Latiblattella avita, Greenwalt and Vidlicka, 2015

Greenwalt, DE & Vidlička, L, 2015, Latiblattella avita sp. nov. (Blattaria: Ectobiidae) from the Eocene Kishenehn Formation, Montana, USA, Palaeontologia Electronica (London, England) 79 (1), pp. 1-9 : 3-4

Latiblattella avita sp. nov.

( Figures 1-3 )

zoobank.org/ 7225896D-EC71-4088-8B05-008C85F3A7B6

Etymology. The new species name is derived from the latin avitus meaning ancient or ancestral.

Holotype. USNM 595139 ; a fragment containing an intact tegmen attached (?) to an intact middle leg. Deposited in the Department of Paleobiology, National Museum of Natural History ( NMNH), Smithsonian Institution, Washington, District of Columbia.

Type Horizon. Kishenehn Formation, middle Eocene (Lutetian).

Type Locality. Dakin site, Middle Fork of the Flathead River , near Pinnacle, Montana .

Differential Diagnosis. The significantly less oblique radial sectors of the tegmen of Latiblattella avita sp. nov. distinguish it from species in the closely related genera Neoblattella, Shelford, 1911 and Lupparia Walker, 1868 . Species of the genus Balta Tepper, 1893 differ from Latiblattella in having a protruded clavus. In addition, the marginal and scapular fields of the tegmina are narrower in Latiblattella than those in Eoblatta Shelford, 1911 (= Balta Tepper, 1893 ; synonymized by Roth, 1990). L. avita differs from most living representatives of the genus Latiblattella in having a basally forked, wide and darkly pigmented Sc vein as well as a more pronounced coloration.

Description. Tegmen (forewing) elongated, 15.1 mm long and 4.4 mm wide (width measured at the distal terminus of the anal field) with a length/width ratio = 3.40. Sc wide and heavily pigmented, arcuate basally with a slight inflection near the anterior margin of the tegmen ( Figure 1 ). Basal of Sc, the tegmen is mottled with black pigmentation ( Figures 2 , 3.1 ). Sc itself is 4.75 mm long and 0.45 mm in width at the point where it diverges from R, and extends to a point about 66% of the length of the anal field. Sc has no anterior branches. The humeral field is 4.79 mm long, arcuate basally and without anterior branches. Sc has a single posterior branch which diverges from Sc at a point

GREENWALT & VIDLIČKA: NEW EOCENE COCKROACH approximately 1/2 the distance from its origin; this vein is heavily pigmented and is 2.18 mm long and 0.12 mm wide. Both Sc and its single branch reach the wing’s margin. The basal portion of the radius is distinctly curved and is pigmented to a point 4.5 mm from the wing’s base. There are 10-12 apical branches of the radius – the origins of these branches are not preserved. These branches are oblique, evenly spaced and approximately half of them are branched. The apical radial branches are complexly branched and, with the anterior branches of M, parallel to subparallel to the anterior margin of the tegmen. Overall number of R branches meeting margin is 26. Posterior branches of M and those of Cu subparallel to the tegmen’s longitudinal margin. The radial field is 8.5 mm long. The apex of the tegmen is evenly curved. Intercalated veins and crossveins are invisible throughout the membrane. The anal field is 6.58 mm long and 2.51 mm wide at its widest point and contains at least 10 near parallel simple longitudinal veins. The plical furrow is subangulate and pigmented basally. The plical notch is distinct although the posterior margin of the tegmen is poorly preserved. The tegmen is brown in coloration, more darkly brown within a wide longitudinal stripe along the central part of the wing with the margins of the wing lighter in color. The anal field is dark brown except for the postero-apical third which is essentially the same color as the shale matrix. Given the poor preservation of the posterior tegminal margin, the distribution of color may have been affected by taphonomic processes. Given the length of the tegmen of this specimen, the insect may have been a male (see Discussion).

In cockroaches, the dorsal aspect of the base of the coxa is very closely apposed to the base of the forewing and, given its size and association with the forewing, the leg of this fossil may be a mesothoracic appendage ( Figure 1 ). It is 13 mm in total length. The coxa, which is attached to the preserved thoracal-coxal joint, is 4.05 mm long, 2.14 mm wide and black/dark brown in color. The basal portion of the coxa and the trochanter are light brown. The trochanter is triangular in shape, 1.13 mm long, 0.80 mm wide and overlaps the basal femur by about 0.5 mm. Its shape resembles that of Ectobiinae [vs. species in Blattellinae ( Bazyluk, 1977) ]. The femur is brown in color, slightly fusiform in shape, 3.76 mm long and 1.0 mm wide. Its posterior margin contains seven or eight relatively short spines approximately 0.4 mm long and 0.04 mm wide, mostly on the apical half of the femur. The tibia, also brown in color, is 3.3 mm long and slightly wider apically (0.49 mm vs. 0.56 mm). The tibia contains 14 visible spines, evenly distributed over its length, 0.8 mm long and 0.08 mm wide. Four of the tibial spines originate at the terminus of the tibia and lie parallel to the first tarsal segment ( Figure 3.2 ). The dimensions of the five tarsal segments are 1.3 mm x 0.31 mm, 0.5 mm x 0.2mm, 0.35 mm x 0.22 mm, 0.2 mm x 0.2 mm and 0.46 x 0.17 mm increasing distally to 0.24 mm wide. T1, T2 and T3 have triangular distal extensions, which may contain remnants of tarsal pads (pulvilli). T4 is bilobed basally, as in Ectobiinae [vs. species in Blattellinae in which the apical and basal margins are parallel ( Bazyluk, 1977)]. The single asymmetrical claw that is preserved/visible is approximately 0.36 mm long. The arolium is about 0.2 mm in length and black/dark brown.

Figures

FIGURE 1. Latiblattella avita sp. nov. (USNM 595139). Tegmen attached (?) to an intact middle leg. Scale bar equals 5 mm.

FIGURE 2. Latiblattella avita sp. nov. (USNM 595139). 2.1. A photograph of the tegmen. 2.2. A line drawing of the forewing venation. The arrow denotes the boundary between the radial and medial fields. M, medial veins; R, radial veins; Sc, subcostal vein. Scale bar equals 3 mm.

FIGURE 3. Latiblattella avita sp. nov. (USNM 595139). 3.1. The subcostal field of tegmen showing the wide and darkly pigmented Sc vein. 3.2. The five segmented tarsus. The arrows denote tarsal segments 1 – 5 and the end of the single visible claw. Scale bars equal 1 mm.