Large Ichthyosaur Vertebra, Penarth, Wales

[PointyKnight]

Hey everyone,

I recently acquired this ichthyosaur vertebra that was originally collected in Penarth, south Wales, UK. What initially struck me was the vertebra's size, since it's by far the biggest one I have of any ichthyosaur:



Now, other large ichthyosaur remains have been described from the very same location. The paper is freely available here:
https://bioone.org/journals/acta-palaeontologica-polonica/volume-60/issue-4/app.00062.2014/A-Mysterious-Giant-Ichthyosaur-from-the-Lowermost-Jurassic-of-Wales/10.4202/app.00062.2014.full

The cliffs at Penarth apparently contain multiple exposures of different formations, which can make assigning isolated remains from there to any one time period problematic. The authors tentatively date the bone described in the paper to the lowermost Jurassic based on attached matrix and microfossils it contains. Finding references for the sediment of each formation from this locality is tough, but the matrix on my vertebra resembles that in the paper at least superficially.

I have tried contacting Dr. Peggy Vincent, a co-author of the study who works on Jurassic marine reptiles from Europe, but sadly no luck thus far.  My questions are:

- Are there any features that might help date this fossil to a certain time period, or identify the formation it originated from?

- The authors of the study assign their fossil to Shastasauridae - are there any features that can identify this vertebra on a family level?

Thank you for your help!

[Ludwigia]

I'm afraid that I'm not versed enough to be able to answer any of your questions, but Temnodontosaurus could be another possibility.

[Mike from North Queensland]

A local collector may be able work out the formation from the colour of the matrix.

From photos there are no diagnostic features visible to confirm ichthyosaur 100% but from overall shape I assume it is.

the only visible bone surface is in the top center of the elevation A and from photos I can not tell if the rest is matrix or exposed inner bone.

A good acetic acid clean may help but confirm that with the local collectors from the area first as I do not know what the preservation from that area is like.

 

Mike

[Welsh Wizard]

Hi

 

i suspect the vert has come from the Triassic (rhaetic) bone bed at Penarth. You can get some big fragmentary bones.

 

Here’s a link to a paper describing a large jaw bone of a Triassic ichthyosaur from Somerset which is directly across the Bristol Channel from Penarth.

 

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194742

[PointyKnight]

Thanks everyone!

18 hours ago, Ludwigia said:

I'm afraid that I'm not versed enough to be able to answer any of your questions, but Temnodontosaurus could be another possibility.

@Ludwigia True! I've read that T. eurycephalus was found not far from there, and depending on the age of the fossil it could be from a number of Temnodontosaurus.
 

12 hours ago, Mike from North Queensland said:

A local collector may be able work out the formation from the colour of the matrix.

From photos there are no diagnostic features visible to confirm ichthyosaur 100% but from overall shape I assume it is.

the only visible bone surface is in the top center of the elevation A and from photos I can not tell if the rest is matrix or exposed inner bone.

A good acetic acid clean may help but confirm that with the local collectors from the area first as I do not know what the preservation from that area is like.

 

Mike

@Mike from North Queensland Absolutely! I've been trying to track down someone local (a guide/collector/museum staff) but no success there. Side A is completely free of matrix (the brighter spots seem to be discoloration) and there is very little on the others except for B, which is under a pretty thick cover which I assume someone tried to remove mechanically but gave up on (the edge between bone and matrix is more clearly visible in person, sorry for the image quality (file size restrictions)).

11 hours ago, Welsh Wizard said:

Hi

 

i suspect the vert has come from the Triassic (rhaetic) bone bed at Penarth. You can get some big fragmentary bones.

 

Here’s a link to a paper describing a large jaw bone of a Triassic ichthyosaur from Somerset which is directly across the Bristol Channel from Penarth.

 

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194742

@Welsh Wizard Alright! Can you share how you came to that conclusion? I can upload better images of the matrix if it helps! [also very interesting paper!]

[Welsh Wizard]

8 hours ago, PointyKnight said:

@Welsh Wizard Alright! Can you share how you came to that conclusion? I can upload better images of the matrix if it helps! [also very interesting paper!]

Just years of collecting from that stretch of coast, I guess. There are big bone fragments in the Triassic which you can recognise from the colour (although obviously that’s no substitute for finding in-situ). The liassic ones tend to be a different colour and smaller. Not an exact science!

[PointyKnight]

On 8.10.2020 at 7:58 PM, Welsh Wizard said:

Just years of collecting from that stretch of coast, I guess. There are big bone fragments in the Triassic which you can recognise from the colour (although obviously that’s no substitute for finding in-situ). The liassic ones tend to be a different colour and smaller. Not an exact science!

Thank you still! Personal experience can become invaluable in situations like this. If you have anyone I might be able to contact over this, or other literature that's available on the subject, I'd love to know!

[pachy-pleuro-whatnot-odon]

To chip in with my 2 cents, I don't think it's possible to get an identification to the species level, or even the genus one, based on a vertebra alone, let alone a partial.

 

Though, of course, size may be indicative of a larger or smaller species, size differences may also be due to other factors, such as: juvenile versus adult individuals of a species, position along the spine, and, possibly, even sexual demorphism - although the latter, to my knowledge, hasn't been documented in ichthyosaurs yet, and would, anyway, probably be less than interspecies size differences. In any case, you'd need enough of the vertebra left to establish whether it concerns a cervical, dorsal (and, if so, which part) or caudal vertebra. In case of the above specimen, I'd say that, though part is missing and no rib attachment facets can be seen, the vertebra concerns a dorsal (based on shape, which seems neither triangular nor pill-shaped).

 

Another metric that may help towards identification is the vertebra's thickness,  i.e. width/height to depth ratio. Thinner vertebra are generally associated with thuniform swimming, and thus with more derived species of ichthyosaur. However, thickness can easily be influenced by compression as part of the fossilization process, thus is not really a good indicator. Moreover, from the above I get the impression that the geological time-span available at Penarth is rather too narrow to distinguish species using this character anyway - that is, the evolution of ichthyosaurs to thuniform swimmers took place during the Jurassic, and thus there would not be too much of a telling difference in vertebral thickness between the Late Triassic and early Jurassic.

 

With the best means of identifying ichthyosaurs being their paddles, pectoral girdles and skulls, the most reliable way of identifying a vertebra would be by association. Obviously, that isn't possible in this case, however...

 

All the same, I'd say that seeing the size of the vertebra, we're probably dealing with a larger species. Looking at the below phylogenetic overview, and taking geography and frequency of occurrence into account, I'd say a Shastasaurid or Temnodontosaurus is the most likely candidate. It should be noted, though, that this depends on how you interpret the ichthyopterygian phylogeny and the geological extent of individual lineages, as there seems to be some variation in this as well...

 

Hope this helps!

 

[paulgdls]

Well, as stated above, its either from Temnodontosaurus or from a giant Shastasaurid. I would agree that its probably Triassic looking at the preservation and matrix and would lean towards Shastasaurid. We cannot tell where along the vertebral column this has come from but vertebrae of greater than 20 cm diameter are known from Shastasaurids, including one from Aust (see paper I co-wrote above). We desperately need more material from these giants which appear to have reached truly gigantic size before the extinction event at the end of the Triassic. A recent discovery will give us much more to work on ....

 

regards

 

Paul

 

[pachy-pleuro-whatnot-odon]

4 hours ago, paulgdls said:

We cannot tell where along the vertebral column this has come from but vertebrae of greater than 20 cm diameter are known from Shastasaurids, including one from Aust (see paper I co-wrote above).

Wow! I never realised these vertebrae could get that big. I've seen some giant Temnodontosaurus vertebrae in my time (one of which is in my personal collection), but have never seen one bigger than about 17 cm (though I've never measured those in museum displays I've seen). One thing I have noticed, though, is that these vertebrae become increasingly massive with increase in diameter... Can't imagine what a 20+ cm would be like! Moreover because the only Shastasaurids I've seen so far are those in the palaeontological collections of the University of Zurich - which are significantly smaller in size...

[paulgdls]

Hi. Yes, here are the dimensions of some of the S. sikkaniensis vertebrae, dimensions up to 24.9cm! Presumably the Somerset specimens could have exceeded these dimensions somewhat: 

 

Vertebra number L H W H/L
3 9.5 20.8 2.2
5 9.5 20.8 2.2
6 9.5 21.0 22.0 2.2
9 8.9 20.8
10 8.8 19.5 20.4 2.2
11 9.1 19.0 2.1
14 8.3 22.0 22.4 2.6
18 9.5 20.6 2.2
19 9.7 20.5 2.1
25 9.9 23.3
26 9.2 22.9
27 10.9 19.1
28 8.7 22.2
29 9.2 23.5
30 8.9 24.0
32 9.3 19.0
33 8.2 24.7
34 9.3 23.9
35 9.4 19.7
36 9.3 23.8
38 9.2 23.1
Presacral vertebra, exact position number unknown
A 8.8 24.9 2.8
D 10.2 22.7 2.2
F 9.3 24.3 2.6

 

Paul

 

[pachy-pleuro-whatnot-odon]

Wow! Those are some astounding numbers, @paulgdls! 

 

Looks like I still have some way to go if I'd like to add an absolutely giant ichthyosaur vertebra to my collection 

[PointyKnight]

On 19.10.2020 at 5:46 PM, paulgdls said:

Well, as stated above, its either from Temnodontosaurus or from a giant Shastasaurid. I would agree that its probably Triassic looking at the preservation and matrix and would lean towards Shastasaurid. We cannot tell where along the vertebral column this has come from but vertebrae of greater than 20 cm diameter are known from Shastasaurids, including one from Aust (see paper I co-wrote above). We desperately need more material from these giants which appear to have reached truly gigantic size before the extinction event at the end of the Triassic. A recent discovery will give us much more to work on ....

 

regards

 

Paul

 

@paulgdls Thank you very much Paul, that's a great help! I'm excited for more research on giant ichthyosaurs, hopefully more complete remains of really large individuals will be discovered at some point!