Aethocrinus is an early-diverging crinoid reported from the Early Ordovician.

[1] Its five arms bifurcate.

The contested Echmatocrinus notwithstanding, it is a candidate for the earliest true member of the crinoid class – though not being a member of the crown group, quite where within the stem group to draw the distinction between eocrinoids and crinoids is a somewhat arbitrary decision.

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