like ) ▁s add les ▁and ▁sub div ided ▁lo bes . ▁ ▁The ▁si ph un cle ▁begins ▁at ▁a ▁central ▁or ▁sub central ▁position ▁and ▁in ▁most ▁species ▁becomes ▁vent ral ▁at ▁the ▁end ▁of ▁the ▁second ▁wh or l . ▁ ▁In ▁all ▁species ▁sept al ▁n acks ▁are ▁short ▁retro cho an it ic ▁( point ▁ad ap ically ) ▁in ▁the ▁first ▁wh or l , ▁are ▁trans itory ▁in ▁the ▁second ▁wh or l , ▁and ▁become ▁pro cho an it ic ▁( point ▁ad or ally ) ▁in ▁the ▁third ▁wh or l ▁and ▁there after . ▁Cl os ely ▁related ▁St en op op an oc eras ▁diff ers ▁in ▁that ▁its ▁si ph un cle ▁starts ▁off ▁vent ral . ▁▁ ▁Par ap op an oc eras ▁was ▁named ▁by ▁H aug ▁in ▁ 1 9 9 4 . ▁The ▁type ▁species ▁is ▁Pop an oc eras ▁ver ne u ili ▁Mo js is ov ics ▁ 1 8 8 6 . ▁ ▁Rel ated ▁gener a ▁include ▁Am ph ip op an oc eras ▁and ▁St en op op an oc eras . ▁ ▁Distribution ▁F oss ils ▁have ▁been ▁found ▁in ▁S val b ard , ▁Jan ▁May en , ▁British ▁Columbia , ▁the ▁Russian ▁Federation , ▁and ▁possibly ▁Pap ua ▁New ▁Guinea . ▁ ▁References ▁Notes ▁ ▁Bibli ography ▁Vladimir ▁V . ▁Ark ad iev ▁ ▁& ▁Mik h ail ▁N . ▁V av il ov ▁ 1 9 8 4