“…This species presents a wide geographic distribution which extends from southern US to northern Argentina (Norrbom and Foote, 1989;White and Elson-Harris, 1992). Based on the variability observed for different biological parameters, it was suggested that the nominal A. fraterculus comprises, in reality, a "complex of cryptic species" (Baker et al, 1944;Morgante et al, 1980;Solferini and Morgante, 1987;Steck, 1991;Steck and Sheppard, 1993;Santos and Matioli, 1995). Recently, based on extensive isozymic, karyotypic, and morphometric studies (Selivon, 1996), eggshell morphology (Selivon and Perondini, 1998), and unusual features of early embryogenesis , two forms belonging to this complex were characterized, and temporarily denominated A. fraterculus sp.…”