Need Help Identifying This Alaskan Bone/fossil!

[gen]

Hello everyone,

I need some help identifying this bone/fossil, which was found in the Yukon river delta (near the sea) in Alaska.

It seems to be rather dense and heavy. The white inner core feels chalky and is detachable from the outer light brown portion.

The light brown portion feels smooth.

There is a concentric zigzag pattern featured in the cross section.

Any input is appreciated!

Sincerely,

Jay

[gen]

An additional picture.

Jay

Edited June 6, 2015 by gen

[Auspex]

It looks to me very much like a weathered piece of ivory tusk.

[Diceros]

This does appear to be a late Pleistocene proboscidean tusk tip. There are rare mastodon remains in Alaska, but as the Ice Age habitat in Alaska was more grassland than forest, most of the proboscidean remains there are of the late-stage mammoth Mammuthus primigenius, not the mastodon Mammut americanum. The age is likely 10-20,000 yrs. - Rancholabrean, in the parlance of N.A. Land Mammal Ages (NALMA).

I'm afraid Plestocene tusks have a tendency to spall apart by their growth rings (as wood sometimes does), so you'll want to soak it in some preservative (glyptal, butvar, whatever). It will fall apart if not preserved somehow. Just a quirk of ivory structure.

Ivory is tooth dentine, the Ice Age proboscideans (technically, only the mammoth is an elephant; mastodons are of a far more ancient lineage) have all lost the enamel layer from their tusks (I believe the upper tusks are the upper second incisors). The zig-zag cross-hatching seen in cross-sections of true ivory is a method used to hold together the ivory between the growth lines, and to strengthen it. You used to be able to see that cross-hatched pattern on white piano keys (before they became plastic, and when the phrase "tickle the ivorys" still meant something).

You'll need a comment from RichW9090, the resident Ice Age mammal specialist, who should be dropping by before long to assist you.

[gen]

Wow thank you both for the input.

I didn't expect it to be fossil ivory, what a pleasant surprise!

Sincerely,

Jay.

Edited June 6, 2015 by gen

[RichW9090]

Diceros is spot on (as is his wont) - it is the tip of a tusk. Proboscidean tusks grow as a series of nestled cones, and they do tend to split like that, in spite of the strengthening pattern of the Schreger Lines. The pattern of those lines can be used to identify whether ivory is mammoth, mastodon or extant elephant.

http://www.fws.gov/lab/ivory_natural.php

I'm sure there are old posts about this on the Forum.

[gen]

Hi Rich,

I took a look at the link you posted, and the Schreger Lines in this specimen perfectly matches those in the sample Mammoth tusk cross section.

I suppose that confirms that this is a Mammoth tusk section.

Thanks alot!

Sincerely,

Jay