Sessile, when fresh gelatinous, pale whitish, lobed to irregularly cerebriform, becoming pale yellowish when dry, 0.5–2.5 cm in diameter, broadly attached to substratum.

Hyphae hyaline, smooth, thin- to thick-walled, 2.0–5.0 µm in diameter, branched, interwoven, with abundant clamp connections and medallion clamp connections (clamp complexes), thick-walled hyphae usually present near to base of basidioma; hyphidia hyaline, smooth, thin-walled, branched; swollen cells, vesicles and haustoria absent; mature basidia thin-walled, globose to subglobose, with a basal clamp connection, 13.0–18.0(–22.0) × 9.0–16.0 μm, L = 15.7 µm, W = 14.8 µm, Q = 1.06 (n = 30/1), sometimes their width greater than length, usually longitudinally septate, rarely obliquely septate, 2–4-celled, with obvious oil drops; sterigmata up to 100 μm long, 1.5–2.0 μm in diameter, slightly protuberant at apex; probasidia thin-walled, subglobose to ellipsoid, mostly proliferating directly from basidial clamps; basidiospores hyaline, thin-walled, mostly ellipsoid to slightly ovoid, apiculate, with oil drops, 7.0–10.0 × 6.0–7.0 μm, L = 8.4 µm, W = 6.5 µm, Q = 1.29–1.40 (n = 60/2), germinating by germ tubes or secondary spores; conidia occasionally present in cluster, originating from conidiophores, hyaline, thin-walled, ellipsoid to subglobose, 2.0–3.0 × 1.0–2.5 μm.

Brazil Rondônia, Municipality of Jaru, in mixed forest near the airport, 9°40'S, 61°50'W, on wood, associated with old pyrenomycete stromata and litter, 10 October 1986, M. Capelari & R. Maziero 944 (SP211759, duplicate BJFC028110); Pernambuco, Recife, Jardim Botânico do Recife, on angiosperm wood, 16 May 2017, R. L. M. Alvarenga 471 (URM).

Tremellafibulifera was probably a species complex including T.olens originally from Australia and T.neofibulifera originally from Japan because they shared cerebriform whitish basidioma and abundant clamp complexes (Möller 1895; Bandoni and Oberwinkler 1983; Malysheva et al. 2015). Two specimens (SP211759, Alvarenga 471) from Brazil bearing the common feature of the complex formed a distinct lineage in our phylogenies (Figs 1, 2). Morphologically, the two specimens agree well with T.fibulifera except for the presence of conidia (Table 3). However, conidia are unstable in T.fibulifera. Möller (1895) described the anamorph of T.fibulifera, but the conidia were not observed when Bandoni and Oberwinkler (1983) re-described T.fibulifera based on the type designated by Möller (1895). Furthermore, T.fibulifera was originally described from Blumenau, Brazil, which is very close to the location of SP211759, Rondônia, Brazil. Therefore, we treat Alvarenga 471 and SP211759 as the representatives of T.fibulifera s.s. In addition, T.fibulifera s.s. are different from T.subfibulifera and T.australe by 8.51%, 9.87% sequence differences in the ITS sequences and 2.10%, 1.57% in the partial nLSU sequences respectively.