CLADOENDESIS OF EPHEMEROPTERA

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Characters of Cloeon/fg1 of unclear phylogenetic status. 

(1) Both mandibles always with stick-like prostheca and with dense setae proximad of it (Kluge & al. 2014: Fig.5-6; Kluge 2016: Fig.8-9, 44-45) [see Turbanoculata (6)].

(2) Labial palp with 3^rd (distalmost) segment always truncate; it is either parallel-sided with obtuse inner-apical margin, or widened, with rectangular or acute inner-apical margin (Kluge & al. 2014: Fig.8; Kluge 2016: Fig.47-48). Similar shape of labial palp is found in some other taxa.

(3) Larval patella-tibial suture often more or less interrupted on outer side, its ends are connected by arched row of long thin hairs; end of the suture on anterior side of tibia is curved distally, to the opposite direction from vestige of the suture on posterior side of femur, and the arched row of setae is connected with the ends of suture under acute angles (Kluge & Novikova 1992: Fig.1:1,2; Kluge 2016: Fig.20, 56).

(4) In larva several last abdominal segments (at least segment IX, often segments VIII–IX) have row of spines on lateral margin (Kluge & Novikova 1992: Fig5:1). The same only in Anafroptilum.

(5) Each tergalius lacks anal rib [which is initially located on anal margin – see Tetramerotarsata (12)]; often anal-proximal expansion of tergalius forms a more or less distinct lobe, which is curved dorsally forming a second (dorsal) lamella of tergalius (Kluge 2016: Fig.1-7, 11-17) (this lamella is absent in selected species of Procloeon/g1 – ibid., Fig.49-54). Nearly unique apomorphy: besides Cloeon/fg1 additional dorsal lamella is present only in Tasmanophlebia/g1; in other mayflies additional lamella, if present, is ventral.

(6) Tergalii always able to intensive rhythmic respiratory movements (see Index of characters [1.3.30]).

(7) Larval caudalii [cerci and paracercus – see Plesiomorphies] at least in their middle part with dark rings on each 4^th joining (Kluge & al. 2014: Fig.1-2; Kluge 2016: Fig.21, 59). Such pattern is not characteristic for other mayflies, while the manner in which number of segments increases in ontogenesis (by division of each segment of proximal part of caudalius in two) leads to formation of repeating structures on each 2^nd or each 4^th segment. Besides Cloeon/fg1, the same coloration is present in Cheleocloeon and Protopatellata-Dabulamanzia.

(8) In subimago process of postero-dorsal angle of postsubalar sclerite [see Turbanoculata (9)] is diminished, pointed, with concave antero-dorsal margin (Kluge 2016: Fig.37) (unlike all other Turbanoculata, in which this process is larger and has convex antero-dorsal margin).

(9) Hind wing [see Turbanoculata (10)], if present, of the «Centroptilum-type»: relatively narrow and long, with long hooked costal projection. Hind wing is present in the single species of Pseudocentroptilum, Pseudocentroptilides/g2, in selected species of Procloeon/g2; it is absent in all Cloeon/fg2, Similicloeon, Psammonella and Waynokiops, in selected species of Procloeon/g2 and (see Index of characters [2.2.59-60]).

(10) In male imaginal genital apparatus [see Liberevenata (4)], gonovectes are fused by their median ends with penial bridge, so they have lost ability for protraction (Kluge & al. 2014: Fig.30-31; Kluge 2016: Fig.30, 65). The same in Rhithrocloeon/fg1 (see Index of characters [2.3.16a]). Sclerotized unpaired external projection of penial bridge is always well expressed, being conic in Cloeon/fg2 and semicircular or truncate in other taxa.

(11) Gonostylus with 2^nd segment thickened apically, 3^rd (distalmost) segment clavate. Non-unique apomorphy, the same in selected species in various groups of Ephemeroptera.

Plesiomorphies of Cloeon/fg1. 

(12) Larval claw symmetric, slightly curved, with 2 similar rows of denticles (Kluge 2016: Fig.19, 57) [see Tetramerotarsata (11)] or without denticles (but not with 1 row of denticles, unlike majority of Baetungulata).

(13) In mature larva which is ready to molt to subimago, buds of  gonostyli are folded under larval cuticle by the "Cloeon-type": 2^nd segment of gonostylus is directed laterally, and 3^rd segment is curved caudally and medially (Kluge & al. 2014: Fig.23) [see Turbanoculata (13)] (unlike Baetovectata – see Index of characters [2.3.9]).

(14) On fore wing in each space always only 1 marginal intercalary can be present [see Liberevenata (2)] (unlike Baetovectata – see Index of characters [2.2.55]).

(15) In subimago of both sexes all segments of all tarsi are covered with pointed microlepides (see Index of characters [2.2.75], [2.2.78.2], [2.2.83]).

Variable characters of Cloeon/fg1. Larva often of siphlonuroid actively-swimming type: legs slender, not tenacious; abdomen large, not flattened ventrally (terga not wider than sterna), paracercus and primary swimming setae well-developed; only Waynokiops has shortened abdomen flattened ventrally.