Geopic of the week: Fossiliferous limestone

archimedes

This is a picture of weathered fossiliferous limestone of the Pitkin Formation.  It was taken in a quarry near Batesville Arkansas.  The picture displays fossil remains of two common aquatic animals that lived in the shallow sea covering northern Arkansas between 360 – 320 million years ago. 

The screw-shaped remains are parts of bryzoans; they are commonly referred to as Archimedes screws.  The nut-shaped fossils- which also resemble rolls of smarties candies- are the remains of crinoids, commonly called sea-lilies, which have living relatives in the ocean today.  Both animals lived by attaching themselves to the sea floor and filtering food, such as plankton, from the ocean water.

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