CLADOENDESIS OF EPHEMEROPTERA
Ephemerella/fg1 Pantricorythi Tricoryptera Afrotricorythi - Dicercomyzon)
Nomen hierarchicum: Dicercomyzon/fg(1) [f:1954; g:1954]
In circumscription fits:
gen. Dicercomyzon Demoulin 1954a: 1
subfam. Dicercomyzinae Edmunds & Traver 1954a: 238
Dicercomyzon/fg(1): Kluge 2004: 332
References. Demoulin 1954a: ; 1954d: ; Kimmins 1957: ; Edmunds & Allen & Peters 1963: ; Demoulin 1964b: ; Kluge 2004: * * *
Autapomorphies of Dicercomyzon.
(1) Larval head is prognathous, frons forms a shield covering mouthparts from above ; clypeus is strongly reduced, so base of labrum is hidden under the head shield (Demoulin 1964b: Fig.4A). Non-unique apomorphy (see Index of characters [1.1.4]).
(2) Mouth apparatus is strongly modified (Demoulin 1964b: Fig.45): Mandibles are shortened perpendicular to axis of articulation. Superlinguae are stretched laterally. Maxilla [with vestigial palp see Ephemerella/fg1 (1)] has a unique structure, being strongly specialized as scraping: short and stout; field of closely situated setae on apical-ventral side [see Ephemerella/fg1 (16)] is greatly enlarged and occupies largest part of maxilla; maxillary canines are lost; only 1 dentiseta is retained [instead of two see Bidentiseta (1)] (Demoulin 1964b: Fig.5D). Labium is strongly widened, with widened paraglossae.
(3) Larval sterna form two roundish disks, the anterior of which overlaps by its posterior margin the posterior one; margins of these disks are fringed by dense setae; the anterior disc is formed by sternites of prothorax and mesothorax, and the posterior one by sternites of metathorax, abdominal segment I and partly segment II (Demoulin 1964b: Fig.3A). Probably these disks are used as adhesive suckers. Similar disk on sterna is present in Ephemerella/fg4 Drunella/g1 doddsi [E.], but there it is formed by abdominal sterna IIIX.
(4) Each tergalius [IIVI see Tricoryptera (5) and (6)] consists of a single lamella with numerous long processes on margins (Demoulin 1964b: Fig.3B-F). Such tergalius sharply differs from the initial one [see Ephemerella/fg1 (7)]; probably it is formed by complete fusion of initial two branches of ventral lobe, while dorsal lobe is completely lost. In some other Ephemerella/fg1 branches of ventral lobe can be fused, but dorsal lobe never has tendency to reduction or loss.
(5) Larval, subimaginal and imaginal paracercus is vestigial, non-segmented . Non-unique apomorphy (see Index of characters [1.3.64]); among Ephemerella/fg1 the same in Teloganodes/f1=g3 only.
(6) Larval body is short, and femora are strongly widened, flat, nearly round; together with large flat frontal shield [see (1)], body and legs form a nearly round disk ; unlike most other mayflies, larva swims not by dorsoventral abdominal movements, but by leg movements: all three pairs of femora make synchronous short movements backward, pressing to the body. The same in some other rheophilous taxa with flattened femora (see Index of characters [1b]).
Characters of Dicercomyzon of unclear phylogenetic status.
(7) On fore wing marginal intercalaries are absent. Among Ephemerella/fg1 the same in Tricorygnatha and Leptohyphes/fg1 (see Index of characters [2.2.55]); possibly synapomorphy.
(9) In male imago fore leg is not elongate. The same in Tricorygnatha and some others (see Index of characters [2.2.74]). On all legs tarsal segments 14 are extremely shortened.
Plesiomorphies of Dicercomyzon. Eyes of male are large. Imaginal and subimaginal mesonotum [without outlined lateral pigmented area see Tricoryptera (4)] retains curved lateroparapsidal suture [see Ephemerella/fg1 (10)] and has no transverse interscutal suture (Kluge 2004: Fig.99:D) (unlike Tricorygnatha and some others see Index of characters [2.2.9] and [2.2.10]). Imaginal wing without setae on amphitornal margin (unlike Tricorygnatha and Leptohyphes/fg1). At rest, subimago and imago keep wings raised up (unlike Tricorygnatha and some others). Claws on fore leg of male imago are ephemeropteroid (as well as other claws of imago and subimago see Plesiomorphies of Ephemerella/fg1).
Size. Fore wing length 46 mm (see Tricoryptera).
Distribution. Afrotropical Region.
Nominal species in Dicercomyzon/fg(1):
costale Kimmins 1957 [Dicercomyzon] syn.subj. femorale [Dicercomyzon]
femorale Demoulin 1954 [Dicercomyzon] --/
marginatum Kimmins 1957 [Dicercomyzon] syn.subj. sjostedti [Caenis]
sjostedti Ulmer 1910 [Caenis] --/
verrierae Demoulin 1964 [Dicercomyzon]
Afrotricorythi INCERTAE SEDIS
Furcatergaliae INCERTAE SEDIS