Plesiosaur propodial with predation marks

[FF7_Yuffie]

Hello. This is sold as Kimmeridge Clay Plesiosaur propodial with predation marks.

 

It matches photos of propodials, but I am wondering if they actually are predation marks? Seller says the marks are probably pliosaur.

 

It's been sold along with a bunch of other plesiosaur fossils that were dredged together. 

 

If anyone can help, that would be great.

[FF7_Yuffie]

Underside

[JohnJ]

I see nothing that could possibly distinguish Pliosaur as leaving any marks on this piece.  Many of the marks I see are fractures in the bone.  I think most actual scavenging marks on marine reptile bones are from sharks.

[FF7_Yuffie]

11 minutes ago, JohnJ said:

I see nothing that could possibly distinguish Pliosaur as leaving any marks on this piece.  Many of the marks I see are fractures in the bone.  I think most actual scavenging marks on marine reptile bones are from sharks.

 

Cheers.

 

The fractures are natural wear then rather than pedation marks?

[JohnJ]

13 hours ago, FF7_Yuffie said:

 

Cheers.

 

The fractures are natural wear then rather than pedation marks?

 

The focus on these images is too poor to see whether there are any scavenging marks.

[FF7_Yuffie]

2 hours ago, JohnJ said:

 

The focus on these images is too poor to see whether there are any scavenging marks.

 

Thanks for taking a look. If it's a fossil I decide to look into further, I'll get some better and clearer pics from the seller that 

 

Cheers

[pachy-pleuro-whatnot-odon]

This is definitely the distal end of a plesiosaurid propodial dredged from the Smallmouth Sands off of Weymouth Bay. You'd be hard-pressed to say whether it's plesiosaur or pliosaur based on the shape, however, as the piece is rather weathered. As to the predation marks, they're there: two parallel grooves can be seen near the break on the last photograph - the one you've marked "underside". It's hard to say what animal made these grooves, however. Could be that @JohnJ is right in that it concerns predation marks from sharks, though they're frequently marketed as pliosaur feeding marks - simply because it sells better. You'll occasionally also see such marks classified as deriving from large marine reptiles - meaning large ichthyosaurus or pliosaurs - marginally better than outright classifying them as pliosaur. Still, true predation marks, but hard to classify as to what made them...

 

The other marks visible across the bone are likely just fractures or worm-burrows. The latter is more likely, in my opinion, and may include modern traces, for the fact that a lot of plesiosaur prododials found at inland UK-sites lack such grooves, whereas they're relatively frequent in Smallmouth specimens. It's also based on the fact that worms and barnacles, today as in the past, have a tendency to attach themselves, and borrow through, bones, whether fossilised or fresh...

[FF7_Yuffie]

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

This is definitely the distal end of a plesiosaurid propodial dredged from the Smallmouth Sands off of Weymouth Bay. You'd be hard-pressed to say whether it's plesiosaur or pliosaur based on the shape, however, as the piece is rather weathered. As to the predation marks, they're there: two parallel grooves can be seen near the break on the last photograph - the one you've marked "underside". It's hard to say what animal made these grooves, however. Could be that @JohnJ is right in that it concerns predation marks from sharks, though they're frequently marketed as pliosaur feeding marks - simply because it sells better. You'll occasionally also see such marks classified as deriving from large marine reptiles - meaning large ichthyosaurus or pliosaurs - marginally better than outright classifying them as pliosaur. Still, true predation marks, but hard to classify as to what made them...

 

The other marks visible across the bone are likely just fractures or worm-burrows. The latter is more likely, in my opinion, and may include modern traces, for the fact that a lot of plesiosaur prododials found at inland UK-sites lack such grooves, whereas they're relatively frequent in Smallmouth specimens. It's also based on the fact that worms and barnacles, today as in the past, have a tendency to attach themselves, and borrow through, bones, whether fossilised or fresh...

 

 

Nice one, thanks for taking a look. The fossil was dredged with a bunch of other bones identified as plesiosaur--a bunch of vertebra, another propodial and a scapula I believe, which, unless they were misidentified took, makes it likely this is plesiosaur.

 

Great spot with the predation marks. That's cool that it does have them. Is it common then for predation marks to be more like that--straight parallel lines rather than jagged and all over the places like the other marks on this? Great info about worm/barnacle damage, I didn't know that and it's good stuff to know.

 

Thanks for taking a look and for the info on the fossil.

[pachy-pleuro-whatnot-odon]

19 minutes ago, FF7_Yuffie said:

 

 

Nice one, thanks for taking a look. The fossil was dredged with a bunch of other bones identified as plesiosaur--a bunch of vertebra, another propodial and a scapula I believe, which, unless they were misidentified took, makes it likely this is plesiosaur.

 

Great spot with the predation marks. That's cool that it does have them. Is it common then for predation marks to be more like that--straight parallel lines rather than jagged and all over the places like the other marks on this? Great info about worm/barnacle damage, I didn't know that and it's good stuff to know.

 

Thanks for taking a look and for the info on the fossil.

No problem, always happy to help a fellow collector

 

Not sure, though, whether the rule of association works for material dredged off of Weymouth, since any information on depositional context and potential later reworking is lost, as is the information on over how large an area the bones were dredged up from. However, as a general rule I believe material from this area is classified as either Colymbosaurus trochantericus if plesiosaur; Liopleurodon ferox if pliosaur; and Brachypterygius extremus if ichthyosaur. So if associated with more plesiosaur material, it seems reasonable to assume Colymbosaurus trochantericus, which has a rounded distal end to its propodials and therefore is a reasonable match...

 

As to the predation marks: it can't be excluded that individual hap-hazard scratches and grooves are evidence of feeding (I recently found a piece of Eocene turtle carapace which a big chunk had been broken out of, with the tooth of a shell-crushing crocodile lying exactly in that cavity - more than likely evidence of predation as well, just to indicate the variations this can take), but as teeth are often of similar size and orientation, and located close together, parallel lines are more common that single ones. Also straight lines are more common than curved ones, as when scraping meat off of a bone, it's unlikely a predator would have made a twisting motion over a small surface.

[JohnJ]

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

As to the predation marks, they're there: two parallel grooves can be seen near the break on the last photograph - the one you've marked "underside".

 

These marks are not definitively scavenging marks.  It looks like the entire piece is coated in some type of consolidant that tends to blend modern scrapes.  Still, I think those are compression fractures similar to the ones radiating above them.  Again, these images are not in focus enough to distinguish scavenging traces.

[pachy-pleuro-whatnot-odon]

9 hours ago, JohnJ said:

These marks are not definitively scavenging marks.  It looks like the entire piece is coated in some type of consolidant that tends to blend modern scrapes.  Still, I think those are compression fractures similar to the ones radiating above them.  Again, these images are not in focus enough to distinguish scavenging traces.

I don't know about the consolidant. Could be, of course, but I've never considered it, since all Weymouth/Smallmouth pieces I've seen have consistently had the same look to them - a look that is, moreover, is not uncommon for other British finds dating to more or less the same time-period. If a consolidant were applied, then it looks like the same one is consistently applied over a long stretch of time, on material from possibly various sources, and by impregnation rather than coating. As such, I doubt that a consolidant has been applied and consider this simply a patina and artifact of preservation.

 

However, I did take another look at the predation marks I thought I saw earlier - this time on my laptop rather than mobile phone - and, unfortunately, have to agree now, @FF7_Yuffie. I no longer believe these are indeed scavenging marks, but rather compression marks as @JohnJ suggested. This doesn't invalidate what I said before about the preservation of bones from this location or about how to recognize predation marks in general, I just no longer believe that I see any on this piece. Sorry!

[FF7_Yuffie]

Thanks very much for taking a look both of you. I will leave this fossil, it was the possible predation that interested me with it.

 

Thanks for having a look, and for the extra info-- very informative