Help identifying some shark teeth from Shark Tooth Hill (STH) Bakersfield, CA

[digit]

A number of years back Tammy and I had a great day in the field digging for shark teeth at the Ernst Quarry in Bakersfield, CA. We were joined by longtime forum member Tony @ynot who drove down from northern CA to meet us. Those interested can read about that trip here:

 

http://www.thefossilforum.com/index.php?/topic/60863-shark-tooth-hill-ernst-quarry-hunt-on-2016-01-22/

 

A number of the nicer loose teeth were wire-wrapped into necklace pendants and given away as presents and a few teeth still in the sandy matrix were prepped out for display (some of which are presently on display in an exhibit at the FLMNH display museum). The bulk of the rest of the interesting teeth are being donated to the FLMNH collection as the museum's collection was a bit deficient in STH material (a few larger teeth donated over 50 years ago). As these are going into the museum's collection I want to have good IDs on the specimens. The hooked Cosmopolitodus (Isurus) planus teeth are reasonably distinctive and I think I have a handle on at least the obvious curved uppers. The rest of them I am not certain of the proper ID and I'm hoping for some help from folks who are very familiar with this locality.

 

I'm starting out with the larger white/mako teeth and then I'll be sorting through the smaller ones. If I have questionable teeth in some of the smaller ones I'll add additional photos. I've labeled all of the teeth with numbers and letters so that there will be no confusion in identifying which tooth we are discussing. Looking forward to getting these teeth sorted out and also learning a bit more about the shark fauna of a site that I've had the fun of collecting (if only once).

 

Cheers.

 

-Ken

 

All of the teeth in image 1 look to be the Hooked-tooth White/Mako (Cosmopolitodus planus) and seem to be all from the upper right quadrant of the jaw.

 

 

More help on these would be greatly appreciated:

 

 

 

 

 

 

 

 

Thanks for looking.

 

 

Cheers.

 

-Ken

 

[digit]

Anybody have any thoughts on these? @isurus90064 @ynot @siteseer @ClearLake

 

 

Cheers.

 

-Ken

[ynot]

1 and 2 look like C. planus uppers. 3b looks like a narrow tooth mako. 3a 3c and all the 4s 5a and 6b look like C. hastalis upper.

Not sure on 6a. Rest look like lowers (which I can't tell apart).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[digit]

10 minutes ago, ynot said:

1 and 2 look like C. planus uppers.

Thanks for the confirmation. I figured the curved ones had to be Cosmopolitodus planus given the shape. What is the distinguishing feature that separates uppers from lowers for this species?

 

14 minutes ago, ynot said:

3b looks like a narrow tooth mako.

That would be Cosmopolitodus/Isurus hastalis? I see there is some debate (there always is) on whether the broad form and narrow form represent variation within the single species hastalis or if the broad form should be considered as the species xiphodon. And then there is the question of the genus Isurus or Cosmopolitodus? There is a good summary from a few years back on the FLMNH website. Anybody know what the state of the art is on these matters?

 

https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/carcharodon-hastalis/

 

A second on-going debate is about whether or not the fossil teeth traditionally assigned to Carcharodon hastalis belong to one or two species (regardless of which genus is applied to the species). Retaining just a single species for these fossil teeth was favored by Cappetta (2006), and this interpretation is followed here. The recognition of two species was formally proposed by Purdey et al. (2001), and has been followed by some researchers, such as Aguilera and Rodrigues de Aguilera (2004), Marsili (2008), Whitenack and Gottfried (2010), and Cione et al. (2012). Under this hypothesis, even after accounting for differences in tooth width between upper and lower teeth, there is one species with relatively narrower teeth and another with relatively broader teeth. The former is more common in early to early late Miocene deposits and the latter in latest Miocene and Pliocene beds. According to Purdy et al. (2001), the narrower-toothed form retains the hastalis species name, and is thus the “true” Isurus hastalis or Cosmopolitodus hastalis, depending on one’s interpretation of lamnid evolution. The broader-tooth species was listed as Isurus xiphodon by Purdy et al. (2001) and as Carcharodon plicatilis by Cione et al. (2012), both species originally named by Agassiz in the mid-1800s.

 

33 minutes ago, ynot said:

3a 3c and all the 4s 5a and 6b look like C. hastalis upper.

That would be normal "broad" form of hastalis then.

 

34 minutes ago, ynot said:

Rest look like lowers (which I can't tell apart).

I assumed that the smaller teeth might start getting tricky to identify if the features that separate the taxa are not well developed on the smaller ones.

 

 

Thanks a bunch for some insight into these STH teeth.

 

 

Cheers.

 

-Ken

[ynot]

upper teeth are flat and broad where lowers are peg like.

[digit]

Gotcha. All in the crown and not in the shape of the root.

 

 

Cheers.

 

-Ken

[siteseer]

Ken,

 

I don't think you really need to identify the teeth.  Someone at or visiting the museum witll do that at some point.  You want to make sure you have good locality data on the labels.  It might be enough to say they are from the Round Mountain Silt, Sharktooth Hill Bonebed, Bakersfield, Kern County, CA but it might be better to add the particular quarry name which might already have a museum locality number.  The Florida Museum would check with the LA County Museum of Natural History for that.

 

In any case Cosmopolitodus is a junior synonym of Carcharodon so I would write Carcharodon for hastalis and planus teeth.

 

Jess

[digit]

I'm donating virtually all my STH material to the FLMNH since there is a great diversity of chondrichthyan material beyond the larger teeth (if you pick the micro-matrix). Presently the museum's collection from this locality consists of 15 specimens (mostly larger teeth attributed to Carcharodon hastalis. Many of the micro-chondrichthyan teeth from STH would be great comparative material for projects we are working on involving Florida micro-chondrichthyan teeth. As I've recently been doing a bunch of cataloging of specimens into the FLMNH collection, I've been working with those with deeper knowledge of shark/ray teeth to help me get the identifications as detailed as possible. Some specimens above may end up simply as "Carcharodon sp." till someone else may come along and refine the taxonomic identity but I certainly want to be as specific as I can. Other than for the most enigmatic of specimens I don't care for labels like "Euselachii".

 

The present STH material (15 specimens) from 50+ years ago are listed under the site "Sharktooth Hill (General)". This new material will have a new more precise site code but with much of the same geologic data.

 

• Site: Sharktooth Hill (General)
• Site Key: US079
• Continent/Ocean: North America
• Country: USA
• State: California
• County: Kern
• Period: Neogene
• Epoch: Miocene, Middle
• Land Mammal Age: Barstovian
• Faunal Zone: Ba1
• Basin/Fauna: Sharktooth Hill
• Formation: Round Mountain Silt

 

The FLMNH seems to be using Carcharodon over Cosmopolitodus and I'll continue with that if it appears to be the current state of the art in our understanding of this lineage of large sharks with big teeth.

 

The natural history museum in LA is a possibly useful pointer for experts in their local fossil fauna. Beyond a single page on Elasmo.com for the STH fauna I'm generally doing internet image searches and mostly ending up back here. Though it is a well known Lagerstätte and has been collected my many fossil enthusiasts, I have not (yet) turned up any good papers describing the chondrichthyan assemblage in the Round Mountain Silt. Without a good reference paper to base identifications on, the best I can do is to consult with knowledgeable folks who have a deeper knowledge of this locality.

 

 

Cheers.

 

-Ken