Fig. 1. Hypotheses of skeletomuscular homologies and evolutionary pathways here proposed based on topological and functional correspondences. Note that, for clarity, proportions and angles in these schemata have been distorted to varying degrees.Muscle names from the literature included in specific figures are either indicated in parentheses,(), or in black boxes (hence square brackets, []). Color coding as follows: Dark grey ¼ tergum or sternum; light grey in (A) ¼ tendon while light grey in (C) ¼ penial sclerites; dark red ¼ pleuron; red ¼ protopod; barred red and grey ¼ coxosternum or tergocoxosternum (¼ pygophore); dark yellow ¼ exopod (¼ stylus); barred yellow and red ¼ protopod- exopod composite;green ¼ endopod; blue ¼ gonopod, penis, or penial sclerite;light blue ¼ lateropenite; barred blue and red ¼ protopodal-penial composite. A1e5, transformation and homology from a pancrustacean groundplan represented by Remipedia (A1: Hessler and Yager,1998) to Protura (A2: [François and Dallai, 1989; Berlese,1910; Schö adl, 2013]), Archaeognatha (A3, 4: [alphabetical labels: Birket-Smith, 1974; numerical labels: Bitsch, 1973, 1974a, b]), and Zygentoma (A5: [Birket-Smith, 1974]). B1e3, transformation from ectognath groundplan represented by A4 to pterygote groundplan (B1: Hessler and Yager,1998), the Ephemeroptera (B2: before slash: Brinck,1957; after slash: Birket-Smith,1971), and the inferred groundplan of the Neoptera (B3). C1e9, transformation from neopteran groundplan (B3) to polyneopteran groundplan (C1) through all polyneopteran orders (C2: Popham,1965; C3: Matsumura et al., 2014; C4: Hünefeld, 2007; C5: Zwick,1973; C6: Eades, 2000; C7: Helm et al., 2011; C8: Walker,1943; C9: Klass,1997). D1, groundplan inferred for Eumetabola. E1e6, transformation from eumetabolan groundplan (D1) to Thysanoptera (E1: Heming,1970) and the hemipteran groundplan (E2); from this latter groundplan to Fulgoroidea (E3: Fennah,1945), Aleyrodoidea (E4: Weber,1935), Pyrrhocoridae and Belostomatidae (E5: before slash: Khanna,1963; after slash: Bhargava,1967), and Lygaeidae (E6: Bonhag and Wick, 1953). F1e5, transformation from phalloneopteran groundplan (F1) to psocodean groundplan (F2: Klier, 1956) and endopterygote groundplan (F5), the latter through precursors showing duplication of the penial protractors and retractors (F3 to F4) and splitting of the lateropenite from the penis (F4 to F5). G1e3, transformation from endopterygote groundplan to hymenopteran groundplan (G3: Schulmeister, 2001). H1e6, transformation from the neuropteridan groundplan, represented by Raphidioptera (H1), to Corydalidae (H4), Sialidae (H5), and Myrmeleontidae (H6: Krivokhatsky, 2002) (note that, although the TgIX and GcxI are fused together in H4 and H5, they are still visually distinguishable, unlike in H6). I1e7, derivation of coleopteridan genital forms from an inferred precursor (I1), including the Strepsiptera (I8: Hünefeld et al., 2011b); inferred "trilobe" groundplan of the Coleoptera (I2), a trilobe form represented by Cantharidae (I3), cucujoid form represented by Curculionidae (I5), and an adephagan form represented by Dytiscidae (I7). J1e6, transformations inferred to derive a groundplan for the Euantliophora (J6) which accounts for all observed genital sclerites and muscles. JIeIV, transformations inferrred for the Nannochoristidae (JI: Mickoleit, 2008), Bittacidae (JIII: Gao and Hua, 2015), and Panorpidae (JIV: Mickoleit, 2008). Jieviii, a transformation series inferred to explain the highly derived skeletomusculature of the Siphonaptera (Jviii: Günther,1961). K1e2, representatives of the Diptera (K1: Spangenberg et al., 2012; K2: Paramonov,2004). L1e3, Amphiesmenoptera, with Trichopteradrepresented by Limnephilidae (L2)dand the lepidopteran groundplan (L3: Kristensen, 1984) derived from an approximated groundplan for the higher clade (L1). Muscle abbreviations indicated in Table 1. Sclerite and other abbreviations: Al ¼ anchoring ligament; (Ars) ¼ arcessus (see Aspö ock, 2002); Ba ¼ basis; bp ¼ "basal piece" (sensu Crowson,1955,1981); (Cin) ¼ cingulum; Cx ¼ coxa (in the carcinological sense); Cxa ¼ coxa (in entomological sense) or secondary gonocoxa (i.e., coxa IX in Ectognatha); (Cxp) ¼ coxopenis; Cxt ¼ coxite or gonocoxite (i.e., coxite of segment IX in Ectognatha); (Daev) ¼ dorsal "aedeagal" valves; Gna ¼ gonapophysis; (Gnr) ¼ gonarcus (see Aspö ock, 2002); Endst ¼ endosternum; Enp ¼ endopod; (Epp) ¼ epiphallus; Exp ¼ exopod; Gpo ¼ gonopore; (Harp) ¼ harpago (sensu Klier, 1956); (Ls) ¼ lateral sclerite; (ml55) ¼ "median lobe" (sensu Crowson, 1955); (Mn) ¼ manubrium (sensu Popham, 1965); (PA) ¼ "penial arm" (sensu Brinck, 1957); Pen ¼ penis; (Phb) ¼ phallobase (sensu Lawrence et al., 2010);Pht ¼ phallotreme; Pl ¼ pleuron; (pm1), (pm2) ¼ "paramere" (Coleoptera, sensu Crowson, 1955, 1981; Lawrence et al., 2010); ("Pm") ¼ "paramere" (Dermaptera,sensu Popham,1965); (pp81) ¼ "penis proper" (sensu Crowson,1981); Prct ¼ proctiger;Prp ¼ protopod (comprises Ba, Cx); (Pyph) ¼ pygophore; scls ¼ sclerites; St ¼ sternum; Sty ¼ stylus; StCxIX ¼ coxosternum; Tg ¼ tergum; (Tig) ¼ tignum (see Aspö ock, 2002); Tl ¼ transverse ligament; (Vaev) ¼ ventral "aedeagal" valves; Vst ¼ ventral segmental tendon. Sclerite abbreviations, Euantliophora (J1e6, IeIV, ieviii; see sections 4.5 and 4.5.4): aed. apod. ¼ aedeagal apodem; aed. apod. prec. ¼ aedeagal apodem precursor; aedt.¼ aedeagaltasche; bulb. ¼ bulbalis; d. ps.par.¼ dorsal pseudoparameren; endot. ¼ endotendons; ham. ¼ hamulus; hypot.¼ hypotendons; inn. tub. ¼ innere tube; kam. ¼ kammersklerit; lun. skl. ¼ lunarsklerit; mittelpl. ¼ mittelplatte; ostial. ¼ ostialsklerit; param. ¼ "paramere"; phb. ¼ "phallobasis"; pistillt. ¼ pistilltrö ager; teg. ¼ tegimen; telom. ¼ telomere; virg. vent. ¼ virga ventralis; Y-skl. ¼ Y-sklerit.