External leg morphology
In general, the sub-chelate type of raptorial forelegs is featured. The coxa of the raptorial foreleg is strongly elongated and the foreleg suspension (‘coxo-thoracic joint'—ctj) consists of large membranous areas (Fig. 2), reaching further posterior in ventral than in dorsal direction. Furthermore, the fronto-coxa shows one articulatory point with the pleural process, and the pleural condyle is connected via a ball and socket type joint with the coxa (Frantsevich 1998). The coxa is covered with a vestiture of small setae along the dorsal, and more strongly along the ventral area (Fig. 2). Here, a distinct posterodorsal ‘rabbet’, consisting of a dorsal and a posterior notch; forming a rabbet-like slot is present on the surface (Figs. 1, 2).
A small number of setae can be found on the trochanter. The trochanter is linked to the femur via a bowl-shaped dorsal oriented joint, becoming narrower towards the pointy distal end. The femur is almost triangular, with a wider and thicker area in the middle. It shows a 'posteroventral carina' (pvc), equipped with a median row of spines (referred to as 'anteroventral spines'—avs; Fig. 3), running from the widest point in the middle up to the proximal end. The most prominent character is a large, at the base bended, spine on the anteroventral side—the 'subbasal spine' (sbs; introduced from Willmann 1990 as major spine)—at the base of the carina, approximately in the middle of the femur (Fig. 3). A vestiture of small setae is almost completely covering the femur. This coverage is dense at the base of the femur, on the dorsal, and the anterior side (except on the mentioned carina; Fig. 3). On the anterior side and in a close radius around the proximal area of the carina, only a small quantity of setae is developed (Fig. 3). The tibial base is widened and reinforced, before bending further distal into a sickle-shape, with a distinct blade-like ‘cutting edge’ (ce) on the ventral side (Figs. 2, 3). A patch of setae can be found on the dorsal base, a few setae along the dorsal side and at the base of the cutting edge. Furthermore, a long triangular-shaped area, densely packed with small and thickened setae is located on the anterior side of the tibia.
Expanding and forming the tip of the sickle-shape, the first tarsal article is an elongation of the tibial sickle. Additionally, the distal tip of the tibia forms a smaller posterior and larger anterior thorn-like protrusion—'distal posterotibial protrusion' (dptp) and 'distal anterotibial protrusion' (datp). The latter (datp) placed into a 'basitarsal notch' (btn) on the anterior side (Fig. 3).
The most prominent parts of the raptorial foreleg (femur, tibia, and tarsus), exhibit a mixture of very different material properties (Fig. 4). The anterior area of the femur is strongly sclerotized (Fig. 4a), whereas the posterior area is a patchwork of resilin-dominated and chitinous parts, showing a median area of resilin-dominated cuticle (‘femoral posterior pad’—fpp; Fig. 4e). At the base of the femur (anterior view; Fig. 4a), a v-shaped, strongly resilin-dominated area stretches dorsally (‘femoral dorsobasal pad’—fdbp; approx. 1/3 the length of the femur) and ventrally (‘femoral ventrobasal pad’—fvbp) up to the subbasal spine (approx. 1/2 the length of the femur) (Fig. 4a) —stretching onto the subbasal spine (‘subbasal spine pad’—sbsp) facing proximal (Fig. 4b). In contrast, the distal face of the subbasal spine is strongly sclerotised (especially at the base), so is the tip. The anteroventral carina with its spines, is embedded in sclerotised cuticle anteriorly and chitinous cuticle posteriorly; the carina itself is also strongly sclerotised (Fig. 4a, e). The sickle-shaped tibia is more sclerotised on its anterior face and shows a line of resilin-dominated cuticle running from proximal to distal on the posterior face ('tibial posterior pad'—tpp; Fig. 4e). Additionally, the base of the tibia is slightly thickened and chitinous, with one anteriorly located resilin-dominated pad ('tibial anterobasal pad'—tabp; Fig. 4d) and one posteriorly oriented at the distal end (Fig. 4c). The mentioned cutting edge of the tibia is strongly sclerotised. At the distal tip of the tibia, a sclerotised protrusion—'distal anterior protrusion' (dap)—on the anterior side is developed.
The entire setae on the femur and tibia show no auto-fluorescence, appearing black in the CLSM maximum intensity projection (Fig. 4); which is presumably due to the presence of melanin in the cuticle.
In all following descriptions, the non-moving end of a muscle will be referred to as a point of origin (O) and its moving end will be referred to as a point of insertion (I). All names for muscles follow the nomenclature introduced by Beutel et al. (2014), supplemented with information from Jandausch et al. (2018). Muscles marked with an asterisk are newly described.
Extrinsic musculature (Fig. 5)
O: Anterior part of pronotum.
I: At anterior procoxal rim next to Ipcm5.
Ipcm4—M. propleuro-coxalis superior
O: Anterodorsal area of propleura.
I: Lateral at procoxal articulation.
Ipcm5—M. propleuro-coxalis inferior
O: Posteroventral face of propleural apodeme.
I: At anterior procoxal rim next to Idvm15.
O: Anteroventral face of propleural apodeme.
I: Posterolateral procoxal rim.
Iscm1—M. profurca-coxalis anterior
O: Lateral face of profurca stem.
I: Median, at proximal procoxal wall.
Iscm3—M. profurca-coxalis medialis
O: Lateral face of profurca.
I: Anteromesal procoxal rim.
Intrinsic musculature (Fig. 5)
O: Posterolateral procoxal rim.
I: Ventral trochanteral protrusion, dorsal of the insertion of M20 and M21.
O: Anteroventral wall of distal coxal half.
I: Ventral trochanteral protrusion, anteroventral of ctm.
M21—M. coxa-trochanteralis medialis
O: Posteroventral wall of distal coxal half.
I: Ventral trochanteral protrusion, posteroventral of ctm.
M22—M. coxa-trochanteralis lateralis
O: Three bundles of muscles, at anterior and posterior wall of distal half of coxa and at dorsal area of proximal coxal rim.
I: Dorsal, at protrusion at trochanteral rim.
M23—M. reductor femoris
O: Ventral area of proximal end of trochanter.
I: Ventral, at most proximal end of femur.
M24a—dorsal median und ventral
M. depressor tibiae a.
O: Anterodorsal to ventral area of proximal 2/3 of femur.
I: Together with M24b with a tendon at the enlarged tibial basis.
M24b—dorsal lateral und ventral
M. depressor tibiae b.
O: Posterio-dorsal to anteroventral area of proximal 2/3 of femur.
I: Together with M24a with a tendon at the enlarged tibial basis.
M25—M. levator tibiae
O: On dorsal area at most proximal region of femur.
I: Dorsal, on proximal rim of tibia.
M26—M. depressor pretarsi
O: Dorsal area of distal tibia.
I: Probably on tendon to claw.
M24c*—M. depressor tibiae O: With two strains on the ventrolateral and ventromedian base of the tibia. I: At the tendon, originating from muscle M24a & M24b.