June 26, 2019 at 11:47 pm #56272
I’m new member thanks to awesome ambassador @vperez, who I met last week at Sharktooth Hill. After returning, I’ve been working my way through the teeth we collected, trying to ID them, but I’m very much a noob at this. If anyone could offer any tips for how to go about IDing these teeth, that would be awesome (ex. Carcharhinus spp. Vs Negaprion? Or Isurus/Carcharodon planus Vs hastalis?) I also suspect I have some Isurus oxyrinchus/desori but not sure how to distinguish them from the rest. So, please feel free to point out what you think any of the pictured teeth are, and/or what features I should look for to get better at this. Thanks in advance!
Attachments:You must be logged in to view attached files.July 1, 2019 at 10:10 am #56325
This site may offer some additional help https://www.fossilguy.com/sites/sharktooth-hill/index.htm
The site operator, Jayson, was one of the guys out at the quarry with me when we met. I think he plans on updating this page with some of his new finds from this past trip as well. @jayson-kowinskyJuly 2, 2019 at 3:31 pm #56358
Note: Cosmopolitodus is now Carcharodon. The images are clickable which brings up a page on the genus (including ones not found in STH). I don’t believe there are any Negaprion found in STH.
As for your image: A5 is Isurus oxyrinchus, the remainder of the A row I would have to examine in person; B3, B4, B5 are Carcharhinus; C row is Carcharodon hastalis; D2, D3 are lower C. hastalis; D4 is lower C. planus; E4, E5 are C. hastalis, the remainder I would have to see; F1, F3, F4, F5 are C. hastalis, F2 is lower C. planus.
I recommend looking at the extant (modern) dentitions as a guide to separating genera: http://www.elasmo.com/frameMe.html?file=paleo/sth/shrkhill_new.html&menu=bin/menu_fauna-alt.html
Bill H.July 2, 2019 at 5:57 pm #56359August 27, 2019 at 11:08 pm #59512
I have been very interested in the teeth at Bakersfield (STH) for the past three years and have come to several conclusions about the identification process of planus and hastalis. (For what it’s worth)
- Planus uppers and hastalis uppers are pretty distinguishable, but even that can be a little confusing when some of the laterals are taken individually.
- When it comes to lowers, then the difficulty becomes tenfold. I have read accounts from museum literature to guides to STH identification stating that there is no difference when it comes to lowers, and that they are the same in both species.
Now, I’m going to stop right here for a moment and say that Bill Heim, who is a good and extremely respected friend of mine, and has already commented before me, is as brilliant as anyone in observing the smallest details in distinguishing shark teeth. I would hang my hat on what he says, but to most mortals some of the ID process is a very difficult and uncertain task.
What makes it even more confusing is that, to my knowledge, no associated dentition of C. planus exists or has ever been discovered. There are composite dentitions but without at least one associated C. planus to compare, then one is simply relying on the preparers imagination of what it might be. From a scientific standpoint I find that to be a real problem. If one takes a large random collection of mixed hastalis and planus uppers and lowers, it seems to me that that it would be very difficult to decide what differences constitute differences between species and what is genetic diversity within the same specie. Then ask yourself what are tooth location differences in the mouth within the same individual. Then ask the same question between different individuals within the same specie, or ask again between species and you load up your problems to even greater uncertainty. The more I look at the two species, the more difficult I find that it is to be sure of what exactly you are identifying in many cases, especially within the lowers. Like I stated earlier, upper anteriors and most mesial position laterals are pretty clear between the species. To compound the hastalis problem, throw in a transitional tooth from I. oxyrhinchus, and you can add another wrinkle to the lateral hastalis problem.
For sure this topic makes for an excellent conversation, and reminds us why more research and future discovery is always important in every field of science.August 28, 2019 at 12:59 am #59513
hastalis lower teeth have more angular roots than planus lower teeth which are more rounded. I will get some scans when I get a chance. As far as hastalis goes, the teeth, particularly the roots are very comparable to Carcharodon carcharias. So you can place them in jaw position by matching them up with a GW jaw. Separating lateral and posterior teeth from I. oxyrinchus can be problematic, but in the end, how much does it matter. As far as STH goes, almost all the oxyrinchus I have seen from there have been pretty small, so I would grade them by size.August 29, 2019 at 1:59 pm #59579
Thank you very much, @lcone and @bill-heim, for the thoughtful responses. They make a lot of sense and frankly it feels good to know that I’m not completely clueless and even pros like you find ambiguity in these teeth. I’m interested in the root differences and will explore that a little more. If you could point me to some scans when you get the chance that would be super. Incidentally, I’ll be heading back to STH in Sept. While I’m there I’ll try to find a completely associated set of teeth from C. planus and another from C. hastilis just to put this matter to rest once and for all. 😉 Thanks again!August 29, 2019 at 3:45 pm #59580
An associated set is where a shark died and dropped all its teeth. It is usually a once in a lifetime find, so I wouldn’t count on finding one.August 29, 2019 at 4:34 pm #59581
Yes – once in a lifetime perhaps, but two of us are going to STH, so I see no problem at all with us finding two fully-associated sets.
…and with that I will cease and desist from attempting any more jokes.
My gratitude was not in jest, though. Thanks again!August 29, 2019 at 6:18 pm #59585
Just to throw it out there, I use a book called Fossil Shark Teeth of the World by Joe Cocke. It’s a pretty good guide with some easy to understand explanations of the tooth anatomy and relatively good (if black and white) pictures. Great collection, by the way!
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