Synarthonia sikkimensis
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| Synarthonia sikkimensis | |
|---|---|
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Arthoniomycetes |
| Order: | Arthoniales |
| Family: | incertae sedis |
| Genus: | Synarthonia |
| Species: | S. sikkimensis |
| Binomial name | |
| Synarthonia sikkimensis S.Joseph & G.P.Sinha (2015) | |
 Type locality: Sikkim, India | |
Synarthonia sikkimensis is a species of corticolous (bark-dwelling) crustose lichen of uncertain familial classification in the order Arthoniales.[1] Found in Sikkim, India, it was formally described as a new species in 2015. It is characterised by the sorediate thallus with a rhizomorph-like prothallus, a combination of features unique in the genus.
Synarthonia sikkimensis was described as new to science by Siljo Joseph and Gopal Prasad Sinha in 2015. The type was collected on bark in the Sikkim Himalaya (Lachung–Dombang, near Yakche) at 3,040 m elevation on 20 March 2012. The species was distinguished at publication by two features not previously recorded in Synarthonia: a sorediate thallus (a lichen body that produces powdery vegetative propagules called soredia) and a conspicuous, rhizomorph-like prothallus (a root-like marginal outgrowth); it also has larger spores than its closest look-alike, S. stigmatidialis. In the world key provided by the authors, S. sikkimensis is the only species with a sorediate thallus.[2]
The genus itself is characterised by fruiting bodies that begin solitary and then merge into clustered synascomata (compound fruiting bodies sharing a single structure) embedded in a shallow pad of fungal tissue (a pseudostroma) with a thin white margin—patterns also seen in this species.[2] A 2026 review of Synarthonia treated S. sikkimensis as one of about 25 recognized species in the genus. In discussing the separation of S. inconspicua, the authors used S. sikkimensis as a comparison taxon, distinguishing it by its sorediate thallus and I+ (reddish) hymenial reaction (a colour change in the spore-bearing layer when treated with iodine).[3]