Notostraca, or Tadpole shrimp, also known as Shield shrimp, are an order of crustacean arthropods closely related to brine shrimp/fairy shrimp, clam shrimp and water fleas.
They appeared during the Devonian and have changed very little since.
Tadpole shrimp are living fossils, as they have not changed since they first appeared during the Devonian, in the Famennian (372.2 million years ago to 358.9 million years ago).
There are only two genera in this small order of crustaceans, Triops (10 species) and Lepidurus (9 species)
Both are distinguished by prescence of a bump between the two tail filaments, or rami.
Tadpole Shrimp feed via filtering particles from the water they live in.
They prey on very small fish and fairy shrimp, and occasionally feed on rice, stirring up the sand
They also commonly feed on rice (in the case of the species Triops longicaudatus).
Most notostracans hatch as late naupliar stage larvae (meta-nauplius), though some species hatch as unsegmented nauplii. Development into adults is very rapid (2-3 weeks) via a large number of moults (up to 40 in some species).
Their lifespan is around 50-90 days depending on how long the water lasts.
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