Docidiadia grimaldii, De SOUZA AMORIM & BROWN, 2022

De SOUZA AMORIM, DALTON & BROWN, BRIAN V., 2022, Docidiadia grimaldii sp. nov. from Myanmar amber (Diptera: Diadocidiidae), with comments on the genus Docidiadia Blagoderov & Grimaldi, Palaeoentomology 5 (5), pp. 505-512 : 506-510

publication ID	https://doi.org/ 10.11646/palaeoentomology.5.5.12
publication LSID	lsid:zoobank.org:pub:9C4266AB-52BA-477E-9D55-506D244892FA
DOI	https://doi.org/10.5281/zenodo.7383741
persistent identifier	https://treatment.plazi.org/id/03C58784-361F-FFDD-B10B-2A8AFB4AF99A
treatment provided by	Plazi
scientific name	Docidiadia grimaldii
status	sp. nov.

Treatment

Docidiadia grimaldii View in CoL sp. nov.

( Figs 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Material. Holotype, male, LACM ENT 479021 View Materials ( LACM), virtually complete specimen in a greenish yellow trapezoid piece of amber trimmed to 25 × 13 × 5 mm ( Figs 1 View FIGURE 1 , 2A–C View FIGURE 2 ) . Paratype, male, LACM ENT 479022 View Materials , virtually complete specimen in a greenish yellow ellipsoid piece of amber trimmed to 17 × 11 × 4 mm ( Fig. 3 View FIGURE 3 ) .

Etymology. The species name honors our good friend David Grimaldi, who has brought an extraordinary contribution to the understanding of insect evolution, dealing with large groups of extant and fossil species of different fly families and of different orders of insects.

Locality and horizon. Known only from amber fossils from the mid-Cretaceous of Myanmar.

Diagnosis. Flagellum ( Fig. 2A View FIGURE 2 ) slightly wider at base, gradually slenderer towards apex, 15 flagellomeres, last flagellomere 8× longer than wide, first seven flagellomeres at least slightly wider than long. First sector of Rs long ( Fig. 2B View FIGURE 2 ), oblique, originating at basal third of wing; cell r1 wide. Veins r-m, base of M 4 and m-cu more or less aligned and pretty much transverse. Distal fifth of M 4, but especially distally fourth of CuA strongly bent posteriorly. Female terminalia ( Fig. 2C View FIGURE 2 ) with long distal lobes of sternite 8; cercus with tip directed distally.

Description. Female ( Figs 1 View FIGURE 1 , 3 View FIGURE 3 ).

Head ( Fig. 2A View FIGURE 2 ). Eyes not large, occupying most of lateral surface of head, no gena; eyes largely separated from each other above antennae, no dorso-ventral differentiation of ommatidia, ommatricha not visible. Three ocelli, placed on a prominent mound; no strong ocellar seta between ocelli. Labellum and palpus well developed, three palpomeres, second palpomere pyriform, about as long as distal palpomere, distal palpomere elongate, with apical setulae. Antenna with short scape, about half of pedicel length, with some few setulae distally, pedicel longer than flagellomere 1, with a whorl of setulae around distal margin. Flagellum with 15 flagellomeres, no scales, first flagellomere about twice as wide as long, gradually slenderer and elongate towards apex; flagellomeres 2–8 slightly wider than long, flagellomeres 9–14 as wide as long or slightly longer than wide, last flagellomere long, slender, style-like, 8× longer than wide, apparently a subdivision of the previous flagellomere.

Thorax. Scutum short, strongly arched, high at anterior end, curved downwards at posterior half, scutellum small. Scattered longer setae over scutum in addition to a pair of rows of slightly longer dorso-central setae, scutellum with a couple of slightly divergent long setae at posterior margin, no setulae on dorsal surface of scutellar disc. Halteres long, reaching almost posterior margin of second abdominal segment. Antepronotum short, proepisternum long, propepimeron short, triangular, clearly separated from katepisternum. Anepisternum with a deep dorsal membranous notch; katepisternum elongate dorsoventrally. Mesepimeron wide, reaching ventral margin of thoracic pleura. Laterotergite not bulging, mediotergite slightly curved. Metepisternum relatively large. Apparently only antepronotum and proepisternum with elongate setae, other sclerites bare.

Legs. Coxae elongate, all of same length. Femora and tibiae thin, long, hind tibia 1.4 longer than femur. Femora with scattered fine setae besides a short row of ventral setae at distal end. Tibiae thin, no distal differentiated area of regular comb of setae at distal inner end of front tibia; mid tibia with a long row of longer thin setae; hind tibia with a row of five stronger dorsal setae. First tarsomeres more than twice length of second tarsomere. Tibial spurs 1:2:2; spurs finely pilose, slender, about twice as long as width of tibiae at apex. Tarsal claws small, apparently no teeth.

Wing ( Fig. 2B View FIGURE 2 ). Elliptical, 1.8 mm long. C, Sc, and radial veins more sclerotized, posterior veins fainter. Macrotrichia on bR, R 1, second sector of Rs, r-m and on distal end of veins M 1, M 2, M 4 and CuA, no macrotrichia on wing membrane. Sc incomplete, ending before level of origin of Rs. C extending beyond apex of R 5 for about a third of distance to apex of M 1. bR forking at about basal third of wing, cell r1 wide, first sector of Rs oblique, long, more weakly sclerotized; R 1 long, reaching almost distal 2/3 of wing length; R 4 absent; r-m almost transverse. M 1+2 and M 4 running almost parallel, no sign of bM; connection of base of M 4 and m-cu aligned with r-m. Medial fork slightly longer than M 1+2. Distal fifth of M 4 slightly arched posteriorly, distal fourth of CuA strongly arched posteriorly. CuP present, incomplete, ending at about two thirds of distance to margin. Anal lobe rounded; no visible alula.

Abdomen. Tergites and sternites well sclerotized, with scattered setae, segments 1 to 8 visible, segment 8 less than half length of segment 7.

Terminalia ( Fig. 2C View FIGURE 2 ). Sternite 8 with a pair of large, more or less pointed setose lobes with a deep medial incision. Tergite 9 wide, about half the length of segment 7, cercus apparently 1-segmented, large, setose, projected more distally than level of tip of lobes of sternite 8.

Male. Unknown.

Remarks. Both specimens are clearly conspecific. Not only the wing venation of both specimens is identical in details, but the shape of the unusual structure of the female terminalia in both specimens is basically identical.

Discussion. In general terms, Docidiadia grimaldii sp. nov. is very similar to the type-species of the genus, Docidiadia burmitica Blagoderov & Grimaldi and there is no question about the species being congeneric. The differences indicating that they are separate species are evident in different aspects of the morphology. In the antenna ( Fig. 2A View FIGURE 2 ), the flagellomeres of the distal half of the antenna are more slender in D. grimaldii . In D. burmitica , the distal palpomere seems to be slightly longer than in D. grimaldii . R 1 in D. grimaldii is slightly longer than in D. burmitica , while the sequence of veins r-m/M 4 /m-cu ( Fig. 2B View FIGURE 2 ) is more transverse in D. burmitica , while in D. grimaldii it is slightly oblique, especially the first sector of M 4 and m-cu. The type series of Docidiadia burmitica has a female paratype ( Fig. 4 View FIGURE 4 ). The cercus in D. burmitica has the distal tip slightly projected ventrally, while in D. grimaldii this tip is directed distally. In D. grimaldii , the distal lobes of the sternite 8 seem longer than in D. burmitica ( Fig. 2C View FIGURE 2 ). The clearest feature separating both species, however, is the distal end of the flagellum: the 14 th flagellomere in D. burmitica is “secondarily segmented in two parts” ( Blagoderov & Grimaldi, 2004: 7), with a short distal segment, while in D. grimaldii ( Fig. 2A View FIGURE 2 ) the subdivided distal segment is very long, about eight times longer than wide.

This second species of Docidiadia shows that the association of the genus to the Diadocidiidae needs additional corroboration. Among the extant families of Sciaroidea, r-m, M 4 and m-cu are perfectly aligned and transverse in the diadocidiids, and there is a short stump of bM projecting basically from the anterior end of M 1+2. The stump of bM is absent in both species of Docidiadia . In Docidiadia burmitica , r-m and the base of M 4 are perfectly aligned and transverse, with m-cu slightly more oblique. In D. grimaldii sp. nov., r-m is more or less transverse, but the first section of M 4 and m-cu are oblique, in such a way that the transverse condition of the set of these three veins is not seen. The distal half of CuA in both species of Docidiadia is particularly different from the condition of CuA in Diadocidia , with M 4 rather strongly diverging from CuA.

On the other hand, the antenna of Docidiadia grimaldii sp. nov. is similar to the condition seen in Archizelmira and Zelmirarcha, in the Archizelmiridae . In the species of Diadocidia , the antenna is more elongate and curved forward, typical of fungus gnats. Docidiadia grimaldii sp. nov. has a straight flagellum and the flagellomeres are slightly wider than long at the basal half of the flagellum and gradually more slender on the distal half, slightly longer than wide. In Archizelmira kazhakstanica Rohdendorf, 1962 (see Grimaldi et al., 2003: fig. 2.4), the antenna is much less modified than in most archizelmirids, but it is indeed slightly derived, with a straight, setiform flagellum. The flagellum in D. grimaldii sp. nov. in particular is similar to the flagellum of Archimelzira americana Grimaldi et al., 2003 (see Grimaldi et al., 2003: fig. 9.1).

This is not a simple and direct indication that Docidiadia belongs to the Archizelmiridae . The wing venation in both species of Docidiadia is definitely much more conservative than in archizelmirids. The wing in Archizelmiridae has a slender cell r1, a short and rather transverse first sector of Rs, and there is a displacement of the point of contact of the tip of the first sector of M 4 and the base of m-cu towards the base of the wing—that produces an acute angle between the first and second sectors of M 4. This possibly derived condition is missing in Docidiadia , as well as in Diadocidia , ditomyiids,

and some other fungus gnats, that have a more or less transverse r-m/M 4 /m-cu. The condition in Docidiadia is, however, comparatively plesiomorphic and does not necessarily join Docidiadia with other genera with a similar wing vein pattern. A more clear solution for the position of Docidiadia amongst the extant and extinct sciaroids actually depends on an analysis of the Sciaroidea as a whole which is still not available.