ran cho id ▁E ly s ia ▁( and ▁und ou bt edly ▁others ) ▁do ▁develop ▁a ▁shell ▁before ▁h atch ing ▁from ▁its ▁egg . ▁ ▁Indeed , ▁at ▁least ▁the ▁E ly si idae , ▁Lim ap ont i idae ▁and ▁Her ma e idae ▁all ▁bear ▁lar val ▁shell s , ▁which ▁are ▁spir al , ▁and ▁possess ▁between ▁three - quarters ▁of ▁a ▁wh or l ▁and ▁one ▁complete ▁wh or l . ▁ ▁The ▁pla k ob ran cho ids ▁have ▁a ▁more ▁diverse ▁feed ing ▁range ▁than ▁the ▁Ox yn o ace a , ▁feed ing ▁on ▁a ▁wider ▁range ▁of ▁green ▁( and ▁sometimes ▁red ) ▁alg ae ▁and ▁even , ▁in ▁three ▁cases , ▁being ▁car n iv orous . ▁ ▁E volution ▁▁ ▁The ▁ancest or ▁of ▁the ▁Sac og loss a ▁is ▁pres umed ▁to ▁have ▁fed ▁on ▁a ▁now - ext inct ▁calc ifying ▁green ▁alg a ▁in ▁the ▁U d ote aceae . ▁ ▁The ▁first ▁foss il ▁evidence ▁of ▁the ▁group ▁comes ▁from ▁b ival ved ▁shell s ▁d ating ▁to ▁the ▁E oc ene , ▁and ▁further ▁b ival ved ▁shell s ▁are ▁known ▁from ▁later ▁ge ological ▁periods , ▁although ▁the ▁thin ▁nature ▁of ▁the ▁shell s ▁and ▁their ▁high - eros ion ▁habitat ▁usually ▁make ▁for ▁poor ▁pres ervation . ▁ ▁The ▁corresponding ▁foss il ▁record ▁of ▁alg ae ▁points ▁to ▁an ▁origin ▁of ▁the ▁group ▁deeper ▁in ▁time , ▁perhaps ▁as ▁early ▁as ▁the ▁Jur