Chiodecton Ach.
Type : Chiodecton sphaerale Ach.
Descriptions : Flora (1985: 91); Thor (1990: 9–22; 32–33).
Chiodecton is a genus of 16 currently accepted species (Thor 1990; Kirk et al. 2001) included in the family Roccellaceae (Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005), although additional undescribed taxa are known from Asia, Africa and America (Thor 1990). There are many species described in the literature but most are referable to other genera, including: Arthonia, Byssoloma, Cryptothecia, Dirina, Enterographa, Lecanactis, Mazosia, Roccellina and Schismatomma (Thor 1990). Thor (1990, 1994) described five new genera (Ancistrosporella, Dichosporidium, Erythrodecton, Graphidastra and Streimannia) closely related to Chiodecton, all sharing the synapomorphy of thin-walled spores. Species of Chiodecton are widely distributed (though often rare and local) in tropical, subtropical and temperate rainforest in America, Africa, Asia and Australasia. Neither isidia nor soredia are known in Chiodecton, with spore dispersal being the main agency of distribution. Spore walls and septa are thin, indicating that spores are probably short-lived and ruling out long-distance dispersal for the genus, thus accounting for the often restricted geographical ranges of particular species (Thor 1990). Two species are known with certainty from New Zealand (Galloway 1985a; Thor 1990). Two additional saxicolous taxa described by Dodge (1971) from Macquarie Island (C. acarosporoides C.W.Dodge and C. maquariensis C.W.Dodge) were also recorded from the Auckland Islands, the Snares, and from alpine localities in the South Island (Dodge 1971: 442–443). Snares material seen of Chiodecton macquariensis, so identified by Carroll Dodge (Fineran 1969: 246), is referable to Pertusaria graphica (Galloway 2004d), and alpine rock specimens determined by Dodge are referable to Porpidia!
