A new species of Plecia from the Green River Formation and new combinations of fossil Bibionidae (Diptera)

Great Basin Naturalist 59(2), ©1999, pp. 182-187 A NEW SPECIES OF PLECIA FROM THE GREEN RIVER FORMATION AND NEW COMBINATIONS OF FOSSIL BIBIONIDAE (DIPTERA) Scott J. Fitzgerald' Abstract. — Plecia akerionana, n. sp., is descrihfcl Iroiii tiie Crecn River Formation, Colorado, and diagnosed with P. iiiimitiild Rice, P. inyersi Peterson, and P. rhodopterina Cockerell. Plecia intermedia (Scudder), the genot} pe of Myce-tophaettis, and Plecia crcedcn.sis James are transferred to the genus Peutluiria. and Uespehnus iiniiiiilahilis Melaiidi'r is transfeiTed to Plecia. Kcij words: Diptcra. Bihinnidac. fossil, Plecia, new species. Green River Formation. Over 20 fossil species in 5 genera of Bil^io-nidae liave been described from the shales of Florissant, Colorado (Oligocene), while only 4 species, all belonging to the genus Plecia, have been described from the Green River Foniiation, ColoradoAVyoming/Utah (Eocene). Although there are few bibionid species known from the Green River Formation, they are among the more abundant Diptera, as was found in a survey of several sites in the Para-chute Creek Member of the Green River For-mation (Codington 1993) in which Bibionidae represented 22% of Diptera specimens. One Green River site (site F-1, Wyoming) is partic-ularly rich in bibionid specimens, with 80-96% of all insects representing Plecia pealei Scud-der (Scudder 1890, Grande 1984). This study describes an additional species o{ Plecia fiom the Green River Formation, Colo-rado, and reassesses generic assignments of several other fossil bibionids described from Colorado. Morphology follows McAlpine (1981). Mea-surements were made with an ocular microm-eter. Wings were illustrated with the aid of a camera lucida. The following individuals made materials available for study: Philip Perkins and Michael Kelley, Museum of Comparative Zoolog)', Harvard University (MCZC); Virginia Scott (entomology) and Peter Robinson (pale-ontology). University of (Colorado, Boulder (UCMC); Conrad Labandeira and Mark Flo-rence, National Museum of Natiu-al Histor\, Smithsonian Institution (USN.Vl). Specimens have been deposited at these institutions. Genus Plecia Wiedemann Plecia Wiedemann, 1S28: 72. Type species: Hirtea fiilvicollis Fabricius, 1805, by subsecjuent desig-nation of Blanchard (1840: 576). Plecia akerionana Fitzgerald, new species (Figs. 1-3) HOLOTYPE. — 9, USA: COLORADO: Rio Blanco County, 4 mi W Rio Blanco, Bob Ham-mon (USNM #498201). Etymology. — The specific epithet is de-rived from the Greek akerios (lifeless) and nan (dwarf). Discussion. — Plecia akerionana was col-lected from the upper Parachute (!!reek mem-ber of the Cirecn Hi\er Formation (l,,ake Uinta Locality U-2 [of Grande 1984|) and is esti-mated to be 45—47 million \r old (Da\\ault ct al. 1995). Diagnosis. — Plecia akerionana can be dis-tinguished from most other North American fossil Plecia by its minute size and is most sim-ilar in size to P. rJiodopterina (>ockerell (Green Rixer Formation, (lolonulo, Focene), P. nu/ersi Peterson ((Canadian amber. Cretaceous), and P. minulnla Rice (British Columbia, Eocene). Table 1 provides wing measmements for com-parison of the 4 smallest (based on wing length) species of Nearctic Plecia. Plecia akerionana is most similar to P. inyer.si but can be distin-guislicd l)\ the longi'i' and r('lati\('i\ nariowcr 'rjcparlliK-nl of KiiloinolciKy. Colorado Slate l'niviTsit>. Kort (.olliiis, CO 8().52;3. I'rcstTit addri'ss: ni-pailiiicnl ol i:nloiiiolo^'\. ()i.-i;(>ii Stale l'iii\ersit\, .:,llis ()Hi)7i:il-2W)7. 182

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A new species of Plecia from the Green River Formation and new combinations of fossil Bibionidae (Diptera)

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