Digitothyrea
Type : Digitothyrea rotundata (Büdel, Henssen & Wessels) Moreno & Egea [=Thyrea rotundata Büdel, Henssen & Wessels]
Description : Thallus homoiomerous, blackish, foliose to fruticose, rosette-forming, divided into flat lobes, horizontal to erect, attached to substratum by a central umbilicus of anticlinally arranged hyphae. Photobiont cyanobacterial, a member of Pleurocapsales or Chroococcales, cells, globose to ellipsoidal, 4–12 μm diam., with a thick, gelatinous sheath, in pairs or clustered, penetrated by fungal haustoria. Ascomata apothecia, hemiangiocarpous, laminal or marginal, immersed to stipitate. Asci prototunicate, clavate or cylindrical, wall thin, non-amyloid, 4–8-spored. Ascospores simple, colourless, subglobose to ellipsoidal, 9–15 × 7–9 μm. Conidiomata pycnidia, laminal, immersed to slightly protruding. Conidia simple, ellipsoidal to bacillar, 2–4 × 1–1.5 μm.
Digitothyrea is a genus of three known species (Moreno & Egea 1992a, 1992b; Schulz 2002a) included in the family Lichinaceae (Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005). The genus is distinguished from other rosette-forming and umbilicate genera in the Lichinaceae by a combination of characters including ascocarp ontogeny, morphology and anatomy (Moreno & Egea 1992a, 1992b). Africa appears to be the main area of speciation in this genus with two of the three known species being found there. Species of Digitothyrea are characteristic of steeply sloping or vertical water-seepage channels or along rain-tracks on outcrops of both calcareous and siliceous rocks in hot, dry, desert or semi-desert habitats. One species is known from the South I., New Zealand, but it is still very poorly collected and understood there, being earlier incorrectly recorded as Gonohymenia sp. (Galloway 1985a, 1992d).
