Shark teeth from the mid-Cretaceous Woodbine formation, Arlington, Texas.

~100 million years old, still shiny--apparently no mineral replacement. The shark that shed these teeth swam in an warm, shallow oyster and scallop reef where the sea was filled with ammonites small and large, and the giants of the deep--Xiphactinus, the mosasaurs, maybe even Lipleurodon or its kin.

The squiggly things in the modeling clay are cat hairs. If you sculpt, and have cats, well, this is what it's gonna look like.