Welsh is such a beautiful language.
There’s definitely a few fungi that clock in at above 25 letters - a few I can think of
Psilocybe ovoideocystidiata (26)
Rhizomarasmius pyrrhocephalus (28)
Candolleomyces candolleanus (26)
Tolypocladium ophioglossoides (27)
Callistosporium purpureomarginatum (32)