Complex sentence: By looking at the exterior of the African manatee, one would not be able to distinguish it from the American manatee, however it is different to the Amazonian manatee, which has characteristic white markings on its abdomen.
Split into simpler sentences: By looking at the exterior of the African manatee, one would not be able to distinguish it from the American manatee. Contrastingly, the exterior of the African manatee differs from that of the last type of manatee, the Amazonian manatee, because the Amazonian manatee has characteristic white markings on its abdomen.