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1a. Periproct lies outside the apical disc.
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1b. Periproct encircled by the apical disc.
Go to 2
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2a. Teeth keeled.
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2b. Teeth grooved.
Go to 3
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3a.Pore-pairs uniserial at ambitus. aboral tube-feet simple.
Go to 4 |
3b.Pore-pairs biserial at ambitus. Umbrella-like aboral tube-feet.
Go to 6 |
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4a. Apical disc (above) dicyclic and firmly bound to the corona; tubercles non-crenulate.
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4a. Apical disc monocyclic or hemicyclic and rather weakly attached to corona; tubercles predominantly crenulate.
Go to 5
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5a. Apical disc (above) monocyclic and not firmly bound to the corona; with ocular plates larger than genital plates. Genital plates rectangular.
Aspidodiadematoida |
5b. Apical disc hemicyclic or monocyclic but integrated into the coronal plating and with genital plates projecting interradially into interambulacral zones. Ocular plates small.
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6a.Primary tubercles crenulate; one primary tubercle per plate.
Pedinothuria (incertae sedis) |
6b.Primary tubercles non-crenulate; multiple primary tubercles per plate.
Micropygoida |
