New Zealand, South Island, Croydon Bush, Dolamore Park, Southland, ca. 46°3.6657'S, 168°49.9135'E, on exudate of Prumnopitystaxifolia. 17 February 2017, Beimforde PDD110749, holotype; New Zealand Fungarium (PDD), Landcare Research in Auckland, GenBank accession OQ308932/OQ308875.

Chaenothecopsismatai differs from other Chaenothecopsis species by forming extensive mat-like pseudostromata on podocarpous plant exudates with long, often multi-branched, partially translucent stipes, predominantly slender capitula and smooth septate spores that are often constricted at the septum.

The specific epithet refers to the Maori name of Prumnopitystaxifolia, the exudate-producing tree on which the species was first discovered.

Apothecia growing on the exudate of Prumnopitystaxifolia, arising from a dense mycelium mat which hardens in dry conditions and swells under humid conditions, forming a loose intertwined network with apices either remaining sterile or developing capitula, sometimes growing individually. Stipe glossy, crustose near stipe apices and pruinose parts, black to brownish, often with a hyaline base and/or apex, 90–240 μm wide, usually 2–7 mm long, or sometimes more than 1 cm long, flexuous or curved, multiple-branched, mostly uniformly thickened, tapering towards the apices, often with an orange to red pruina below the capitula. Stipe hyphae 2–8 µm wide, with walls two-layered, the outer wall brown and the cell walls fused, the inner walls hyaline, c. 0.5–1 µm wide, with the hyphae intertwined (textura prismatica-intricata), swelling in KOH; hyphae in the inner part of stipe hyaline to greenish, 2–6 µm wide, swelling in KOH. Capitulum black, 110–220 µm wide, 100–200 high, lentiform to cupulate, sometimes narrower than or as wide as the stipe. Excipulum hyphae brown to emerald green, 4–7 µm wide, intertwined (textura prismatica-intricata), with outer cell walls fused, swelling in KOH and some brown pigment leaking into the medium. Epithecium brownish to emerald green to hyaline, appearing as crusty layer, usually with crystals, composed of the hyphae of the excipulum and paraphyses forming a variously thickened layer. Containing various amounts of orange to ruby-red pigments in most ascomata, usually occurring as crystals on the outer walls of hyphae, and sometimes also inside their lumina. Hypothecium light brown to greenish hyaline, with the hyphae swelling in KOH. Hymenium brownish to emerald to hyaline, with the hyphae swelling in KOH, orange to red pigments present, full of amorphous material strongly congealing asci and paraphyes together. Paraphyses hyaline, filiform, 1.5–2 µm wide (n = 10), branched, usually slightly longer than the asci, variously covered with amorphous material, septate at 9–19 µm intervals. Asci cylindrical, 47–77 µm high, 5–7 µm wide (n = 8), with the apex variously thickened, often penetrated by a poorly developed canal; mature asci usually without a thickening, formed with croziers, tightly embedded in the hymenium, with light brown-green to hyaline amorphous material making individual asci difficult to observe. Ascospores, smooth, uniseriate, periclinally (to slightly obliquely) oriented in asci, 1-septate, brown, cylindrical to slightly ellipsoid, (7.3–) 8–12.5 (–14) × (2.8–) 3–4.5 (–4.7) µm (n = 60), [mean 10.3 × 3.4 µm, Q = (2–) 3–4.3 (–4.5), mean Q = 3.2]; septa as thick as spore wall, sometimes constricted.

Chaenothecopsismatai has been found at several locations in temperate broad-leaved rain forests of New Zealand on semi-hardened exudate and exudate-soaked wood and bark on the main trunk of Prumnopitystaxifolia, sometimes growing mixed with Chaenothecopsisnovae-zelandiae. Some specimens of a morphologically-similar Chaentohecopsis species have also been collected from exudate of Phyllocladustrichomanoides (Podocarpaceae), but their detailed analysis awaits more material.

PDD110746 (Fig. 1D–E), PDD110747, PDD110748, PDD110749 (Figs 5, 6) on exudate of Prumnopitystaxifolia. The specimens are deposited in the New Zealand Fungarium (PDD), Landcare Research, Auckland, with a duplicate of specimen JR13032 in Helsinki (H). The collection data and GenBank accession numbers are given in Suppl. material 1.