Chandler Bridge "Micro" teeth ID

[Sonickmonx]

I have been working on sorting teeth I've collected from the Chandler Bridge Formation (Oligocene, ~28 MYA) from one site by species.  I've not put adequate time into learning how to differentiate the smaller teeth such as these, and am working on filling those gaps in my knowledge.  Here I have isolated 6 "distinct" types of teeth that I am attempting to put a name on. Apologies on the photo quality, I was in a bit of a rush, hopefully there is enough detail to understand the general characteristics I am attempting to distinguish between.

 

1. Wide root, flat and, typically, curved to one side.  Is serrated from where the enamel meets the root all the way down onto the blade.

 

2. Wide thin root, thin straight blade, serrations.

 

3. Almost identical in shape to number 2, except straight blade with no serrations.

 

4. Larger teeth in general compared to the others, curved and straight blade with nos errations, has enamel "wrinkles" similar to serrations near the root only.  

 

5. Very stubby root (horizontally compressed and somewhat more bulbous than the other teeth).  Long, straight blade with no serrations. 

 

6. Smaller in general than the other teeth.  Serrations along root, but not on the blade.  Blade is slightly curved.

 

 

These are my proposed identification of the teeth:

1. Reef/Requiem shark upper teeth of some kind

2. Unknown

3. Lemon shark lower lateral teeth

4. Lemon Shark upper teeth

5. Lemon shark lower central teeth

6. Requiem shark lower teeth

 

Edited March 24 by Sonickmonx

[Al Dente]

23 minutes ago, Sonickmonx said:

These are my proposed identification of the teeth:

1. Reef/Requiem shark upper teeth of some kind

2. Unknown

3. Lemon shark lower lateral teeth

4. Lemon Shark upper teeth

5. Lemon shark lower central teeth

6. Requiem shark lower teeth

I think you’ve done a good job of sorting. There are probably some lower Carcharhinus teeth mixed in with your lower Lemon shark teeth. I think your #6 are upper teeth, not lower. They might be C. gibbesi.

[Sonickmonx]

@Al Dente thanks for the input.  C. Gibbesi is the most likely candidate as that is a published taxon from this deposit.  I might be missing some publications but I've had a hard time finding a comprehensive published faunal list of the Chandler Bridge Formation... maybe that's a job for me to tackle someday since I have an absolute wealth of specimens from this particular site (Although I am certainly missing some of the smaller micros as not much screen washing has been done).  Might need to do that before the site is defunct.

[siteseer]

See Ciccimuri and Knight (2009) for something close to what you are looking for.  Also look for papers on Oligocene carcharhinids like Adnet et al., (2007). 

 

https://www.app.pan.pl/article/item/app20080077.html

 

https://www.sciencedirect.com/science/article/abs/pii/S1367912006002732