Globidens alabamaensis?

[Tripermiblast]

While collecting at a location in SE Virginia which produces a mixture of material from the Eocene Nanjemoy Formation and late Miocene/early Pliocene Yorktown Formation, I was shocked to find what I believe to be a cretaceous Globidens sp. anterior tooth fragment.  My only explanation for this would be that it must have been redeposited into the Eocene beds and finally exposed with rest of the material.  The texture is classic Globidens.  The only other species with a slightly similar texture found within these formations (though still markedly different), would be Squalodon sp., however if the tooth were more complete it would clearly prove to be hollow with a conical interior consistent with squamates like mosasaurs.  The fragment is approximately 7/8" x 1/2".  This is the first bit of possibly cretaceous material I have found from these exposures, so it would be quite interesting if the general consensus is a Globidens sp.  Your thoughts would be much appreciated!

Thanks,

Ash

Edited February 18, 2019 by Tripermiblast

[Tripermiblast]

Does this appear to be a Globidens species tooth fragment?  Any other ideas?  I would really like to hear what others think.

Thanks,

Ash

[FossilDAWG]

@MarcoSr has enormous experience with these formations, and he likely can offer an authoritative suggestion.  The fossil does not look very toothy to me but I don't have a lot of experience collecting those horizons.

 

Don

[MarcoSr]

13 hours ago, FossilDAWG said:

@MarcoSr has enormous experience with these formations, and he likely can offer an authoritative suggestion.  The fossil does not look very toothy to me but I don't have a lot of experience collecting those horizons.

 

Don

 

Not much locality information in the post.  SE Virginia is a huge area.  I don’t know if the specimen was found in float (along a river or stream) or in situ (in an actual formation).  The rivers in Virginia typically have exposed Cretaceous formations in the far west.  Rivers like the Potomac River have exposed marine Cretaceous.  As you head south, the rivers have exposed terrestrial Cretaceous in the far west not marine Cretaceous.  As you head downriver in Virginia the exposed formations get younger and younger.

 

I have found much earlier fossils far downriver in float on very rare occasions.  However a lot of the Virginia Rivers only have exposed Cretaceous terrestrial formations far upriver so you couldn’t find marine Cretaceous fossils that washed far downriver.  So if from southern Virginia, I don’t really see any way of finding a Cretaceous marine specimen that washed far downriver.

 

The other possibility is a reworked layer in the formations themselves where Cretaceous marine formations were reworked by later ocean transgressions.  I have studied the Nanjemoy Formation extensively in both MD and Virginia and have never seen any evidence of a Cretaceous reworked layer in it.  So to me it is extremely doubtful that the specimen came from a Cretaceous reworked layer in the Nanjemoy Formation.

 

So based upon the above, I don’t see any way the specimen is a Cretaceous Globidens tooth fragment unless it is a contaminant dropped by another collector.  If you look at one side of the specimen only, the most likely fossil possibilities include croc/alligator tooth or hollow Cetacean tooth like a sperm whale tooth.  However if you look at the other side, the texture isn’t right for a croc/alligator tooth.  Might be a Cetacean tooth fragment.  It is possible that the specimen is a very suggestive concretion.  However, it doesn’t look like a concretion.  It is really difficult to id a piece of something from pictures.  Take it to a museum and see what they say.

 

Marco Sr.

[Plax]

I wouldn't rule out a terrestrial animal tooth fragment. I don't know of any Eocene terrestrial mammal teeth being found in the nanjemoy but there's a lot I don't know. The ornamentation is unusual that's why I'm suggesting this is something we don't usually see in the area.

[Tripermiblast]

    Thank you for the replies.  This was found on a bank of the James River in Prince George County, which is private property, and rarely ever collected from.  For that reason I will rule out another collector dropping it on the beach.  The enamel's pattern of peculiar ridges and valleys seems nearly identical to Globidens, but comparatively very different from early cetaceans that had bumpy textured or striated teeth.  It is hard to tell from my photos, but this tooth is not bumpy.  There is a quarry maybe 4 miles away (Vulcan) in which a pocket of the Cretaceous Potomac Formation has produced insect and plant material.  The range of this formation and it's relationship to the Nanjemoy and Yorktown are unclear to me.

    And that is true, I haven't really considered a terrestrial species.  After 15 years of collecting from this location, I have yet to find any definitively terrestrial material, but that is a possibility.  Though when considering possible terrestrial species, I am even more at a loss.  I am not letting the affinity to Globidens blind me, but it is striking.

[MarcoSr]

14 hours ago, Tripermiblast said:

    There is a quarry maybe 4 miles away (Vulcan) in which a pocket of the Cretaceous Potomac Formation has produced insect and plant material.  The range of this formation and it's relationship to the Nanjemoy and Yorktown are unclear to me.

  

 

The Cretaceous Potomac Formation extends from New Jersey to southern Virginia.   The Traditional view of the Potomac Formation is that it was deposited in a fluvial environment.   Plant and insect fossils would definitely fit within this fluvial environment.  Out of the Potomac (three divisions of the Potomac are formally recognized: the Patuxent, Arundel, and Patapsco), the Arundel Clay is the only one that contains an appreciable vertebrate fossil record.  The Arundel Clay has produced dinosaur, mammal, reptile and fish vertebrate fossils.   If you want a good overview of the Arundel Clay environment check out the paper at the below link:

 

https://palaeo-electronica.org/content/pdfs/847.pdf

 

The paper’s conclusion : "Traditionally,  the  Arundel  has been  interpreted  as being  of  fluvial  origin,  deposited  in  a  freshwater  system  of  stranded  channels  or oxbows. Based on faunal composition, together with published geological and sedimentological  evidence,  we  propose  that  at  least  some  of  the  Arundel  facies  was deposited in close proximity to the Atlantic Ocean."

 

Whether you consider the environment as fluvial or near Atlantic Ocean brackish water swamp, you wouldn’t find Globidens in this environment. Take the specimen to a museum for a proper id.

Marco Sr.

[va paleo]

nice find for sure 

[siteseer]

I've been looking at this tooth today.  It certainly does have a texture more like Globidens than any crocodilian I'm familiar with.  I agree that it doesn't match up well to any of the "squalodont" whales of the Oligocene to Miocene but here are the possibilities laid out again, going with the assumption that it came from either the Nanjemoy (Early Eocene) or Yorktown (Early Pliocene):.

 

Globidens - It seems an unlikely find given the local geology unless we are saying that perhaps Globidens survived into the Early Eocene of Virginia.  There are no records of Paleocene finds anywhere.  It's a long time for such a large animal to go undetected in the fossil record (roughly ten million years) especially with the Late Cretaceous-Early Eocene phosphate deposits across North Africa and into the Middle East being well-studied over the past seventy years at least.

 

We must consider the possibility that the fragment is a contaminant dropped by a collector passing through even if that's unlikely given that the property isn't open to collecting.  People sneak in all kinds of places but it is a weird specimen to lose or drop intentionally.  I've heard of trilobites being left at a Miocene site as a joke but how many collectors are going to notice a tooth fragment with odd texture?

 

Crocodilian -  This seems like a likely possibility because it does appear to be a piece of a somewhat conical to dome-shaped tooth.  There were some funky crocs in the Late Cretaceous to Early Eocene.  The size of the fragment indicates a rather large tooth which would be within the realm of possibility for a one of the sea-going crocs of the Early Eocene.  Then again, the texture isn't right.  The croc teeth I've seen don't have that kind of complex ornamentation but maybe there's some rare larger form I haven't seen.

 

Terrestrial animal - Large freshwater croc or mammal.  I have some experience with Early Eocene land mammals of the Rocky Mountain area of the U.S.  I haven't seen any croc teeth that would be large enough to have a fragment that big.  The largest land mammal in North America at the time was Coryphodon which was about the size of a barnyard cow.  The molars have similar texture to that tooth but they are low-crowned.  I'm not sure they would be high enough to have a fragment that big.  It would be an unusually large tooth, I think.  I have some partial teeth to look at so I will have to get those out.  It seems unlikely Coryphodon is the answer, though.

 

Whale - I think we can rule out a whale from the Nanjemoy because it's a little too old to have a whale.  Whale fossils of that age are found but only in the Pakistan area and it was a time before they had fins.  It couldn't have crossed the Atlantic and the teeth didn't have anything like the ornamentation of the fossil in question.  That leaves the Yorktown.  Squalodont-type whales had died out by the Early Pliocene so we can eliminate those as a group to take a look at.

 

There are whales with rugose texture on the enamel of their tooth crowns.  I've seen sperm whale teeth from the Middle Miocene to Early Pliocene like that but I don't know how good of a match any would be.  The teeth tend to be rare but they can be big enough and the roughly the right shape to have a fragment that size and shape.  Maybe Bobby can say if he's seen that kind of texture in any whale tooth or other marine vertebrate.  @Boesse 

 

What seems to left is that there is a lesser-known Latest Cretaceous marine deposit in the area.  That seems to have been eliminated as a possibility especially if there were such a deposit, wouldn't more common fossils of the time be found by now rather than a very rare one?  What are the odds?

 

Jess

 

 

[Boesse]

What a puzzle! This absolutely could be a cetacean tooth. It's so incomplete though, it's not possible to say much more. I will say that here in SC, which in terms of deposition rate is not very different, we will find fossils that correspond to "missing" time periods. For example, we don't have any lower Miocene rocks more than about 5 miles in from the coast, but in bonebeds further inland we still find early Miocene cetaceans and C. chubutensis teeth in the basal Pleistocene bonebed along with Oligocene marine vertebrate fossils. And for that matter, Pliocene fossils even where the Pleistocene unconformably overlies the Oligocene. Point is - the local formations that are still around can be a good guide, but fossil preservation isn't restricted to them - the fossils can stick around as a lag deposit long after their host sediment is eroded away.

 

That being said, it could be any number of cetaceans, likely to be an odontocete but texture like that occurs in some protocetid archaeocetes (but generally not basilosaurids); many stem odontocetes have that texture, as do some sperm whales as Jess pointed out.

 

Don't take this to mean that IT IS a cetacean tooth - it's too incomplete. But I think a more likely ID than a mosasaur.