The belly-thrower is a fierce, predatory monopedalien from the northern hemisphere of Darwin IV that catches its prey in a unique way. It lives in Planitia Borealis, including the northern perimeter of the Equatorial Mountains and close to the tundra near Glacier Cape North. It is a ricochetal saltator.

Darwin IV's monopedaliens are mostly air-sifters. An exception is the belly-thrower, a fierce predator that ejects its stomach from its oral sphincter and throws it over its prey like a net, then pulls it in slowly, digesting its unfortunate victim even as it struggles to get free.