CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Tricoryptera. Characters listed here are evidently apomorphic in comparison with other Ephemerella/fg1; however, some characters are common with Caenoptera, that has no explanation (see Classifications of Furcatergaliae II). About other characters common with Caenoptera and occurring in selected taxa of Tricoryptera – see below, Tricorygnatha (6)–(12), Leptohyphes/fg1 (3)–(8) and Tricorythodes (2)–(5).

(1) On fore wing tornus is lost [in connection with reduction of hind wing – see (2)], and venation is modified: portion of CuP proximad of the point where it connects with cup-aa [see Ephemerella/fg1 (6)] is partly or completely lost; because of this CuP looks as arising not from CuA, but from AA; cubital field has only one bifurcate vein – 1^st cubital fork (x₁, x₂) [see Ephemerella/fg1 (15)] which usually (but not always) arises from CuP (Kluge 2004: Fig.89:M, Fig.99:A, Fig.100:A). This is similar to Caenoptera [see Classifications of Furcatergaliae II and Caenoptera (10)].

Similar structure, when CuP arises close to base of AA, occurs in Tetramerotarsata and some Leptophlebia/fg1, but origin of such veins position is different: in Tetramerotarsata and Leptophlebia/fg1 CuP at its base is curved and set apart from CuA (Kluge 2004: Fig.106:F), while in Ephemerella/fg1 the base of CuP is never curved or set apart from CuA, but can disappear.

(2) Hind wing is diminished  (as long as 0.1–0.2 of fore wing length) and has a long, narrow, pointed costal projection; at the same time, larval hind protopteron has no costal projection, but retains a shallowly rounded convexity on costal margin; when adult hind wing develops in protopteron, its costal projection locates in the costal convexity of protopteron, being arched in apiclal direction (Kluge 2010: Fig.2-3, Fig.8-9). Such hind wings are present in Ephemerythus (which belongs to Tricoryptera-Afrotricorythi) and Leptohyphes s.str. and some other taxa belonging to Tricoryptera-Letohyphes/fg1. Shape of hind protoptera in these taxa is similar, but shape of adult hind wing is different: in Ephemerythus costal projection is directed anteriorly, can be straight (Gillies 1960: Fig.2; Kluge 2004: Fig.99:C) or somewhat ached apically (Kluge 2010: Fig.2-3); in representatives of Leptohyphes/fg1 costal projection is arched proximally (Kluge 2004: Fig.100:B). In other Tricoryptera hind wings and their larval protoptera are completely lost, so this character is not expressed.

By structure and development of hind wing, Tricoryptera differ from most Ephemeroptera and most insects in general, whose adult wings and protoptera have similar shape and retain evolutionary correlation. Similarly diminished hind wing with enlarged costal projection occurs in many non-related mayfly taxa, but in these cases larval hind protopteron has a costal projection, whose apex corresponds to apex of costal projection of adult hind wing.

Characters of Tricoryptera of unclear phylogenetic status.

(3) Infrascutellum is interrupted medially, scutellum is more or less enlarged, with enlarged lateral impressions (Kluge 2004: Fig.89:B). The same in Teloganodes/f1=g3 (possibly synapomorphy) and Caenoptera (see Classifications of Furcatergaliae II).

(4) On subimaginal mesoscutum [see Ephemerella/fg1 (10)] relief line is lost, and subimaginal lateral pigmented area is either dispersed to most part of submedioscutum and medioscutum (Kluge 2004: Fig.98:D, 99:D), or disappears (Kluge 2004: Fig.104:I). Possibly, synapomorphy with Teloganodes/f1=g3.

(5) Tergalii I [initially stick-like – see Ephemerella/fg1 (13)] are lost. Non-unique apomorphy (see Table and Index of characters [1.3.33]).

(6) Tergalii VII are reduced; usually they are completely absent, only two species of Sparsorythus/g1 (jacobsoni [Tricorythus] and bifurcatus [Sparsorythus]) have vestiges of tergalii VII. Unlike larva with developede tergalii, yang larvula has tergalii VII, which appear before others (this was observed for tuinctus [Tricorythus]); thanks to this, loss of tergalii VII in mature larva is reversable. Loss of tergalii VII is a non-unique apomorphy (see Index of characters [1.3.59]); particularly, tergalii VII are lost in Melanemerella/f1=Teloganodes/g1 (possibly synapomorphy) and Caenoptera.

(7) Larval abdominal terga without paired dorsal projections [see Ephemerella/fg1 (19)]; usually terga have no dorsal projections, rarely have unpaired projections; the same in some other taxa (see Index of characters [1.3.3]).