predator/scavenger puncture marks ???? in an Oligocene tortoise carapace

[MarcoSr]

7 hours ago, doushantuo said:

"Haynes, G. 1983. A guide for differentiating mammalian carnivore taxa
responsible for gnaw damage to herbivore limb bones. Paleobiology,
9:164–172." might possibly help?

BTW: the Miocene lignites of Ahnikov*(Czech Republic)  contains a hefty amount of gnawed bones,and some new ichnotaxa have been erectd for the traces

*diacritics omitted

 

Jaguar-Panthera-onca-predation-of-marine-turtles-conflict-between-flagship-species-in-Tortuguero-Costa-Rica.pdf

Predation on the tent tortoise Psammobates tentorius a whodunit with the honey badger Mellivora capensis as prime suspect.pdf

Kahlkee2015_BadgerpredationonpondturtleemianinterglaciPalaebiodivndPalaeoenvironments.pdf

 

6 hours ago, doushantuo said:

dgfbull66-repturtcrocpredaMILAN211-218.pdf

 

 

Thank you for the PDF links.  The papers are very useful.

 

Marco Sr.

 

[MarcoSr]

I'm posting a few more pictures.  I just happened to look at the tortoise without much light on it and noticed two important things.  There is a crescent gouge below two of the circular marks (44mm spacing on centers).  It is really difficult to see this gouge in the light and in pictures with the flash so I took a low light picture without flash.  Looking at the low light picture, I also noticed two other marks/small gouges.  I took a coyote skull with 40mm canine spacing and lined up the canines which fit just between the two holes and the coyote's incisors lined up with the crescent gouge. Now I know there weren't any coyotes in the Oligocene but this helped me to realize that I may be seeing two canine holes and a gauge from the incisors of a predator/scavenger.  To top it off I also noticed in the low light picture, two other holes/small gouges (55mm spacing on centers but 45mm between the inner edges of the holes/small gouges) which I hadn't noticed before.  What I'm thinking now is that the predator/scavenger didn't try to grasp the tortoise with its upper teeth in the carapace and lower teeth in the plastron which would require a very large set of jaws that had to open very wide but instead tried to grasp the tortoise just across the high point of the carapace.

 

This is an original picture that I posted above where I added a blue ellipse around the gouge.  You can see that the gouge doesn't show up very well in the bright light.

 

 

 

 

Here is the new low light picture.  You can now see the gouge and the other set of marks/small gouges.  I've circled the two holes and gouge and the other two marks/small gouges with red ellipses so you can see them better.  In the next picture I added yellow ellipses directly around each of the 4 holes and the crescent gouge:

 

 

 

 

 

Edit: I added this dog bite mark picture for comparison to the above pictures:

 

 

 

 

 

 

@jpc @sharkdoctor @Troodon @Peat Burns @caterpillar @aplomado @Randyw @doushantuo  Do the new pictures change your opinions any?

 

 

Marco Sr.

[Randyw]

I’m still in the some type of predator tried to eat him camp myself...LOL!

[MarcoSr]

9 minutes ago, Randyw said:

I’m still in the some type of predator tried to eat him camp myself...LOL!

 

I was almost convinced of shell disease until I noticed these new holes and crescent gouge.

 

Marco Sr.

[turtlesteve]

So here are some thoughts.  I don’t know all that much about these tortoises but I’m maybe half qualified since I have spent many years with living ones:

 

1.  Despite the symmetry of the punctures, nothing with a jaw that size could have gotten its teeth into position.  The punctures are too close to the center of the shell.  Think about where the other jaw would have been, and the only thing that might work would be a very large crocodile.

 

2.  The tortoise was a fully grown adult male. The concave plastron is a give away.  This species (there are clearly multiple species in the formation) was likely adapted for burrowing.

 

I went back and looked through your other posts - really awesome tortoise!  I’d absolutely love to find a whole one sometime...

[caterpillar]

5 hours ago, turtlesteve said:

Despite the symmetry of the punctures, nothing with a jaw that size could have gotten its teeth into position.  The punctures are too close to the center of the shell.  Think about where the other jaw would have been, and the only thing that might work would be a very large crocodile.

 

I'm agree and I think it's disease

[Troodon]

I stand with my initial remarks that its would be pretty difficult for a predator with that small of a tooth spacing to get its mouth to the center of the shell.

[MarcoSr]

 

9 hours ago, turtlesteve said:

So here are some thoughts.  I don’t know all that much about these tortoises but I’m maybe half qualified since I have spent many years with living ones:

 

1.  Despite the symmetry of the punctures, nothing with a jaw that size could have gotten its teeth into position.  The punctures are too close to the center of the shell.  Think about where the other jaw would have been, and the only thing that might work would be a very large crocodile.

 

2.  The tortoise was a fully grown adult male. The concave plastron is a give away.  This species (there are clearly multiple species in the formation) was likely adapted for burrowing.

 

I went back and looked through your other posts - really awesome tortoise!  I’d absolutely love to find a whole one sometime...

 

4 hours ago, caterpillar said:

 

I'm agree and I think it's disease

 

7 minutes ago, Troodon said:

I stand with my initial remarks that its would be pretty difficult for a predator with that small of a tooth spacing to get its mouth to the center of the shell.

 

Thank you for looking at the new pictures.  I value your opinions.

 

The only thing that I would like to say again is that the predator/scavenger didn't try to grasp the tortoise with its upper teeth in the carapace and lower teeth in the plastron or edge of the carapace which would require a very large set of jaws that had to open very wide but instead tried to grasp the tortoise just across the high point of the middle of the carapace. Both upper and lower jaws bit into the carapace on either side of the somewhat higher center of the carapace.  The two holes plus the crescent gouge represent two canines and the incisors of one jaw and the other two holes represent the canines of the other jaw.  In the dog bite picture below the marks are from both the upper and lower jaws not just one jaw.  The  holes/gouge on the tortoise match this really well.

 

 

 

 

 

Marco Sr.

[caterpillar]

I understand your reasoning but it is not possible. An animal cannot bite a hard, round object like a turtle shell. The teeth will slide because the angle is not good. In the case of the bite of the dog on the arm, it is the skin which deforms and allows a good grip

[sharkdoctor]

 

Thanks for a fun conversation ! 

 

Intriguing data!. I wonder what you would get if you did a cast of the surface in question with a non-marring substance. As I recall, Dr Godfrey did a non-destructive negative of bite marks for his paper on a shark-bitten coprolite a few years ago. It might give you a different perspective and make the impressions a bit easier to study.

 

The new hypothesis would suggest that the pressure applied by the teeth would be applied at an oblique angle to the shell. It seems that would have resulting impacts on the shapes of the tooth impressions. 

[MarcoSr]

38 minutes ago, sharkdoctor said:

 

Thanks for a fun conversation ! 

 

Intriguing data!. I wonder what you would get if you did a cast of the surface in question with a non-marring substance. As I recall, Dr Godfrey did a non-destructive negative of bite marks for his paper on a shark-bitten coprolite a few years ago. It might give you a different perspective and make the impressions a bit easier to study.

 

The new hypothesis would suggest that the pressure applied by the teeth would be applied at an oblique angle to the shell. It seems that would have resulting impacts on the shapes of the tooth impressions. 

 

Aaron

 

I need to get my microscope to the carapace of the tortoise to look at the holes.  However, the big unknown is did the tortoise prep using mechanical tools and air abrasion distort the holes. 

 

If the turtle carapace was pock marked with holes, I could accept that some of the holes just randomly lined up to be suggestive of a bit mark/marks.  But I've counted only 15 holes total in the carapace which is very large.  The holes are not concentrated in any area which I would expect if they were a result of a shell disease but distributed across the whole carapace. There are four sets of two holes with 45mm ,45mm, 45mm, and 44mm center spacing.  What are the odds of 8 out of 15 just random disease holes doing that.  There are another set of two holes that go with the 44mm spaced holes that I highlighted in yellow above.  So I can tie10 of the 15 holes into possible bit marks from a single predator. Random disease holes just wouldn't line up like that.

 

Marco Sr.

[MarcoSr]

2 hours ago, caterpillar said:

I understand your reasoning but it is not possible. An animal cannot bite a hard, round object like a turtle shell. The teeth will slide because the angle is not good. In the case of the bite of the dog on the arm, it is the skin which deforms and allows a good grip

 

How the predator could have grasped the carapace which is only slightly domed also bothers me with my theory.  So I fully understand what you are saying.  I wouldn't expect the lower canine teeth to get enough grip to allow the upper jaw to bite down.  However, there is enough of a slope in the carapace that I can grip the center of the tortoise carapace where the holes are with my hand.  I think the reason that two of the holes, that I think are from the lower canines, are more like elliptical gouges than circular holes is that the lower canines slipped a little trying to get a firm grip before the upper jaw bit down.  I also think that is why there is a slight angular difference in what I think are the lower jaw and upper jaw canine holes.

 

Marco Sr.

[MarcoSr]

This is the last post that I will make in this thread unless replying to a new reply.  I don't want to turn this thread into a turtle egg thread which some TFF members will know right away what I mean by that.  I had broken my tripod so I couldn't get any new steady pictures.  I got a new tripod delivered yesterday (much better than my old ones which I kept breaking).  So I took a few more pictures of the carapace and started circling marks.  I found four sets of marks which I feel are from the upper and lower canines of a predator/scavenger.  I didn't stretch or fudge by even a millimeter or two any of the measurements.  They are as exact as I could measure.  The measurements for the four sets of marks between centers of the holes or small gouges are 1. 45mm 55mm 2. 45mm 55mm 3. 45mm 55mm and 4. 44mm 55mm (yellow set).  There were a lot more holes in the carapace than I could originally see and the pictures, especially the low light ones, help me to see them better.  I didn't try to find more four hole patterns because I feel four sets of holes with identical center spacing can't be the result of random shell disease.

 

 

 

 

 

Marco Sr.

[caterpillar]

Your reasoning is judicious but I continue to think that during a bite on a hard and curved surface like a turtle shell, the canines cannot make simple holes but a furrow because they slide along the bone. The angle of attack is too large.

There are lots of traces on this shell. There are other holes that you do not report. But for me, it has nothing to do with predation. it's my humble opinion

 

[MarcoSr]

 

20 hours ago, caterpillar said:

Your reasoning is judicious but I continue to think that during a bite on a hard and curved surface like a turtle shell, the canines cannot make simple holes but a furrow because they slide along the bone. The angle of attack is too large.

There are lots of traces on this shell. There are other holes that you do not report. But for me, it has nothing to do with predation. it's my humble opinion

 

I agree there are more marks than I originally thought.  The marks show up much better in the pictures than they do in normal light even looking closely at the carapace. 

 

I see the same problems that you note above.  I'm not saying that all the marks on the carapace are the result of predator/scavenger bite marks.  I fully agree that there are marks on this carapace that could be the result of shell disease.  There could also be bite marks from more than one predator/scavenger which would have different hole spacing between canine centers (I am seeing a possible different hole pattern in some of the other holes that you noted but I need to investigate it further).  Using one of the holes that you noted, I found another 4 hole pattern (white circles) with the identical 45mm 55mm spacing Edit: Using two more of your holes, I found a second 4 hole pattern (orange) with the identical 45mm 55mm spacing.  I need the lighting just right to be able to see these marks clearly enough on the tortoise to measure the hole center spacing accurately.  So now I'm up to six hole patterns with that spacing.  Can random holes from shell disease or other causes line up like this?  I know that very strange things can happen in nature.

 

 

 

 

 

Marco Sr.

[caterpillar]

14 hours ago, MarcoSr said:

I know that very strange things can happen in nature.

 

Yes, you're right and I think it's disease.

I suggest you make an earth molding of the shell. Just a rounded shape like the shell. You make a pseudo jaw with 2 pieces of wood articulated on an axis. Instead of canines, you plant nails respecting the angle of inclination of the teeth and you try to "bite" the earth ball. Knowing that in the earth ball, the nails will be planted, you compare the traces. On a hard earth ball, they will just scratch the surface.
Practice is better than theory

 

 

[MarcoSr]

1 hour ago, caterpillar said:

 

Yes, you're right and I think it's disease.

I suggest you make an earth molding of the shell. Just a rounded shape like the shell. You make a pseudo jaw with 2 pieces of wood articulated on an axis. Instead of canines, you plant nails respecting the angle of inclination of the teeth and you try to "bite" the earth ball. Knowing that in the earth ball, the nails will be planted, you compare the traces. On a hard earth ball, they will just scratch the surface.
Practice is better than theory

 

 

 

Looking at the tortoise in low light this morning, I found a sixth hole pattern (orange) of 45mm 55mm using two more of your marks.  Please see my previous post which I just edited.  I am not fudging or making these dimensions fit the 45mm 55mm dimensions.  I'm myself very surprised by this.  If I wasn't making the measurements, I might not believe them myself.

 

I think building a model is a good idea if you can simulate the canines and where the jaw hinges properly.  However, using a straight nail won't allow me to try to fit the model teeth accurately into the holes.  Somehow the actual length of the canines has to be replicated (that will be different for upper and lower canines) as well as any curve and side slant (that will be different in the upper and lower canines).  Also the two parts of the model have to hinge at the right place to match where the jaw hinged.  I'll try to get at some point my older son to bring some of his predator skulls/jaws from our ranch to my house so we can try them on the carapace.

 

I have a coyote skull from my property (unfortunately it is missing the lower jaw) that has 40mm center spacing between the tips of the canines.  I just placed this skull at a reasonable angle pointing down every place where the hole spacing is 45mm (the coyote canines fit just between both holes).  Since there are only two of the canines there wasn't any problem making firm contact. Note that because of the size of this carapace it is sloping rather than an "earth ball".  For the yellow indicated holes the coyote incisors lined up with the yellow circled grove.  Envisioning a lower jaw, it looked like the lower canines would also have no problem making firm contact.  What I don't know is what the angles of the canine's tips would be at the carapace surface.  The coyote upper canines curve backwards.  So with the coyote skull angled like it would have to be to make the bite, the tips of the upper canines weren't at a large angle at all to the carapace surface as I originally expected.  So if the predator/scavenger had similar curved canines, I just don't see a problem with the teeth gripping and biting at a reasonable angle to the carapace surface.

 

Edit: I added a picture below showing the slope of the carapace.  The ruler is across the carapace where the yellow circled marks are.  I don't know if fossilization raised up the center or changed this any.

 

 

 

 

Marco Sr.

Edited July 11, 2020 by MarcoSr
added picture of sloping carapace

[caterpillar]

It is a good idea to do a test with a real actual skull and its mandible. We will see if the holes can match.
I'm waiting for the test