Preliminary results in the sexual dimorphism determination of the sea urchin Lytechinus variegatus variegatus (Lamarck, 1816), Echinoidea, Toxopneustidae

First Record of Sexual Dimorphism in Toxasterid Echinoid Heteraster from the Early Cretaceous Deposits of the Kopet‐Dagh Basin, NE Iran

“…SSD is common in many invertebrates and is probably best interpreted as the result of sexual selection (Hedrick and Temeles, 1989;Anderson, 1994;Cox et al, 2003;Silina, 2016). In most invertebrates, female individuals are larger than male ones, for example, in some Mesozoic ostracodes the females have a larger carapace (Ozawa, 2013), also in bivalves (Silina, 2016), starfishes (Ohshima and Ikeda, 1934), ammonites (Parent and Zatoń, 2016;Zell and Stinnesbeck, 2016), gastropods (Morse, 1876;Má rquez and Averbuj, 2016;Ng et al, 2019) and echinoids (Hamel and Himmelman, 1992;Abessa et al, 2001;Jeffery et al, 2003). However, this is not always the case, and in some invertebrates the males are larger than the females, as in some Cenozoic podocopid ostracodes (Ozawa, 2013) and scleractinian Plastron type is semiamphisternous, Labrum (Lb) is triangular and attached anteriorly to the peristome (Pr) and followed by two asymmetrical sternal plates (St).…”