Litoleptis fossilis Arillo, Peñalver & García-Gimeno, 2009

Arillo, Antonio, Peñalver, Enrique & García-Gimeno, Victoria, 2009, First fossil Litoleptis (Diptera: Spaniidae) from the Lower Cretaceous amber of San Just (Teruel Province, Spain), Zootaxa 2026, pp. 33-39 : 34-38

Litoleptis fossilis Arillo, Peñalver & García-Gimeno sp. nov.

Figs 1–2; Pl. 1

Derivation of name: From the Latin fossilis (dug out of the earth, excavated, etc.). This is the first fossil representative of the genus.

Holotype: CPT-3344 housed in the Fundación Conjunto Paleontológico de Teruel-Dinópolis (Teruel Province, Spain). Complete, well preserved specimen (Pl. 1, fig. 1) present in a transparent, clear piece of amber of 4 x 4 x 2 mm into an epoxy resin preparation of 22 x 13 x 2 mm.

Type locality and stratigraphy: Specimen from San Just outcrop, in the municipality of Utrillas, near the village of Escucha (Teruel Province, Spain). It was collected in a thin level of grey-black claystones very rich in amber, charcoal and also fusinite formed by a palaeofire, which implicates an exceptional resin production in the palaeoforests. Escucha Fm. (La Orden Member), Lower Cretaceous (Lower Albian).

Diagnosis: Antennal flagellomere III prolonged medially into a long, densely pubescent, unsegmented style with its basal part bulbous. Labium as long as antennae. Presence of a small spur on metathoracic tibia. R4 and R5 end in the costal margin. R4+5 and M1+2 forked at same distance from wing base.

Description: Body length 2.17 mm from head frons to terminalia apex (Fig. 1 and Pl. 1, fig. 1).

Head. Eyes bare, large, 0.49 mm long, 0.40 mm aprox. wide (estimated); dorsal and ventral facets undifferentiated (Fig. 2a and Pl. 1, fig. 2). Eyes nearly holoptic, separated only by distance less to diameter of facet. Postocciput with a dorsal line of fine setae. Ocellar triangle prominent and setulose (ocellar diameter 0.07 mm) (Figs. 1 and 2a). Antennae 0.38 mm long, with flagellomere I ovoid; flagellomere II short, nearly spherical (0.06 x 0.06 x 0.04 mm); flagellomere III prolonged medially into a long (0.30 mm), densely Figure 1. Camera lucida drawing of Litoleptis fossilis sp. nov. ( Spaniidae ), female holotype (CPT-3344), in lateral habitus, from San Just amber. Arrow indicates the metathoracic tibial spur.

Thorax: Notum high and rounded (Fig. 1). Scutum with numerous setae partially arranged in rows (Pl. 1, fig. 2). Scutellum strongly acuminate in lateral view, with 4 pairs of long setae in dorsal position (Pl. 1, fig. 2). Wings elongate, 2.02 mm length, 0.73 mm width. C, R4+R5 and h veins strongly sclerotized (Fig. 2d and Pl. 1, fig. 5). R2+3 and distal part of Sc slightly sclerotized. C vein is circumambient but only strongly sclerotized up to end of R5. Stigma large, filling space between veins R1 and R2+3. (Pl.1, fig. 5). R2+3 slightly sinuous. Stem of R2+3 and R4+5 contacts R1 at level of h or slightly basally. R4+5 and M1+2 forked at same distance from wing base and near the distal margin, forming broad, short cells. R4 and R5 end in the dorsal margin. Stem of M separates cells br and bm. Discal cell absent. Vein CuA2 complete, reaching margin of wing but not meeting A1 before wing margin (they separate distally 0.06 mm). Basal margin of anal lobe with long, fine setae. Halter bare, ca. 0.5 mm long, having elongate knob.

Legs long and thin (Fig. 1 and Pl. 1, fig. 1). Protarsus 0.60 mm length (tarsomere I 0.25, II 0.10, III 0.08, IV 0.06, V 0.09). Mesothoracic leg 1.57 mm length (femur 0.48, tibia 0.59, tarsomere I 0.26, II 0.08, III 0.06, IV 0.04, V 0.06). Metathoracic leg 1.72 mm length (femur 0.63, tibia 0.59, tarsomere I 0.21, II 0.09, III 0.07, IV 0.06, V 0.07) (Fig. 1). Mesothoracic tarsomeres with at least four strong distal setae, not present in pro- and metathoracic ones. Very short tibial spur in posterior subapical position on metathoracic leg (Fig. 1). Empodium pulvilliform; pulvilli smaller than empodium (observed in left mesothoracic tarsus) (Fig. 2b and Pl. 1, fig. 4).

Abdomen broad and short (1.19 mm long including terminalia and 0.46 mm wide) with abundant setae. Genitalia with segment 1 of cercus not visible (probably short and hidden by tergum). Segment 2 of cercus elongate. Sternum 8 nearly rhombic (Fig. 2c and Pl. 1, fig. 3).

Discussion: The new species clearly belongs to the Spaniidae due to the shape of the antenna and the pulvilliform empodium [it is remarkable that James & Turner (1981) erroneusly represented the antenna of L. alaskensis as segmented]. The lack of a discal cell is typical of the genus Litoleptis but this feature has appeared independently in other taxa. The genus Hilarimorpha Schiner (Hilarimorphidae) has a very similar wing venation ( Webb 1974) but the shape of the antenna and the presence of a pulvilliform empodium easily differentiates the new species. Curiously, fossil Hilarimorphidae have a well developed discal cell as well as does the extant genus Apystomyia Melander, 1950 ( Grimaldi & Cumming 1999; Mostovski 1999). Among rhagionoids, loss of the discal cell is also a character present in one species described by Webb (1969) from New York, USA: Bolbomyia andiscalcella Webb, 1969 . However, the antenna of B. andiscalcella has a clearly segmented antennal style.

Figure 2. Camera lucida drawings of Litoleptis fossilis sp. nov. ( Spaniidae ), female holotype (CPT-3344). Details of the a) head, b) distal mesotarsomere showing claws, pulvilli and the pulvilliform empodium, c) female terminalia in dorsolateral (top), lateral and ventral views, and d) wing.

The new species is differentiated from the extant species of Litoleptis by having a small spur on metathoracic tibia. It is also easy to distinguish the new species from L. alaskensis and L. orientalis by having a complete CuA vein ( Grimaldi & Cumming, 1999 erroneously figured a complete CuA vein in L. alaskensis ). Litoleptis fossilis sp. nov. is differentiated from L. chilensis and from the two undescribed Japanese and Nepalese species ( Nagatomi 1982) by the shape of the third antennal segment. In the new Plate 1: Litoleptis fossilis sp. nov. ( Spaniidae ), female holotype (CPT-3344), from San Just amber. 1) habitus in dorsal, ventral and lateral (below) views, 2) thorax and head in dorsal view showing chaetotaxy in scutum and scutellum, 3) genitalia in dorso-lateral view, 4) distal left mesotarsomere showing claws, pulvilli and the pulvilliform empodium, and 5) wing.

species R4 and R5 end in the costal margin, while in the wing apex in all extant species whose venation is known, and R4+5 and M1+2 forked at same distance from wing base and near the distal margin, determining broad, short cells. Also, new species is separated from extant ones by having a long labium that protrudes as much as the antennae.

The female genitalia of extant species of Litoleptis are poorly known. The genitalia of L. fossilis sp. nov. seems closely related to genera Spania and Spaniopsis ( Nagatomi & Iwata 1976) .

Palaeoecology: Litoleptis fossilis sp. nov. has a long proboscis and could have been a hematophagous fly. In fact, it has a proboscis larger than the proboscis of ceratopogonids from the same outcrop (see Arillo et al. 2008). Blood-feeding behaviour is not common among living rhagionoids, occurring only in some Spaniidae and Rhagioniinae ( Lehane 2005).

Palaeobiogeography: Rhagionoids are among the earliest and most diverse brachycerans in the fossil record. The finding of a Cretaceous Litoleptis proves that Spaniidae is an old lineage that was already separated from the rest of rhagionoids in the Cretaceous. However, its appearance in Spanish amber is quite surprising if we consider its currently known Asio-Nearctic disjunt distribution ( Saigusa 2006). Obviously, the genus had a wider distribution during the Mesozoic, but a more precise palaeogeographic distribution can be understood only when further fossil records are available. An undescribed specimen of Litoleptis is known from the late Eocene of Florissant (Colorado, USA) (Mostovski pers. comm.).