Leptonetidae

Synapomorphies. Synapomorphies for the Leptonetidae include an unusual iridescence, especially on the legs and carapace (Figs. 1–3), autospasy at the patella-tibia joint, the presence of tartipores on the ALS (Fig. 50, 58, 62, 70), male palpi with a fused tegulum and subtegulum but with an expandable basal haematodocha, and a respiratory system consisting of a pair of short median branches with long laterals that open to a single spiracle anteriad of the ALS (Fig. 114).

Respiratory system. (Fig. 114) The respiratory system is unlike other Haplogynae in that there is a single tracheal spiracle anteriad of the anterior lateral spinnerets, which opens to a pair of long lateral branches with a pair of short median branches, similar to that found in many Entelegynae (Ramirez, 2000). The tracheae are restricted to the abdomen. Anteriorly, the respiratory system consists of a pair of book lungs.

Expandable palpi. Brignoli (1979) was the first to note the expandable morphology of leptonetid male palpi. While it is tempting to make comparisons with the palpi of some Entelegynae, homology between these structures is difficult to assess. Leptonetid palps are generally far less expandable, i.e. the bulb twists up to 180° from a basal hemotadocha with some accessory sclerites and the embolus slightly changing orientation but not ballooning out as in typical entelegynes.