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.


References

  1. ^ Philip, G. M.; Strimple, H. L. (1971). "An Interpretation of the Crinoid Aethocrinus moorei Ubaghs". Journal of Paleontology. 45 (3): 491–493. JSTOR 1302696.


Allikas: https://en.wikipedia.org/wiki/Aethocrinus
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