No ifs, ands or butts about it: A teeny roughly 530-million-year-old critter that lacks an anus is not, as previously thought, the oldest member of a wide-ranging animal group that includes everything from starfish to humans.
Despite its absent anus, Saccorhytus coronarius had no shortage of holes on its wrinkly potato-shaped body, including a ring of small openings around its gaping mouth. Previously, those holes had been identified as an early version of gill slits, typically used for respiration (SN: 2/3/17). Gill slits are commonly found in deuterostomes, so their presence seemingly nailed the critter’s spot on the animal family tree.
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