giant freshwater stingray known as himantura polylepis exhibits its distinctive and smooth skin while resting on a

himantura polylepis stingray freshwater fish aquatic life marine biology wildlife detailed view animal features smooth skin resting anatomy unique species river habitat fauna biodiversity elasmobranch taxonomy dwellers endangered ecosystems environmental conservation tropical rivers benthic organism flat nature behavior illustration large stingrays exotic underwater creatures identification research diversity animals observation natural ai generated