Claw? triassic

[Tooth or Dare]

Here is another of last months finds.  I set it aside because of the beautiful rugose texture on one side thinking I aught to be able to find something about bones with this unusual texture.  Now that I look at it again I'm wondering if it is a claw.  It is three sided....the rugose side which has a slight outward curve; the opposite side which is much smoother and flat; and the underside(?) which has a smooth very concave surface. Any opinions?

[Vieira]

Dont looks like a claw to me. I think maybe a fragment of turtle shell.

[Tooth or Dare]

Gee, I live in the desert so turtles are not the first thing to come to mind!  I looked them up and discovered there is a shelled turtle from the Chinle formation from the exact age, chinlechelys.  Unfortunately the shell thickness for chinlechelys is 1-3 mm maximum and this piece is 5 mm minimum.  While I am unconvinced of the claw ident. a new species of very early freshwater turtle would be a real stretch, although it would be way cooler than a claw. 

 

Any other ideas?

[jdp]

I wonder if this is a chunk of metoposaurid skull.

[pachy-pleuro-whatnot-odon]

5 hours ago, Vieira said:

Dont looks like a claw to me. I think maybe a fragment of turtle shell.

The texture on the top of the specimen seems consistent with turtle shell. I think what you've got here is an edge if the shell.

 

2 hours ago, jdp said:

I wonder if this is a chunk of metoposaurid skull.

It doesn't look like skull to me. If part of a skull, I'd expect the bone to be a process or part of the orbit, and neither seems to match here... Also, I'd expect both narrow ends of the bone to show signs of having broken. Not that the second narrow end is visible on any of the photographs, but the bone does seem to taper on one end... For an example of what I mean concerning marine crocodiles, see below:

 

In any case, definitely not a claw. A claw wouldn't have a concave side - one that,  moreover, has a break suggestive of continuation in that direction...

[Tooth or Dare]

I broke out the macro lens and took a couple more shots of the texture......definitely not typical metoposaur.....maybe jaw bone but where are the tooth sockets?  Unless it's the front toothless section of a aetosaur jaw say Desmatosuchus smalli....

 

Also a photo of the small pointed end...which appears worn and not broken.  The other end appears broken and a small piece is missing from the back edge...

[Tooth or Dare]

Also, what are those tiny pores all about?  Didn't see them before the closeups...

[pachy-pleuro-whatnot-odon]

9 hours ago, Tooth or Dare said:

Also, what are those tiny pores all about?  Didn't see them before the closeups...

I think those pores are just where the shell naturally wears thin or has worn down to reach some of the vascularisation of the inner bone. They seem too small for worm borings...

 

But exactly because one of the ends of the bone appears worn rather than broken, thus likely marking the bone's outline, and the bone can therefore only be determined to continue in two directions: one thicker, rounded end, and one that's thin and flat and part of a concavity in the bone. This to me suggests the edge of a turtle shell. To show what I mean, below are images of Late Cretaceous and Oligocene turtles housed in the Museum voor Natuurwetenschappen in Brussels (first two) and the Naturmuseum Senckenberg in Frankfurt respectively. First two specimens concern Allopleuron hofmanni, the other is a Glarichelys gwinneri. Note especially the edge of their shells. 

 

 

To illustrate that the texture on the bone sample discussed here is very much reminiscent of turtle carapace, here are some images from various vendors I plucked off of the internet:

 

 

However, as turtles only came about in the Late Triassic, what stage of the Triassic did you make your found in, @Tooth or Dare?

 

[Tooth or Dare]

Until some expert comes out and corrects my interpretation.....the fossil was found in a reddish brown bentonitic mudstone 1-3 meters below the eroded remnant of the Black Forrest bed of the Painted Desert member of the Chinle formation, so approximately 209-213 mya.

 

This corresponds with the only turtle fossils found in North America, chinlechelys, which had a very thin shell 1-3 mm compared to this fossil at 5 mm.

 

Unfortunately, if this is a fragment of turtle shell it is probably a float from the adjacent early cretaceous sandy conglomerate from which I have only found one poorly preserved cycad leaf impression.....and some stream worn agatized mississipian redwall limestone crinoids....

 

Because of the bentonite nature of the mudstone (when it dries out surface cracks form that can be 3-4 cm wide and up to 20 cm deep - they close up during the winter snows) and the slight slope of the site I consider everything in the top 30 centimeters to be float.....and it could be any age from Mississippian to Holocene......

This is why I considered it pointless to do any excavating for the last 12+ years.  Too much time on my hands and an inviting near vertical bank 1 1/2 m tall got me to try a test dig into the underlying undisturbed mudstone a couple months ago.   I discovered several teeth and a huge phytosaur vertebrae almost right away as soon as I got past the disturbed soil.   

 

Anyway, the chinlechelys specimen is about a three hour drive away in Albuquerque.  I'll try to get over there and check it out when the pandemic thing settles down.  Thanks for your help.

[jdp]

On 11/13/2020 at 12:22 PM, Tooth or Dare said:

Here is another of last months finds.  I set it aside because of the beautiful rugose texture on one side thinking I aught to be able to find something about bones with this unusual texture.  Now that I look at it again I'm wondering if it is a claw.  It is three sided....the rugose side which has a slight outward curve; the opposite side which is much smoother and flat; and the underside(?)

 

Just a note, this is the surface that I think represents the cortex of the bone and therefore is the sculpture that looks vaguely metoposaurid-y. The other surface is worn, probably prior to deposition, and preserves traces of the vascular system inside the bone. The groove on the edge of the bone is something you see on the edges of a lot of bones either where they wrap around other bones or where they wrap around other tissues.  I don't see any reason to think this is any sort of Triassic turtle, and the sculpturing doesn't look like any of the Triassic archosaurs I've seen. There are a few other temnospondyls this could conceivably come from, but I am pretty comfortable calling it temnospondyl.

[pachy-pleuro-whatnot-odon]

Although I agree the concavity in the bone could represent a place where the bone connected to other (bone) tissue - which is indeed not uncommon, with examples including rib bones, long bones and skull bones - I'm having a hard time matching the shape of this particular piece of bone up with anything I'm familiar with (predominantly Mesozoic marine reptiles). Likewise, I consider all sides of the bone to represent the original cortex - their preservation looks extremely similar - expect, of course, for the obviously broken edges, which I consider as post-depositional (dry-bone) damage that occurred prior to excavation (though maybe not prior to fossilisation). To consider the texture on one side of the bone vascularisation doesn't make sense to me, as 1) the pattern looks way less regular than I'd expect vascularisation to be, and 2) I think it would be very unlikely for just the once side of the bone to wear down without even affecting any of the other sides. 

 

Then again, I'm not as versed in Triassic material (yet), nor do I know the location. So I could be very wrong on this...

[Tooth or Dare]

18 minutes ago, jdp said:

and the sculpturing doesn't look like any of the Triassic archosaurs I've seen.

Exactly.....see the new photo of a koskinonodon interclavical and various osteoderms from koskinonodon and what is presumably an apachesaurus from the same location (only not float material)

 

And I can assure you it isn't a wear pattern....so far as I can determine the best match is the rugose pattern on some later crocodylomorph jaw bones.....when I first picked it up I said to it "Are you lost little guy?  You're not like any of these other bones!"

[pachy-pleuro-whatnot-odon]

On 11/14/2020 at 5:06 PM, Tooth or Dare said:

And I can assure you it isn't a wear pattern....so far as I can determine the best match is the rugose pattern on some later crocodylomorph jaw bones.....when I first picked it up I said to it "Are you lost little guy?  You're not like any of these other bones!"

It really does stand out amongst the bunch...! 

[Troodon]

Try email paleontologist W. Parker he's published on the Chinle Fm.  Might have an answer versus guessing.

 

 

FAUNAL REVIEW OF THE UPPER TRIASSIC CHINLE FORMATION OF ARIZONA
WILLIAM G. PARKER 
Division of Resource Management, Petrified Forest National Park
Box 2217, Petrified Forest, AZ 86028-2217,
William_Parker@nps.gov
 

[Tooth or Dare]

I have recently forwarded photos of some other finds to him.....I am waiting to hear back.  I'm going to add this one to the box I'm hoping to haul over there for his perusal.  Pandemic permitting.

[jdp]

On 11/14/2020 at 5:06 PM, Tooth or Dare said:

Exactly.....see the new photo of a koskinonodon interclavical and various osteoderms from koskinonodon and what is presumably an apachesaurus from the same location (only not float material)

 

And I can assure you it isn't a wear pattern....so far as I can determine the best match is the rugose pattern on some later crocodylomorph jaw bones.....when I first picked it up I said to it "Are you lost little guy?  You're not like any of these other bones!"

 

Again, the surface of the element is the one I highlighted, which does seem to have weakly-developed ridges similar to those seen in metoposaurids. The side you are emphasizing absolutely 100% is eroded down to the vascular beds within the bone.

[Pemphix]

15 hours ago, jdp said:

 

Just a note, this is the surface that I think represents the cortex of the bone and therefore is the sculpture that looks vaguely metoposaurid-y. The other surface is worn, probably prior to deposition, and preserves traces of the vascular system inside the bone. The groove on the edge of the bone is something you see on the edges of a lot of bones either where they wrap around other bones or where they wrap around other tissues.  I don't see any reason to think this is any sort of Triassic turtle, and the sculpturing doesn't look like any of the Triassic archosaurs I've seen. There are a few other temnospondyls this could conceivably come from, but I am pretty comfortable calling it temnospondyl.

I'm more in the Temnospondyl camp. I'm not very familiar with the triassic fossil-bearing sediments in US, but of those in Europe. If i would find such piece, i would say for sure it i not a piece of turtle but a Temnospondyl amphib fossil. BUT only, if the sediment is definitely triassic in age and no float from other material / age....

Troodon is right to ask the local specialist for suggestion here.

 

[Tooth or Dare]

I may have just solved the mystery.  It is probably a piece of a Placerias beak which is described as "turtle like" keratinous and has the same texture on the outside.  Yesterday I found a tusk....it fits in the groove.  I will let y'all know what the experts say.

[jdp]

It's not Placerias.