Basionym: Physcia endopyxinea Müll. Arg., Proc. R. Soc. Edinb. 11: 459 (1882); Dirinaria endopyxinea (Müll. Arg.) C.W. Dodge, Beih. Nova Hedwigia 38: 181 (1971).
Type: Africa, Yemen, Socotra Islands, 'ramulicola partim cum Pyxine convexa Müll. Arg. crescens', 1881, Balfour 1359 ('BCS' = Balfour, Cockburn & Scott) (G–66116 A, collector's number 1359 red-underlined, selected here as lectotype!), 1400 ('BCS') (G–66116 B syntype, number cited in protologue), 1563 ('BCS') (G–66116 C syntype, number cited in protologue).
With its weakly pruinose thallus, a pale white surface and weakly pruinose discs this African species appears rather similar to D. neotropica (especially the second, most commonly found morphotype). Superficially the two taxa are difficult to distinguish, although thalli of D. neotropica typically have a pinkish hue and those of D. endopyxinea are ivory white to pale beige. Further, D. neotropica is a saxicolous species whereas D. endopyxinea is epiphytic.
The type of D. endopyxinea differs from D. neotropica in having a subhymenium that consistently lacks oil droplets and an epihymenium that is brown, rather than olivaceous. The epihymenium of D. endopyxinea lacks the diffuse greenish pigment present in D. neotropica which reacts K+ violet. Both species have ascospores with ±pointed ends similar to the Dirinaria-type, initially with angular cell lumina, but their spore-walls soon becoming thin. Although the ascospore dimensions of the two species fall into the same range, the spores of D. endopyxinea are generally more narrowly elongate. In the Galapagos all specimens of D. neotropica occur exclusively on rock. The Socotran species is known only as an epiphyte (the substrate of the type material are decorticated branches).
Chemistry: Thallus P+ yellow, K+ yellow, C−, KC−, UV- (dull yellowish); medulla P-, K-, KC-, C-, UV- (dull yellowish); atranorin (minor), chloroatranorin (minor or trace), diploicin (major); Swinscow & Krog (1978) examined the type and confirmed that the specimen contains the same secondary metabolites as Diploicia canescens, rather than divaricatic acid as originally suggested by Awasthi (1975). We did not re-analyze this material.
Ecology and distribution: The checklist of lichens included in Brown & Mies (2012) suggests that 'Physciaendopyxinea Müll. Arg.' is endemic to Socotra, even though Awasthi (1975) cites one collection from Angola. The identity of this Angolan specimen appears doubtful considering Awasthi's confusion with the chemistry of the specimens.