S otal ia ▁flu vi at ilis ), ▁altern atively ▁in ▁Peru ▁buf e o ▁gr is ▁or ▁buf e o ▁negro , ▁is ▁a ▁species ▁of ▁fresh water ▁dol ph in ▁found ▁in ▁the ▁rivers ▁of ▁the ▁Amazon ▁bas in . ▁The ▁word ▁t uc ux i ▁ ▁is ▁derived ▁from ▁the ▁T up i ▁language ▁word ▁t uch uch i - ana , ▁and ▁has ▁now ▁been ▁adopted ▁as ▁the ▁species ' ▁common ▁name . ▁Despite ▁being ▁found ▁in ▁ge ographic ▁locations ▁similar ▁to ▁those ▁of ▁' true ' ▁river ▁dol ph ins ▁such ▁as ▁the ▁b oto , ▁the ▁t uc ux i ▁is ▁not ▁closely ▁related ▁to ▁them ▁gen et ically . ▁Instead , ▁it ▁is ▁class ed ▁in ▁the ▁ocean ic ▁dol ph in ▁family ▁( Del ph in idae ). ▁ ▁Phys ically , ▁the ▁species ▁res emb les ▁the ▁bott len ose ▁dol ph in ▁but ▁diff ers ▁sufficiently ▁to ▁be ▁placed ▁in ▁a ▁separate ▁genus , ▁S otal ia . ▁The ▁cost ero ▁( S otal ia ▁gu ian ensis ), ▁related ▁dol ph ins ▁present ▁in ▁coast al ▁and ▁est u ar ine ▁environments ▁and ▁formerly ▁grouped ▁together ▁with ▁the ▁t uc ux i , ▁have ▁recently ▁been ▁recognized ▁as ▁a ▁distinct ▁species . ▁ ▁Description ▁The ▁t uc ux i ▁is ▁frequently ▁described ▁( see ▁references ▁below ) ▁as ▁looking ▁similar ▁to ▁the ▁bott len ose ▁dol ph in , ▁but ▁it ▁is ▁typically ▁smaller ▁at ▁around ▁ 1 . 5   m