What is it called if you're half mermaid half vampire?

Cats in general (house cats, wild cats, lions, tigers, etc.) are famously cross-fertile across species (if members of the cat family are physically compatible ... that is, adult members of the two species are about the same size ... there's a fair chance that they can interbreed), and there are creatures called "vampire bats", but bats are not even in the same biological order as cats (cats are in order Carnivora, bats are in order Chiroptera) and therefore are not at all genetically compatible.