Horn Coral, Devonian Aged From New York

Here is a piece of horn coral from the Windom Shale of NY. It's Devonian in age, or approximately 385 million years old.

Horn coral or Rugose coral first appeared in the geological record 488 million years ago and went extinct during the create Permian extinction 251 million years ago. They get their name from the hornlike structures built by the coral animal. They are very often used as an index fossil to help correlate the geological age of different formations.