North Carolina Holden Beach Mosasaur Finds!

[fossil_lover_2277]

The best mosasaur material from my Holden Beach, NC trip! Top left two bones are prognathodon jaw fragments, top right three bones are vertebra, bottom left three bones are ribs, lower right two bones are from the flipper. For scale, the two largest mosasaur teeth are ~5cm each.

 

Btw about a third of this stuff ppl had walked over or picked up and tossed aside..

Edited June 2, 2022 by fossil_lover_2277

[Neanderthal Shaman]

Nice!

[fossil_lover_2277]

8 minutes ago, Neanderthal Shaman said:

Nice!

Thanks! Hadn’t collected the PeeDee formation much in NC to this point, fun to try it

[Hipockets]

I am curious as to how you determined the mosasaur bones to be prognathodon ?

[Mart1980]

Great finds! You make me jealous

Edited June 5, 2022 by Mart1980

[sixgill pete]

1 hour ago, Hipockets said:

I am curious as to how you determined the mosasaur bones to be prognathodon ?

 

@fossil_lover_2277 I also am wondering this 

[fossil_lover_2277]

11 hours ago, Hipockets said:

I am curious as to how you determined the mosasaur bones to be prognathodon ?

 

10 hours ago, sixgill pete said:

 

@fossil_lover_2277 I also am wondering this 

 

Both dentary pieces have the same structure, both are from the same type of organism.

 

Narial emarginations are present on both specimens, consistent with prognathodon. Part of the tooth alveoli are present on both specimens, and some of the alveolar bone is even preserved. Alveoli are way too big for dolpin, only thing they might could be is sperm whale. But the narial emarginations are inconsistent with sperm whale. Both features are consistent with mosasaur-type dentaries, definitely not whale or dolphin. The only two large mosasaur genera I’m aware of from the PeeDee formation in this area are Mosasaurus spp. and Prognathodon spp., if I am missing some please let me know. However the narial emarginations on Mosasaurus spp. dentaries such as Mosasaurus maximus look to be closer to the ventral side of the dentary than those of these specimens. Although I’m not an expert at distinguishing between Prognathodon spp. and Mosasaurus spp. skull elements, so I would welcome an expert’s opinion. However they’re certainly not marine cetacean. I collected quite a few marine cetacean bones at Holden, and even part of a Pleistocene mammal jaw. The bone type alone, not even considering the different structural features at the macroscopic level, is quite easy to distinguish apart from the reptilian mosasaur material.

 

 

Edited June 5, 2022 by fossil_lover_2277

[fossil_lover_2277]

7 hours ago, Mart1980 said:

Great finds! You make me jealous

 

Haha thanks! But y'all have some pretty nice fossils over in Europe too 

[JohnJ]

@fossil_lover_2277

From what I can see, the two pieces do look like reptile bone.  And, I can see your rationale; but, I don't see exclusively definitive characteristics to assign a genera.

[fossil_lover_2277]

13 hours ago, JohnJ said:

@fossil_lover_2277

From what I can see, the two pieces do look like reptile bone.  And, I can see your rationale; but, I don't see exclusively definitive characteristics to assign a genera.

Thanks, then I’ll just refer to them as large indeterminate mosasaur, they look closer to prognathodon from what I can tell, but I’m not about to try to argue mosasaur genera on a dentary fragment, don’t know them that well 

[Hipockets]

I didn't mean to sound like I was questioning if it was mosasaur. I am not doubting that. 

[fossil_lover_2277]

1 hour ago, Hipockets said:

I didn't mean to sound like I was questioning if it was mosasaur. I am not doubting that. 

 I was defending them being mosasaur because that’s more what I care about (and several ppl tried to convince me they were cetacean when I first found them), I’m not worried over what genera they are, I’m just happy to have me some NC mosasaur jaw pieces! 

 

Edited June 6, 2022 by fossil_lover_2277

[JohnJ]

16 minutes ago, fossil_lover_2277 said:

Only other large mosasaur genera I know of in the PeeDee of this area is Mosasaurus,

 

This is the kind of presumption we should be careful of; mosasaur diversity found in the Late Cretaceous deposits of North America would suggest caution making such a conclusion.  New genera are being discovered fairly often.

[fossil_lover_2277]

25 minutes ago, JohnJ said:

 

This is the kind of presumption we should be careful of; mosasaur diversity found in the Late Cretaceous deposits of North America would suggest caution making such a conclusion.  New genera are being discovered fairly often.

For sure, but the collection of these specific specimens for me is for fun, and it is enjoyable to try to figure out what they are, and I learn a lot by doing so. There’s a big difference in that and making the claim for a scientific paper. Obviously if you place a claim in a published paper you’d better be certain of it to the level of an expert. With these, I want to be clear I am just trying to learn, I’m not saying I’m an authority on mosasaurs nor does this have anything to do with scientific research. You can be a bit wreckless and try to learn knew things in this situation. I would argue it’s good to do so, I personally have learned a lot by it.

Edited June 6, 2022 by fossil_lover_2277

[Fossildude19]

But that should be (and now, has been) made obvious for the readership here. 

Pronouncement of something as being identified as one thing or another cannot be nailed down here.

Probably just best to consider them Mosasauroidea indet.

[fossilhunter21]

Those are some wonderfull finds! I really enjoy mosasaur fossils. 

 

Thank you for sharing,

 

-Micah

[fossil_lover_2277]

13 hours ago, fossilhunter21 said:

Those are some wonderfull finds! I really enjoy mosasaur fossils. 

 

Thank you for sharing,

 

-Micah

Same, I love finding these ancient reptiles! If you happen to live near Holden Beach NC, you should definitely make a trip, good chance you’ll at least find a tooth if you go beach combing on a falling tide.

[Plax]

Great finds! I can't tell Mosasaurus hoffmani from Prognathodon fragments myself but your explanation seems thorough. M. hoffmani (formerly maximus?) is a frequent find in the Peedee. It should also be pointed out here that resistant clasts such as bones and teeth are concentrated by the dredge and wave action. You could walk miles of natural Peedee exposure and not find a mosasaur bone or tooth. Lots of Exogyra and maybe echinoids but in general few vertebrate finds. Were there any modern epibionts on your mosasaur material?

[fossil_lover_2277]

On 6/15/2022 at 11:42 AM, Plax said:

Great finds! I can't tell Mosasaurus hoffmani from Prognathodon fragments myself but your explanation seems thorough. M. hoffmani (formerly maximus?) is a frequent find in the Peedee. It should also be pointed out here that resistant clasts such as bones and teeth are concentrated by the dredge and wave action. You could walk miles of natural Peedee exposure and not find a mosasaur bone or tooth. Lots of Exogyra and maybe echinoids but in general few vertebrate finds. Were there any modern epibionts on your mosasaur material?

 

On 6/6/2022 at 12:17 PM, JohnJ said:

 

This is the kind of presumption we should be careful of; mosasaur diversity found in the Late Cretaceous deposits of North America would suggest caution making such a conclusion.  New genera are being discovered fairly often.

 

On 6/5/2022 at 6:44 AM, Hipockets said:

I am curious as to how you determined the mosasaur bones to be prognathodon ?

 

On 6/5/2022 at 7:50 AM, sixgill pete said:

 

@fossil_lover_2277 I also am wondering this 

Thanks! So here are some pictures explaining my reasoning on the assignment of Prognathodon to the dentary fragments:

 

 

The two images above are of Mosasaurus maximus (hoffmanni) skulls. Notice the distance between the line of narial emarginations to the gum line, and then to the ventral side of the dentary. The narial emarginations are clearly closer to the ventral side of the dentary. 

 

Now, the next two images above are of Prognathodon spp. skulls. The line of narial emarginations in this case are much closer to the gum line in comparison to Mosasaurus maximus. This is consistent with the dentary fragments I collected.

 

Further, the dentaries of other genera of mosasaurs, such as Halisaurus or Clidastes, clearly do not match the dentary fragments I collected, on top of these genera not being commonly reported from the PeeDee, if at all.

 

Mostly the PeeDee material had limestone still attached to it, some sorts of molluscs were growing on some of them, but not a lot. Also, much of it was fossilized having already been fragmented. For example, one of the mosasaur ribs showed a large gash, maybe a bite mark, but it was formed prior to fossilization, it was not fresh.

Edited June 19, 2022 by fossil_lover_2277

[Plax]

Could be the material originated from the Peedee / Goose Creek lag. Depressions in the Peedee are filled with various neogene formations along the coastal plain in that area. In one that's now a lake near Conway the lag at the top of the Peedee included Peedee and any other resistant verteclasts from the intervening time up to Goose Creek time. So you'd find whale bones, beat up meg teeth and occasionally mosasaur material. At Holden most everything is burrowed or encrusted by modern taxa but it could also have been happening in a neogene lag. Resistant clasts are prone to repeated reworking just like quartz pebbles. In my experience, at least here in the eastern US, abundant vertebrate fossils are concentrated by geological processes. Not to say there aren't rare occurrences of vertebrate fossils that are shed or from dead animals.

[fossil_lover_2277]

2 hours ago, Plax said:

Could be the material originated from the Peedee / Goose Creek lag. Depressions in the Peedee are filled with various neogene formations along the coastal plain in that area. In one that's now a lake near Conway the lag at the top of the Peedee included Peedee and any other resistant verteclasts from the intervening time up to Goose Creek time. So you'd find whale bones, beat up meg teeth and occasionally mosasaur material. At Holden most everything is burrowed or encrusted by modern taxa but it could also have been happening in a neogene lag. Resistant clasts are prone to repeated reworking just like quartz pebbles. In my experience, at least here in the eastern US, abundant vertebrate fossils are concentrated by geological processes. Not to say there aren't rare occurrences of vertebrate fossils that are shed or from dead animals.

That’s interesting. Would make sense with the type of specimens I found, were heavily biased towards PeeDee material, except for the great white teeth.
 

And your comment about east coast vertebrates, that’s definitely consistent with how people find those Paleocene “Otodus” teeth at Green’s Mill Run, or those NC dino fossils (not naming the sites) concentrated in lags. Or especially the Charleston area. You’d find all sorts of stuff in the phosphatic lag layers. And the Black Creek group formations, vertebrate fossils are rare except in select locations they’ve been concentrated. That’s really cool that it evidences ancient geologic processes. Correct me if I’m wrong, but Black Creek and PeeDee material are often found reworked into the Eocene Castle Hayne, but near Greenville they’re reworked into the Pliocene Yorktown formation. And in Charleston it’s Pleistocene lags. That’s an interesting point you bring up.

[Plax]

You are correct. Neogene sediments are found on successively older cretaceous deposits as one goes inland. Greenville is unusual in that the Tarheel through Peedee formations occur together in that area leaving longer cretaceous history in the basal Yorktown lags. I have never been to GMR but the abundance of Exogyra cancellata and Belemnitella in situ seems to suggest the Peedee / Donoho Creek contact as seen elsewhere in NC. Squalicorax yangaensis is an index fossil for the much older Tarheel formation and is frequently found in the stream.

[mattthegerman]

On 6/2/2022 at 12:10 PM, fossil_lover_2277 said:

The best mosasaur material from my Holden Beach, NC trip!

Hey fossil_lover_2277 and Co, I went to Holden Beach yesterday and found a rib bone fossil, so I'm curious how you know your rib finds are from mosasaurus? I'd like to be confident in calling mine a mosasaur rib as well.