CLADOENDESIS OF EPHEMEROPTERA

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Dicercomyzon

(Panephemeroptera Euephemeroptera Euplectoptera Anteritorna Bidentiseta Furcatergaliae  
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.4–5): 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 II–IX.

(4) Each tergalius [II–VI – 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.

(8) Hind wings [initially vestigial – see Tricoryptera (2)] are lost. Non-unique apomorphy (see Index of characters [2.2.59]).

(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 1–4 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 4–6 mm (see Tricoryptera). 

Distribution. Afrotropical Region.


Nominal species in Dicercomyzon/fg(1):  

 costale Kimmins 1957 [Dicercomyzon] --/

 femorale Demoulin 1954 [Dicercomyzon]

 marginatum Kimmins 1957 [Dicercomyzon] — syn.subj. sjostedti [Caenis]

 sjostedti Ulmer 1910 [Caenis] /

verrierae Demoulin 1964 [Dicercomyzon]


Examined also:

sp.


See also: 

Afrotricorythi INCERTAE SEDIS

Furcatergaliae INCERTAE SEDIS

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