I read the bit about the slow drying sub-fossils. That sound like unnecessary work for preparing a mastodon tooth. The term "sub-fossil" is mis-used on that page to refer to a state of preservation. I think "sub-fossil" is a term of art relating to the age of remains. "Sub-fossil" sounds to me like a cow bone or an Native American dog jaw from a midden. A sub-fossil may or may not have residual collagen, but collagen does not survive long when exposed to weathering. Sub-fossils may be hig