Hilarimorphites burmanica Grimaldi & Cumming

Grimaldi, David A., Arillo, Antonio, Cumming, Jeffrey M. & Hauser, Martin, 2011, Brachyceran Diptera (Insecta) in Cretaceous ambers, Part IV, Significant New Orthorrhaphous Taxa, ZooKeys 148, pp. 293-332 : 317-318

Hilarimorphites burmanica Grimaldi & Cumming sp. n. Fig. 9

Diagnosis.

Distinguished from the 4 other species in the genus (known only in New Jersey amber) by venation: vein C ending just slightly beyond apex of R4 (not at apex of R5); Sc long, distally incomplete (more so than in Hilarimorphites superba Grimaldi and Cumming 1999, the only other species with this trait); veins CuA2 and A1 not joined before meeting wing margin (anal cell open distally). Distinguished from Apystomimus by the larger (normal-sized) wings, with an open cup (anal) cell. Also, basal flagellomere is more elongate and triangular in Hilarimorphites burmanica , and the antennal stylus longer than in the other species of Hilarimorphites .

Description.

Based on a virtually complete, well-preserved female. Body length (excluding antennae) 1.40 mm; thorax length 0.50 mm; wing length 0.95 mm. Head: Antenna with first flagellomere an elongate triangle in lateral view; apical antennal article(s) form a thin style, with possibly a minute apical article. Eyes large, glabrous. Frons with sparse, scattered setae. Proboscis with broad, flat labellum (palps not visible). Thorax: Notum dome-shaped, with sparse, fine, stiff setae; scutellum with 2 pairs of erect setae. Legs very slender, of moderate length, without distinctive spines or tibial spurs. Wing: typical of Hilarimorphites , except as given in diagnosis above [also, anal lobe may be less developed than in other species, but this area slightly folded under and obscured]. Halter of moderate length, knob slender. Abdomen: Slender, tergites unmodified, cerci and genitalia not fully visible.

Type.

Holotype female, AMNH Bu-098, in amber from Myanmar: Kachin, Tanai Village (on Ledo Rd. ca. 105 km Myitkyna). Amber is a deep, clear yellow, 15 × 10 × 5 mm, and was embedded in epoxy and trimmed to a wedge shape in order to maximize a full lateral view of the fly and its venation. The piece also contains a male chironomid and a thrips ( Thysanoptera ).

Etymology.

From Burma (Myanmar).

Discussion.

Hilarimorphites was known only from Turonian-aged amber of central New Jersey, USA, and besides the new species in Burmese amber a very similar taxon is also now known from the Upper Jurassic of Kazakhstan. Mostovski (1999) described Apystomimus zaitzevi , preserved as a compression from the Karabastau Formation (Upper Jurassic) of the famous Karatau-Mikhailova Lagerstätte. That well-preserved specimen has a venation indistinguishable from that of Hilarimorphites Grimaldi & Cumming, 1999. Apystomimus differs from that genus by having small, brachypterous wings (ca. 0.5 × length of the body) and very long cerci (nearly 0.5x length of wing; Hilarimorphites has very small cerci typical of lower Brachycera). Since these are autapomorphic features of Apystomimus , it could be appropriate to synonymize one of the genera (although Apystomimus is more aptly named, Hilarimorphites has date precedence by two months). Hilarimorphites was originally placed in the Hilarimorphidae , and Mostovski placed Apystomimus in Asilomorpha family-incertae sedis (but near the extant genus Apystomyia ). Recent Hilarimorpha lack the discal cell, they have the cup cell closed, and lack a well-developed anal lobe while retaining a vestige of the anal vein, so the venation of the fossils is far more easily derived from Apystomyia . Thus, we agree that Hilarimorphites and Apystomima should both be classified in Apystomyiidae . The wing of Hilarimorphites differs from that of Apystomyia by the following: slightly shorter R1 and R2+3 veins; fork of R4+R5 less divergent, the branches slightly longer; cells br and bm significantly larger; cell cup significantly larger, with veins CuA2 and CuP meeting just before or at the wing margin, or not all (vs. CuA2+CuP with a long stem in Apystomyia ); anal lobe of wing not protruding; and cell d much shorter, its length ca. 3 × the width in Hilarimorphites (vs. 5 × the width in Apystomyia ).

Hilarimorphites burmanica is intermediate in age between the previously known fossils, and greatly extends the geographic range. An extinct clade or grade of Apystomyiidae occurred minimally throughout Laurasia from the Upper Jurassic to the Upper Cretaceous, which is an age that is consistent with its hypothesized sister-group relationship near Eremoneura (Grimaldi and Cumming, 1999; Grimaldi and Engel, 2005; Wiegmann et al., 2011). Oddly, there are no other fossils as yet known of the family, not even from prolific and diverse Tertiary deposits like Baltic amber.