Jump to content
Ainokc

Difference Between "fossilized" And "petrified"...and Other Stuff.....

Recommended Posts

Ainokc

Where to start.....?

Okay, so I have done some research the last few days but I still can't quite get my head wrapped around this. First: what is the difference between something that has fossilized, and something that has petrified??? There is an actual difference, correct? I have to admit that i am rather confused...

The reason I originally began to try to figure this out was in attempt to understand questions regarding bison skulls collected by my dad over the years from Beaver Creek in Jefferson Co, Ok. The very first skull he ever found was many years ago...20 or more...and it is BEAUTIFUL! Completely turned to stone and extremely heavy. It isnt a complete skull, as you can see in the first picture, but truly fantastic in my eyes. Several years later during a time of extreme drought, that creek dried up almost completely for the better part of 10 miles between Waurika and Ryan. That summer while he worried about the regular things farmers and ranchers worry about when the grass dies and the ponds dry up, and you can't get your fields plowed and prepared for planting, he spent DAYS walking up and down that 10 mile stretch of creek looking for more bison skulls. By the end of that summer, he had managed to collect a total of 4 or 5 including the original one i spoke of that spurred me to create this post. Of those he found that summer, he has a favorite. That skull would be the one in the second photograph. While this particular skull is more intact than the first (contains at least the majority of the maxilla including teeth), it nowhere near compares to the first in terms of weight and durability. One would have a difficult time breaking off a piece of the first one, Not so at all with the second. In fact, I don't even want to touch it.

Lacking much knowledge and ANY understanding in the processes involved and going entirely on common sense, one might assume that the first skull must be MUCH older than the others, though I am reasonably certain due to what I have read so far that this might not be considered a safe assumption. So based on the fact that all (4 or 5) skulls were found on the same creek within an approximate 10 mile stretch. And of that total, 1 has an entirely altered physical/chemical/geological(?) structure while the others are essentially "preserved bones". What would be an educated explanation of why this one particular skull is so different? Is is older? How long would it take to turn something organic into something inorganic? If it isn't older then why/how is it so different? And anything else you feel like sharing on the subject I would be very eager to hear.

I decided to make two separate posts, so the "and other stuff" will be added shortly, proceeded by "part 2. So thanks ahead of time for your comments and time taken, to help me understand this matter. I have read quite a bit trying to figure it out on my own, but I simply lack the grasp of a fundamental understanding of the sciences involved.

Angie

On second thought, I'm gonna have to wait a bit on part 2. As i began the post i realized that due to having paid so little attention due to time restraints on my weekend trip, I don't have all of my facts straight and as a result the post would have been too ambiguous. The subject is related to an old newspaper article that i had not seen before, dating back a bit. (Though how much of a bit happens to be one of the areas of ambiguity i mentioned, and that alone made me stop.) Anyhow, the article is in my dads office and i just asked my sister to snap a close up and text it to me as soon as she gets a chance, so i will get back to that post when she gets me the picture.

post-9527-0-11741700-1348432190_thumb.jpg

post-9527-0-37263400-1348432218_thumb.jpg

Edited by Ainokc

Share this post


Link to post
Share on other sites
Auspex

Petrifaction (literally, "turned to stone", where the original material is replaced with mineral while preserving the original structure) is a form of fossilization; "fossilized" is just a much broader category. With bones, if the conditions are right, the first step is the loss of the collagen (proteins); this can leave a comparatively fragile, "weathered" bone. If the bone is resting in a mineral-rich environment, its porous natural mineral structure may become permeated with soluble minerals; "permineralized". This is heavier and (usually) tougher than weathered bone. For it to become truly "petrified", the bone's original minerals would slowly be replaced (often cell-by-cell) with inorganic minerals from the environment.

This is the short version; there are many circumstances where the lines get blurry.

Share this post


Link to post
Share on other sites
Ainokc

Okay, so "permineralized" isn't necessarily the same as "petrified"? Is that correct so far?

Headed back to google.....

Thx Auspex!

What I read so far that might have summed up at least part of my question. Would it be a fair assumption that the first skull may have been completely immersed in water (aka the creek), immediately from death and deeply enough to remain immersed for a long time? While perhaps the others were perhaps exposed or partially exposed throughout the years?

Edited by Ainokc

Share this post


Link to post
Share on other sites
Auspex

Rapid burial is the first prerequisite for fossilization; keeps the scavengers from recycling it. Immersion is no substitute for burial, but it is a route to getting there.

Share this post


Link to post
Share on other sites
Ainokc

Okay, I understand most of what you've said so far. For the sake of (my) clarity though, help summarize please.... The first skull is "permineralized" and not "petrified", and based the information at hand which is minimal, one could not conclude any timeline or age of these specimens. In fact, the softer skull could just as easily be much older than the harder one?

Share this post


Link to post
Share on other sites
Auspex

Correct! Making assumptions as to age, based solely on state of preservation, is tempting but hazardous; there are many variable factors, many of which are not dependent on a fixed chronology. Even radiometric dating has a 'fudge factor'.

Share this post


Link to post
Share on other sites
Boesse

Generally speaking there isn't really a distinction between petrified and fossilized. Petrification is sort of a Victorian-era garbage can word for fossilization. Fossilization doesn't connotate anything specific other than being biological elements being incorporated into the rock record.

There are many ways in which a bone can be preserved - in "rocks" that are young enough, there may be no changes aside from the complete loss of collagen (holocene zooarchaeological material, for example). Most of the time, bones have undergone some degree of remineralization - the original apatite mineral of the bone changes into different 'species' of phosphate minerals, often due to substitution of dissolved chemicals in groundwater. Often times, bones can be phosphatized - additional phosphate will form in addition to phosphatic recrystallization of the bone. Various phosphatic remineralization styles are the most common ways bones fossilize. Bones can also (rarely) be silicified, where silica dissolved in groundwater will precipitate in bone pores.

That all being said, this doesn't mean that you can tell the age of a fossil (or even the environment it was deposited in) from its mineral content (or similarly, its weight): these modes of fossilization are mostly contingent upon groundwater chemistry after deposition.

Share this post


Link to post
Share on other sites
Harry Pristis

Another iteration of Bobby's explanation is this:

"Fossilized" (along with "petrified") is a near meaningless term. The term is often substituted for "mineralized" in describing a bone or tooth. But, fossilized doesn't always equate to mineralized because many fossils are not reinforced or replaced by minerals.

Bone is primarily composed of hydroxyapatite and collagen. Hydroxyapatite is an inorganic compound of calcium, phosphate, and hydroxide which is organized in a crystal latticework that gives bone (and teeth) structural rigidity. It preserves well as a fossil under some conditions.

Collagen is a fiberous protein that serves as connective tissue in bones and muscles. It does not preserve well in a fossil. As collagen decomposes, it may be replaced in the hydroxyapatite latticework by minerals from the depositional environment (e.g. silica dioxide dissolved in groundwater).

If bone (the hydroxyapatite structure) is reinforced with exogenous minerals, it is said to be "mineralized." If the bone components (including the hydroxyapatite) are entirely replaced by exogenous minerals such as silica, it is said to be "replaced by -".

A 'burn test' or 'match test' will usually indicate only whether there is collagen remaining in a bone -- scorched collagen has an awful smell. Teeth - dentin and enamel - contain hydroxyapatite, but don't contain collagen, so the 'burn test' on a tooth would be a waste of time.

Share this post


Link to post
Share on other sites
Ainokc

Thanks guys! I will pass this along to my dad. Well, I will tell him that neither is necessarily older based upon composition. And if he cares to know the reasoning (or science) behind it, I will attempt to explain. Or else I will let him read what you have said. He will understand. I understand, but you guys have explained it better than I could.

Thanks again!

Share this post


Link to post
Share on other sites
bear-dog

Another iteration of Bobby's explanation is this:

"Fossilized" (along with "petrified") is a near meaningless term. The term is often substituted for "mineralized" in describing a bone or tooth. But, fossilized doesn't always equate to mineralized because many fossils are not reinforced or replaced by minerals.

Bone is primarily composed of hydroxyapatite and collagen. Hydroxyapatite is an inorganic compound of calcium, phosphate, and hydroxide which is organized in a crystal latticework that gives bone (and teeth) structural rigidity. It preserves well as a fossil under some conditions.

Yeh,what what he said.

Collagen is a fiberous protein that serves as connective tissue in bones and muscles. It does not preserve well in a fossil. As collagen decomposes, it may be replaced in the hydroxyapatite latticework by minerals from the depositional environment (e.g. silica dioxide dissolved in groundwater).

If bone (the hydroxyapatite structure) is reinforced with exogenous minerals, it is said to be "mineralized." If the bone components (including the hydroxyapatite) are entirely replaced by exogenous minerals such as silica, it is said to be "replaced by -".

A 'burn test' or 'match test' will usually indicate only whether there is collagen remaining in a bone -- scorched collagen has an awful smell. Teeth - dentin and enamel - contain hydroxyapatite, but don't contain collagen, so the 'burn test' on a tooth would be a waste of time.

Share this post


Link to post
Share on other sites
siteseer

You might be able to tighten the age range by identifying the skull to species or subspecies though any two bison researchers may not agree on the subspecies. First, Bison appears in North America south of 55 degrees N latitude roughly 160,000 to 200,000 years ago. The appearance of Bison in that time frame has been used to define the Rancholabrean Land Mammal Age, the youngest time unit in the North American Land Mammals Ages (NALMAs).

In general larger-horned species of Bison lived before shorter-horned species but species overlapped too. Since your skull appears to belong to a shorter-horned species, that would indicate that it is much younger than 160,000 years old. I know little about Bison but just thought I would throw out some rough numbers for you to work with. You might want to read this thread from early this year:

http://www.thefossilforum.com/index.php/topic/26805-bison-skulls/

You might want to contact the members who made comments on the species to get their opinions. You might want to look for this book as well:

McDonald, J.N. 1981.

North American Bison: Their Classification and Evolution. University of California Press.

The author also co-wrote this article which offers a more recent reference list:

McDonald, J.N. and G.E. Lammers. 2002.

Bison antiquus from Kenora, Ontario, and Notes on the Evolution of North American Holocene Bison. In Emry, R.J (ed.). Cenozoic Mammals of Land and Sea: Tributes to the Career of Clayton E. Ray. Smithsonian Contributions to Paleobiology 93.

Okay, I understand most of what you've said so far. For the sake of (my) clarity though, help summarize please.... The first skull is "permineralized" and not "petrified", and based the information at hand which is minimal, one could not conclude any timeline or age of these specimens. In fact, the softer skull could just as easily be much older than the harder one?

Share this post


Link to post
Share on other sites
painshill

Just to add to the confusion :D

The word “fossil” derives from the Latin “fossus” (meaning “dug up”). A fossil is defined as the preserved remains of an animal, plant or other organism and would generally infer some kind of lithification, mineralisation, chemical alteration or diagenesis. Various types of preservation processes proceed at different rates for different kinds of tissues and conditions of exposure or burial and chemical interaction.

Some types of mummification (beyond simple dehydration) would also be regarded as fossilisation processes. Although most ordinary folk tend to think of fossils in millions of years of age, for palaeontologists there is a generally accepted (but completely arbitrary) cut-off date of 10,000 years. For recent fossils, the preservation may be dehydration or enrobement coupled with some level of mineralisation – even if only as a surface effect. For ancient fossils, complete mineralisation and replacement of the original organic item (or the voids within it) is more typical.

Organic material trapped in fossilised tree resin represents a process where the mineralisation may largely be a surface effect and the preservation is assisted by the consequent exclusion of oxygen. Some substances allied to amber (many insect-containing copals for example) would be excluded from the fossil definition by the 10,000 year rule rather than excluded by virtue of the preservation process.

There are other examples of mineralisation processes which – although recent – are no different than some of the processes which create fossils as we know them. Such instances have been reported for the buried portions of old fence posts and also modern fruits which have been exposed to highly saline or mineral-rich water. Here in the UK there are several areas of salt-marsh where you can find siderite nodules containing recent items. Typically they contain mineralized bits and pieces of WWII ordnance since these areas were frequently used for bombing practice, but there’s no reason why they couldn’t contain something recent and organic, formed in a time-frame of tens of years.

Such items would not be regarded as fossils since, again, they don’t meet the 10,000 year rule. Obviously, the distinction between fossilised and non-fossilised status does not switch over at midnight 10,000 years ago, but that’s the general rule.

Share this post


Link to post
Share on other sites
Ramo

Is that a bullet hole in the brain case of the one on the right?

Ramo

Share this post


Link to post
Share on other sites
Ainokc

Is that a bullet hole in the brain case of the one on the right?

Ramo

Sorry, I've been absent from the site for a few weeks and just checked back in. I have wondered the same thing Ramo. I happen to be visiting my folks as we speak. I will see if I can get a better look. My dad doesn't think so, but I am not sure... I will try to take some better photos and get them posted.

Thanks to all of you for your time and explanations!

Share this post


Link to post
Share on other sites
StultusNomen

Hi, I came here with a specific query and this thread seems most apt.

The question is simple and not so.

What percentage of dinosaur fossils are completely permineralized; i.e. with the original inorganic structure (hydroxyapatite?) replaced or reconfigured?

Share this post


Link to post
Share on other sites
Harry Pristis

The last estimate I saw was 97.8%.

.

.

.

Forty-two point seven percent of all statistics are made up on the spot.

--------------Steven Wright

.

.

Share this post


Link to post
Share on other sites
Auspex

I'm pretty sure that such data has never been systematically collected. My supposition is that the vast majority of dinosaur bones are completely permineralized.

Share this post


Link to post
Share on other sites
Quarryman Dave

very interesting conversation here! I enjoyed reading it

Share this post


Link to post
Share on other sites
StultusNomen

I do love statistics - are you 100% certain of the 97.8% and is there a better than evens chance you might know from whence the figure comes?

Share this post


Link to post
Share on other sites
Harry Pristis

I am only 91.6% certain of the 97.8% estimate (which IIRC had a 1.67% margin of error).

.

.

Forty-two point seven percent of all statistics are made up on the spot.

--------------Steven Wright

Share this post


Link to post
Share on other sites
StultusNomen

I may have mispoke. I think I am talking about Recrystallization. If permineralization is only concerned with filling in gaps.

Or perhaps in English. Is a typical dinosaur bone still bone or has its structure [inorganic] been altered to a point where it should no longer be called bone?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Recently Browsing   0 members

    No registered users viewing this page.

×