Procloeon Bengtsson 1915

Kluge, Nikita J., 2025, Contribution to the knowledge of psammophylous representatives of Procloeon Bengtsson 1915 - Psammonella Glazaczow 1987 and Pseudocentroptiloides Jacob 1987 (Ephemeroptera: Baetidae), Zootaxa 5691 (3), pp. 449-494 : 451-453

publication ID	https://doi.org/10.11646/zootaxa.5691.3.3
publication LSID	lsid:zoobank.org:pub:7D944AD3-0FA0-4549-AEB1-CF3F0348D1A0
DOI	https://doi.org/10.5281/zenodo.17372245
persistent identifier	https://treatment.plazi.org/id/039187C0-FFD3-FFF4-83CF-FE7D37B364EA
treatment provided by	Plazi
scientific name	Procloeon Bengtsson 1915
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Treatment

Genus Procloeon Bengtsson 1915 View in CoL View at ENA (s. l.), or Procloeon/g1

( Figs 1–219 View FIGURES 1–8 View FIGURES 9–24 View FIGURES 25–28 View FIGURES 29–31 View FIGURES 32–59 View FIGURES 60–66 View FIGURES 67–73 View FIGURES 74–79 View FIGURES 80–83 View FIGURES 84–88 View FIGURES 89–93 View FIGURES 94–97 View FIGURES 98–102 View FIGURES 103–108 View FIGURES 109 View FIGURES 110–116 View FIGURES 117–122 View FIGURES 123–131 View FIGURES 132–135 View FIGURES 136–143 View FIGURES 144–150 View FIGURES 151–154 View FIGURES 155–158 View FIGURES 159–164 View FIGURES 165–173 View FIGURES 174–180 View FIGURES 181–189 View FIGURES 190–197 View FIGURES 198–203 View FIGURES 204–206 View FIGURES 207–212 View FIGURES 213–216 View FIGURES 217–219 )

In circumscription corresponds to:

—branch «11»: Kluge & Novikova 1992: fig. 11;

— Procloeon View in CoL /g1: Kluge 2012: 362;

—genus Procloeon View in CoL : Kluge 2016: 494.

Type species: Cloeon bifidum Bengtsson 1912 .

Systematic position of Procloeon View in CoL . The taxon Procloeon View in CoL , or Procloeon View in CoL /g1 belongs to the higher taxon Cloeon View in CoL / fg1 (as defined by Kluge 2012), which can be treated as the tribe Cloeonini (as defined by Kluge 2016). Diagnosis and composition of Cloeon View in CoL /fg1 = Cloeonini is given in the previous publications ( Kluge & Novikova 1992: branch «6» on figure 11; Kluge 2016: 492).

Diagnosis. The taxon Procloeon s. l. is characterized by peculiar structure of the denticles located on distal margins of segments of larval cerci: in distal part of cercus, each cercomere has one greatly enlarged denticle located on its lateral side; this denticle is much larger than others, usually longer than the next cercomere and is usually widened ( Kluge & Novikova 1992: fig. 9. 19) ( Kluge 2012: 362; 2016: 494). Such structure of larval cerci occurs in all examined representatives if the plesiomorphon Procloeon s. str. ( Figs 2–8 View FIGURES 1–8 ; Kluge & Novikova 1992: fig. 9. 19), the examined representative of the subgenus Pseudocentroptiloides s. str. ( Fig. 1 View FIGURES 1–8 ), in both representatives of the subgenus Monilistylus Kluge 2020a ( Kluge et al. 2014: figs 1–3; Kluge 2020a: figs 7–8), in all representatives of the subgenus Oculogaster Kluge 2016 ( Kluge 2016: figs 21–22, 59–60; Kluge 2020b: figs 8–9, 43–44, 85–86, 112, 141); in all examined representatives of the subgenus Securiops Jacobus et al. 2006 ( Kluge 2023: figs 71–72, 105, 124–125) and in all examined representatives of the subgenus Psammonella described in this paper ( Figs 86–88 View FIGURES 84–88 , 129–130 View FIGURES 123–131 , 156 View FIGURES 155–158 , 189 View FIGURES 181–189 ). In most of these species, the enlarged denticle is longer than the next cercomere, in certain species up to three times longer ( Kluge 2023: fig. 125); in exceptional case the denticle is a little shorter than the next cercomere ( Kluge et al. 2014: fig. 3). The enlarged denticle is usually widened, with convex margins, so that in dorsal and ventral views its width at midlength exceeds its width at base ( Figs 130 View FIGURES 123–131 , 156 View FIGURES 155–158 , 189 View FIGURES 181–189 ); in some species these denticles are not widened, with margins straight ( Fig. 86 View FIGURES 84–88 ).

Psammophylous taxa within Procloeon

Larvae of some Procloeon s. l. are specialized for inhabitance on a bottom consisting mostly of clean sand. These are species of the subgenus Securiops (recently revised by Kluge, 2023) and the species originally placed by Jacob & Glazaczov (1987) in the genus Pseudocentroptiloides .

These psammophylous larvae differ from other Procloeon by especially long and slender claws lacking denticles ( Figs 74 View FIGURES 74–79 , 114–116 View FIGURES 110–116 , 151–153 View FIGURES 151–154 , 174–176 View FIGURES 174–180 ) and by modifications of mouth parts. In contrast to other Procloeon , which have rather uniform mouth parts structure ( Figs 9–17 View FIGURES 9–24 ), the psammophylous larvae have labium enlarged and directed backward ( Fig. 18 View FIGURES 9–24 ), glossae diminished, paraglossae elongated, and labial palps especially greatly widened apically ( Fig. 23 View FIGURES 9–24 ; Kluge 2023: figs 40, 116).

Besides this, the genus Pseudocentroptiloides in the original sense (i.e., including the subgenus Psammonella ) differs from Securiops and other Procloeon s. l. by widely incised distal margin of labrum ( Fig. 19 View FIGURES 9–24 ), widened and concave distal margin of hypopharynx ( Fig. 22 View FIGURES 9–24 ) and shortened maxillae with more or less developed setal crest laterad of incisors ( Figs 24 View FIGURES 9–24 , 25–31 View FIGURES 25–28 View FIGURES 29–31 ). This lateral transverse setal crest originates from a row of setae which are few and small in other species ( Fig. 194 View FIGURES 190–197 ). These features of mouth parts structure are regarded to be diagnostic characters of the genus Pseudocentroptiloides s. l. (including the subgenus Psammonella ) ( Jacob & Glazaczow 1987).

However, a recently described species Cheleocloeon psammonella Kluge 2025 demonstrates that similar shape of labrum, maxillae, glossae and paraglossae can independently evolve in a non-related species which has psammophylous specialization ( Kluge 2025: figs 56, 59–63). This fact does not disprove the idea about holophyly of Pseudocentroptiloides s. l., but makes it less strongly argued.

Larva of Procloeon macronyx ( Kluge & Novikova 1992) has long and slender claws lacking denticles, like that of Pseudocentroptiloides ; eggs of this species have equatorial girdle ( Fig. 218 View FIGURES 217–219 ) similar to that of Procloeon ( Pseudocentroptiloides) shadini ( Fig. 215 View FIGURES 213–216 ); imagines of these two species are very similar. Both species are known under the name « Centroptilum nana » (see discussion below, «Status of species name Centroptilum nana »). Possibly, P. macronyx is related to P. shadini , but in contrast to it has no features of psammophylous specialization in structure of labrum, hypopharynx, maxillae and labium ( Figs 9–17 View FIGURES 9–24 ). Based on this, Belfiore & D’Antonio 1990 placed both species in the genus Pseudocentroptilum , to which they attributed all Procloeon having hind wings, and regarded Pseudocentroptiloides to be a synonym of Pseudocentroptilum .

The new species, Procloeon furcalabrum sp. nov., described below, also has long and slender claws ( Fig. 202 View FIGURES 198–203 ); besides this, it has distal margin of labrum widely incised ( Fig. 190 View FIGURES 190–197 ) and apex of hypopharynx widened and concave ( Fig. 195 View FIGURES 190–197 ), as in Pseudocentroptiloides s. l.; but its maxillae are not shortened and retain long, slender canines ( Fig. 194 View FIGURES 190–197 ); its glossae and paraglossae retain the shape usual for Procloeon s. str. ( Figs 191–192 View FIGURES 190–197 ).

The equatorial girdle on eggs, being present in P. macronyx and P. ( Pseudocentroptiloides) shadini , is absent in P. ( Psammonella) magnificum sp. nov. ( Figs 103–108 View FIGURES 103–108 ), that suggests independent origin of Pseudocentroptiloides and Psammonella.

While status and circumscription of the taxa Pseudocentroptiloides s. l. (including Psammonella) and Pseudocentroptiloides s. str. (without Psammonella) are unclear, the taxon Psammonella represents a clearly holophyletic taxon comprising not less than 6 species distributed on Oriental Region. Holophyly of Psammonella is proven by unique structure of its maxillae (see below).