Comparative Studies of Recent and Fossil Echinoid Jacksonaster depressum (L. Agassiz) from the Northern Bay of Safaga, and Late Pliocene rocks, Red Sea coast, Egypt.

Statistical correlation, ontogenetic development and sexual dimorphism have been studied in recent and fossil specimens of Jacksonaster depressum (L. Agassiz, 1841). A large number of dead and living tests of this species have been collected from bottom sediments of the Safaga Bay, Red Sea, Egypt. Out of two hundred specimens, one hundred and seventy seven (20 living and 157 dead, including 25 females and 95 males) were measured, analyzed statistically and correlated with measurements of 61 fossil tests (32 females and 29 males) collected by Elattaar (2003) from the Late Pliocene sediments of Wadi Wizr, south of Quseir City, along the Red Sea coast. Morphological and statistical differences between recent and fossil tests and gender include test shape, apical system, length, width and number of pore pairs of petals, and position and shape of periproct and peristome; these are discussed in detail. Scatter diagrams for ontogenetic development of both recent and fossil tests are plotted and discussed in detail. Sedimentary facies of the recent and fossil tests are explained.