dfwphotoguy Posted September 23, 2009 Share Posted September 23, 2009 So this guy has puzzled me for about a year but I have never manned up and asked about it. So I tentatively am calling this a Shark Centrum but I dont feel 100% on that. The Centrum is supposed to be the thin cartilage membrane that goes in between the sharks vertebra. I also have flipped over sand dollar or something man made that comes to mind. Its incredibly delicate and I think I am lucky its made it this far! So guys and gals, what do you think? Location : Mineral Wells Texas road cut - Probably mid-late Pennsylvanian (maybe...?) Link to comment Share on other sites More sharing options...
tracer Posted September 23, 2009 Share Posted September 23, 2009 well, probably pennsylvanian, but shark vertebral column definitely didn't come to mind when i saw it. no reason to feel from looking at it that it was cartilaginous in original form. don't know, man. i'm interesting in seeing what others say about it. Link to comment Share on other sites More sharing options...
siteseer Posted September 23, 2009 Share Posted September 23, 2009 So this guy has puzzled me for about a year but I have never manned up and asked about it. So I tentatively am calling this a Shark Centrum but I dont feel 100% on that. The Centrum is supposed to be the thin cartilage membrane that goes in between the sharks vertebra. I also have flipped over sand dollar or something man made that comes to mind. A shark centrum is a vertebra. When complete, it looks more like a hockey puck with concave (instead of flat) surfaces. The centrum of the modern shark orders, all having appeared by the Early Cretaceous, is at least partly calcified in life so it can survive as a fossil but has rather uncommonly (the cartilaginous neural and hemal arches do not preserve, leaving a pair of holes on opposite sides of the flat "edge"). The hexanchiforms (the oldest order - sixgill and sevengill sharks) have very weakly calcified centra (sometimes they don't leave an image when x-rayed) while the more "advanced" orders have better-calcified centra. Sharks of the Paleozoic had fully-cartilaginous centra that have fossilized only after quick burial in fine sediment under low oxygen conditions that slowed decomposition. That object does resemble a partial centrum (the interior of one articular surface) but I would doubt one could be preserved like that (as a 3D object rather than a near 2D carbon film/remnant). Link to comment Share on other sites More sharing options...
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