Graphis syzygii is a species of script lichen in the family Graphidaceae. This bark-dwelling lichen forms white to pale grey crusts with distinctive elongate, irregularly branching fruiting structures () that have finely lined edges and blackened internal walls. It is known only from Costa Rica, where it grows on tree bark in open meadow habitats within Tenorio Volcano National Park.
The species was described by André Aptroot in 2009 as part of a large-scale revision and update of the script lichen genus Graphis. The type locality is Volcán Tenorio National Park in Costa Rica, where the holotype specimen was collected on the bark of a Syzygium tree in a meadow at an elevation of . It closely resembles Graphis stenotera in morphology and chemistry but differs in having a completely (blackened) and an hymenium that is (filled with minute ). The few other species that combine (finely lined) , a completely carbonized excipulum, an inspersed hymenium, and transversely septate ascospores (G. cinerea, G. leucaenae, and G. inspersolongula) differ in having much larger ascospores (75âÂÂ200 à15âÂÂ30 üm).
The thallus is corticate (with a distinct outer ), smooth to uneven in texture, and white to pale grey in color. The lirellae are , with or without a basal , and are elongate with irregular branching. They measure 1âÂÂ5 mm long by 0.2âÂÂ0.3 mm wide, and their edges () are . The excipulum is completely carbonized, and the hymenium is inspersed. Each ascus contains eight hyaline (translucent) ascospores, which are transversely 9âÂÂ13-septate and measure 25âÂÂ35 à5âÂÂ7 üm.
Graphis syzygii produces stictic acid as a secondary metabolite. It is known from Costa Rica, where it grows on tree bark in open meadow habitats within the range of Tenorio Volcano National Park.