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List of Ways Fossils are Preserved


BobWill

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8 minutes ago, DPS Ammonite said:

The original organism’s hard part can be dissolved away leaving a void that is later filled by a void.

That´s a cast!

 

8 minutes ago, DPS Ammonite said:

The original hard part can also be replaced but by bit by silica where a large void is never created.

That´s replacement, point 7. However, no cells are involved in that case, only minerals.

 

7 minutes ago, DPS Ammonite said:

A cast can also be created when a material such as calcium carbonate of a shell recrystallizes into  larger crystals.

That´s recrystallization, point 8.

 

Franz Bernhard

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2 hours ago, Harry Pristis said:

Good grief!  A steinkern is NOT any kind of mold.  It is a cast.  A mold is empty; a cast is the filling.

Here is one reason why a steinkern is best defined as a mold. It acts as one. A steinkern is a mold because it is empty in the directions pointing away from the solid part. If a material is pressed against the steinkern (akin to filling the empty space) then a partial cast of the original shell is created.

 

We have to blame a minority of peer reviewed literature and some dictionary definitions that helped create confusion between casts and molds. I have seen dictionary definitions that said that casts and molds could be synonyms.
 

96762711-149A-4B45-8B16-9AC4B204EE2E.jpeg
 

Here is a similar example of a cast creation. A shell falls out of the sediment creating a mold. The mold is empty above the sediment. Material is pressed against the mold (filled) creating a partial cast of the shell. 
 

The big difference between the two sets of diagrams in the shape of the molds and resulting casts. In the first set of diagrams the mold is convex; in the second set the mold is concave. A cast is created by material pressing against a mold. The shape of the mold does not change the name of the material pressed against it. Pressing/filling a material against a cast does not create directly another cast.

8E966231-F2F1-4F4C-B45D-40A50F152DC1.jpeg
 

If you wanted a cast of a brachiopod would you expected to get a steinkern? It is confusing if you call the silicified shells of a brachiopod and the steinkern inside both as casts.

7997F1E8-8E09-4E0F-93DC-EDAECCEFFF64.jpeg

My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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3 hours ago, Harry Pristis said:

Good grief!  A steinkern is NOT any kind of mold.  It is a cast.  A mold is empty; a cast is the filling.

In paleontology as in sculpture, a cast is a copy of the original whether it's concave or convex and mold is the thing that can produce a cast.

I had this wrong and before and was corrected by someone on the forum.

See E and J on this diagram from Invertebrate Paleontoogy Twenhofel and Shrock

 

5e5061b01407d_internalandexternalcastsandmolds.thumb.jpg.ff0dc45acd890f1e07571be48470c817.jpg

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18 minutes ago, BobWill said:

In paleontology as in sculpture, a cast is a copy of the original whether it's concave or convex and mold is the thing that can produce a cast.

I had this wrong and before and was corrected by someone on the forum.

See E and J on this diagram from Invertebrate Paleontoogy Twenhofel and Shrock

 

5e5061b01407d_internalandexternalcastsandmolds.thumb.jpg.ff0dc45acd890f1e07571be48470c817.jpg

Here is another good diagram showing casts and molds.

 

http://paleo.cortland.edu/tutorial/Taphonomy%26Pres/preservation.htm

9DFE338B-CE6D-4CCF-AD49-8239D468525B.gif

64B018E7-C5CE-4A6D-8E3E-3680C82393E1.jpeg

My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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Finally.  I thought we sorted this out a couple of years ago.

 

The Cortland.edu diagram is mistaken. 

In the left-hand column, a void occurs (the first mold) and is filled creating the first cast. 

The first mold (e.g. a clamshell) that created the first cast dissolves away creating another void (the second mold). 

This second mold is filled creating the second cast (an external cast of the clamshell). 

Yet, in the upper left drawing, the second cast is correctly called a cast while the first cast (an internal cast of the clamshell) is incorrectly called an internal "mold."  

It's not an internal mold at all: it's still the first cast, an endocast of the interior of the clamshell.

 

BTW:  One might be tempted to argue that the second cast is also a mold; however, the internal cast (the steinkern) was already formed before the second cast was laid down.  Therefor, the second cast is not a mold for the steinkern.

 

Edited by Harry Pristis

http://pristis.wix.com/the-demijohn-page

 

What seest thou else

In the dark backward and abysm of time?

---Shakespeare, The Tempest

 

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1 hour ago, Harry Pristis said:

Finally.  I thought we sorted this out a couple of years ago.

 

The Cortland.edu diagram is mistaken. 

In the left-hand column, a void occurs (the first mold) and is filled creating the first cast. 

The first mold (e.g. a clamshell) that created the first cast dissolves away creating another void (the second mold). 

This second mold is filled creating the second cast (an external cast of the clamshell). 

Yet, in the upper left drawing, the second cast is correctly called a cast while the first cast (an internal cast of the clamshell) is incorrectly called an internal "mold."  

It's not an internal mold at all: it's still the first cast, an endocast of the interior of the clamshell.

 

BTW:  One might be tempted to argue that the second cast is also a mold; however, the internal cast (the steinkern) was already formed before the second cast was laid down.  Therefor, the second cast is not a mold for the steinkern.

 

We need to know what definitions you are using for cast and mold. Once we know that then we can deduce what a steinkern is.
 

Using this definition:

“a cast is a replica (not a mirror image) of hard parts of an organism such as a shell or skeleton.” This definition precludes the use of a cast to refer to a steinkern which is the filling of space (which was never hard) in an organism such as a clam.

 

Referring to your quote “The first mold (e.g. a clamshell)” a mold (you claim could be a clamshell) cannot directly create another mold (the sediment surrounding a clam). Similarly, a cast (such as a silicified clam) cannot directly produce another cast (your steinkern).

 

 

28BDF968-D598-4BEE-9A31-1D45C84D5FC4.jpeg

My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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31 minutes ago, Harry Pristis said:

 

I think we've exhausted our capacity to follow the logic of this subject.

Thanks Harry for the spirited and respectful debate even if we could not convince each other what we each thought was obvious.

My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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3 hours ago, Harry Pristis said:

Finally.  I thought we sorted this out a couple of years ago.

 

The Cortland.edu diagram is mistaken. 

In the left-hand column, a void occurs (the first mold) and is filled creating the first cast. 

The first mold (e.g. a clamshell) that created the first cast dissolves away creating another void (the second mold). 

This second mold is filled creating the second cast (an external cast of the clamshell). 

Yet, in the upper left drawing, the second cast is correctly called a cast while the first cast (an internal cast of the clamshell) is incorrectly called an internal "mold."  

It's not an internal mold at all: it's still the first cast, an endocast of the interior of the clamshell.

 

BTW:  One might be tempted to argue that the second cast is also a mold; however, the internal cast (the steinkern) was already formed before the second cast was laid down.  Therefor, the second cast is not a mold for the steinkern.

 

Endocast is another name for internal mold or steinkern, most often refering to a braincase but can be used for other things. If the terms internal or external are used instead of "endo" it is a mold. This is from Wikipedia page on endocasts:

"Endocast fossils from animals with shells that easily disintegrate or dissolve can often be encountered free from their mold fossil, like the aragonite shells of certain molluscs and the tests of sea urchins. A frequently occurring form is the internal mold of brachiopods and bivalves"

 

Are there no professors of paleontology on the forum who can settle this?

It just seems unlikely that three references can all be wrong.

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Here is one reason why there is so much confusion. A search of peer reviewed literature will reveal a minority of papers that call steinkerns interior casts. Dictionary definitions sometimes give reasonable definitions of cast and mold then go on to say that casts are sometimes called molds and molds sometimes called casts. Ouch!!! I guess that some dictionaries give incorrect usages of the terms if they were made by professionals. 
 

Here are some definitions found

in the Glossary of Geology by Bates and Jackson from 1987. 
 

Definition for mold. The first part “a” of the definition is good. Skip to part c, ouch!! They just called the mold a cast. 
7C31D4EB-7630-477D-B618-71C9BB8AE8CE.jpeg
 

Look at the definition for an internal mold. The first part is not so bad until you see that it can be defined as a cast of the interior. More confusion ensues.

DCC9E17F-8A19-4B6D-8095-C4A6B8E5B316.thumb.jpeg.9d7d06ed28fce38f836d462ec469f8bf.jpeg

 
55B38367-891C-42D1-9D72-11AB8A01EC05.jpeg
 

At least the definition of cast does not include calling it a mold.

A69437F2-213F-4A15-A7C2-9EE60A42373C.jpeg

 

Internal cast definition: “A syn. of steinkern. The term should not be used far an internal mold.” So, this dictionary calls a steinkern a cast. Yet, the definition above for an internal mold sure looks like they are describing a steinkern.

 

Note that the Cortland.edu says that an internal mold is sometimes called a steinkern. 

 

A dictionary needs to look at all the related definitions to see if they make logical sense with each other.

 

My goal is to leave no stone or fossil unturned.   

See my Arizona Paleontology Guide    link  The best single resource for Arizona paleontology anywhere.       

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54 minutes ago, BobWill said:

Are there no professors of paleontology on the forum who can settle this?

Lets stick to the definitions of casters/founders/sculpturists and everything is totally clear!

 

As already discussed, it is not easy for a caster/founder to obtain an internal mold of an original object without destroying the original object. Nature does that regularly.

 

Btw, what about the nice term "Prägesteinkern" :zzzzscratchchin:

@BobWill, @DPS Ammonite, @Harry Pristis. @Ludwigia

 

Franz Bernhard

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12 hours ago, BobWill said:

Endocast is another name for internal mold or steinkern, most often refering to a braincase but can be used for other things. If the terms internal or external are used instead of "endo" it is a mold. This is from Wikipedia page on endocasts:

"Endocast fossils from animals with shells that easily disintegrate or dissolve can often be encountered free from their mold fossil, like the aragonite shells of certain molluscs and the tests of sea urchins. A frequently occurring form is the internal mold of brachiopods and bivalves"

 

Are there no professors of paleontology on the forum who can settle this?

It just seems unlikely that three references can all be wrong.

 

Bob, you are confusing the readers when you insist that a cast is a mold.  You should check your Wikipedia quotation.  It says, "A frequently occurring form is the internal cast of brachiopods and bivalves."  There are hundreds and hundreds of definitions and examples of endocast, none of which call them an internal mold.  Mistakes in word usage creep into the scientific literature over time.  Many workers, whose first language is something else, publish in English.  Many workers, who have mastered the science, haven't mastered the language.  Examples are "scutes" for osteoderms and "fang" for tooth root.  Common sense allows us to take the appropriate meaning as we read the text.  But, we should not fall into the trap of defending the mis-used terms.

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http://pristis.wix.com/the-demijohn-page

 

What seest thou else

In the dark backward and abysm of time?

---Shakespeare, The Tempest

 

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12 hours ago, FranzBernhard said:

 

Lets stick to the definitions of casters/founders/sculpturists and everything is totally clear!

 

@BobWill, @DPS Ammonite, @Harry Pristis. @Ludwigia

 

Franz Bernhard

 

I will endorse this idea, having done some mold-making and casting in the past. 

 

Examples:

 

 

castcarnasials.jpg

castcarnivoreepoxy.jpg

castjaws.jpg

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http://pristis.wix.com/the-demijohn-page

 

What seest thou else

In the dark backward and abysm of time?

---Shakespeare, The Tempest

 

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2 hours ago, Harry Pristis said:

 

Bob, you are confusing the readers when you insist that a cast is a mold.  You should check your Wikipedia quotation.  It says, "A frequently occurring form is the internal cast of brachiopods and bivalves."  There are hundreds and hundreds of definitions and examples of endocast, none of which call them an internal mold.  Mistakes in word usage creep into the scientific literature over time.  Many workers, whose first language is something else, publish in English.  Many workers, who have mastered the science, haven't mastered the language.  Examples are "scutes" for osteoderms and "fang" for tooth root.  Common sense allows us to take the appropriate meaning as we read the text.  But, we should not fall into the trap of defending the mis-used terms.

I know it said "mold" yesterday because I copied and pasted it so someone changed it since then. Otherwise why would I have gone to the trouble? The only change I made was to make it bold. If mistakes creep in that would explain either interpretation as possibly wrong. If the appropriate meaning of cast is "a copy of the original" and the original is the inner surface, then a steinkern would be the mold that could produce that cast.

 

I've done mold and cast making since I was a kid but neither of us has ever had to reproduce the inside of something. That's what makes this confusing.

 

edit: a look at the history of the wikipedia page quote shows it was changed to 'internal cast" today, something anyone can do or undo. The point is that the original author wrote it the way I quoted it.

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I've been getting helpful advice for my list so here it is with some rearrangement, corrections and additions. I'm still looking for advice and dissent so feel free. Anyone is welcome to use to for educational purposes. It still fits on a single page using  font size 10.

 

               32  WAYS  FOSSILS  CAN  BE  FORMED

                                     DUPLICATION

1    Internal Mold  (minerals in contact with inner surface solidifiy then original dissolves)

2    External Mold  (sediment in contact with outer surface solidifies then original dissolves)

3    External Cast   (original outer surface dissolves and space fills with solidifying material)

4    Internal Cast    (original inner surface dissolves and space fills with solidifying material)

                                  MINERALIZATION

5    Permineralization    (space between cells fills with minerals that solidify)

6    Petrification    (space between cells fills with silica binding to cellulose)

                              CHEMICAL CHANGES

7    Replacement    (cells replaced with new minerals that solidify)

8    Recrystallization    (replacement when the new minerals are a crystal form)

9     Carbonization    (thin carbon film formed by chemical change)

10   Coalification    (carbonization occurring by much slower processes)

11   Hardened plant resin  (amber or cobalt)

                                                          DESICCATION

12    Remains preserved in a Peat Pit

13    Remains preserved in a Tar Pit

14    Remains preserved in Frozen Tundra

15    Remains preserved by Mummification

                                             ICHNOFOSSILS OR TRACE FOSSILS

16   Tracks (prints, tail dragging, claw marks)

17    Infilled burrows

18    Coprolotes or droppings

19    Feeding traces

20    Urolites or urine splatters

21    Regurgitants or vomit

22    Body rests

23    Gastroliths

24    Bite marks

25    Bio-sedimentological structures like stromatolites

26    Termite mounds

27    Banded Iron Formations  (periods of presence or absence of microbes such as cyanobacteria)

                                                            OTHERS

28   Adpression      (compression-impression)

29   Resin Inclusion   (Life trapped in resin which hardens into amber or copal)

30   Bioimmuration   (impression formed on a shell by growing over another life form)

31   Condensed Phosphorite Pseudo-Steinkerns  (bioimmuration replica cast in phosphorite)

32   Unaltered remains

 

 

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