Strange bone pattern

[cck]

I found this shard of bone on the York River  in the Yorktown formation, and the pattern on one side is curious. I’m wondering if anyone has seen this, or if it’s a diagnostic texture? Thanks for any help! 

[cck]

[cck]

[cck]

This is a Pliocene marine environment by the way

[caldigger]

I think you have something us yanks call turtle carapace.

[cck]

I might think so too, but if you look at the end shot, the bone structure is wrong for turtle... it seems this is the inside of the bone that has the texture...

[cck]

Maybe something to do with baleen? Just a thought...

[cck]

A few more pics with hopes that @boesse might chime in...

[cck]