Dugong rib with signs of predation

[wilsotc]

This is a dugong rib bone. It appears to have cuts slicing cleanly through growth rings before fossilization.

[Troodon]

Can you post additional photos using different angles and a straight in one 

[digit]

Predation marks on dugong ribs are rare but I've seen (photos of) some nice examples. The most definitive ones tend to have several scrapes/grooves spaced out more or less evenly corresponding with the tips of teeth from adjacent tooth positions. Your example may well be showing predation marks but IMHO it is more likely to just be a chip of the outer layers of bone flaking off. If you look in the image just to the right of the steep (right) edge of the missing piece you will see a surface crack extending further to the right before curving back up toward the top of the photo. It is quite common for these surface cracks to form and for flakes to peel off as these bones are tossed about in the river.

 

While I am not stating definitively that this IS NOT a predation mark, I am pointing out a more likely diagnosis to explain this missing bit. I've seen enough dugong rib bones to build a Lincoln-log style cabin out of them and have yet to see one with clear indications of the parallel grooves usually seen on bones demonstrating predation very obviously.

 

Novices (once, myself included) wonder about the circular pits often found on these bones and I've even inserted a few gator teeth to check the fit. These are, of course, the borings of piddock clams (pholadids) which burrow into rocks (and bones).

 

https://en.wikipedia.org/wiki/Pholadidae

 

 

Cheers.

 

-Ken

[GeschWhat]

My first impression was chip/flake as well.

[wilsotc]

Still think these are chips?

[Troodon]

Nothing jumps out saying predation.

[wilsotc]

Strangest cleaving stone I've ever seen.

[digit]

Yup. Consistent with flaking that I've seen in other rib bones.

 

Definite predation marks tend to be in the form of several parallel scratch lines (from adjacent teeth scraping on the bone). Really hard to be convinced that a single injury to the bone would have been from a shark with a mouth full of closely packed teeth. Seeing several grooves running parallel is very consistent with a bite from a toothy shark.

 

 

Cheers.

 

-Ken