Plesiosaur or Myliobatis ray vertebra from Cretaceous of North Carolina

[fossil_lover_2277]

Anyone know what type of vertebra this is? Found in North Carolina, could be from either Cretaceous Black Creek group. 2.5 cm from left side to right. Could it be a plesiosaur cervical vertebra? Or is it Brachyrhizodus spp., a Myliobatis ray? I already have one Brachyrhizodus spp. vertebra and it doesn’t look like this, but maybe this is a different part or the backbone. Just based on size I’m leaning towards Brachyrhizodus, but it looks almost identical to a plesiosaur vertebra.

Oooo

Edited May 2, 2022 by fossil_lover_2277

[fossil_lover_2277]

Here’s a chart showing plesiosaur cervical vertebra. Looks exactly like the one in the 2nd row 1st column

[Mahnmut]

Hi,

does it have rib or chevron facets (last row) ? that would nail the ID I think.

Best Regards,

J

[pachy-pleuro-whatnot-odon]

19 minutes ago, Mahnmut said:

does it have rib or chevron facets (last row) ? that would nail the ID I think.

 

If plesiosaur, this would be a very small and thin vertebra and would be missing the subcentral foramina such vertebrae normally have. However, with rays being elasmobranch and therefore, at least in my understanding, not having any hema- or parapophyses, identifying those on this specimen would indeed be conclusive evidence against the vertebra having belonged to a cartilaginous fish.

 

Now it's clear from the last photograph that there are no attachment sites for hemal arches/chevrons, which scars would be found ventrally on the very edges of the vertebra. However, in order to check for the attachment sites of cervical or caudal ribs (it could still be an anterior caudal, though cervical would be the more likely option in absence of evidence for chevrons), better photographs of the entire circumferences (i.e., all sides) of the vertebra would be needed, as I think we've already learned all that we can from the centrum's faces and ventral side of the vertebra.

 

7 hours ago, fossil_lover_2277 said:

Here’s a chart showing plesiosaur cervical vertebra.

 

What publication is this from? The vertebra on this chart look somewhat atypical and certainly don't have the best preservation, making identification of certain generic plesiosaur features somewhat tricky.

 

7 hours ago, fossil_lover_2277 said:

Or is it Brachyrhizodus spp., a Myliobatis ray? I already have one Brachyrhizodus spp. vertebra and it doesn’t look like this, but maybe this is a different part or the backbone.

 

For purposes of comparison I've included some references to Brachyrhizodus vertebrae from the forum, to start with Landon's own specimen.

 

 

 

 

From those examples I'd say that the presence of a notachordal pit, otherwise rather diagnostic for plesiosaur vertebrae, can, in this case, not be used to distinguish the types of vertebrae. Likewise for the presence of attachment sites of the neural arch. What does seem more diagnostic, however, is the general width of the vertebra, as plesiosaur vertebrae are more rounded and the batoid ones more pill-shaped, wider than tall. Finding subcentral foramina would also be indicative of plesiosaur, but it's unclear whether their absence here is due to the vertebra being ray or rather due to it being so small. Scarring for rib-attachments therefore remains the clearest diagnostic feature.

[Plax]

Not positive but looks quite a bit like a big Squatina vert.

[fossil_lover_2277]

7 hours ago, Plax said:

Not positive but looks quite a bit like a big Squatina vert.

You’re right, I looked it up and yes there’s some features on my vert. that convince me it’s an angel shark.

[fossil_lover_2277]

12 hours ago, pachy-pleuro-whatnot-odon said:

 

If plesiosaur, this would be a very small and thin vertebra and would be missing the subcentral foramina such vertebrae normally have. However, with rays being elasmobranch and therefore, at least in my understanding, not having any hema- or parapophyses, identifying those on this specimen would indeed be conclusive evidence against the vertebra having belonged to a cartilaginous fish.

 

Now it's clear from the last photograph that there are no attachment sites for hemal arches/chevrons, which scars would be found ventrally on the very edges of the vertebra. However, in order to check for the attachment sites of cervical or caudal ribs (it could still be an anterior caudal, though cervical would be the more likely option in absence of evidence for chevrons), better photographs of the entire circumferences (i.e., all sides) of the vertebra would be needed, as I think we've already learned all that we can from the centrum's faces and ventral side of the vertebra.

 

 

What publication is this from? The vertebra on this chart look somewhat atypical and certainly don't have the best preservation, making identification of certain generic plesiosaur features somewhat tricky.

 

 

For purposes of comparison I've included some references to Brachyrhizodus vertebrae from the forum, to start with Landon's own specimen.

 

 

 

 

From those examples I'd say that the presence of a notachordal pit, otherwise rather diagnostic for plesiosaur vertebrae, can, in this case, not be used to distinguish the types of vertebrae. Likewise for the presence of attachment sites of the neural arch. What does seem more diagnostic, however, is the general width of the vertebra, as plesiosaur vertebrae are more rounded and the batoid ones more pill-shaped, wider than tall. Finding subcentral foramina would also be indicative of plesiosaur, but it's unclear whether their absence here is due to the vertebra being ray or rather due to it being so small. Scarring for rib-attachments therefore remains the clearest diagnostic feature.

 

12 hours ago, Mahnmut said:

Hi,

does it have rib or chevron facets (last row) ? that would nail the ID I think.

Best Regards,

J

 

7 hours ago, Plax said:

Not positive but looks quite a bit like a big Squatina vert.

I compared it to online pics based on all of your suggestions and it’s an angel shark vertebra, Squatina spp. Thanks!!!

[Plax]

Those pics get around! Glad you have an ID.