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ag·na·than | \ ˈag-nə-thən 
\
\ plural agnathans
Definition of agnathan
: jawless fish Two jawless fishes (agnathans) are recognized in these fossils … based on differences in the shape and histology of their tubercles …— Moya Meredith Smith, Science, 18 Jan. 1991
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The first known use of agnathan was in 1939
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