Fossilized bones found on river bank

[Loxodonta45]

Would love to gain some insight on these bones I recently found on an exposed river bank (east Texas) after a few weeks of heavy rain. Note: Vertebrae specimen measures approx 3x3.5 inches. 

 

Also wondering how ya'll differentiate between fossilized bone and modern bone specimens? Can modern bones change in appearance/feel and be confused with fossilized bone due to exposure to various elements? Thank you!

[Lone Hunter]

Im horrible with bones but, bison axis maybe?  Think the last ones are turtle.  As far as your question about differences in bones it can be hard to tell sometimes, modern bones can appear to be fossils sometimes and not all fossil bones completely mineralize.   Someone else can probably explain better You can try the burn test, hold a flame to an end of bone for several seconds and see if there is any bad smell which would mean it's more than likely not fossil.

Edited February 27 by Lone Hunter

[CDiggs]

First one looks to be a bovid cervical (neck) vertebra, I agree bison is definitely a possibility but I think this is a little further back than the axis. As Lone Hunter explained a flame test may help determine if it's more recent. Also keep an eye on the weight as they dry out, modern bones can feel quite heavy and look mineralized when waterlogged only to dry out and be relatively lightweight. The middle two don't look super identifiable as there's enough damage/erosion to remove many of the features that would be diagnostic. The bottom two I agree are turtle shell, specifically they appear to be parts of the plastron or the bottom part of the shell.