Eosciadocera pauciseta, Grimaldi, 2018

Grimaldi, David A., 2018, Basal Cyclorrhapha In Amber From The Cretaceous And Tertiary (Insecta: Diptera), And Their Relationships: Brachycera In Cretaceous Amber Part Ix David A. Grimaldi, Bulletin of the American Museum of Natural History 2018 (423), pp. 1-97 : 1-97

Eosciadocera pauciseta , new species

Figures 16 , 47D ; 49A, D, E

DIAGNOSIS: Similar to Eosciadocera setosa , also in Baltic amber, by the very large body size (6–7 mm), protibia with only a ventroapical macroseta; one large pair of vertical setae; pair of small (divergent) postocellar setae; basal flagellomere subspherical; 1 to several rows of large acrostichals; proepisternum with many large setae; and anepisternum without large setae. Proleg with stridulatum. Differs from E. setosa by the following: two (vs. four) pairs fronto-orbital setae; frons broad, greater than ½ head width (vs. ¼); palp relatively large, flat, with stout black setae on distal margin (vs. small, fine setae); proscutellum absent (vs. present); notopleurals 4 (vs. 5–8); scutellars in two pairs (vs. 5–6 pairs); metafemur without macrosetae (vs. 5–6 long ones).

DESCRIPTION: Large, ca. 6.7 mm body length; color appears brownish overall, with thick, black macrosetae. Head: Eyes well separated, bare, no differentiation of facets, no emarginations. Frons without median sulcus, broad (ca. 0.65× width of head), length (from anterior ocellus to anterior margin) shorter than width. Ocellar triangle approximately in middle of dorsum of head (including frons). Frontal setae: two pairs frontoorbitals (posterior pair lost, but sockets visible), situated near middle of frons length; ipsilateral fronto-orbitals separated by distance ca. 5× diameter of fronto-orbital seta socket. Supraantennal interfrontals possibly absent (or just lost in specimen). One pair of vertical setae present (setae lost, but sockets visible), situated midway between posterior fronto-orbital and row of postocular occipital setae. Ocellar setae: 1 pair (lost, but sockets visible, apparently large); postocellars minute, fine, length slightly greater than diameter of ocellus, located between posterior ocelli. Occiput just behind posterior margins of eye with 19–20 long, stout postocular setae; 7–8 additional large occipital setae mesal to this row. Face deeply concave, with very thin vertical carina, flanked by pair of recessed areas (fossae) for antennae. Vibrissa absent. Antenna: Scape very narrow, ringlike, no setae; pedicel short, conical, no setae. Basal flagellomere subspherical (length slightly greater than width), covered with short, velvetlike pile. Arista dorsal; 3-merous, basal two articles short (lengths ca. 2× their widths). arista micropubescent. Mouthparts: Oral margin protruding, such that oral cavity faces forward, surrounded by short sleeve. Palp large, flattened, distal margin with thick, short setae. Labellum fully recessed into oral cavity (as preserved); opened lobes nearly forming circle, pseudotracheae not visible, though minute microtrichia are.

Thorax: Heavily bristled; scutum gently arched; proscutellum absent or very reduced; prosternum large, fully exposed, bare. Acrostichals large, in even central row of ~10 setae; row of ~10 dorsocentral setae lateral to acrostichals (setae in both rows about same size). Other thoracic setae: 1 large postpronotal; oblique row of 6 supraalars (1 very large); 1 large postalar; 4 large, presutural notopleurals; 6–7 large proepisternals (rest of pleuron without setae). One pair of large dorsocentrals, sockets slightly lateral to line formed by outer row of acrostichals; 2 pairs of large scutellars (lengths very similar), apical scutellars very close. Wing: Very long, ca. 8 mm, nearly twice length of abdomen. Membrane of wing clear, no infuscation, entirely covered with microtrichia. Tegula bristly, with 7–8 thick setae; basicosta with row of 4 large setae; vein h thick; Sc thick, fused to R 1 at 0.30× length of R 1; C with 2 rows thick spinules, vein ends at apex of R 4+5; R 2+3 ends midway between apices of R 1 and R 4+5. Vein R 4+5 ends well before apex of wing, fully fused to C. Base of M 1 lost, evanescent, apex of M 1 ending at wing tip; M 2 complete, including base. Cu veins complete; anal vein present, incomplete. Cell r-m complete (closed basally); cell dm slightly opened basally and distally; cell cup present, apex of CuA 2 not fused to A 1. Alula small, with fringe of 10–12 stiff, nonfeathered setae. Legs: Pretarsi with curved bristle near where empodium would be (as in Ironomyia ); tarsomeres 1–4 with hair seam on mesal surface, 2 longitudinal rows of dark, small, spinulelike setae ventrally. Foreleg: Coxa heavily setose overall, with>30 thick, large macrosetae; femur without macrosetae; stridulatum present, “scraper” exposed on bare, light patch at base of inner surface of right fore femur, with about 12 minute ridges; tibia with only ventroapical macroseta, no others. Midleg: coxa setose, ca. 10 setae; femur without macrosetae; tibia with 2 middorsal setae, 4 apical ones. Hind leg: coxa with a few fine setae; femur with single ventrolateral macroseta; tibia with pair of middorsal macrosetae, plus 4 apical ones. Abdomen (female): Sternites well developed; apical segment with longer, thicker setae; pair of long, fine setae just above cerci (on epiproct?); cerci short, pointed downward, setose.

SPECIMENS EXAMINED: Holotype, female, AMNH Ba-JVe565, in Eocene Baltic amber. The specimen is complete, but portions of it are covered in milky coating or are obscured by fractures.

ETYMOLOGY: From Latin paucus (“few”), in reference to its fewer setae compared to setosa .

Figures

FIG. 16. Eosciadocera pauciseta, n. sp. (Sciadocerinae), holotype in Baltic amber, AMNH Ba-JVe565. A. Habitus, ventrolateral view. B. Head, dorsolateral view. C. Head, ventrolateral view. D. Base of wing. E. Thorax.

FIG. 47. Wings of Sciadocerinae preserved in Eocene Baltic amber (B, D), and Cretaceous ambers (A, C), to different scales.A. Hennigophora pria in New Jersey amber, AMNH NJ-Ch1. B. Hennigophora robusta in Baltic amber, AMNH Ba-JH51. C. Prophora dimorion in Burmese amber, JZC Bu242. D. Eosciadocera pauciseta in Baltic amber, AMNH Ba-JVe565.

FIG. 49. Legs of Sciadocerinae in Baltic amber, showing large bristlelike macrosetae. A, B. Midleg; C, D. hind leg. A. Eosciadocera pauciseta, femur and tibia, AMNH Ba-JVe565. B. Hennigophora robusta, AMNH Ba-JH58. C. Eosciadocera pauciseta, femur, tibia, basitarsomere. D. Hennigophora robusta, entire leg. E. Base of proleg (coxa and base of femur) of Eosciadocera pauciseta, showing position of exposed scraper of the stridulatum.