Psathyrella euryspora is characterized by its small sporocarps, its flocculose yet relatively persistent veil consisting of rather thin walled and moderately encrusted, cylindric hyphae as well as by its small, broad (QAV. <1.5) and pale spores without a visible germ pore.
According to DNA-analysis, P. euryspora is closely related to P. aberdarensis and P. sulcatotuberculosa. The latter, seemingly rare species had been listed as a variety of P. typhae (Kalchbr.) A. Pearson & Dennis for a long time and was later placed into the /candolleana clade (Battistin et al. 2014; Matheny et al. 2006). Both species, however, can bear lageniform cheilocystidia and seem to be restricted to humid/wet habitats, which is in contrast to P. euryspora (Battistin et al. 2014; Ludwig 2007).
Another closely related species is Psathyrella singeri A. H. Sm (Melzer et al. 2018), which was described as a twig-dwelling fungus from Florida (Smith 1972). Smith did not mention any veil and described the lamellae being crowded. The ITS sequence of a specimen collected in China and determined as P. singeri was deposited in GenBank (compare Table 1) and differs from sequences of P. euryspora. It is unclear, however, whether this specimen is in fact P. singeri (Melzer et al. 2018). Nevertheless, all mentioned species have very pale spores and share the same branch /sulcatotuberculosa within the Candolleanae clade (compare Fig. 3). However, P. euryspora differs from other species within /sulcatotuberculosa by having smaller and more rotund spores. Obviously, there are two different veil types within /sulcatotuberculosa. The veil of P. aberdarensis consists of two types of cells, i.e. (i) diverticulate, often thick walled and brownish pigmented cells and (ii) globose elements (Melzer et al. 2018). In contrast, the veil elements of P. euryspora consist of cylindrical, subhyaline to pale brown and - in some parts - slightly encrusted hyphae, and therefore resemble the veil hyphae of P. sulcatotuberculosa (Battistin et al. 2014).
Other species with more or less pale spores, lacking or indistinct germ pore and without pleurocystidia were already discussed in Melzer et al. (2018) but shall be mentioned here again.
Psathyrella acutisquamosa Dennis has abundant veil as pyramidal warts, equally sized (5–7 × 4–5 µm) but reddish spores (Dennis 1961).
Psathyrella aequatoriae Singer is a small species without veil and larger spores (7–8 × 4–5 µm) (Singer 1978).
Psathyrella avilana Dennis grows caespitosely and terrestrially, has only fugacious veil and less broad spores (6-6.5 × 3.5-4 µm; Dennis 1961).
Psathyrella bivelata Contu has a different veil structure and larger, thick-walled spores (9-9.5 × 5-5.5 µm in av.; Contu 1991; Melzer et al. 2018; Sammut and Melzer 2012; Voto 2011).
Psathyrella efflorescens Berk. & Broome has also equally sized and pale spores but differs in having smaller cheilocystidia (12–15 × 7.5–10 µm), by its caespitose habit, purplish tints in the pileus and by its ITS-sequence (compare Fig. 1; Pegler 1977).
Psathyrella glaucescens Dennis has olive shades on the cap as well but differs by a larger pileus (1.5-5 cm), an only slightly translucently striate margin, fugacious veil made of ventricose elements and by truncate spores with a porus (Dennis 1961; Pegler 1977).
Psathyrella pallidispora Dennis has 8–11 × 4–5 µm large and slenderer spores, and sometimes capitate caulocystidia (Dennis 1970).
Psathyrella pusilla Pegler has only clavate cheilocystidia, no veil and spores that are apically truncate by a germ pore (Pegler 1977).
Psathyrella subsingeri T. Bau & J.Q. Yan is a slightly larger species with longer and more slender spores (Q = 1.4-2.0) and differs in ITS sequence (compare Fig. 1; Yan and Bau 2018).