One of two orders in the class Pentastomida of the phylum Arthropoda. This order includes primitive pentastomids with six-legged larvae. The hooks are simple, lacking a fulcrum, and disposed in trapeziform pattern, with the anterior pair internal to the posterior pair. The mouth is anterior to the hooks. In both sexes the genital pores are located anteriorly on the abdomen. There is no cirrus sac; the cirrus is short and united with the gubernaculum. In the female the uterus is straight or saccate.