Siphoniulus

Siphoniulus is a poorly known genus of millipede containing only two living species: S. alba from Indonesia, and S. neotropicus from Mexico and Guatemala. An additional two fossil species are known from Cretaceous amber. Siphoniulus species are the only members of the family Siphoniulidae and order Siphoniulida, making Siphoniulida the smallest millipede order. Few specimens are known, and their classification is contentious, although most recent studies place them as basal members of the Helminthomorpha ("worm-like millipedes").

== Description == Siphoniulids are small and eyeless. The head is drawn out into a conical beak, and lacks Tömösváry organs. The body is relatively long and narrow, containing up to 51 segments and reaching up to long, and 0.25 mm (0.01 in) wide. The body color ranges from pure white to tan, and has been described as resembling a nematode. The exoskeleton is smooth and has few setae, and ozopores (defensive glands) are lacking. The third segment is legless. Males possess a single pair of gonopods (modified copulatory legs) consisting of the anterior limbs on the seventh segment, and which are partially recessed into the body. The telson (rear-most segment) possesses small bristle-like structures called spinnerets.