Sciara lacoei Cockerell, 1915

Dale E. Greenwalt, Daniel J. Bickel, Peter H. Kerr, Gregory R. Curler, Brian V. Brown, Herman de Jong, Scott J. Fitzgerald, Torsten Dikow, Michal Tkoč, Christian Kehlmaier & Dalton De Souza Amorim, 2019, Diptera of the middle Eocene Kishenehn Formation. I. Documenting of diversity at the family level, Paleontologia Electronica 22 (2), No. 50, pp. 1-56 : 23-24

Sciara lacoei Cockerell, 1915 , reassigned Figure 19.2-3

Material examined. Holotype, USNM 61436 , and specimen 7583, both housed in the National Museum of Natural History , Washington, D.C., USA.

Type horizon. Bembridge Marls , UK, latest Eocene

Type locality. Gurnard Bay , Isle of Wight, UK

Remarks

This fossil is of the dorsal aspect of the insect (Figure 19.2). The specimen is an impression fossil with the head, with well-preserved and clearly separated eyes, having formed a deep hemispherical depression in fine-grained mud; the face of the head contacted the bottom of the depression. Poorly preserved remnants of the basal antennomeres lie on the surface of the fossil above the hemispherical depression. The posterior portion of the head is not preserved and it is therefore impossible to determine whether or not an eye bridge is present.

C, R 1 and R 4+5 are clearly present; Sc is absent (there is a gouge in the fossil at that point). R 1 and R 4+5 extend to 0.48 and 0.89 of the wing’s total length. The cubital veins are well preserved, but the medial veins are not. The fossil contains several creases that confound identification of these veins. In Cockerell’s figure, there is a short apical portion of M 2 preserved, and this vein does indeed appear to be present in the fossil. M 1, labeled with a “?” in figure 18.3, if not a crease, takes an uncharacteristically straight path to the margin; the base of the medial fork appears to be too basal for Sciaridae . As discussed above, M 4 originating very basally in the wing in this species is seen in some Cecidomyiidae , Rangomaramidae and Mycetophilidae . The very long R 5 also suggests that S. lacoei is not a sciarid. We, therefore, assign this specimen to Sciaroidea incertae sedis.

A second specimen (#7583, also labelled USNM 61436) is not a type but is labelled Sciara lacoei . This specimen (Figure 19.3) is 1.7 mm long, although the end of the abdomen is not visible; it contains no structures of value other than the wing. The preserved portion of the wing (the apical portion is missing) is approximately 1.4 mm in length, the same length as that of the holotype. R 1 is preserved, but the end of R 4+5 is not. Apical portions of M 1 and M 2 are preserved, but the base of the fork is not. This specimen appears to be a sciarid, although it is impossible to assign this specimen to Sciara ; we assign it to Sciaridae incertae sedis.