干旱区生态环境知识资源中心

Nummulites pachoi Said, 1951 is described and illustrated for the first time from topotypic material from the Late Lutetian Mokattam Formation of El Arag Oasis, Egypt, including the first photographs of both microspheric and megalospheric generations. Nummulites pachoi spans the SBZ 16 of Late Lutetian age. This species is phylogenetically parallel to N. praelyelli Boukhary & Kamal, 2003. Although, N. pachoi and N. praelyelli exhibit the same ontogenetic trend, from tight to lax, the development of granulation in the megalospheric form of N. pachoi is a progressive character through time, unlike that in N. praelyelli. Nummulites pachoi is larger, flatter and with an opposite ontogenetic trend compared with Nummulites gize-hensis, although both have similar protoconch diameters. The author who first recognized the name "pachoi" as a species level designation should be given credit for naming the species. Because Said (1951) raised the rank of de la Harpe’s race pachoi to specific level, according to the rules of zoological nomenclature, Said should be recognized as the author of the species.