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Spinosaurid Vertebra?


DinoFossilsUK

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I'm looking for a little help identifying this bone from the Kem Kem Beds.  It looks to part of a vertebra - it's almost 6 inches long so I immediately thought that narrows it down to being a partial Spinosaurid or Charcharodontosaurus vertebra.  After spending ages looking through previous post and searching for detailed pictures of vertebrae, I came to the conclusion it belongs to a Spinosaurid (Spinosaurus or Sigilmassasaurus) because the shape just looks wrong for Carch (although there isn't much to go off for Carch vertebrae).  Just looking for some input as to whether I'm correct as I know some members are far more familiar with Kem Kem bones.  Would you say this looks like a partial Spino vertebra or is it far too fragmentary to say?

IMG_9488.JPG

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It's not a vertebra.

 

I saw this piece when it was being sold. I immediately recognized this piece between the other random bones.

It's part of a spinosaur braincase. It's identical to the one I have, just bigger. Since there are at least two type of Spinosaur in the Kem Kem beds we cannot be sure which taxon this belongs to. It could be Spinosaurus aegyptiacus or Sigilmassasaurus brevicollis.

 

This is the basisphenoid. It's the dangly bit that extends on the bottom of the braincase. Spinosaurids have really weird braincases that can be recognized by their elongate shapes. Most other theropod braincases are much more compact. This looks like a hefty big piece. The smooth triangle shape we see in the second picture is the front. The two "legs" hang down on the bottom. Those are the basipterygoid processes. Maybe the top 1/4 of the bone is missing. This must have been a very big animal.

 

Here is some reference for other spinosaurids.

 

Irritator. Note the bone labled "bs" for basisphenoid in the bottom middle.

irritator.thumb.png.ce5e92df4baa00829857f58c892b576d.png

 

Baryonyx. This is the back half of the braincase. Like Irritator you can see the elongate lower half and again the basisphenoid is labled "BS".

5ec046ca024bb_36949190500500.thumb.jpg.163def6630c17fb6917417a415cb8559.jpg

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Olof Moleman AKA Lord Trilobite

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16 minutes ago, LordTrilobite said:

I saw this piece when it was being sold. I immediately recognized this piece between the other random bones.

It's part of a spinosaur braincase.

 

This is the basisphenoid. It's the dangly bit that extends on the bottom of the braincase. Spinosaurids have really weird braincases that can be recognised by their elongate shapes. Most other theropod braincases are much more compact. This looks like a hefty big piece.

 

Here is some reference for other spinosaurids.

 

Irritator. Note the bone labled "bs" for basisphenoid in the bottom middle.

irritator.thumb.png.ce5e92df4baa00829857f58c892b576d.png

 

Baryonyx. This is the back half of the braincase. Like Irritator you can see the elongate lower half and again the basisphenoid is labled "BS".

5ec046ca024bb_36949190500500.thumb.jpg.163def6630c17fb6917417a415cb8559.jpg

It's honestly jaw dropping how you managed to identify this, I feel pretty silly for thinking it was part of a vertebra now!  Thank you so much Olof, I think I'll hold onto this one.  Out of interest, do they turn up very often, I guess they must if you identified it so easily from those original photos?

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This is the third one I've seen.

There's this fairly well known Spinosaurus composite skull. It seems to have a partial braincase. But it's unclear how many individuals this is a composite of.

skull_spinoskullchimere.jpg.86dd86b4c0b5fa1882b0d88d9d28912a.jpg

 

And I have a partial braincase which is roughly as complete as the Baryonyx braincase in that drawing I posted here.

I just checked, and mine is much, much smaller. It's about 21 cm tall (just over 8 inches). And it's pretty much complete in it's height. Yours seems to be easily twice the size as the basisphenoid is under 3 inches long on mine. So you're looking at maybe a 40 cm(16 inch) tall braincase for your specimen. And the braincase itself isn't the full height of the skull. The quadrates would extend the height maybe to say 50 cm (20 inches) tall. This could be from a skull that's maybe 2 meters long.

 

Ibrahim's reconstruction. I don't think they had a braincase though.

skull_spino_quadrate.png.e046428f4edcab365e9fbe0112860feb.png

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Olof Moleman AKA Lord Trilobite

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That's awesome.  So I guess it comes from a large, fully grown Spino (if I'm correct their skulls only went up to just under 2m).

 

Thanks again for the explanation and drawings!

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