Two more mystery finds from France (Wimereux & Villers-sur-mer)

[ADfossils]

Hello everyone!

 

I recently visited France twice to hunt for fossils. I wanted to visit Villers-sur-mer at least once before the interdiction to collect and I was rewarded with an amazing vertebra:

 

 

Guess it's marine crocodile, since the shape doesn't fit with ichthyosaurs, plesiosaurs or dinosaurs.

 

Here it is cleaned up sitting in it's little box:

 

 

I also found this mystery really eroded bone. It's quite big and chunky:

 

 

 

Would anyone have an idea on what it's from/which bone it is?

 

Then the mystery from Wimereux. At first I thought it was petrified wood, but it's dry now and it doesn't crumble. It's hard, heavy and there's some pyrite going through it:

 

 

 

 

 

 

 

Would anyone have an idea?

 

Thank you!

 

[jpc]

the first vert look like a plesiosaur from here...

 

[Tidgy's Dad]

My first thought was also plesiosaur.

 

[ADfossils]

Ah yes, I can see why you say that based on the angle of the pictures. Here are some pictures to clear that up.

Do you any idea about the mysteries?

 

[jpc]

Hmmmmm... no paired foramina on the ventral surface.  And deep holes on the sides.  I recall my plesiosaur call and say... I don't know. 

 

[pachy-pleuro-whatnot-odon]

First of all, nice finds! Especially the vertebra is really cool! I've been trying to find something like that from Vaches Noires for some years now, but with the new collection regulations coming into force, I doubt I'll ever find myself something like that

 

Anyway, here are my interpretations of these fossils:

 

1. While I agree that the subcentral foramina seen on plesiosaur vertebrae are very diagnostic for the clade, they're not present in all species nor all across the full length of the vertebral column. With this in mind, I still believe the vertebra to be plesiosaurian, rather than crocodilian. That's because:
   1. The vertebra is rather short and with minimal waisting, while those of marine crocodiles are typically longer and have a more pronounced waist.
      
      
      Thalattosuchus 'Metriorhynchus' superciliosus from the Callovian of Peterborough.
       
   2. The centrum morphology of this vertebra is amphiplatian, with plesiosaur vertebrae being either amphiplatian to platycoelous, while those of thalattosuchia are usually platycoelous to amphicoelous.
      
   3. The neural arches in marine crocodiles and plesiosaur differ, such that they attach differently and leave different scarring. That seen on this vertebra match what you'd expect from a plesiosaur vertebra. Compare that to the below crocodilian caudal vertebra from Lourinhã Formation in Portugal.
      
   4. This vertebra appears to have a nutritive foramen in the middle of its centrum, which is typical for plesiosaurs - pliosaurs specifically - but not marine crocodiles.
      
      
      
      
      
      Here are a couple marine crocodile vertebrae for comparison.
      
      
      
      Dakosaurus maximus vertebra from Audresselle in the Boulonnais region of France
      
      
      
      Kimmeridgian Steneosaurus sp. vertebra from Weymouth
      
      
      
      
      Thalattosuchia indet. vertebra from Bielefeld in Germany
      
      
      
      Thalattosuchus 'Metriorhynchus' superciliosus vertebra from the Oxfordian of Peterborough
      
      
      Now compare that to the scars on this - admittedly giant - Pliosaurus cf. westburiensis cervical vertebra from Westbury Quarry, Wiltshire:
      
       
2. I'm not quite sure whether this is bone. Sure, there does seem to be something of a fibrous patterning going on, if you use a bit of imagination. However, realistically, I don't quite see the traditional honeycomb texture that I'd expect from bone. I expect this is a large piece of sponge, which are commonly found in the area, especially towards the direction of Villers-sur-Mer itself.
3. This is a bit of a tricky one, due to the chondritic fractures seen in certain spots on the fossil. However, other parts do show more of the fibrous texture that I'd expect to see from bone, especially the outsides and one of the cross-sections. As such, I think this could be a piece of jaw bone, likely from the lower jaw and somewhere towards the back, due to the lack of foramina and alveoli. Hard to say what animal this could then have come from, as there's little diagnostic features to go off of. But seeing as both crocodilians and pliosaurs are often found in the area and would have bits of jaw where this piece could fit, both would be good candidates.

Edited November 12, 2023 by pachy-pleuro-whatnot-odon

[ADfossils]

Hello Pachy, thank you very much for your detailed reply! 

I am indeed really pleased with the vertebra. Especially since I wanted to visit and hunt at Villers-sur-mer at least once before the restrictions. The latest updates were talking about maybe not completely forbid collection, but rather making sure that hunters are informed on how to collect in a durable and safe manner, as well as making sure that scientifically important finds are at the very least reported to the museum there. Let's cross our fingers! 

[pachy-pleuro-whatnot-odon]

Indeed, let's hope they end up implementing a system like this - which is very similar to the one in use, with great success, in the UK. It would be such a shame if collection would simply be prohibited point blank!