CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Nesameletus/f1=Metamonius/g1.

(1) Mandibular incisor is enlarged, straight, blade-like, and kinetodontium is reduced; kinetodontium can be retained as a setiform vestige (Kluge 2004: Fig.31:D,F), or lost.

(2) Maxilla is elongate, with short biting edge; all 3 canines have characteristic shape – short, with rounded outer margin; setation laterad of canines is reduced: either vestigial setae of apical-ventral row are present (in Nesameletus/f2=Metamonius/g2 – Kluge 2004: Fig.31:A-C), or all setae are lost (in Siphluriscus – Kluge 2004: Fig.31:E). For other character of maxilla – see (3), (4) and (7).

(3) On maxilla [see (2)] 2^nd and 3^rd dentisetae [among 3 dentisetae – see Anteritorna (2)] can be situated on a common base; besides dentisetae, this base bears some smaller setae. In other respects dentisetae are modified differently [see below – Nesameletus/f2=Metamonius/g2 (3) and Plesiomorphies of Siphluriscus].

(4) 3^rd segment of maxillary palp is shortened (Kluge 2004: Fig.31:C).

(5) Glossae and paraglossae are elongate, narrowed, ventral surface with irregular long slender outstanding setae; glossae bear stout setae on apex (Kluge 2004: Fig.30:F); paraglossae can also bear such setae (in Siphluriscus – Zhou & Peters 2003: Fig.10) or not (in Nesameletus/f2=Metamonius/g2). General shape of glossae and paraglossae resembles that of Turbanoculata, but paraglossae retaine lateral (not apical) attachment to mentum.

(6) Imaginal and subimaginal vertex has unpaired projection; in Nesameletus/f2=Metamonius/g2 it is well-expressed in both sexes (Kluge 2004: Fig.30:C), in Siphluriscus – in male only (Zhou & Peters 2003: Fig.22,28).

Characters of Nesameletus/f1=Metamonius/g1 of unclear phylogenetic status.

(7) Maxilla [see (2)–(4)] bears a gill located laterally at articulation of cardo and stipes; in Nesameletus/f2=Metamonius/g2 this is a single small process (Kluge 2004: Fig.31:C), while in Siphluriscus this is a tuft of gill processes, and another tuft arises medially (Zhou & Peters 2003: Fig.8). Gill similar to that of Nesameletus/f2=Metamonius/g2 is present in Rallidens; possibly, synapomorphy.

(8) In imago and subimago claws (initially ephemeropteroid) on each leg are similar and pointed. Non-unique apomorphy (see Index of characters [2.2.85]); among Tridentiseta the same in Siphlonurus/fg1 and Dipteromimus.

(9) On each tergalius I–VII anal rib is situated on dorsal surface near middle of tergalius, just behind main trachea (the same in Siphlonurus/fg1, Dipteromimus and some Ameletus/fg1); tergalii II–VII have costal rib well-developed along entire costal margin, with denticles at distal part; thus, such tergalius has either 2 distinct ribs (in Siphluriscus – Zhou & Peters 2003: Fig.14) or 3 ribs [see Nesameletus/f2=Metamonius/g2 (5) below]. Costal rib of tergalius I can be either lost, or small and located at a distance from costal margin (in lacusalbinae [Ameletoides]).

Plesiomorphies of Nesameletus/f1=Metamonius/g1. Larva has primary swimming siphlonuroid specialization: legs are able to stretch posteriorly; abdomen is large, able to make undulate swimming movements; caudalii are not long, paracercus is well-developed, primary swimming setae are dense, secondary swimming setae are absent (photo ). Head is hypognathous; labial palp is 3-segmented [for other features of mouthparts see (1)–(5)]. Larval (and adult) patella-tibial suture is developed on middle and hind legs only. Probably, tergalii [see (9)] retain ability of rhythmical respiratory movements (see Index of characters [1.3.30]); only Nesameletus/f2=Metamonius/g2 anceps [Siphlurus] was observed: it makes make fast rhythmical respiratory movements by tergalii I –IV only.

In imago and subimago: Mesonotal suture is nearly transverse, either not stretched backward medially (in Siphluriscus) or shortly stretched (in Nesameletus/f2=Metamonius/g2 – Kluge 2004: Fig.30:D). Anterior paracoxal suture is complete (Kluge 2004: Fig.30:A-B) (unlike Rallidens and some Bidentiseta). Metathoracic nerve ganglion is situated in posterior part of furcasternum; furcasternal protuberances are either contiguous except for extreme hind part (in Siphluriscus – Zhou & Peters 2003: Fig.29) or separated by narrow median impression widened posteriorly (in Nesameletus/f2=Metamonius/g2 – Kluge 2004: Fig.30:A). In cubital field of fore wing several branched or simple veins go from CuA to basitornal margin [see Anteritorna (1)], hind wing is well-developed; in Siphluriscus hind wing is especially large, a little longer than half of fore wing, with RS, MA and MP forked in proximal part, and fore wing has especially long narrow cubital field with 10–15 veins going from CuA to basitornal margin (Demoulin 1955h: Fig.1; McCafferty & Wang 1994: Fig.1-2); in Nesameletus/f2=Metamonius/g2 hind wing has more usual size, as long as 0.35–0.4 of fore wing length, with MA forked distad of middle, and fore wing has moderately long cubital field with 3–6 veins. Imaginal and subimaginal tarsi are 5-segmented, 1^st segment is non-shortened and fused with tibia. Gonostylus with 2 distal segments. Imaginal and subimaginal paracercus is more or less developed: at least much longer than abdominal segment X, multisegmented, with normally developed setation; in lacusalbinae [Ameletoides] it is subequal to cerci, in other species – many times shorter than cerci.