Mediothele Raven & Platnick, 1978 : 74

T, Duniesky Rios & Goloboff, Pablo A., 2012, New species of Chilean Hexathelidae (Araneae, Mygalomorphae), Zootaxa 3422, pp. 32-51 : 41

Mediothele Raven & Platnick, 1978: 74 .

Until now, the genus Mediothele included a single species, M. australis , described from a single male from Southern Chile; no further males are known of the genus. The genus was originally included in Dipluridae , but later transferred ( Raven, 1985) to Hexathelidae , proposing Scotinoecus as its sister group.

In this genus, morphological differences between species are more marked than in Scotinoecus , especially in leg, cephalothorax and sternum shape, and chaetotaxy. The much simpler spermathecae have only minor differences between species (often within the observed range of individual variation among specimens of a single locality).

Type species. Mediothele australis Raven & Platnick, 1978

Diagnosis. Differs from Scotinoecus in the labium and maxillae having few (female) or no (male) cuspules; fangs with basal outer tooth. PLS spinnerets short, ALS two-segmented much shorter than PMS; thickened femora III; patellae III with strong prolateral spines; patellae III and IV with many prolateral and dorsal anterior strong setae. Male tibia I with one large and one small spur, and associated thorn on metatarsus; bulb pyriform, without conductor.

Many of these somatic characters (fang tooth, shorter spinnerets, thickened femora, and patellae with strong spines and setae) are probably associated with a burrowing lifestyle.

Habits. Spiders of all known species live in small silk-lined burrows with an open entrance.

Monophyly. By out-group comparison, essentially all of the characters in which it differs from Scotinecus are synapomorphies of Mediothele . The monophyly of the genus is thus well established. The low numbers of labial (and maxillary) cuspules are best interpreted as a reversal, as (according to Raven’s 1978, 1985 hypotheses of hexathelid relationships) they occur in several successive sister groups.