CLADOENDESIS OF EPHEMEROPTERA

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(1) Mandibular tusks [curved medially – see Polymitarcys/f1=Ephoron/g2 (8)] with denticles on inner side; incisor and kinetodontium are extremely diminished (Kluge 2004: Fig.79:C–D) [about tusk modifications – see below, Asthenopus/fg1 (1), Campsurus/fg3 (2) and Tortopus (2)]. Unlike Polymitarcys/f2=Ephoron/g3, dorsal and outer sides of tusks without tubercles.

(2) Paraglossae are crescent-shaped, with apices stretched and pointed; in normal position paraglossae are directed ventrally, and their pointed apices are directed dorsally (Eaton 1883–1888: Pl.25:11); if put labium in one flatness and spread paraglossae laterally, their apices become convergent. Unlike it, in Polymitarcys/f2=Ephoron/g3 paraglossae have more usual semicircular shape with rectangular apices (Eaton 1883–1888: Pl.28: 14).

(3) On larval prothorax suture separating collar from the rest part of pronotum [see Fimbriatotergaliae (1)] does not bent forward by sides, but has a form of transverse groove terminating at dorsal condyli of coxae; propleura [vestigial – see Furcatergaliae (1)] are fused with notum. This structure of pronotum is especially well-expressed in larva with its strong burrowing fore legs [see (6)], and is retained in subimago and imago as well.

(4) Imaginal furcasternal protuberances of mesothorax are separated. Non-unique apomorphy (see Index of characters [2.2.23]), but not occurring in other Fossoriae.

(5) Wing venation is modified in following manner (Kluge 2004: Fig.79:A–B, 80:A–B).

Fore wing:

Number of RS branches is diminished: usually RSa₂ does not form a triad (non-unique apomorphy – see Index of characters [2.2.37]).

Bifurcation of MA [transferred proximally – see Polymitarcys/f1=Ephoron/g2 (4)] is transferred to extreme wing base (the same in some other taxa – see Index of characters [2.2.43]).

In cubital field number of intercalaries [see Polymitarcys/f1=Ephoron/g2 (5)] is constant and equal to 2. In some species selected individuals have one or two additional intercalaries (Baumgardner & Peters & Ghanic & Hubbard 2012).

From AA backward toward wing base goes an arched vein. Trachea going into CuA and MP₂, goes from wing base posteriad of this arched vein, crossing AA and CuP; a chain of crossveins can enclose this trachea partly (Kluge 2004: Fig.79:A) or completely (Kluge 2004: Fig.80:A) (in other mayflies this trachea passes anteriorly, in a common bunch with tracheae of RA, RS and MA).

Hind wing:

In costal field the proximalmost crossvein, which supports costal projection, is thickened (crossveins distad of it can be developed or absent) (the same in some Geminovenata).

Normal bifurcation of MP is lost: MP₂ either arises not from MP₁, but from CuA, or has a form of intercalary, or is lost.

(6) On larval fore leg [which is specialized as burrowing – see (3) and Polymitarcys/f1=Ephoron/g2 (1)] tarsus is strongly shortened, widened and fused with tibia, thus it seems that claw is directly jointed to tibia (Edmunds & al. 1976: Fig.33,39). Non-unique apomorphy, similar fusion in Protobehningia. In connection with shortening of larval fore tarsus and great length of fore tarsus in male imago (as in many mayflies), in male subimago fore tarsus is moniliform, with strongly thickened segments (Eaton 1883–1888: Pl.5).

(7) Patella-tibial suture (initially present on middle and hind legs) is lost on all legs. Non-unique apomorphy (see Index of characters [1.2.18]).

(8) Male fore leg claws are blunt not only in imago [see Polymitarcys/f1=Ephoron/g2 (6)], but in subimago as well; they are strongly elongate, stick-like (Eaton 1883–1888: Pl.5).

(9) In imago and subimago middle and hind legs of male and all legs of female [non-functional – see Polymitarcys/f1=Ephoron/g2 (3)] are vestigial, tarsal segmentation and claws are non-expressed (in Campsurus/fg3 they are greatly reduced).

(10) Gonostylus without distal segments [i.e. 1-segmented – see Polymitarcys/f1=Ephoron/g2 (7)]. Non-unique apomorphy (see Index of characters [2.3.12]).

(11) Imaginal and subimaginal paracercus is reduced not only in male [see Cryptoprosternata (5)], but in female as well. Non-unique apomorphy (see Index of characters [2.3.22]).

(12) Larval cercus [with secondary swimming setae on lateral side – see Furcatergaliae (6)] lost longitudinal row of primary swimming setae on median side; instead of it, apex of each cercal segment on median side bears a transverse row of long setae which are thicker and shorter than secondary swimming setae on lateral side of cercus. Unlike Campsurus/fg1, other Fossoriae (including Polymitarcys/f2=Ephoron/g3) retain longitudinal row or stripe of primary swimming setae on median side of cercus.

(13) Larval abdominal terga are weakly sclerotized; when larva moults to subimago, larval cuticle is cracked by a median dorsal line, which stretches not only on head, pronotum and mesonotum (as in other mayflies), but also on most part of abdominal terga.

Plesiomorphies and variable characters of Campsurus/fg1 (unlike Polymitarcys/f2=Ephoron/g3). Larval fore legs without rows of tubercles. Hind wing of both sexes without additional vein between RA and RS. Eggs without anchors-bearing polar caps: they either have no polar structures (in some Asthenopus/fg1 and some Campsurus/fg2), or have long threads on one or both poles, which being coiled to a large spiral, can form a polar cap [see below, Campsurus/fg2 (3) and Plesiomorphies of Asthenopus/fg1].