Petseleh, Shlang etc.

Modern penises come with all kinds of frills and accoutrements, like bristles, barbs, foreskins and multiple heads (some marsupials have forked penises; the echidna's penis has four heads). Some penises engorge themselves with blood or lymph fluid; others rely on a mineral bone to get a boner (in fact, humans are one of the only primates without a penis bone). When erect, penises might be rather stiff and inflexible, or—as in the case of whales and dolphins—retain a rubbery agility. Some penises are unexpectedly small for an animal's overall size, such as the gorilla's typical nubbin (1.25 inches erect on average). Others are astoundingly large: the humble barnacle claims the longest penis relative to body size of any animal. A sedentary creature, the barnacle probes for a mate with its impressive penis, which can be eight times its own length.

-- Ferris Jabr