Tmemophlebia carolinae Evenhuis and Greenwalt, 2022

Greenwalt, Dale E., Amorim, Dalton De Souza, Hauser, Martin, Kerr, Peter H., Fitzgerald, Scott J., Winterton, Shaun L., Cumming, Jeffrey M., Evenhuis, Neal L. & Sinclair, Bradley J., 2022, Diptera of the Middle Eocene Kishenehn Formation II, Palaeontologia Electronica (a 22) 25 (2), pp. 1-52 : 21-24

Tmemophlebia carolinae Evenhuis and Greenwalt sp. n.

Figures 12-13

zoobank.org/ 7BB0C21B-2DCA-4831-B0E7-9BB85B110674

Type species. Cyclorhynchus testaceus Macquart, 1840 , automatic (same type species as for Cyclorhynchus Macquart ).

Holotype. Male, USNM 768156 , deposited in the Department of Paleobiology , National Museum of Natural History ( NMNH), Smithsonian Institution, Washington, District of Columbia, USA.

Locality and horizon. Dakin site, Middle Fork of the Flathead River (Pinnacle, Montana, USA). Middle Eocene Coal Creek Member, Kishenehn Formation.

Etymology. The new species is named for Dr. Carolina Yamaguchi (of São Paulo), for her current work on the phylogenetics and taxonomy of New World Phthiriinae .

Diagnosis. Tmemophlebia carolinae is the first described fossil species of the New World genus Tmemophlebia . It can be distinguished from the congeners by the costal vein ending just beyond the end of R 4 (others in the genus have this ending at M 1 or M 2; other phthiriines have the costa entire); the presence of a short ventral prong at the tip of the postpedicel (congeners usually without it or very reduced), and the shallow cleft of the epandrium (congeners usually have this cleft much deeper or broader).

Description (male). Ventrolateral view. Black to dark brown, body length 4.3 mm (including genitalia, artefactual intersegmental portions of abdomen not included). Head dark brown/black, subspherical, 0.45 mm long, nearly all morphologcal aspects distorted ( Figure 12A ). Proboscis long, 1.44 mm in length, 0.2 mm wide; labellum 0.31 mm long, 0.1 mm wide; palpus 0.57 mm long, 50 mm wide; labrum 1.13 mm long, 60 mm wide. Postpedicel short, slightly diamond-shaped, 0.27 mm long, 0.1 mm wide, with apical sulcus, 15 μm deep, with short triangular ventral and larger bulbous dorsal prongs ( Figure 12 B-C). Thorax black, 1.65 mm long, maximum width 1.4 mm; wing (left) 3.2 mm long, 1.35 mm wide, L/W = 2.4, wing/body length = 0.74; C and R 1 heavy, darkly pigmented, C ending at wing apex and R 4, distance between termini of Sc and R 1 equal to that between R 1 and R 4, R 4 origin at basal quarter of cell r 5, cell dm 0.95 mm long; M 2 present, CuA distinctly recurved to meet CuA+CuP about 0.18 mm from wing margin ( Figure 13 A-B). Legs poorly preserved, distorted. Abdomen dark brown, setose, length 2.25 mm, maximum width 1.3 mm; tergite VII narrow, about half the width of tergite VI; epandrium 0.25 mm long, 0.16 mm wide, with distinct apical notch; gonocoxite and phallic complex 0.23 mm long, 0.16 mm wide; gonostylus 0.13 mm long, 30 mm wide ( Figure 13C ).

Female. Unknown.

Synimpressions. None

Remarks. The genus was first created under the name Cyclorhynchus by Macquart in 1840. Subsequently determined to be preoccupied, Evenhuis proposed the replacement Tmemophlebia in 1986. The genus currently contains 16 extant species and is endemic to Nearctic and Neotropical regions ( Evenhuis and Greathead, 2015). While the family Bombyliidae , with 59 described fossil species, has a reasonable fossil record, that of the subfamily Phthiriinae is poor with only two previously known. Elektrophthiria magnifica Nel, 2006 was described from the Eocene French Oise deposits and the Oligocene Geronites stigmalis Cockerell, 1914 , was assigned to Poecilognathus Jaennicke, 1867 by Evenhuis (1994) after examination of the type specimen. The Oligocene Phthiria fossa Lewis, 1975 is incertae sedis within the subfamily ( Nel, 2006) and Phthiria oligocaenica Timon-David, 1943 was assigned to Geron Meigen, 1820 ( Evenhuis, 1994) although more recently suggested to be incertae sedis within Bombyliidae ( Nel, 2006) . Tmemophlebia carolinae is the third phthiriine fossil known as identified to the tribe Poecilognathini based on vein R 4+5 forked, M 2 present and postpedicel with apical sulcus. The cleft in the epandrium and the relatively small genitalia puts it in or close to Tmemophlebia and the short antennae are reminiscent of some species of Poecilognathus and Tmemophlebia . The incomplete costa is a feature distinguishing Tmemophlebia . Tmemophlebia are small, 2 to 6 mm in length ( Evenhuis, 1990); Tmemophlebia carolinae fits well within that range.

The extant species of Tmemophlebia are primarily dune or light-colored sand dwellers and have a pale color that either acts as camouflage or helps reflect sunlight and regulates temperature in such arid regions. Pale colors are characteristic of many bee fly species that inhabit arid environments while dark coloration is a common adaptation in forested/non-arid areas. Bombylius albicapillus Loew, 1872 , collected in the southern Sierra of California (Walker Pass), consisted of a pale variety in the Mojave Desert side of the pass and a dark variety in the adjacent pine woodland (NLE, pers. obs.). The lacustrine environment of the Coal Creek Member of the Kishenehn Formation is thought to have consisted of the shores and shallow waters of a large lake and associated semitropical forest. That Tmemophlebia carolinae is dark may reflect on its more lacustrine habitat. We speculate that Tmemophlebia evolved from a less arid dwelling taxon to one that transitioned successfully through the desertification process in the western United States since the Miocene.

Figures

FIGURE 12. Tmemophlebia carolinae Evenhuis and Greenwalt sp. n., USNM 768156, male. A, Habitus; B, Proboscis. Arrows from left to right denote labellum, labrum and palpus, respectively; C, Postpedicel. Arrow denotes bulbous dorsal prong of apical sulcus. Scale bars equal 2.0 mm (A) and 0.5 mm (B).

FIGURE 13. Tmemophlebia carolinae Evenhuis and Greenwalt sp. n., USNM 768156. A, Right wing; B, Drawing of wing; C, Terminalia. TVII denotes 7th tergite of abdomen. Arrows from left to right denote epandrium (E—light area in middle of epandrium has lost the thin carbonaceous layer that constitutes the fossil), apical notch of epandrium (N), gonostylus (S) and gonocoxite and phallic complex (G). Scale bars equal 1.0 mm (A) and 0.2 mm (C).