▁in ▁Italy ▁( 2 3 5 ▁to ▁ 2 3 2 ▁million ▁years ▁ago ) ▁on wards . ▁About ▁ 4 0 ▁ext inct ▁species ▁are ▁known . ▁▁ ▁F oss ils ▁of ▁these ▁m oll us cs ▁can ▁be ▁found ▁in ▁foss il ifer ous ▁marine ▁str ata ▁all ▁over ▁the ▁world . ▁ ▁For ▁example , ▁they ▁are ▁present ▁in ▁C ret ace a ous ▁rocks ▁in ▁the ▁Fort ▁W orth ▁Form ation ▁of ▁Texas , ▁and ▁in ▁the ▁Tr ent ▁River ▁Form ation ▁of ▁V ancouver , ▁as ▁well ▁as ▁in ▁other ▁parts ▁of ▁North ▁America . ▁ ▁Distribution ▁Sp iny ▁o yst ers ▁are ▁found ▁in ▁all ▁subt rop ical ▁and ▁( es pecially ) ▁tropical ▁se as , ▁usually ▁close ▁to ▁the ▁coast s . ▁ ▁E col ogy ▁Sp ond yl us ▁are ▁filter ▁feed ers . ▁The ▁adult s ▁live ▁c ement ed ▁to ▁hard ▁substr ates , ▁a ▁characteristic ▁they ▁share , ▁by ▁conver gent ▁evolution , ▁with ▁true ▁o yst ers ▁and ▁j ew el ▁boxes . ▁Like ▁the ▁latter , ▁they ▁are ▁protected ▁by ▁sp ines ▁and ▁a ▁layer ▁of ▁ep ib ion ts ▁and , ▁like ▁the ▁former , ▁they ▁can ▁produce ▁p ear ls . ▁The ▁type ▁of ▁substr ate ▁they ▁use ▁depends ▁on ▁the ▁species : ▁many ▁only ▁attach ▁to ▁cor al , ▁and ▁the ▁largest ▁divers ity ▁of ▁species ▁is ▁found ▁in ▁tropical ▁cor al ▁re ef s ; ▁others , ▁( part icular ly ▁S . ▁sp inos