Ostracods

Ostracods, or ostracodes, are a class of the Crustacea, sometimes known as Seed Shrimp. Some 70,000 species (only 13,000 of which are living today) have been identified by scientists. They are small crustaceans, typically around 1 mm in size, but varying from 0.2 to 30 mm. Their bodies are flattened from side to side and protected by a bivalve-like, calcareous valve or "shell".

As of 2014, ostracods made news when a discovery in New York showed what was "said to be the earliest evidence for parental care". *

*Siveter, David J.; Tanaka, Gengo; Farrell, Úna C.; Martin, Markus J.; Siveter, Derek J.; Briggs, Derek E.G. (2014). "Exceptionally Preserved 450-Million-Year-Old Ordovician Ostracods with Brood Care". Current Biology