Lingula is a genus of Brachiopods that is extant today with fossils that have been found back to the Cambrian period. Over that time they show very little change with only minor variation on the theme. Why change something if it's already working?!
Here is a specimen of Lingula coburgensis from the Coburg formation. I found it while on a field trip to the St. Mary's Cement Quarry in Bowmanville, Ontario, Canada. The shell is phosphatized and so retains some color while other brachiopod shells, made of Calcite or Aragonite, loose their color when fossilizing. Specimens of this species are fairly common in the Coburg Fm. but they are delicate and often break while trying to extract them from the hard limestone matrix. The specimen below shows some damage including a rectangular window of shell that is missing. Otherwise the fossil is very nice with a deep mahogany color and thin concentric growth lines. It's embedded in the matrix so I don't have a way to show my usual view of the shell from different perspectives. You will have to make due with some angle shots that show just how flat the shell is.
The Coburg formation is Ordovician in age (late Ordovician, Katian/Mohawkian stage).
This fossil was collected from the St. Mary's Limestone Quarry in Bowmanville, Ontario. I used William Hessin's book "South Central Ontario Fossils", 2009, Self Published, pg. 117 to help identify it.