Seed Shrimp

Seed shrimp, class Ostracoda, are tiny crustaceans whose entire body is enclosed within a hinged, bean-shaped shell resembling a seed, found in nearly every aquatic environment on Earth, from oceans to ponds to damp soil. Despite their small size, Ostracoda is one of the most diverse crustacean groups by number of described species, and their durable shells fossilize extremely well, making them one of the most useful groups in the fossil record for reconstructing past environments and dating rock layers.