Christelenkidae Rohacek, 2023

Rohacek, Jindrich, Hammel, Joerg U. & Baranov, Viktor, 2023, Christelenkidae, a new extinct family based on a new taxon from Eocene Baltic amber (Diptera: Acalyptratae), with X-ray synchrotron microtomography imaging of its structures, Arthropod Systematics & amp; Phylogeny 81, pp. 475-498 : 475

3.1. Christelenkidae Rohacek fam. nov.

Type genus.

Christelenka gen. nov., designated here.

Diagnosis.

Body: relatively slender and elongate, particularly the abdomen, ca 3 mm long (Figs 1 - 4 ). Head: Antenna exclinate (Figs 6 , 9 ) and distinctly geniculate between pedicel and 1st flagellomere, the latter strongly decumbent (Figs 5 , 8 ), discoidal but slightly elongate (somewhat longer than scape + pedicel); arista extremely dorsobasal; pedicel cap-like, with distal margin simple. Frontal triangle not developed; lunule absent (Figs 6 , 9 ). Cephalic setae long but only present on posterior third of frons and on vertex (Figs 8 - 10 ); pvt small, convergent (crossed); vti by far the longest cephalic seta, upright and reclinate; vte strongly exclinate; oc upright to proclinate and divergent, longer than pvt; only 1 reclinate and slightly exclinate ors; frons in front of ors bare; vibrissa small but distinct, strongly medially curved; no genal seta or setulae. Thorax: with 1 postsutural dc, 1 prs, 1 sa, 1 pa, 2 sc (apical crossed, laterobasal the longest thoracic seta); 0 mspl, 1 stpl, 0 ppl. Mesonotum convex, somewhat hump-like; prosternum bare; mesopleuron with posterodorsal ridge developed (Fig. 14 ); subscutellum distinctly protruding (Fig. 17 ), metasternal area bare. Wing: with apex at end of R4+5, somewhat pointed; membrane not distinctly patterned; C extending to apex of M, with 2 breaks (humeral and subcostal) proximally, and with uniform dark setulae (none spine-like) ending between apices of R2+3 and R4+5 (see Fig. 18 ); Sc basally distinct but distally fused with R1, the latter without a preapical kink; no distinct humeral crossvein; cells dm, bm and cup complete; alula (not clearly visible) small and anal lobe well developed. Legs: cx1 elongate (Fig. 13 ), and with 1 ventral seta in middle (Fig. 15 ); f1 with 1 dorsal seta and an anteroventral ctenidium-like row of small blunt spines (Fig. 21 ); f3 with 1 dorsal and 1 anteroventral seta (Fig. 23 ); all tibiae with 1 dorsal preapical seta. Abdomen (of male) with unusual preabdominal sclerites: segments 1-4 with both terga and sterna short, while T5 and S5 are unusually strongly elongate (Figs 25 , 28 ). Male postabdomen: T6 reduced (transversely band-like) but distinct and slightly asymmetrical; S6 of moderate length and symmetrical; T7 absent; S7+S8 fused to form a somewhat asymmetrical dorsal synsclerite with a pair of strong posterior setae. Male genitalia: epandrium arch-shaped, slightly asymmetrical and open ventrally (Figs 29 , 30 ); cerci separate, large, inserted below large anal fissure; gonostyli somewhat asymmetrical, simple, elongate, tapered towards blunt apex, articulated with epandrium; hypandrium, short, obviously frame-shaped and symmetrical (Fig. 35 ); postgonites simple, elongate and pointed, symmetrical; distal part of aedeagus (considered to be distiphallus) short, broad distally (Figs 32 , 35 ).

For more detailed description see below under Christelenka gen.n.

Figures

Figure 17. Christelenka multiplex sp. nov., male holotype, anterior part of body: sagittal section right laterally. Scale bar: 0.5 mm. For abbreviations see 2.2.4. Morphological terminology. Microtomograph image by V. Baranov.

Figures 1, 2. Christelenka multiplex sp. nov., male holotype. 1 specimen in the whole amber preparatum, left laterally, with blue background; 2 whole specimen dorsally, with blue background. Scale bars: 1.0 mm. Photos by J. Rohacek.

Figures 3, 4. Christelenka multiplex sp. nov., male holotype. 3 whole specimen, left laterally; 4 ditto, right laterally. Scale bars: 1.0 mm. Photos by J. Rohacek.

Figures 5 - 7. Christelenka multiplex sp. nov., male holotype. 5 head left laterally; 6 ditto, frontally; 7 ditto, laterocaudally. Scale bar: 0.5 mm. Photos by J. Rohacek.

Figs 8 - 10. Christelenka multiplex sp. nov., male holotype, cephalic chaetotaxy. 8 head left laterally; 9 ditto, frontally; 10 ditto, laterocaudally. - Scale bar: 0.5 mm. For abbreviations see 2.2.4. Morphological terminology.

Figures 13, 14. Christelenka multiplex sp. nov., male holotype. 13 whole specimen, left laterally; 14 ditto, right laterally. Scale bar: 1.0 mm. Microtomograph images by V. Baranov.

Figures 18, 19. Christelenka multiplex sp. nov., male holotype, wings. 18 right wing, dorsally; 19 left wing, dorsally. Scale bar: 1.0 mm. For abbreviations see 2.2.4. Morphological terminology.

Figures 15, 16. Christelenka multiplex sp. nov., male holotype, thoracic chaetotaxy. 15 thorax, left laterally; 16 ditto, dorsally. Scale bar: 0.5 mm. For abbreviations see 2.2.4. Morphological terminology.

Figures 20 - 23. Christelenka multiplex sp. nov., male holotype, legs. 20 left fore femur, dorsally; 21 right fore femur, anteriorly; 22 right mid femur and tibia, anteriorly; 23 left hind femur, tibia and tarsus, anteriorly. Scale bar: 0.3 mm. For abbreviations see 2.2.4. Morphological terminology.

Figures 24, 25. Christelenka multiplex sp. nov., male holotype. 24 abdomen, left laterally; 25 ditto, with some structures coloured. Scale bar: 0.5 mm. For abbreviations see 2.2.4. Morphological terminology. Microtomograph image by V. Baranov.

Figures 28 - 30. Christelenka multiplex sp. nov., male holotype, abdominal structures. 28 abdomen, left laterally; 29 postabdomen with terminalia, right laterally; 30 ditto, left laterally. Scale bars: 28 - 0.5 mm; others - 0.2 mm. For abbreviations see 2.2.4. Morphological terminology.

Figures 31 - 35. Christelenka multiplex sp. nov., male holotype, abdominal structures. 31 abdomen (without 1 st segment), sagittal section right laterally, with some structures coloured; 32 posterior end of abdomen, right ventrolaterally, with structures coloured; 33 ditto, without colours; 34 posterior end of abdomen, ventrally; 35 ditto, enlarged and coloured. Scale bars: 0.2 mm. For abbreviations see 2.2.4. Morphological terminology. Microtomograph images by V. Baranov.