Suggestively shaped rock

[Ossicle]

I picked this up a year ago as it is convex on both sides and looks a bit like a vertebra. It's from the Jurassic Callovian Lower Oxford Clay at Yaxley, and a year on I still can't decide if it's just a suggestively shaped rock or a very worn vertebra. It's really hard to show the convex shape in the photos.

 

ETA: I meant concave, not convex

[WhodamanHD]

Yeah, looks like a vertebrae to me. I'm no expert but I'm gonna guess mosasaur, plesiosaur, or pliosaur.

[Rockwood]

Agreed with one notable exception. Mosasaurs hadn't evolved yet had they ?

[abyssunder]

Not a rock.
The porosity structure reminds me of cetacean bone. Maybe a whale vertebra centrum?

The geological time and location would be good.

[Ossicle]

Thank you . It's lower Jurassic, from Yaxley in Peterborough. The main vertebrates are fish (including sharks and Leedsycthis), pliosaur, plesiosaur and icthyosaur. Terrestrial animal remains were sometimes swept out to sea, but it's marine sediment and likely to be marine vertebra. It seems quite big, so I'm wondering if it might be pliosaur or big fish.

 

I'll move this from my interesting rock pile

 

ETA and marine crocodiles 

[abyssunder]

Martill, D. M. et al. 1994. The trophic structure of the biota of the Peterborough Member, Oxford Clay Formation (Jurassic), UK. Journal ofthe Geological Society, London, Vol. 151, pp. 173-194

[Ossicle]

Thank you for the article.

It can't be shark, as they're cartiliginous, and I can't see concentric circles for fish. I have come across some larger icthyosaur vertebrae online now, so I think I've narrowed it down a little, but there's still multiple marine reptiles it could be. 

 

[Taogan]

I can see bone texture and a general shape. Looks like a worn Ichthyosaur vert to me, far too worn to work out the species though

[Ossicle]

23 minutes ago, Taogan said:

I can see bone texture and a general shape. Looks like a worn Ichthyosaur vert to me, far too worn to work out the species though

Only two species of Opthalmosaurus have been described from the Oxford clay (at the point Martill was writing Fossils of the Oxford Clay, there may have been some since), and I wouldn't be able to tell from a vertebra which one, so I'd be happy with genus. If you cut it in half I think it would look quite like the cross section of an Ichthyosaur vertebra in Fossils of the Oxford Clay. It is very worn and has lots of cuts and scratches like hybodont sharks used it as a chew toy (but probably just from rolling around on the sea floor).

[abyssunder]

You are correct. Ichthyosaurs from the Oxford Clay have been referred to the genus Ophthalmosaurus with two recognized species, I. icenicus and I. monocharactus. In I. icenicus the coracoids have posterior and anterior notches, while in I. monocharactus there is only a single notch in the coracoids. Both species were recorded from Peterborough, Cambridgeshire. - according to Martill, 1991

 

Yaxley is 4 miles south of Peterborough.

[DE&i]

Hi @Ossicle,

 

It would appear to be rather worn O.incenicus vertebra as suggested. Also Ophthalmosaurus monocharactus has been rejected as a junior subjective synonym of Ophthalmosaurus icenicus due to a lack of diagnostic characters and pathology of the specimen. 

 

You will find as I did that certain pieces of information from the book Fossils of the Oxford Clay could do with revising.

 

Perhaps even a second edition could be published in my honest opinion.

[Carl]

Vertebra is singular, vertebrae is plural. *bows*