A large earthstar with broad rays and a prominent collar, though the collar (apophysis) only forms reliably in fully mature fruitbodies. Immature or mid­stage specimens often show only a slight thickening, a partial rim or no collar at all. Their large size is the best indicator when this occurs. The NZ lineage resembles G. triplex, but it is genetically distinct.

Basidiome (immature): Subglobose, 20-30 mm diam., dark brown to buff, often with a slightly roughened or powdery surface. Outer peridium thick, sometimes showing faint cracks as it expands.
Basidiome (mature): When fully expanded, 5-10 cm across, with the exoperidium splitting into 6-9 rays.
Rays: Broad, thick, and fleshy when fresh. Inner surface pale buff to tan, often forming a distinct raised cup (the “collar”) around the spore sac — the hallmark of the triplex group. Outer surface brown, sometimes cracking or flaking. Rays typically reflexed, forming a shallow bowl beneath the spore sac.
Collar (apophysis): A prominent, well‑defined cup formed by the inner layer of the exoperidium. Often deep and sharply margined, giving the species its characteristic “triple layer” appearance.
Spore sac: Globose, 1.5–3 cm diam. Surface smooth to finely granular, grey‑brown to fawn. Apex with a well‑defined peristome, typically fibrous or slightly grooved, but not strongly beaked. Gleba white when young, becoming dark brown and powdery at maturity.
Rhizomorphs: White, slender, attached at the base of the spore sac.