Ultrastructure of attachment specializations of hexapods (Arthropoda): evolutionary patterns inferred from a revised ordinal phylogeny Author R. G. Beutel Author S. N. Gorb text J. Zool. Syst. Evol. Research 2001 39 177 207 journal article 10.1046/j.1439-0469.2001.00155.x 95b3d62f-8fcc-4088-873f-b33f4a63d3fc 2360323 4 Archaeognatha The tarsus is three­ or rarely two­segmented ( Watson and Smith 1991 ). A well­defined, segment­like pretarsus is not developed in archaeognathans and all following groups. The reduced pretarsus bears two simple claws. A median claw or empodium is not developed.