Palaeorhincodon?

[John Hamilton]

I was getting familiar with my new microscope and decided to look at some of my whaleshark teeth from Lee Creek matrix and I noticed one of them had cusp. I was wondering if it could be a Palaeorhincodon tooth?

[sixgill pete]

John, that is a beautiful tooth. I see what could be called cusps on it, a first for me at least for a Whale Shark tooth from Lee Creek. Palaeorhincodon is known from the lower to middle Eocene, much earlier than the deposits at Lee Creek. I know they are found in the Nanejemoy formation of Virginia, but I have never heard of them in any of the Eocene deposits here in NC. I have one in my collection that came from Egem, Belgium.

With that said, I can see why you would wonder but I would say it is Rhincodon sp. Maybe someone with a little more knowledge than me will be able to shed more light on it.

Don

[Al Dente]

The one thing this tooth has in common with Palaeorhincodon is the side cusps, other than that it looks very much like Rhincodon. Look up some images of Palaeorhincodon and one of its main features is the basal furrow on the root that expands labially. Rhincodon basal root furrow doesn't expand and neither does the one on your tooth from what I can see in the images. Your tooth is very interesting and the preservation is nice.

[MarcoSr]

John

Really nice tooth!!! I agree with Al Dente that other than the cusps the tooth looks very much like a Rhincodon. I have a large number of Palaeorhincodons from Morocco, Belgium and Virginia and definitely wouldn't call your tooth a Palaeorhincodon. I have seen multiple examples in genus which lost cusps through evolution yet I have found specimens with a single cusp or cusps when that species didn't have them anymore. I always took it to be that a recessive gene caused the abnormally versus the specimen being from a new species or from a holdout from a much older time period. Your tooth is definitely a conversation piece.

Marco Sr.

[siteseer]

John Hamilton,

I agree with Sixgill and Marco Sr. that it is a Rhincodon. Even Rhincodon teeth from the Late Oligocene Chander Bridge Formatiion lack cusplets (see Cicimurri and Knight, 2009). I also see it as an example of atavism - an rare expression of an ancient ancestor. Sometimes, I find a Carcharodon hastalis or planus with weak lateral cusplets.

Jess

Ciccimurri, D.J. 2009.

Late Oligocene sharks and rays from the Chandler Bridge Formation, Dorchester County, South Carolina, U.S.A. Acta Palaeontologica Polonica. 54(4): 627-647.

You should still be able to download it for free.

I was getting familiar with my new microscope and decided to look at some of my whaleshark teeth from Lee Creek matrix and I noticed one of them had cusp. I was wondering if it could be a Palaeorhincodon tooth?