The Echinoid Directory
Salenioida: Key to major taxa
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1a. Ambulacral plating trigeminate adorally, unigeminate aborally. Adapical interambulacral tubercles perforate. |
1b.Ambulacral plating bigeminate or (rarely) unigeminate adorally. Interambulacral tubercles always imperforate. |
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2a. Apical disc without sutural pitting; periproct displaced towards genital plate 5. |
2b. Apical disc with obvious sutural pitting - those pits having small tubercles. Periproct displaced towards ocular plate I. |
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3a. Ambulacra with every third tubercle enlarged; ambital and adoral ambulacral tubercles perforate and crenulate. |
3b. Ambulacra narrow with simple plating except close to the peristome; ambulacral tubercles imperforate. |
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4a. Ambulacral plating trigeminate below the ambitus and bigeminate above. Ambital and adapical tubercles obviously perforate. |
4b. Ambulacral plating polygeminate with well developed phyllodes adorally and trigeminate aborally. Adapical interambulacral tubercles with rudimentary perforations only. |
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5a. Primary tubercles on all adapical interambulacral plates. |
5b. Adapical interambulacral plates lacking a primary tubercle. |