Echinoidea note details

Fossil range
Durham (1940) described possible fossil representatives of E. grandis as ancestral species/subspecies, with E. shepherdi restricted to the Late Pliocene and E. grandis inezana restricted to the Pleistocene. Morphological differentiation between E. grandis, and E. grandis inezana are very slight, and relates to small differences in the size of the marginal notches, the size of the interambulacral lunule, and the concavity of the abactinal system. Coppard & Lessios (2017) observed such characters to vary greatly in extant E. grandis and, thus, do not reliably differentiate these forms. They therefore used the Gelasian Stage of the Early Pleistocene for the minimum age of E. grandis.
Coppard, S.E. & Lessios, H.A. (2017). Phylogeography of the sand dollar genus Encope: implications regarding the Central American Isthmus and rates of molecular evolution. <em>Scientific Reports.</em> 7(1): 11520. 
2019-11-09 18:24:26Z