Question about bones

[naturegirl]

Hi fossil people. I was wondering how long it takes bones to fossilize? I'm asking because I've found some bones, they aren't fossils, I don't think. But they are hard as stone, and really heavy. Old bones should be lighter the longer they decay, right? These were found in a creek, moss very thick on them, and if the jawbone is a black bear, they haven't been around here for 100 years. I know that isn't long enough to become a fossil, but wouldn't a bone just decay in the water also? There isn't a bone section in the forum, so I thought you guys might could help me on the "ways of a bone" on it's way to becoming stone. My husband said whack it with a hammer, but I don't think I want to do that. Here's some pics of the jawbone. I squeezed the empty teeth sockets really hard, and they don't break. Thanks.

naturegirl

 

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[Harry Pristis]

Well, it does appear to be a black bear, Ursus americanus.

You can give it the "match test." Hold a lighted match (or butane lighter) under a corner of the bone. If you get a smell like burning hair, there is still collagen left in the bone.

If you get no smell from the heated bone, all the collagen has deteriorated and has been replaced by minerals (commonly silica from ground water).

And that's all that the match test will tell you. It doesn't distinguish between "fossil" and "non-fossil."

I would call this a fossil. My label might say, "Pleistocene to Recent" since we don't really know just how old it is.

Go back and find some more of those bones.

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[terryo]

I used to find bone pieces(mastodon, mammoth, etc) in our local rivers that were at least 10,000 years old or more, so water doesnt hurt them much, and some of them wern't completely fossilized yet.If they stay submerged pretty much continously, they would probably last forever, barring being tumbled into powder by water movement. Try the match test, that is a good idea.If it seems to weigh more than a comparable "new" bone, it may very well be on it's way to being fossilized.A lot depends too on the minerals in the ground surrounding the bone. Nice find either way!

 

[Harry Pristis]

Mis-perceptions and inexact language abound around this subject.

"Mineralization" and "fossilization" are not at all synonymous -- that is a common mis-perception. Bones do not necessarily become heavier as they "fossilize."

As painstaking as this website author was, his description of "permineralization" is at least mis-leading. This should read, "Some bones, teeth and marine organisms are preserved in this way."

Perimineralization
Permineralization takes place when ground water carrying dissolved minerals infiltrates the microscopic pores and cavities in bone, wood or shell. The minerals being deposited produce stony fossils that still contain a good deal of their original solid material. Bones, teeth and many marine organisms are preserved in this way. The fossil wood from the Petrified Forest of Arizona are a famous example of this type of preservation. The teeth and bones of the Oligocene badlands of South Dakota and Nebraska are also common example of this type of fossilization, as well as the extensive deposits of Jurassic dinosaur bones in Utah and Colorado.

The elephant remains that 'terryo' mentions may be evidence that "mineralization" and "fossilization" are not the same thing. Let me give you another example: European cave bear (and other extinct animal) remains are certainly fossils; but, they are NOT permineralized at all. They are not heavier than in life, but are lighter, having lost collagen.

"Fossilization" is a very broad term. "Permineralization" is just one manner in which fossils may be preserved.

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[naturegirl]

Oh thank you Harry, terryo and 11 kbp. I had always thought a fossil would be heavier, now I know different. I'm headed back to that creek as soon as I can, besides this jawbone, I found a long staight leg bone, very heavy, and it feels very much like stone. I will try the match test, even if they aren't fossils I very excited to find evidence of an animal driven from here decades before I was born. Of coure I know the stories are true, but this really makes it real for me. It's so easy to imagine a bear and cubs along this creek. Wow!

naturegirl

 

[FireFlowerPower]

Is it common for just that part of the jaw bone to remain? The pics of other jaw bones are of the same section of the jaw. And BuckShot's wolf jaw bone is almost like that.

Is the jaw bone much stronger or denser than the rest of the skull to be the part that survives the longest?

 

[Harry Pristis]

Is it common for just that part of the jaw bone to remain? The pics of other jaw bones are of the same section of the jaw. And BuckShot's wolf jaw bone is almost like that.

Is the jaw bone much stronger or denser than the rest of the skull to be the part that survives the longest?

That is a very good question. In my experience, mandibular sections of jaws are far more common than the maxillary (upper) jaw sections.

The reason for that disparity seems to be (as you surmise) that the mandible is very dense bone.

The upper teeth are rooted in spongy cancellous bone -- rigid and light-weight in life, but vulnerable during deposition and preservation as a fossil. The maxilla tends to break apart, scattering the teeth.