This is a cool, free-standing association with many Hoploscaphities ammonites and three section of Baculites (straight cephalopods). The ammonites average about 1.2" wide and the entire specimen is 3.6 inches tall and 3.3 inches wide. All of the specimens have iridescent shell and it has been wonderfully prepared to create a very aesthetic display that would look great on a shelf or desk.
These 70 million year old ammonites lived when South Dakota was a shallow inland sea. It was found preserved in a concretion that was split open. It then had to be hand prepared to remove the hard rock surrounding it from the shell, a very time consuming task.