▁ 6   met res , ▁or ▁ 2 0   fe et ▁long ) ▁were ▁counted ▁among ▁the ▁largest ▁animals ▁in ▁their ▁e cos ystem . ▁Their ▁only ▁real ▁compet itors ▁in ▁terms ▁of ▁size ▁are ▁the ▁r or qu als , ▁such ▁as ▁the ▁blue ▁wh ale . ▁But , ▁unlike ▁wh ales , ▁sau rop ods ▁were ▁primarily ▁terrest rial ▁animals . ▁ ▁Their ▁body ▁structure ▁did ▁not ▁vary ▁as ▁much ▁as ▁other ▁din osa urs , ▁perhaps ▁due ▁to ▁size ▁constraints , ▁but ▁they ▁displayed ▁am ple ▁variety . ▁Some , ▁like ▁the ▁di pl od oc ids , ▁possessed ▁trem end ously ▁long ▁t ails , ▁which ▁they ▁may ▁have ▁been ▁able ▁to ▁crack ▁like ▁a ▁wh ip ▁as ▁a ▁signal ▁or ▁to ▁d eter ▁or ▁inj ure ▁pred ators , ▁or ▁to ▁make ▁son ic ▁bo oms . ▁Sup ers aur us , ▁at ▁ ▁long , ▁was ▁the ▁longest ▁sau rop od ▁known ▁from ▁reason ably ▁complete ▁remains , ▁but ▁others , ▁like ▁the ▁old ▁record ▁holder , ▁Di pl od ocus , ▁were ▁also ▁extremely ▁long . ▁The ▁hol ot ype ▁( and ▁now ▁lost ) ▁verte bra ▁of ▁Am ph ico el ias ▁frag ill im us ▁( now ▁Mar a ap un is aur us ) ▁may ▁have ▁come ▁from ▁an ▁animal ▁ ▁long ; ▁its ▁verte br al ▁column ▁would ▁have ▁been ▁substantial ly ▁longer ▁than ▁that ▁of ▁the ▁blue ▁wh ale . ▁However , ▁a ▁research ▁published ▁in ▁ 2 0