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SC🦕 Triops are a group of freshwater crustaceans commonly called tadpole shrimp or dinosaur shrimp (Via: @adarleibovitch). They look like ancient armored tadpoles, a look they've rocked for hundreds of millions of years. The word "Triops" means "three eyes" in Greek, and the group is so named because they have two main compound eyes and a third simple organ called an ocellus eye that helps them detect light.
The animals are not shrimp, which is a name usually reserved for marine crustaceans in the order Decapoda (Triops are in the order Notostraca). But like shrimp, Triops — one of two genera in its own family and order — live in water. In fact, Triops have adapted to an extreme life in temporary freshwater or slightly salty pools that may only last a few weeks before drying out.
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🦀 Triops' appearance hasn't changed much since the group first emerged in the Devonian period (419 million to 359 million years ago), according to Central Michigan University(opens in new tab) in Mount Pleasant, Michigan. This ancient and morphologically consistent lineage led some people to call the creatures "living fossils," a term that's also commonly used to describe deep-sea fish called coelacanths and horseshoe crabs — another animal that looks a bit like Triops.
Scientists used to consider one Triops species, Triops cancriformis, as being the same animal seen in 250 million-year-old fossils. That would mean Triops cancriformis had survived to the present day from the Triassic period (about 252 million to 201 million years ago) when dinosaurs first emerged — hence the name "dinosaur shrimp." However, a 2013 study of Triops DNA published in the journal PeerJ found that the current species evolved within the last 25 million years. "Living fossils evolve like any other organism, they just happen to have a good body plan that has survived the test of time," an evolutionary biologist at the University of Hull in England Africa Gómez, stated in 2013.
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