jamesp
Cave Dweller 
Member since October 2012
Posts: 36,607
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Post by jamesp on Jul 18, 2014 7:30:10 GMT -5
The link you supply is mis-naming the pieces he has. Those are not scutes. They are bones.  The three lines on this hypoplastron bone are the edges of the scutes layerd on the outside of the turtle. Here are the names for the bones of a tortoise. I guess your long narrow narrow wedge shaped piece is the marginal plate.  I found out why they use the term scutes in the fossil world. Simply to avoid controversy. For instance scutes are defined as scales that move with the ribs. So they argue that turtles scutes are not scutes because they don't move with the ribs. Or alligators have osteoscutes, or are they corneoscutes, or are they osteoderms. The structures on a dinosaur cause argument too. "Hence, ankylosaur scutes and spikes, stegosaur plates, spikes, and ossicles, crocodylian scutes, the ossicles of several lizards, etc., are all osteoderms. Of course, things like turtle carapaces are problematic because they do seem to articulate with the ribs, but as Michael noted, they’re problematic anyway!" Read more archosaurmusings.wordpress.com/2011/05/08/scutes-and-osteoderms/The word scutes is used as a catch all and simply follows the simple Webster definition. It may not go over well on a snake forum but is acceptable for the fossil world. |
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Joe
spending too much on rocks
Member since July 2014
Posts: 274 
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Post by Joe on Aug 11, 2014 14:22:55 GMT -5
Wow that is huge for a turtle!!! Great information in this thread of the difference between a turtle and tortoise. Me and a fellow member have been finding quite a few chunks of what I can now confirm as fossilized tortoise shell. We have located two different locations to them both different from the other in color. Very neat, thanks!  |
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,607
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Post by jamesp on Aug 11, 2014 15:09:38 GMT -5
Wow that is huge for a turtle!!! Great information in this thread of the difference between a turtle and tortoise. Me and a fellow member have been finding quite a few chunks of what I can now confirm as fossilized tortoise shell. We have located two different locations to them both different from the other in color. Very neat, thanks! I sawed one of these marginal bones to see the marrow configuration. The marrow is placed in a logical position to be a turtle shell. Please post your finds.  |
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Joe
spending too much on rocks
Member since July 2014
Posts: 274
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Post by Joe on Aug 11, 2014 15:51:17 GMT -5
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,607
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Post by jamesp on Aug 11, 2014 19:36:39 GMT -5
Wow that is huge for a turtle!!! Great information in this thread of the difference between a turtle and tortoise. Me and a fellow member have been finding quite a few chunks of what I can now confirm as fossilized tortoise shell. We have located two different locations to them both different from the other in color. Very neat, thanks! What part of the country did you find those Joe ? |
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Joe
spending too much on rocks
Member since July 2014
Posts: 274
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Post by Joe on Aug 11, 2014 20:53:04 GMT -5
Wow that is huge for a turtle!!! Great information in this thread of the difference between a turtle and tortoise. Me and a fellow member have been finding quite a few chunks of what I can now confirm as fossilized tortoise shell. We have located two different locations to them both different from the other in color. Very neat, thanks! What part of the country did you find those Joe ? Up here in southwestern Wyoming. |
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,607
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Post by jamesp on Aug 12, 2014 7:48:25 GMT -5
Ice age mammal bones are there in Wyoming, cool. The land tortoise was a 600 pounder, similar to the Galapagos tortoise. You can
search 'turtle scutes' and see may turtle bones/shell parts on 'for sale' sites to see the variations.
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Post by Peruano on Aug 12, 2014 16:00:21 GMT -5
Guys, Giant land turtles (tortoises) were fairly widely distributed until man came along and temperatures cooled. As you can imagine, giant tortoises were easy prey for paleoman and were likely exterminated as humans dispersed through North America. Another factor was temperature. Tortoises are vegetarians and depend on protozoans and microbes to digest the "hay" that they eat. If temps are too cool, the digesters don't work and you form sour kraut and gas ( a lethal combination).
Joe, The fossils that are different colors are a result of the mineraliza tion process and not necessarily the color of the turtle. However, I did participate in the description of a fossil turtle in which we thought we could see the color patter (not necessarily the original color) -- it had spots.
In a loose sense, the word scutes is the equivalent of scales. The scutes of turtles are not bone (they are keratinized material covering the boney carapace (shell). The osteoderms or boney scutes of crocodilians are scales but they are formed in part of bone. Alligators and crocodiles have some scutes that are strictly keratinzed and some that have internal structure of bone. If they are close together they can form a hard protective cover much like a carapace (shell ) of a turtle. BTW the shell of the tortoise is a combination of 'dermal" bone and the ribs (all fuse together as the turtle matures). Yes the vertebral column and ribs fuse into one solid mass, but they are further fortified when they are fused together distally by dermal bone (marginals, plastral plates, etc.).
In short life is not simple.
Here's an enigma for you. Imagine the evolutionary process of the scapula of a turtle moving inside the rib cage whereas it is outside the rib cage in amphibians and other vertebrate groups (birds and mammals). The intermediate stage is mind bogling.
I'm not going to guess off the top of my head what age the turtle material from Wyoming is, but it would not be hard to find out from the scientific literature (OK, I will guess and say its Miocene or Pliocene) - Just check to see what major fossil faunas have been described from there.
Turtle bone if fairly spongy. There are lots of spaces in the bone that store fat, and or blood cell producing cells. As the turtle grows the spongy part expands and the hardest, most solidly calicified bone continues to occupy the periphery of the bone.
Thats my turtle lecture for today. Forgive me if it went past the bell. Tom
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,607
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Post by jamesp on Aug 12, 2014 17:45:55 GMT -5
I think my friend found a dermal bone. It was close to the marginals that I found. It was flat and about 8" X 8". May have been part of the pubis bone.
Need to keep poking around in that 10 foot circle, as we rarely find mineralized bones at this location. Turtles are a unique creature.
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