New Zealand marine reptile vertebra

[Paleoworld-101 353]

I've got this very worn vertebral centrum from the marine Conway Formation near Oaro (Late Cretaceous; about 79-73 Ma) on the south island of New Zealand. The only two logical candidates are plesiosaur or mosasaur from this formation, both of which are known here. There are characteristics of both groups seen on this bone which is tripping me up a bit. One end face seems a bit concave and the other more convex which is a mosasaur feature, but then there also looks to be two distinct holes on the ventral side (see photo three) which could be the paired foramina that are characteristic of plesiosaur vertebrae. So i am left scratching my head! What do others think? 

 

 

Front face

 

 

Dorsal view

 

 

Ventral view (note what look like paired foramina)

 

 

Lateral view

[Rockwood 1,670]

Hang on to the ladder because the limb you're out on could snap at any time. 

[Fossildude19 8,915]

I think it is too worn, to call it anything more than chunk-o-saur.   

[Haravex 704]

I think your correct in vertebrae but anything beyond this has been lost to the elements sadly.

[Pemphix 239]

1 hour ago, Fossildude19 said:

I think it is too worn, to call it anything more than chunk-o-saur.   

I agree - exact.

[Paleoworld-101 353]

16 hours ago, Fossildude19 said:

I think it is too worn, to call it anything more than chunk-o-saur.   

I'm confident it is a worn vertebra. You don't see it? 

[KimTexan 1,704]

It is a worn vertebra. I agree. Personally I would lean towards mosasaur. I have 7 or 8 mosasaur vertebrae. All the Plesiosaur I have seen are slightly concave on both sides. The bone seems to preserve better and be harder than mosasaur. At least around here. I don’t know if it is true of all Plesiosaur verts, cervical and caudal could be different, but all the ones I’ve seen are either wider than they are tall or pretty close to equal to the same on height and width.

 

@believerjoe may have thoughts to add. He’s our DPS go to on mosasaur and Plesiosaur.

These are some of his Plesiosaur vertebrae he posted on Facebook. See what I mean about width to height ratio?

 

I spent 2 weeks in New Zealand many years ago. I fell in love with the South Island. North was OK, but South was better.

[Paleoworld-101 353]

@KimTexan thanks for the response! 

Yes i see what you mean about the height and width. A shame that this bone is so worn so it is not really possible to gauge what the true height to width ratio would have been. 

 

Regarding the two little holes on the ventral side of my bone: i am wondering what the internal structure of paired foramina on plesiosaur verts is like. On a crisp vert the holes are located pretty much in the middle as shown on the picture you posted (also note how the spacing between them varies, some close together and others further apart). However, on mine (if that is what they are) they are nearer to one of the ends. So i wonder, do the paired foramina continue far inside the bone and perhaps shift position away from the middle (internally)? Because if those two little holes are what i think they are, a plesiosaur identification is pretty much guaranteed. 

[Rockwood 1,670]

On 1/7/2019 at 11:43 PM, Paleoworld-101 said:

One end face seems a bit concave and the other more convex which is a mosasaur feature,

The piece has no end faces. How can you assign these values to something that doesn't exist ?

[Paleoworld-101 353]

4 minutes ago, Rockwood said:

The piece has no end faces. How can you assign these values to something that doesn't exist ?

Actually, one side does have part of the face or very close to the face surface (first photo) and it is quite clearly not convex. The other side was inferred as probably convex from textural similarity to many of my crocodilian verts with convex ends that are beach worn in much the same way. 

[Rockwood 1,670]

5 minutes ago, Paleoworld-101 said:

The other side was inferred as probably convex from textural similarity to many of my crocodilian verts with convex ends that are beach worn in much the same way. 

Then why not go with croccodillian vert ?

[Paleoworld-101 353]

2 minutes ago, Rockwood said:

Then why not go with croccodillian vert ?

I don't believe any crocs are confirmed from this formation. All other material has been either from plesiosaurs or mosasaurs. Whether mosasaur convex vert ends are indeed texturally similar to those of crocodiles is another matter i haven't dove into yet. 

[Rockwood 1,670]

3 minutes ago, Paleoworld-101 said:

I don't believe any crocs are confirmed from this formation.

Perhaps because there is insufficient evidence ? 

[believerjoe 126]

Mosasaur is most likely.  This looks just like buckets I have of these.  It is almost all internal bone structure except the top which has some outer left.  It’s a good mosasaur fit, but obviously no guarantees with so much gone.  

[Paleoworld-101 353]

On 12/01/2019 at 1:18 AM, believerjoe said:

Mosasaur is most likely.  This looks just like buckets I have of these.  It is almost all internal bone structure except the top which has some outer left.  It’s a good mosasaur fit, but obviously no guarantees with so much gone.  

Thanks for the comment! I was hoping it was mosasaur actually, but what about the two holes on the underside? You don't think they might be the internal remnants of the paired foramina on plesiosaur verts? 

[believerjoe 126]

I actually don’t see the foramina here and they would be on the badly eroded side which is the bottom.  So based on comparable bones we find, I still think mosasaur.  It is tough given what is left.  I also think the width is too great, but could always be some variant species.  I am afraid that you can’t do much better.  Go find a complete one!  :-)

[Dave (POM) Allen 110]

you say it was found near Oaro I would say that you're correct with your guess,  a lot of worn mosasaur  verts are found there. I have picked up many over the years.