Unknown Oligocene Shark Tooth

[historianmichael]

A few weeks ago I completed a road trip from New Jersey to Texas for work and although Hurricane Ida sadly canceled nearly all of my plans, I was able to sneak in a couple quick fossil collecting stops. One such stop was at an outcrop of the Oligocene Vicksburg Group in Mississippi. I was primarily looking for echinoids- I sadly did not find any- but ended up finding this small shark tooth. I am by no means an expert on shark teeth and have tried in vain to research Oligocene sharks of Mississippi. Does anyone know what shark this tooth is from or of a good resource where I might be able to figure it out? It strikes me as similar to photos of Carcharhinus gibbesi from the Chandler Bridge Formation (see D in attached photo). Any help is greatly appreciated!

 

 

 

Source: Late Oligocene Sharks and Rays from the Chandler Bridge Formation, Dorchester County, South Carolina, USA

 

Edited September 7, 2021 by historianmichael

[Al Dente]

1 hour ago, historianmichael said:

It strikes me as similar to photos of Carcharhinus gibbesi from the Chandler Bridge Formation (see D in attached photo).

C. gibbesi and C. gilmorei are similar looking teeth that are lumped together by some authors. C. gilmorei don’t have the coarse serrations on the shoulders that C. gibbesi has. I think your tooth looks more like C. gilmorei. I can easily see both being different tooth positions of the same shark because they are usually found together.

[siteseer]

Yeah, that tooth follows a form you often find in the middle Eocene to late Oligocene - weakly-serrated heels, unserrated cusp.  I've seen a tooth like that from Harleyville, SC.  I never know what to call them so I just go with Carcharhinus sp.  It tough to say because you can find teeth with coarsely-serrated heels and finely-serrated cusps, much like Miocene-modern teeth even in the middle Eocene though that's a rarer form than unserrated heels/cusps (apparent upper teeth).  You can be tempted to group them into species based on levels of serratedness but the serration type is a variable within species especially those of Carcharhinus as we see today.

 

You can look for this paper that also discusses early Carcharhinus:

 

ADNET, S., P.O. ANTOINE, S.R.H.  BAQRI, J.Y. CROCHET, I.  MARIVAUX, J.L. WELCOMME, and G. MÉTAIS.  2007.
New tropical carcharhinids (Chondrichthyes, Carcharhiniformes) from the late Eocene-early Oligocene of Balochistan, Pakistan: Paleoenvironmental and paleogeographic implications.Journal of Asian Earth Sciences, 30: 303-323.