Abstract The geologically oldest known crinoid pentacrinoid larva is reported from Verulam Formation (Katian) from the Lafarge Cannifton Agg Quarry in Cannifton, Ontario, Canada. The entire specimen (arms, aboral cup, and incomplete column) is ~4.2 mm high with the aboral cup only ~1.3 mm high. The specimen is comparable in size to the early pentacrinoid larva of the living crinoid Metacrinus rotundatus Carpenter, 1885. As known, the morphology of this pentacrinoid larva does not correspond in all details with any adult crinoid in the Cannifton area or from the nearby Brechin Lagerstätte fauna, suggesting that considerable morphological change occurred during ontogeny of this taxon.
Ausich et al. (Thu,) studied this question.
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