An acorn worm, a small marine animal that has gill slits in its throat like fish and is considered a distant relative of vertebrates.
From Greek 'enteron' (intestine) + 'pneustikos' (breathing, from 'pnein' meaning to breathe). The name refers to the creature's intestinal gill slits used for breathing.
Enteropneusts are mysterious living fossils that reveal your own ancestry—these humble acorn worms have the same gill slits that eventually evolved into your jaws and inner ear bones, making them crucial to understanding vertebrate evolution.
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