CLADOENDESIS OF EPHEMEROPTERA
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Fig. 1–24. Right tergalii of Securiops with dorsal lamella turned out. 1–7 – Procloeon (Securiops) falcatum, tergalii I–VII; 8–17 – two individuals of P. (S.) macafertiorum: 8–11 – tergalii I–II and V–VII; 12–16 – tergalii I–V; 17 – the same individual, margins of abdominal segments VII–IX with tergalius VII in natural position; 18–24 – P. (S.) primasia, tergalii I–VII.