Protura ( Janitschek 1970 )

R. G. Beutel & S. N. Gorb, 2001, Ultrastructure of attachment specializations of hexapods (Arthropoda): evolutionary patterns inferred from a revised ordinal phylogeny, J. Zool. Syst. Evol. Research 39, pp. 177-207 : 179

1 Protura ( Janitschek 1970)

The tarsus is undivided as in all other entognathous hexapods. A very short, ring­shaped pretarsus is present. It bears a single claw, an unmodified empodial seta and a ventral empodial appendage. The claw is usually knife­shaped. Mid­ and hind claws have a navicular shape in protentomids and acerentomids and are equipped with lateral teeth, which are connected by a membrane in members of the latter group ( Janitschek 1970). Specialized adhesive structures such as arolia, pulvilli, or dense fields of hairs are absent as in all other apterygote hexapods. However, empodial structures may be potential preadaptations for formation of pulvilli.