CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Demoulinia.

(1) In male imago, the terminal (3rd) segment of gonostylus has unique structure: it is hooked and pointed; this shape is determined by the fact that cuticle of its outer side (directed mainly caudally) is thick, rigid, smooth and sharply convex, while cuticle of its other sides is thin and covered with microlepides (Kluge 2020: Fig.60–61). In subimago, the terminal segment of gonostylus is also pointed, with larger outer side and smaller inner side (Kluge 2020: Fig.66), but its subimaginal cuticle is entirely thin and covered with microtrichia, as other gonostylar segments and most of other body parts. This shape of the terminal gonostylar segment is already expressed in subimaginal gonostyli which are crumpled under larval cuticle before moult to subimago (Kluge 2020: Fig.57–58, 65).

(2) Larva has unique shape of labial palp (which retains all 3 segments and muscle moving 3rd segment): its 2nd segment bears large distal-medial projection of nearly quadrate form; more distal angle of this projection is rounded, and more proximal angle bears a small sclerotized point; distal margin of projection of 2nd palpomere and apex of 3rd palpomere bear heavy spine-like setae (Kluge 2020: Fig.29,31; Wuillot & Gillies 1993: Fig.21; Gattolliat 2003: Fig.6). Shape and setation of other parts of labium are also peculiar [see (9)].

(3) Tibiae of all larval legs lack patella-tibial suture. Row of long hairs on outer-anterior side (at the place corresponding to the outer-proximal end of the patella-tibial suture) is stretched along tibia and curved S-shaped (Kluge 2020: Fig.34).
Unlike larvae, subimago and imago of both sexes have patella-tibial suture on middle and hind legs, but not on fore leg (Kluge 2020: Fig.69–70). Absence of this suture on fore legs of female subimago and imago testifies that Demoulinia belongs to the plesiomorphon Protopatellata, while the larval structure is derived. Among Tetramerotarsata, patella-tibial suture is smoothed out or lost in some taxa whose larvae have strengthened legs and are adopted for inhabitancy in rapid streams, such as Centroptiloides/g and Dicentroptilum among Protopatellata or Moribaetis among Anteropatellata. The complete loss of patella-tibial suture on slender legs of the «Cloeon»-type [see (4)] is a unique feature of Demoulinia, not found in other Tetramerotarsata.

Characters of Demoulinia of unclear phylogenetic status. 

(4) Larva of the «Cloeon-type», adopted for inhabitance in stagnant water (Kluge 2020: Fig.1): abdomen is relatively long, cerci and paracercus are subequal, with dense and long primary swimming setae (Kluge 2020: Fig.41–42) [see (15)] (that is the siphlonuroid swimming specialization initial for Ephemeroptera); legs are long and slender, with slender femora [see (11)] and long claws [see (13)]; tergalii are large and adopted for effective respiratory movements [see (14)].

(5) Labrum with long setae irregularly scattered on outer surface, i.e. without constant submedian pair and without pair of regular disto-lateral rows (Kluge 2020: Fig.7-11). The same in some other baetid taxa (see Index of characters [1.1.14]).

(6) Mandibles of «Centroptilum-type»: kinetodontium is separated from incisor (but immovable) and rotated perpendicular to the plane of mandible, so that its denticles hide one another in dorsal or ventral view; left prostheca is bifurcate and rotated in the same manner (Kluge 2020: Fig.14–15) (see Index of characters [1.1.22], [1.1.24]).

(7) Maxilla with a regular row of long setae on apico-ventral side just laterad of canines (Kluge 2020: Fig.21) (see Index of characters [1.1.32]). All three maxillary canines and all three dentisetae are long, slender and bent toward one direction («Cloeon-type» of maxilla).

(8) Maxillary palp is 3-segmented, with 3rd segment short and and separated from 2nd segment by integral ring groove (Kluge 2020: Fig.21 ) (see Index of characters [1.1.]).

(9) Labium has peculiar structure of glossae and paraglossae (Kluge 2020: Fig.26-30). Glossa is widened, wider than paraglossa, semicircular; two glossae are closely contiguous medially; spine-like setae of median row are few and shifted on dorsal side of glossa. Ventral side of glossa is entirely covered with numerous irregularly situated long hair-like setae. Dorsal side of glossa, besides setae of median row and a regular dorso-lateral row, has irregularly situated setae in distal half. Paraglossa with concavity on median side, thanks to which overlaps glossa not only laterally, but partly ventrally; setae of latero-apical and ventro-median longitudinal rows are long and situated irregularly, not forming regular rows; only dorso-median row is regular. Labial palp has peculiar structure [see (2)].

(10) Hind wings are lost; larval metanotum without vestiges of hind protoptera (among Protopatellata the same in Indocloeon, part of Rhithrocloeon/fg1, part of Anafroptilum and – see Index of characters [2.2.59]).

(11) Femora of larval legs are slender, parallel-sided; spine-like setae are pointed, irregularly situated and equally small on outer and inner sides of femur (Kluge 2020: Fig.32). As in most other Turbanoculata, outer side of femur with 2 stout subapical setae (Kluge 2020: Fig.34) (on individual legs their number is 3 or 1).

(12) Larval tibiae of all legs without outer-apical stout seta (see Index of characters [1.2.17]). Tibia [lacking patella-tibial suture – see (3)] with small pointed spine-like setae on outer side and longer spine-like setae on inner side (Kluge 2020: Fig.32).

(13) Larval claw is long and slender, with 2 rows of small denticles on proximal part; distal part of claw slightly bent, with fine longitudinal striation (Kluge 2020: Fig.35–38). 

(14) Tergalii are able to make rhythmical respiratory vibration (see Index of characters [1.3.30]); tergalii of all pairs I–VII wide, with anal rib poorly developed or absent (Kluge 2020: Fig.5, 45–51).

(15) Gonovectes are fused with penial bridge (Kluge 2020: Fig.62–64). Among Protopatellata, the same in Anafroptilum and Rhithrocloeon/fg1 – see Index of characters [2.3.16a].

Plesiomorphies of Demoulinia.

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