Resembling a fist in shape, form, or function; shaped like a clenched hand.
From fist combined with the suffix -like meaning 'resembling or similar to.' This is a productive compound construction in English that can be applied to many nouns.
When scientists describe a creature's 'fistlike appendages,' they're basically saying it has bumpy things that look vaguely like clenched fists—it's a helpful way to describe something weird that doesn't fit normal categories!
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