Pannaria howeana and P. streimannii are described here as new to science. Both species are restricted to the isolated Lord Howe Island in Australia. The former is known only from one collection and the latter from two sites. Pannaria howeana is a primarily fertile species, with rather broad lobes and few rhizines restricted to the central part of the lower side of the thallus. The lower sides of the lobes have a pattern of characteristic radiating hyphae and narrowly recurved margins similar to the New Zealand lichen P. araneosa (C. Bab.) Hue, which is considered to be its closest relative. Pannaria streimannii is a phyllidiate counterpart of P. howeana. Both species share a new chemosyndrome consisting of porphyrilic acid in combination with vicanicin and leprolomin. Local endemic species are uncommon among tripartite Pannaria species, and the coarse vegetative propagules of both species appear to be an adaptation to local dispersal on a small, isolated island.
