CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Branchitergaliae.

(1) Maxilla on ventral surface bears a longitudinal row of setae. This row is well-developed in Isonychia/fg1 (Kluge 2004: Fig.41:C), Arthroplea and Radulapalpata (Kluge 2004: Fig.55:H, 61:D, 64:B,E,H,L, 65:F); among Radulapalpata, only in Ecdyonurus/fg1 this row is transformed to a field of irregularly situated setae (Kluge 2004: Fig.58:E,H). In Discoglossata this setal row is transferred far laterally (Eaton 1883-1888: Pl.26:12), often being indistinct; in Coloburiscus/fg1 and Pseudiron this row is lost.

(2) Imaginal and subimaginal posterior arm of prealar bridge of mesothorax is strongly shortened and does not reach incision on ventral margin of prelateroscutum (Kluge 2004: Fig.39:A, 40:F, 46:C, 54:J). Unique apomorphy. The same character was erroneously described for Rallidens (Kluge & al. 1995: 128); in that paper Fig.50 has a mistake: abbreviation PA instead of the posterior arm is attributed to prelateroscutum (for correct lettering – see Kluge 2004: Fig.36:D).

(3) Tergalius [see Bidentiseta (2)] has an additional ventral (posterior) fibrillose gill lobe; anal rib is usually located on anal margin (rarely at a distance from it – see Index of characters [1.3.28]), and the fibrillose lobe arises from ventral side of tergalius close to its base between costal and anal ribs (Kluge 2004: Fig.41:A, 44:B, 56:O, 57:C-E, 62:H-O, 65:C-E). Only in rare cases this fibrillose lobe is secondarily lost; anal rib can be also lost (see Index of characters [1.3.25] and [1.3.28]). Presence of the fibrillose lobe is probably a non-unique apomorphy: the same in Rallidens and certain Ameletopsis/fg1 (which are placed to Tridentiseta with some doubts). See also Furcatergaliae (4).

(4) Eggs have knob-terminated coiled threads (KCT: Koss & Edmunds 1973) – anchors, each consisting of a long cable formed by fused threads, and a small apical cap-like knob; cable is spirally coiled forming a small cylindrical papilla apically covered by the knob (Needham & Traver & Hsu 1935: Pl.15:9-18, Pl.17:42-45; Kopelke 1980: Fig.30-32; Studemann & al. 1987: Fig.1-4; Belfiore & al. 1999: Fig.5-11; Kluge 2004: Fig.43:G). Such anchors, either scattered by egg surface or concentrated at certain areas, occur on eggs of various species of Pentamerotarsata, Isonychia/fg1 and Coloburiscus/fg1; Discoglossata have vestigial anchors (Kluge 2004: Fig.43:H) [see Discoglossata (11) below].

In other mayflies anchors, if present, have different structure (see Index of characters [3.4]): in Ameletus/fg1, Metretopus/fg1, Acanthametropus/fg1 and Rallidens each anchor is formed not by an integral cable, but by a bunch of threads covered by a knob, and is inserted into a chorionic crater (Kluge & al. 1995: Fig.65-75,79-81); Siphlonurus/fg1 have bunches of threads without knobs (ibid., Fig.61-63); in Potamanthus/fg1 and Ephemerella/fg1 the knob is surrounded by coiled thread rather than cover it (Bae & McCafferty 1991: Fig.79; Studemann & Landolt 1997a: Fig.29).

Plesiomorphies of Branchitergaliae. Mesonotal suture is never strongly curved posteriorly by sides from median suture, usually nearly transverse (Kluge 2004: Fig.39:A,C-E, 40:D,F, 42:D, 52:C, 54:I-J, 56:L-M, 61:A-B, 63:A-E, 64:A); only in Geminovenata it is curved backward as a whole (Kluge 2004: Fig.46:A,C), and in Epeorus/fg1 is lost (Kluge 2004: Fig.64:D). Hind wings are well-developed, usually as long as 0.3–0.5 of fore wing length (only in Bleptus and selected specimens of Paegniodes smaller); bifurcation of MA is usually retained, but lost in Arthroplea and one species of Cinygma; bifurcation of MP is usually retained; only in Geminovenata venation is greatly modified.