Tetramerocerata

Tetramerocerata is an order of pauropods containing 11 families and more than 900 species. This order was created in 1950 to distinguish these pauropods from those in the newly discovered genus Millotauropus, which was found to have such distinctive features as to warrant placement in a separate order (Hexamerocerata) created to contain that genus. The order Tetramerocerata includes the vast majority of pauropod species, as there are only eight species in the order Hexamerocerata, which remains the only other order in the class Pauropoda.

== Description == Adult pauropods in the order Tetramerocerata feature antennae that have four stalk segments and are not telescopic, whereas species in the order Hexamerocerata have strongly telescopic antennae with six stalk segments. Two antennal branches emerge from the distal end of the fourth segment in Tetramerocerata, one dorsal and one ventral; in Hexamerocerata, however, the dorsal branch emerges from the distal end of the fifth segment, and the ventral branch emerges from the distal end of the sixth segment. In Tetramerocerata, the ventral branch features two long flagella, one anterior and one posterior, but the dorsal branch features only one; in Hexamerocerata, each branch features only one flagellum. In Tetramerocerata, the distal part of the ventral antennal branch also features a spheroid sense organ, the globulus. The lateral sides of the head feature two large eye-like organs, and in Tetramerocerata, these temporal organs are flat or somewhat convex; in Hexamerocerata, these organs are shaped like cups or umbrellas attached to a shallow depression in the head.