Triops longicaudatusWIKIPEDIA, STEVE JURVETSONToday’s tadpole shrimp, or notostracans, have a shield-shaped body, ending in a forked pair of filaments—a shape that makes them almost indistinguishable from their ancestors in the Triassic period some 265 million years ago. This outward constancy has earned them the description of “living fossils”—a term referring to species with no close living relatives, which seem to have gone unchanged for long spans of time.
But according to a genetic analysis of notostracans published today in PeerJ, these animals have by no means stopped evolving. Indeed, researchers are coming to realize that the term “living fossil” is a misnomer. One by one, the classic examples—horseshoe crabs, coelacanths, cycads, and more—have turned out to be very different from the fossils that they apparently resemble, either at a genetic level or through subtle physical changes. Their recognizable nature is a red herring—these creatures simply did not exist in their current form millions of years ago.
“I would favor retiring the term ‘living fossil’ altogether as it is generally misleading,” said Africa Gomez at the University of Hull who led the study.
In the latest study to disprove the concept of a living ...
