Cretoxyla 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 : 295-296

Cretoxyla Grimaldi & Cumming gen. n.

Diagnosis.

Antenna thick, greatest width (in middle) 0.25x total length, with apparently 7 flagellomeres; protibia without apical spur; most distinctive features are in venation, which distinguishes this genus from other Mesozoic xylomyids by: vein M (separating cells br and bm) weak; cell m3 very small, width and length approximately half that of cell d (these are of equivalent size in other xylomyids, or m3 is slightly smaller), and, very distinctively, vein R2+3 is uniquely lost.

Type species.

Cretoxyla azari sp. n., by present designation.

Etymology.

From Cretaceous, and Xylomyiidae.

Discussion.

The closed wing cell m3 is a feature also seen in some Xylophagidae . Cretoxyla , however, apomorphically has no protibial spur (as in Stratiomyomorpha ) and plesiomorphically does not have a reduced alula (a greatly reduced alula occurs in the Xylophagidae ). The extent of vein C, particularly whether it extends only to the apex of M1 or M2 ( Woodley 1986: 1377), unfortunately cannot be checked since the apical quarter of the wing is lost. Vein C is definitely not circumambient. Other features that are important for xylomyid relationships that cannot be observed in the incomplete fossil are the number of palpal segments (1 vs. 2), presence of denticles on the ventral surface of the hind femur (e.g., Solva Walker), and various male and female genitalic structures.

The oldest fossil record of Xylomyiidae is?Xylomyia [sic] shcherbakovi Mostovski from the Upper Jurassic (Karabastau Formation) of Kazakhastan ( Mostovski 1999). Zhang and Zhang (1993) indicated that Mesosolva Hong and Prosolva Hong, also described as xylomyids from the Upper Jurassic of China, belong in another lower brachyceran family. Undescribed Cretaceous xylomyids are from the Upper Cretaceous amber of Siberia ( Zherikhin and Sukacheva 1973), and an incomplete specimen of an undescribed species in Spanish amber (vide infra), so Cretoxyla is the oldest Cretaceous xylomyid (Early Cretaceous, Neocomian). Tertiary fossil xylomyids are Solva inornata Melander, 1949 and Xylomya moratula Cockerell, 1914 in late Eocene shale from Florissant, Colorado; and Solva nana Loew, 1850 in mid-Eocene Baltic amber.