Circular depressions in Kem Kem bone

[Aurelius]

I recently obtained some large, but pretty ugly chunks of bone from the Kem Kem formation. Given that they seem to have no identifiable features, I don't imagine they could be easily identified. However, one has these depressions visible on it, and I wondered whether anyone might know what they are?

 

 

Close up of the depressions.

 

 

This is the other side of the bone.

 

 

They don't look like teeth marks to by uneducated eyes, nor the borings that you typically see on marine rocks (which these aren't, of course). I'm also not convinced they can be the series of depressions that you sometimes see on crocodile bone, although I'm quite willing to be told I'm wrong.

If anyone has any suggestions, I'd be interested to hear them.

 

 

[Rockwood]

1 minute ago, Aurelius said:

If anyone has any suggestions, I'd be interested to hear them.

Weathering.

[Troodon]

Bone does not typically weather with depressions like that.   Are you sure it's bone and not geologic

[Aurelius]

4 minutes ago, Troodon said:

Bone does not typically weather with depression like that.   Are you sure it's bone and not geologic

 

I'm not sure of much, to be honest. But this (on the same block) looks like bone? 

 

Most of the block actually closely resembles the material of the shark vertebrae I see from Kem Kem (greenish, with flecks running through it), so perhaps it could be cartilage? Or just a bunch of rock that's become mixed up with random bits of bone and cartilage?

[Bone guy]

It resembles the dimples you see on a croc scute. 

[Miocene_Mason]

42 minutes ago, Bone guy said:

It resembles the dimples you see on a croc scute. 

I’m thinking the same thing, possible croc material.

[abyssunder]

Maybe not (only) erosion (weathering), but bioerosion might be the cause of the features in question.

First of all, it will be important to know the environment where it cames from, second, is relevant if it could be considered a lithic, xylic or osteic substrate.

 

" First, in their revision of records of bivalve borings in bone, Belaustegui et al. (2012) are well able to differentiate fresh from degraded or cemented bone substrate. They correctly agree that the bivalve-bored bones reported by Frey et al. (1975) and Tapanila et al. (2004) represent lithic substrates due to their taphonomic alteration at the time of perforation. It should be expected that in the future a brief taphonomic analysis of the strata yielding bored bone can clarify its condition and the environment at the time of attack as well. Secondly, xylic matter has a similar taphonomic fate: Its changes usually occur much earlier and are much more intense than in any other substrate of bioerosion, but no author has ever questioned the validity of wood as an ichnotaxobase in bioerosion, for good reason. Finally, it is hard to comprehend why Pirrone et al. (2014a) themselves refer to bone as a type of substrate in the title of their article, but dismiss it as a major ichnotaxobase in the text. We agree that bones only represent a special type of substrate, as long as their structure is not altered by cementation or other diagenetic processes. " (...)

" Boring is distinguished from biting and scraping by removal of substrate via interior action. In the hierarchy of ichnotaxobases in bioerosion, the formof a structure builds the next level below the principal substrate type. " (...)

" With the great importance of principal substrate types in ichnotaxonomy (Bertling et al., 2006) and with almost all bone bioeroders being restricted to this type of substrate (Table 1), their trace fossils should be identified by their own names. In other words, an ichnotaxon established for lithic or xylic substrates should not be used for bone, and vice versa. As a consequence, new ichnogenera for bone substrate are established: Osteichnus n. igen. for pouch-like borings of Asthenopodichnium-type, and Clavichnus for vertical clavate structures. " (...)

 

excerpts from S. Hopner & M. Bertling. 2017. Holes in Bones: Ichnotaxonomy of Bone Borings. Ichnos 0 (0): 1-24

 

[LordTrilobite]

I agree with either croc or weathering as possible explanations.

[Haravex]

For me this is croc pieces from the kem kem vary rarely weather away.