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Acorn Worm_Bst 5-22-17--63.jpg

Acorn Worm bst, Enteropneusta, Saccoglossus kowalevskii;ince acorn worms and the human lineage diverged 570 million years ago, pharyngeal slits for filtering food evolved into gills for extracting oxygen, and later into today’s human upper and lower jaw and pharynx, which encompasses the thyroid gland, tongue, larynx (voice box) and various glands and muscles between the mouth and the throat. Humans and other terrestrial vertebrates actually initiate vestigial gills while embryos, though they disappear quickly and rarely persist in infants;  from UC Berkeley.