Turtle shell stain question and another unknown bone fragment

[Plantguy]

Hey gang. So a couple more odd questions for you. 

 

I stopped by a dirt pile on the way home after work earlier this week and found some vertebrate bits including some turtle, horse teeth, ivory, dugong bone,etc. I found two larger flat shapes (bottom middle 2 specimens in the 1st picture) that intrigued me the most that were covered in clay so I brought them home---both I thought were large turtle shell plates. 

The first one I could see definitely see a grainy turtle shell texture of the larger types that I've already run across as well as the various boney layers within the shell but when cleaned up I noticed this black orbicular staining on just the one side and Im wondering if you all have seen that and know if it might be caused by something within the actual turtle shell...disease/fungus, etc or is it just a random mineral stain? 

The 2nd specimen I again thought was a large piece of turtle shell.  Again when I cleaned it up I first noticed the textured flat side but there is a canal/vessel of some sort going thru the entire midsection of the fragment and then upon further rinsing I noticed two crescent shapes reminiscent of tooth root cavities on the top of the fragment. I went from thinking turtle shell and then seeing no laminations in the bone to wondering if it was some sacral element and now I'm wondering if those crescent shapes might indicate something crazy like a piece of sloth mandible. Someone please set me straight. 

Appreciate any opinions. 

 

Forgot to add scale and show the position of the canal/opening. It appears that the canal/vessel runs right between and beneath the two outer crescent shapes (the arrows in the photo indicate its location) and the top of it is very thin/narrow and has been broken/collapsed-the area which I have also circled in red. If it had not been broken in that area I think all you would see in the top view is just the two crescent shapes. 

 

Hoping there is enough detail to suggest what critter this came from. Thanks.

 

Regards, Chris 

 

 

Edited July 1, 2017 by Plantguy
Forgot to add scale and additional shots

[GeschWhat]

[abyssunder]

Nice finds, Chris!

The big plate is indeed intriguing with its black orbicular staining on just one side.
The color and the shape of the spots remind me of manganese dendrites. With their variable shape and size these dendrites usually form on rock surfaces or discontinuity planes, but they could be present also on fossil bones. (I just checked one of my fossil bones and the black mineral stainings are there, but almost on the entire bone surface, not only on one side).

 

I remember J. F. Thackeray's interesting hypothesis related to the manganese stainings on the fossil bones of Homo naledi from the Dinaledi Chamber/ Rising Star cave complex, in which he proposed that lichens produced mineral staining on the skeletal remains of H. naledi .

 

" Dirks et al.1 state that ‘some bones and teeth are dotted with black iron-manganese oxy-hydroxide deposits and coatings’. The question arises as to what factors contributed to the ‘dotted’ or spotty distribution of manganese oxy-hydroxide on bone surfaces. Abiotic geological factors may account for continuous (matted) deposition of manganese oxy-hydroxide coatings in some cases, but why should these be dotted or spotted in the instance of many bones from the Dinaledi Chamber – or from other nearby sites, such as Sterkfontein? To try to answer this question, it is appropriate to refer to observations by Thackeray et al.4 in which we noted, firstly, that in the Cradle of Humankind, lichen can grow on certain substrates (including bone or rock) with a dotted or spotted distribution. Secondly, the spotted distribution of lichen is sometimes associated with dotted distributions of manganese oxy-hydroxide on the same surfaces.4 The source of manganese would include dolomite and chert, 2 billion years old, relating to the shallow saline sea that existed at that time.
Lichen are symbionts5 that include a fungus (a mycobiont) and a photosynthetic partner (a photobiont). This partner could be a cyanobacterium or a green alga. The growth of the symbiont results in a lichen body called a thallus. On substrates such as chert or bone, under suitable micro-environments the spottiness of lichen may relate to the dispersal of fungal spores. An example of lichen growth is shown on chert at Kromdraai in the Cradle of Humankind (Figure 1). In this case, small thalli of lichen – possibly Rhizocarpon – grow adjacent to older central thalli in which the lichens form continuous mats. The size of lichen thalli generally decreases outwards from the central thalli. Very small spots at the edge of lichen growth are relatively young growths of lichen." - link

 

P. S. Randolph-Quinney et al. reject Thackeray’s hypothesis that lichens deposited mineral staining upon the surface of these skeletal remains.

 

" Briefly, we review Thackeray’s1 chain of inference: (1) lichens can be found today growing as colonies on the surface of chert, dolomite and sub-aerially exposed bones found within the Cradle of Humankind; (2) some colonies of lichen on extant rocks overlie deposits of black manganese oxy-hydroxide on the rock surfaces; (3) some manganese (Mn) mineral deposits appear as diffuse spots, which have some resemblance to the shape and surface patterning of some lichen colonies; (4) small dots or spots of Mn present on the surface of the bones of H. naledi may, therefore, have been produced as a consequence of lichen growth; (5) the growth of lichen colonies requires light, either in the open environment or within the light zone of caves; (6) by extension, the growth of lichen on the bones of H. naledi required the presence of subdued, but essential lighting; (7) the presence of such lighting indicates the existence of a second entrance into the Dinaledi Chamber; therefore (8) a re-assessment of the deliberate body disposal hypothesis is required.
We must state from the outset that we have no disagreement with conditions (1) to (3) above, which comport with our own first-hand observations from geological outcrops within the Cradle of Humankind. Lichens do indeed grow on chert, dolomite and bone; they do sometimes overlie Mn deposits; and there is often a diffuse spot pattern in their surface distribution. But available evidence is not consistent with the rest of this line of reasoning. We here combine previously published taphonomic and geological data from the Dinaledi Chamber2, together with a fuller review of the literature and re-interpretation of photographic evidence presented by Thackeray1.

Abundant actualistic research documents mechanisms of Mn deposition on bone that have nothing to do with lichens.3 Mn and iron (Fe) deposition on bone in dark, wet, alkaline cave contexts like that found in the Dinaledi Chamber is normally a result of diagenetic recrystallisation of bone, incorporating trace elements from surrounding sediment and water via a diffusion–absorption process.4 In dolomitic caves, which have relatively high pH and oxidising redox, the alkali metals sodium and potassium and the alkaline earth metals calcium and magnesium are the most abundant soluble cations, while the transition metals copper, Fe and Mn are the least abundant, and the alkaline earth metals strontium and barium, and the transition metal zinc are of intermediate availability.5 Under these cave conditions, the stable forms of Fe and of Mn are hydrates and manganese oxide compounds, respectively. Precipitation of these highly insoluble hydrates and oxides varies with pH and tends to form crusts and coatings.6 Mn is mainly located on the surface and crack edges of fossil bones, whereas Fe shows deeper penetration into the bone matrix.7,8 Mn, which naturally occurs in groundwater, enters the bone environment as mobile Mn2+. In the presence of free O2, the oxidation of Mn2+ to Mn3+ and ultimately to insoluble Mn4+ is thermodynamically favourable, but proceeds extremely slowly unless mediated by microbial action, which is chemotrophic and does not require light.9,10 Oxidised Mn precipitates as a number of manganese oxides and hydroxides.11 Similarly, under the same conditions, mobile ferrous iron (Fe2+) approaching the bone may be oxidised to ferric iron (Fe3+) which rapidly precipitates as limonite (FeOOH.nH2O), which later usually undergoes transformation to goethite (FeOOH). Alternatively, pyrite (FeS2) is formed instead of haematite via precipitation of iron sulfide as decaying collagen releases sulfide ions into solution.12 Black or dark brown colour of fossil bones is a result of high levels of pyrite and manganese and iron oxide and hydroxide coatings. To summarise, processes that do not involve lichens are sufficient to explain the presence of Mn stains on fossil bone in contexts like that found within the Dinaledi Chamber today.
Mn, Fe and other mineral deposition occurs on a large fraction of the skeletal material from the Dinaledi Chamber in a variety of depositional forms. Thackeray1 chose to illustrate the pattern of Mn staining (specifically spotting) on only a single specimen. In his Figure 6 he provides a photograph of tibial specimen U.W. 101-996 (his figure caption misidentifies this specimen as U.W. 101-1070) with the figure legend: " - link

 

 

 

I do believe that the first specimen in question has manganese staining on one side, but I don't know who or what is responsible in creating that.

Question: Was the surface with the staining exposed to light in the position of the find, or the other side, or was the specimen entirely embedded  in sediment? If the latter, in which position was it found?

 

 

 

 

 

 

[Plantguy]

30 minutes ago, abyssunder said:

Nice finds, Chris!

The big plate is indeed intriguing with its black orbicular staining on just one side.
The color and the shape of the spots remind me of manganese dendrites. With their variable shape and size these dendrites usually form on rock surfaces or discontinuity planes, but they could be present also on fossil bones. (I just checked one of my fossil bones and the black mineral stainings are there, but almost on the entire bone surface, not only on one side).

 

I do believe that the first specimen in question has manganese staining on one side, but I don't know who or what is responsible in creating that.

Question: Was the surface with the staining exposed to light in the position of the find, or the other side, or was the specimen entirely embedded  in sediment? If the latter, in which position was it found?

 

 

 

 

 

 

Thanks Lori for the info. I was just online looking around for info on the web for additional ideas for the other boney fragment and another small dugong element I have. So as far the best far out idea I can come up with is the canal visible in the 2nd specimen is an infraorbital foramen found just above a tooth socket in some large critter. Thats absolutely just a wild guess and so as to not embarass myself further I should really not even throw that out! I'll have to bug Dr. Hulburt and see if there is enough there to offer any ID at all unless someone else comes up with something more. 

 

Good info on the stain. I agree with you and as for its origin maybe Dr. Hulburt has some thoughts on this as well. It appears to only be on the interior portion of the shell and here's a shot of how it was found.

It was literally found stained side down in a small gully in the dirt pile and unfortunately I have no idea of where it was removed from as are so many of the fossils from Florida---surface and/or creek/river finds. Once in awhile you'll find something in place that hasnt been dugup or reworked somehow. The pile was created in the last several months. Maps of the area suggest it may be derived from the Peace River Formation but that cant be confirmed. 

 

Thanks again! 

 

Regards, Chris  

 

[darrow]

I believe the "turtle shell" is actually a proboscidean skull fragment, part of the cranium.  The "canal/vessel" being the path of cranial arteries on the surface of the brain.

I have a piece below that looks similar to yours...

Darrow

[Plantguy]

On 7/1/2017 at 10:29 PM, darrow said:

I believe the "turtle shell" is actually a proboscidean skull fragment, part of the cranium.  The "canal/vessel" being the path of cranial arteries on the surface of the brain.

I have a piece below that looks similar to yours...

Darrow

Hey Darrow, thanks for the reply. Yours is similar isnt it. 

 

Dr.Hulbert here in Florida took a look at the photos of my finds this week. The staining is indeed on part of a tortoise shell but he didnt know why the manganese stain made that particular pattern. I was afraid I was chasing another of my unanswerable questions and he confirmed it. As for the 2nd specimen with the cavities its too incomplete to be sure but he thought it might be part of a mammoth skull. 

 

So, I now have 2 more pieces for my ever growing unknown/not known fragment bucket. Darn it! The curiosity is killing me. LOL. 

 

Continued hunting success! 

 

Regards, Chris