Xiphactinus (or Protosphyraena) Fin?

[ShadyW]

Looking through my selection of bones from my most recent North Sulfur River trip, I noticed that this relatively large bone, which I had assumed was from some part of a Mosasaur shoulder, has a very odd surfacce texture, with rays or radiating grooves. That, and its odd shape with a long-radius smooth curvature, got me to thinking that it looks similar to some pictures online of various fish fins. In particular, it looks a lot like the Protosphyraena pectoral fin shown here, on the Oceans of Kansas page.

It's very difficult to get the texture to show clearly in the pictures, but you get a sense of it if you look at the full-scale images with and without flash.

What do y'all think? I know it's quite badly worn, but it really looks more like a fin than a Mosasaur bone to me, and it was found within 20 yards of my big fish vertebra (which may not be Xiphactinus after all) on the NSR.

[Xiphactinus]

Looking through my selection of bones from my most recent North Sulfur River trip, I noticed that this relatively large bone, which I had assumed was from some part of a Mosasaur shoulder, has a very odd surfacce texture, with rays or radiating grooves. That, and its odd shape with a long-radius smooth curvature, got me to thinking that it looks similar to some pictures online of various fish fins. In particular, it looks a lot like the Protosphyraena pectoral fin shown here, on the Oceans of Kansas page.

It's very difficult to get the texture to show clearly in the pictures, but you get a sense of it if you look at the full-scale images with and without flash.

What do y'all think? I know it's quite badly worn, but it really looks more like a fin than a Mosasaur bone to me, and it was found within 20 yards of my big fish vertebra (which may not be Xiphactinus after all) on the NSR.

Shady -

I don't think it's Protosphyraena. If you look at a Proto fin, it's comprised of many long rays that come from the "shoulder" of the fin and extend to the jagged "tooth" looking thing on the anterior edge. (see photo)

It could be a Xiphactinus fin ray, but it is a little hard to tell from the photo....