Large Crystal Filled Baculites Fossil - South Dakota

This is a section of a large Baculites fossil which is filled with calcite crystals, almost like a fossil geode. It is in two pieces which fit together, allowing the interior crystal cavities to be easily seen. One section still has part of the concretion it was found in attached, and stands up on it's own. Both sections put together are 9 1/2 inches in length.

Baculites ("walking stick rock") is an extinct cephalopod genus with a nearly straight shell. The matrix it is preserved in has been sculpted so that it stands up freely, making for a very aesthetic display. It's approximately 75 million years old, and comes from a time when a shallow sea covered much of South Dakota.