CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Ameletopsis/fg1.

(1) Larval head is greatly enlarged, wide, mouth apparatus is highly modified and specialized for carnivorism (Kluge 2004: Fig.35). Labrum is strongly widened, usually semicircular (photo ) (only in Chiloporter with large median incision – see below). Mandibles are highly modified: primary asymmetry of mandibles is lost; incisor, kinetodontium and mola are elongate, mola lacks grater; prostheca is lost. Superlinguae are strongly diminished (the same in some other carnivorous mayflies – see Index of characters [1.1.27]). Maxilla is highly modified in a unique manner: instead of canines, dentisetae and other setae, its apex bears 5 similar long, stout, mobile articulated appendages; these appendages are not setae, and appendages of next instar develop inside them (Kluge 2004: Fig.34:D); being pressed together, these appendages form a kind of claw, which is used to grasp a prey; bases of these appendages semicircularly surround apex of sclerite, which is situated on inner margin of maxilla and to which a strongly thickened lacinia-stipital muscle is attached. Lateral sides of submentum bear a pair of lamellate lateral lobes projecting anteriorly and posteriorly. Maxillary and labial palps have unique structure: each palp retains a normal 1^st segment with muscles moving the next segment; the rest part of palp (initial 2^nd+3^rd segment) represents a multisegmented flagellum similar to flagellum of antenna: it is narrowed toward apex, with large indeterminate number of segments increasing from age to age by division of proximalmost segments. Structure of maxillae and mandibles are uniform in all species of Ameletopsis/fg1, while other parts have species-specific differences.

Characters of Ameletopsis/fg1 of unclear phylogenetic status: non-unique apomorphies.

(2) Imaginal and subimaginal furcasternal protuberances are not contiguous at least in posterior part, with furcasternal median impression widened posteriorly; metathoracic nerve ganglion is situated in posterior part of furcasternum (Kluge 2004: Fig.34:C). Non-unique apomorphy (see Index of characters [2.2.23]); among Tridentiseta the same in other Amphinotic groups – Nesameletus/f2=Metamonius/g2, Vetulata and Rallidens. 

(3) Subimaginal lateral pigmented sclerotized area of mesonotum has peculiar form, includes whole anterior part of lateroscutum (Kluge 2004: Fig.34:A). The same in Nesameletus/f2=Metamonius/g2.

Characters of Ameletopsis/fg1 of unclear phylogenetic status: present not on all representatives.

(4) Each tergalius I–VII can have an additional lobe arising from ventral side near base and bearing numerous branched marginal processes [present in Mirawara (2) and Chiloporter (4), but absent in Ameletopsis/fg2 (1) and Chaquihua (1)]. The same fibrillose lobe is present in Rallidens and Branchitergaliae – see Index of characters [1.3.25]). While costal rib is always well-developed, anal rib can be either lost, or located at anal margin, or near middle of tergalius (see Index of characters [1.3.28]).

(5) Larval caudalii, besides primary swimming setae (see Plesiomorphies) often have secondary swimming setae on lateral margins of cerci; only Mirawara has no them (see Index of characters [1.3.67]).

Character of Ameletopsis/fg1 of unclear polarity.

(6) Larval tarsus can have 3 or 2 movably articulated segments (Kluge 2004: Fig.35:A) (adult has normal tarsal structure, with 5 segments, among which 1^st one is fused with tibia). In all other recent mayflies larval tarsus in non-segmented or with indistinct grooves corresponding to joints separating all five segments of adult tarsus. Segmentation of larval tarsus of Ameletopsis/fg1 can be either a unique plesiomorphy among Euplectoptera, or a result of secondary restoration, when adult character appears in larva. 

Plesiomorphies of Ameletopsis/fg1. Larval (and adult) patella-tibial suture is developed on middle and hind legs only. Larval claws without denticles on inner margin (if not take into account proximal denticle in Chiloporter). Larval caudalii are not long, paracercus is equal to cerci, primary swimming setae are always dense [see (5)].

In imago and subimago: Mesonotal suture is somewhat stretched backward medially or transverse (Kluge 2004: Fig.34:A; photo ); anterior paracoxal suture is complete (photo ) (unlike Rallidens and some Bidentiseta). In cubital field of fore wing several (4–8) veins go from CuA to basitornal margin (photo ) [see Anteritorna (1)]; hind wing is well-developed, as long as 0.4–0.5 of fore wing length (photo ; Demoulin 1955c: Fig.2a,3a,f). Imaginal and subimaginal tarsi are 5-segmented, 1^st segment is non-shortened and fused with tibia. All claws of imago and subimago are ephemeropteroid.