Chaetospermum Sacc., Syll. fung. 10: 706 (1892)
Agaricomycetes, Incertae sedis, Sebacinales, genera incertae sedis
Saprobic on the host plant or submerged wood in freshwater stream. Sexual morph: see Wells and Bandoni (2001) and Kirschner and Oberwinkler (2009). Asexual morph: Conidiomata off white or pearl white when moist, yellowish-brown and waxy when dry, stromatic, pycnidial, solitary to gregarious or confluent, superficial, initially closed, ultimately opening by an irregular fissure in the apical wall, globose to subglobose or irregular in shape, unilocular, with the locule occasionally irregularly divided or convoluted, glabrous. Conidiomata wall heavily gelatinized, composed of hyaline, thick-walled cells of textura intricata to textura oblita. Conidiophores hyaline, loosely aggregated, branched, septate at base, formed from innermost cells of the conidiomata. Conidiogenous cells hyaline, subcylindrical or irregular, discrete, bearing an apical cluster of up to 3 conidia. Conidia hyaline, cylindrical, or broadly ellipsoidal, rounded at both ends, straight or slightly curved, aseptate, smooth, bearing polar or subpolar, filiform, or narrow and attenuated, flexuous, unbranched appendages.
Type species: Chaetospermum chaetosporum (Pat.) A.L. Sm. & Ramsb., Trans. Br. mycol. Soc. 4(2): 328 (1914) 
Notes: Patouillard (1888) described a fungus from decaying grass as Tubercularia chaetospora Pat. Later, this fungus was designated, as C. tubercularioides Sacc., to be the type species for a new genus Chaetospermum Sacc., because of its distinct morphology (Saccardo 1892). This name was legitimized by changing it to C. chaetosporum by Smith and Ramsbottom (1914). A detailed developmental study of the type species was published by Fonseka (1960), and several generic synonyms were noted by Sutton (1977a). Subsequently, Sutton (1980) accepted three species in the genus namely, C. carneum Tassi, C. chaetosporum and C. gelatinosum Petch, based on distinct conidial dimensions. Nag Rag (1993) revised the genus considering C. gelatinosum as a synonym of Mastigonema gelatinosum (Berk. & Broome) Nag Raj, and C. carneum a nomen dubium. Ciliospora gelatinosa Zimm. and C. elasticae var. artocarpi Koord. previously regarded as a synonym of C. carneum were made as new combinations of C. artocarpi (Nag Raj) Nag Raj and C. camelliae Agnihothr., respectively. Pestalozziella gossypina G.F. Atk. was reduced to a synonym of C. gossypinum (G.F. Atk.) Nag Raj, and a key to four species was provided (Nag Raj 1993).
Chaetospermum has been less well-studied with molecular data. Rungjindamai et al. (2008) showed that Chaetospermum species were related to Sebacinales (Agaricomycetes, Basidiomycota) based on LSU and SSU sequence data, but the type species of Chaetospermum was not included in their study. Crous et al. (2014a) designated a neotype for C. chaetosporum and revealed that it was a member of Sebacinales. In addition, a connection between C. chaetosporum and its sexual morph Efibulobasidium albescens (Sacc. & Malbr.) K. Wells (type species of Efibulobasidium) was made based on ITS sequence data. This agrees with Wells & Bandoni (2001), who recorded a Chaetospermum morph in culture of Efibulobasidium albescens. Kirschner and Oberwinkler (2009) observed both sexual and asexual morphs in the one specimen. According to the International Code of Nomenclature for Algae, Fungi, and Plants (ICN; Melbourne Code), Crous et al. (2014a) recommended the use of the older generic name Chaetospermum over Efibulobasidium.
To date, including C. setosum Rajeshk. et al. (Rajeshkumar et al. 2010) and C. malipoense X.M. Tan & S.X. Guo (Tan et al. 2014), six species are accepted in the genus. We re-examined the type of C. artocarpi and C. camelliae and provide a detailed description; we did not examine the type species, which is not in good condition.
Distribution: China, France, India, Pakistan, Thailand, Switzerland, (Rungjindamai et al. 2008, Crous et al. 2014a, Tan et al. 2014).
Li WJ, McKenZie EHC, Liu JK, Bhat DJ, Dai DQ, Caporesi E, Tian Q, Maharachcikumbura SSN, Luo ZL, Shang QJ, Zhang JF, Tangthirasunun N, Karunarathna SC, Xu JC, Hyde KD (2020) Taxonomy and phylogeny of hyaline-spored coelomycetes. Fungal Diversity 100: pages279–801.