CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Dilatognathus.

(1) Mouth apparatus of "Dilatognathus-type" (Kluge 2012) (see Index of characters [1.1.12]), with following modifications: 

Labrum is widened, its median incision [see Atalophleboculata (2)] is widened; proximal transverse row of setae [see Atalophlebopectinata (2)] is shifted to proximal part of labrum and can be interrupted medially (Kluge 2012: Fig.133) (see Index of characters [1.1.14]).

Maxilla (Kluge 2012: Fig.129-132; Kluge 2014: Fig.6–12, 14-15, 16-18, 19-20): Ventral row of pectinate setae [see Leptophlebia/fg1 (1)] is vestigial: it always consists of three setae, whose pectinate structure is poorly expressed, and in ultimolarva lost.

Other characters of maxilla can be either usual for Atalophlebomaxillata (only in nicobarensis [Choroterpes (Dilatognathus)]), or modified as following: Ventroapical flange [see Atalophlebomaxillata (2)] is either strongly shortened, or lost. Dentiseta [initially  single, comb-like and bent apically – see Atalophlebomaxillata (1)]  is either straight and directed medially, or lost. At least in ultimolarva, inner-apical angle of maxilla is produced to a long and heavily sclerotized tusk (see Index of characters [1.1.29]), so that all three vestiges of ventral pectinate setae are located on its proximal part (see Index of characters [1.1.31]); dentiseta is lost (see Index of characters [1.1.37, 39]); ventro-apical flange is very small, smoothed or absent. Maxillary structure in previous larval instars is either the same as in ultimolarva, or different: tusk can be shorter or absent, dentiseta can be present, small ventro-apical flange can be present; in cataractae [Choroterpes] its ontogenesis has sexual dimorphism (Kluge 2014: Fig.6–12).

Maxillary palp is elongate and bears long filtering setae: 2^nd segment in apical part of inner side has a few such setae forming a longitudinal row; 3^rd (terminal) segment has a proximal semicircular transverse row of such setae on its inner side and fields of irregularly situated setae along its ventral and dorsal sides (Kluge 2012: Fig.130–131) (see Index of characters [1.1.46]).

Labium has paraglossae widened, expanded laterally (Peters & Edmunds 1970: Fig. 165). Labial palp is elongate and bears long filtering setae which form regular longitudinal rows: 2^nd segment has a double row on outer side and a row on dorsal side; 3^rd segment has a row on outer side and a row on inner side; dorsal side of 3^rd segment also bears smaller irregularly situated setae (Kluge 2012: Fig.139) (see Index of characters [1.1.58] and [1.1.59]).

(2) Tergalius I [initially different from others – see Choroterpes/g1 (2)] is lost, thus only tergalii II–VII are present [see (3)].

(3) Tergalii have the same structure in all species (Kluge 2012: Fig.138,140-141). Each of two lamellae of tergalii II–VII is widened, its 3 apical processes [see Choroterpes/fg2 (2)] are brought together, side processes of ventral lamella are wide basally. Each tergalius II–VI normally has all 6 apical processes (only in individual cases some processes can be absent); tergalius VII has 5 apical processes only: its dorsal lamella has no costal process (Kluge 2012: Fig.138). Tergalii II–V have equal size and shape, tergalius VI is smaller, tergalius VII (with 5 apical processes) is the smallest.