▁( 4 . 9   ft ). ▁The ▁dol ph in ▁is ▁colored ▁light ▁to ▁bl u ish ▁grey ▁on ▁its ▁back ▁and ▁sides . ▁The ▁vent ral ▁region ▁is ▁much ▁l ighter , ▁often ▁p ink ish . ▁It ▁is ▁the or ized ▁that ▁this ▁p ink ish ▁color ▁may ▁be ▁caused ▁or ▁intens ified ▁by ▁increased ▁blood ▁flow . ▁The ▁d ors al ▁flu ke ▁is ▁typically ▁slightly ▁hook ed . ▁The ▁be ak ▁is ▁well - defined ▁and ▁of ▁moder ate ▁length . ▁There ▁are ▁ 2 6 ▁to ▁ 3 6 ▁pairs ▁of ▁teeth ▁in ▁the ▁upper ▁and ▁lower ▁j aws . ▁ ▁Tax onomy ▁The ▁t uc ux i ▁S otal ia ▁flu vi at ilis ▁was ▁described ▁by ▁Ger va is ▁and ▁De ville ▁in ▁ 1 8 5 3 , ▁and ▁the ▁cost ero ▁S otal ia ▁gu ian ensis ▁by ▁Pierre - Jose ph ▁van ▁B éné den ▁in ▁ 1 8 6 4 . ▁These ▁two ▁species ▁were ▁subsequently ▁syn onym ized , ▁with ▁the ▁two ▁species ▁being ▁treated ▁as ▁sub species ▁of ▁marine ▁and ▁fresh water ▁vari eties . ▁The ▁first ▁to ▁re assert ▁differences ▁between ▁these ▁two ▁species ▁was ▁a ▁three - dimensional ▁morph ometric ▁study ▁of ▁Monte iro - Fil ho ▁and ▁colle agues . ▁Sub sequently , ▁a ▁mole cular ▁analysis ▁by ▁C un ha ▁and ▁colle agues ▁un ambigu ously ▁demonstrated ▁that ▁S otal ia ▁gu ian ensis ▁was ▁gen et ically ▁differenti ated ▁from ▁S otal ia ▁flu