The amended the group by excluding species with veil

The
systematic account for Crepidotus dates back to 1821 when Fries in his work
Systema Mycologicum established Tribus Crepidotus and incorporated it within
the genus Agaricus to include agarics with variable form, eccentric or lateral
stipe, fibrillose veil and rust, pale clay, or reddish-tinged spores.  Fourteen species under his tribus Crepidotus
included Paxillus atrotomentosus, Lentinellus vulpinus, Panellus
violaceo-fulvus and Entoloma depluens which nowadays are placed in different
genera and families.  Later Fries
(1836-38) amended the group by excluding species with veil and retaining those
with resupinate habit or with lateral or eccentric stipe and with rust,
brown-rust or brownish spore prints. 
Tribus Crepidotus of Fries was elevated to the rank of genus later by
Staude (1857) who treated only single species Crepidotus mollis (type species
of the genus).  Following Staudes genus
status for Crepidotus, later several researchers contributed more species under
it (Kummer 1871, Quelet 1872, 1888, Peck 1886, Murrill 1913, Kauffman 1918,
Imai 1938, Lange 1938).  By this time the
concept of the genus was to include those pleurotoid, laterally or
eccentrically stipitate agarics with coloured spores.

First
monographic treatment of the genus was given by Singer (1947) where he used
microscopic characters to delineate infrageneric relationships of the genus and
in this revision work he included 30 species of Crepidotus from North and South
America. Other comprehensive systematic treatment and account on Crepidotus were
given by subsequent researchers.   Pilat (1948) limited species with brown to
yellow brown spore prints varying to ocher-flesh colour only under the genus
Crepidotus and in this work on European Crepidoti has recognized 12
subgenera.  Later in 1950 he made a study
on 69 Extra European species (including 7 new species) and also proposed a key
based on a combination of Singer’s and his own type studies. In his monumental
treatise Agaricales in modern taxonomy (1951,1986) Singer recognized many
crepidotoid genera. Description of 109 species and 16 varieties of North
American Crepidotus which included 64 new species and 14 new varieties was
contributed by Hesler & Smith (1965). Singer’s monograph on the Neotropical
species of Crepidotus (1973) is an extensive work with the description of 61
species.  He proposed several new species
and varieties in this monograph.  Imazeki
and Hongo (1984) provided key to 16 species of Crepidotus from East Asia.  They also described in detail three species
in this book.  In her monograph for
European species, Senn-Irlet (1995) recognized 17 species and 8 new varieties.  In this treatment she also proposed an
infrageneric classification based on pileus
trama type giving importance to gelatinization.  Significant contribution to the
understanding of the Genus Crepidotus also came from work from various regions
like British Isles (Watling & Gregory, 1989), Spain (Ortega & Buendia,
1989), Germany (Stange et al, 1991), Norway (Nordstein, 1990), Italy (Lonati,
2000), Korea (Han et al, 2004), Greece (Gonou-Zagou & Delivorias, 2005), Austria
(Hausknecht and Krisai-Greilhuber, 2010). 
Consiglio & Setti (2008) has provided a very comprehensive coverage and
bilingual description for numerous species of the genus from Europe.

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The
knowledge of the genus Crepidotus through description of new species and revision
of types has been enriched from time to time by various workers (Orton 1960;
Dennis 1961; States 1973; Ueki & Smith 1973; Horak 1977; Bigelow 1980;
Luther & Redhead 1981; Poder 1983; Pegler 1983,1986; Hausknecht &
Krisai 1988; Singer 1989; Pereira 1990; Senn Irlet 1991,1992, 1993, 1995; Jung
1993;  Liu 1995; Senn-Irlet &
Krieglsteiner 1996; Astier 1998; Mu & Ming-Sheng 1999; Senn-Irlet & De
Meijer 1998; Bandala & Montoya 1999,2000,2004; Vrinda et al 2000; Kriesel
& Amelang 2001; Aime et al 2002,2009; Krisai-Greihuber & Senn-Irlet
2002; Migliozzi and Camboni 2002; Ripkova 2002,2009; Takahashi 2003; Senn-Irlet
& Immerzeel 2003; Horak & Desjardin 2004; Pouzar 2005; Prydiuk 2005;
Capelari 2007,2011; Bandala et al 2008; Uzun et al 2009; Antonin & Dvorak
2010; Chouhan et al 2010; Ripkova & Glejdura 2010; Delivorias &
Gonou-Zagou 2011; Jancovicova et al 2011, 2017; Wartchow et al 2011; Ouabbou et
al 2012; Banares-Baudet & Beltran-Tejera 2014; Gungor et al 2014; Kasuya et
al 2014; Yang & Tolgor 2014; Desjardin & Perry 2016; Senthilarasu &
Kumaresan 2016; Ge et al 2017; Guzman et al 2017).

Taxonomic
work on Crepidotus is less in Asia compared to as from America and Europe (Ge
et al, 2017).  From India few studies
have been conducted which report the presence of this interesting genus.  C. uber 
from Karnataka (Pushpa et al, 2012) and Tamil Nadu (Natarajan and Raman,
1981), C. herbarum & C. quitensis from Rajasthan (Gehlot et al, 2014), C.
payattensis from Karnataka (Senthilarasu et al, 2016), C. mollis from West
Bengal (Acharya et al, 2010) and Maharashtra (Sathe et al, 1980), C. variabilis
from West Bengal (Acharya et al, 2010) and Karnataka (Karun et al, 2014), C.
alveolus and C. applanatus from Uttar Pradesh (Hennings, 1901), C. cystidiosus,
C. eucalypticola, and C. nephrodes from Tamil Nadu (Natarajan and Raman, 1981),
C. lundelii from Rajasthan (Chauhan et al, 2010), C. fimbriatus from Gujarat
(Rajput et al, 2015) and C. luteolus from Nagaland (Ao et al, 2016) are the
reported or described ones, excepting Kerala state.

From
Kerala only 11 species of Crepidotus (C. cystidiosus, C. citrinus, C. pezizula,
C. nephrodes, C. calolepis, C. epicrocinus, C. grumosopilosus, C. melleus, C.
reversus, C. uber and C. asiaticus) are known (Mohanan, 2011; Vrinda  et al, 2000 and Guzman et al (2017).

The Family Crepidotaceae (Imai)
Singer 1951

The
genus Crepidotus (Fr.) Quelet was elevated to the status of tribe Crepidoteae
within Agaricaceae by Sanshi Imai (1938) to include species of agarics with
eccentric, lateral or absent stipes, subdecurrent lamellae, and ochreous or
ferruginous spores.  Eight species of
Crepidotus with Agaricus mollis Schaeff.ex Fr. as the type was included in this
tribe.  Later Singer (1951, 1962, 1967,
1973, 1986) in his work on Agaricales recognized nine genera within his family
Crepidotaceae.  The represented agaricoid
genera are Crepidotus Kummer, Melanomphalia Christiansen, Simocybe Karsten,
Pleurotellus Fayod and Tubaria(W.G. Smith) Gillet.  The four cyphelloid genera included are
Chromocyphella De Toni & Levi, Episphaeria Donk, Pellidiscus Donk, and
Phaeosolenia Speg. in the family.  The
type genus designated was Crepidotus (Schaeff. ex Fr.) Kummer.  Singer (1986) included genera with
pleurotoid, collybioid, omphalioid or cyphelloid habit, gymnocarpic or
hemiangiocarpic development, pip-shaped globose to ellipsoid, inamyloid, either
smooth walled or ornamented basidiospores usually lacking germ pore, pale
yellow to dark brown spore deposits, hyphae with clamps or not, cheilocystidia
nearly always present and pleurocystidia rare under the family Crepidotaceae.

            Other classification systems also
have been proposed to include all or some of the genera into other
families.  Tubaria is included in
Strophariaceae (Moser 1978) and Cortinariaceae (Watling & Gregory, 1989).  Simocybe is included in Cortinariaceae
(Hawksworth et al, 1995).  Kuhner (1980)
places Crepidotus, Tubaria and Simocybe within Strophariaceae and also does not
treat Melanomphalia or pleurotellus. 
This is supported by Nordstein (1990). However, according to Pouzar
(1985) the name Crepidotaceae has been a legitimate family name since 1951,
when it was raised to family rank by Singer.

            More recent molecular phylogeny
based studies have led to the retention or exclusion of the genera of
Crepidotaceae with inclusion of other genera also and scientists are divided in
their opinion in this regard.  After a
phylogenetic study based on 28S rDNA sequences, Aime et al. (2005) envisaged
that there are three separate lineages for crepidotoid fungi. Crepidotus and
Simocybe cluster in Crepidotaceae sensu stricto. Melanomphalia is related to
light-spored omphalinoid agarics and Tubaria is allied with Phaeomarasmius
Scherff. and Flammulaster Earle.  Using
sequences of six-gene regions Matheny et al. (2006), proposed the inclusion of
Pleuroflammula Singer in addition to Crepidotus and Simocybe within Crepidotaceae.  He also considers Inocybaceae as a sister
family to Crepidotaceae. Canon and Kirk (2007) treat Crepidotaceae and
Inocybaceae as separate family and include only Crepidotus and Simocybe under
Crepidotaceae.  Kirk et al. (2008)
clumped together the two families Inocybaceae and Crepidotaceae giving
nomenclatural priority to Inocybaceae and included 13 genera. The new Nordic
flora edited by Knudsen & Vesterholt (2008) lumps together the families
Crepidotaceae and Inocybaceae, while giving nomenclatural priority to
Crepidotaceae. Two genera, Mythicomyces and Stagnicola, are also
classified in their Crepidotaceae.  Later,
Petersen et al. (2010), using sequence data for larger subunit of rDNA, amended
the family Crepidotaceae to include Crepidotus, Episphaeria, Simocybe,
Pleuroflammula and Inocybe while Pellidiscus was included in Crepidotus and
Chromocyphella and Phaeosolenia were excluded from the family.  Alvarado et al. (2010), using RNA polymerase
II subunits 1 (RPB1) and 2 (RPB2) and 28S, treated Crepidotaceae and
Inocybaceae Jülich as independent families. Finally, Neopaxillus was recently included
as a member of Crepidotaceae (Vizzini et al. 2012; Watling and Aime 2013).

            In the present study the genus
Crepidotus is included in the family Crepidotaceae following Singer (1986).