeth in any proposed dentition I've seen to the point that the tip does not extend beyond the maximum width of the root.  Even if we want to push for it being a gigantic lateral, it's not hooked enough for that either because laterals become increasingly hooked as a planus adult reaches old age in my opinion.  I would have to consider that some deeply-hooked laterals may be pathologic, but if they don't show any irregularity beyond that (ie. no ripples nor unusual labio/lingual bending nor an uncharacteristically-increased root thickness), I would have to conclude that the deep curvature is a sign of old age. 

 

We could still claim that the tooth is atypical for planus crown morphology but still belongs to that species because it became relatively misshapen as a result of its extreme size but we run back into the problem of the root being the wrong shape for planus but the right shape for hastalis.  Shark teeth change slowly in a lineage with the root being even more conservative in terms of variation than the crown whether within a genus, a species, or the individual.  The crown also takes up more space than the crown, so the larger the crown, the more opportunity for variation to be expressed.  In other words in the absence of injury, we would expect more weirdness in the crown than the root so we would assume the root would carry at least as much if not more weight in the identification if the crown shows characters atypical for the taxon.

 

I'll try to get Isurus90064 to comment because he has seen a ton of planus and hastalis from the STH Bonebed and elsewhere as well.  I have another friend who was digging "the hill" before I was born so it will be interesting to get his opinion as well.

 

Jess