Talbragaria australis, Sroka & Prokop, 2023

Sroka, Pavel & Prokop, Jakub, 2023, New fossil stoneflies (Plecoptera: Arctoperlaria) from Australia testify ancient dispersal across Pangea, Arthropod Systematics & amp; Phylogeny 81, pp. 881-888 : 881

3.2. Talbragaria australis sp. nov.

Figs 1 , 2

Plecoptera sp. in Beattie and Avery (2012: fig. 8D, F)

Diagnosis.

The new species is distinguishable from all other known fossil Notonemouridae by the combination of the following characters: crossvein mp-cua ca 1.2 × longer than rp-ma; mp-cua crossvein ca 1.6 × longer than the longest crossvein in the area between CuA and CuP (on contrary, mp-cua crossvein more than twice as long as the longest crossvein in the area between CuA and CuP in closely related genus Paranotonemoura Cui and Béthoux, 2018); length of second tarsomere subequal to two thirds of third tarsomere length; female with pronounced corrugated subgenital plate on abdominal sternite VIII and corrugated anal plates on segment IX, narrowed posteriorly.

Etymology.

The name refers to country where holotype and paratype specimens were found.

Type material.

Holotype: F.136 856 (part) and F.136 857 (counterpart), female imago. - Paratype: F.137 576 (part) and F.137 577 (counterpart), female imago.

Type locality and strata.

The Talbragar Fossil Fish Bed site is approximately 25 km northeast of Gulgong in New South Wales, Australia ( Beattie and Avery 2012). Stratigraphically the unit is correlated with the Purlawaugh Formation of the Surat Basin and corresponding to the latest Oxfordian-Tithonian, Upper Jurassic.

Description.

Body length ca 10-12.5 mm. - Head: Prognathous, ca 1.2 × longer than wide (Fig. 2C ). Antennae probably nearly completely preserved, visible portions up to 0.7 × body length (Fig. 2A, B ). Compound eyes rounded, positioned laterally. Ocelli not visible. Clypeus trapezoidal, approximately twice wider than long (Fig. 2C ). Labrum rounded anteriorly. Other mouthparts not recognizable. - Thorax: Prothorax rectangular, ca 1.5 × wider than long, lateral margins rounded (Fig. 2A, B ). Meso- and metathorax equal in length, each ca 1.4 × longer than prothorax. Two pairs of fully developed wings. Forewing incomplete, probably slightly longer than body. Forewing venation only partially preserved (Fig. 1A, B, F-H ), ScP adhered to RA and again diverges from it more distally, RA simple, crossvein between RA and RP close to the point of connection of ScP with RA. Further two crossveins between RA and PR more basally. RP bifurcated just distally from the crossvein between RA and RP. Two crossveins between RP and M in proximal portion of wing, further oblique slightly sigmoidal crossvein between RP and M more distally, close to RP bifurcation. Hind wings preserved only fragmentary in anterior part, course of discernible veins (C, ScP, RA and RP) identical to forewing (Fig. 1A, B, F-H ). Legs slender, length increases from forelegs to hind legs. Femora and tibiae elongated, femora ca 4-6 × longer than wide, tibiae ca 10-14 × longer than wide. Tarsi incomplete, with only second and third tarsomeres preserved; length of second tarsomere subequal to two thirds of third tarsomere length (Fig. 1C ). Claws approximately as long as third tarsomere width. - Abdomen: Elongate, narrow, ca 5 × longer than wide. In female, pronounced, well sclerotized and corrugated subgenital plate on sternite VIII (Figs 1D, E , 2D, E ). Sternite IX produced posteromedially into narrow corrugated subanal plates. Male genitalia unknown. Cerci short, one-segmented (Fig. 1D, E ).

Additional Plecoptera specimens.

Apart from the holotype and paratype of Talbragaria australis gen. et sp. nov., two further specimens of Plecoptera from the same locality were identified in the collection of the Australian Museum, Sydney, Australia under accession numbers F.136 851 (part and counterpart, Fig. 2F,G ) and F.137 324 (Fig. 2H ). Due to their state of preservation and lack of diagnostic characters, it is not possible to attribute them unambiguously to T. australis gen. et sp. nov., although due to their similarity in size they might be conspecific.

Figures

Figure 1. Talbragaria australis gen. et sp. nov. A Holotype specimen, part F. 136 856, general view. B Holotype specimen, counterpart F. 136 857, general view. C Distal part of tarsus (F. 136 856). D Posterior part of abdomen (F. 136 856). E Posterior part of abdomen (F. 136 857). F Drawing with reconstruction of the venation pattern (F. 136 856). G Detail of forewing (F. 136 857). H Course of CuP vein in forewing (F. 136 857); arrows indicate curve diverging from posterior wing margin. I Detail of subanal plate (F. 136 856). J Detail of subanal plate (F. 136 857). Rectangles in A, B and G mark positions of detailed figures. Abbreviations: ce - cercus, sap - subanal plate, sgp - subgenital plate. Roman numbers indicate abdominal segments. Scale bars: 5 mm (A, B), 2 mm (D), 1 mm (F - H), 0.2 mm (C, I, J).

Figure 2. Talbragaria australis gen. et sp. nov. and additional stonefly specimens from Talbragar Fish Beds. A T. australis sp. nov., paratype specimen, part F. 137 576, general view. B T. australis sp. nov., paratype specimen, counterpart F. 137 577, general view. C detail of head (F. 137 576). D Posterior part of abdomen (F. 137 576). E Posterior part of abdomen (F. 137 577). F, G Plecoptera sp., part and counterpart (both F. 136 851). H Plecoptera sp. (F. 137 324). Rectangles in A and B mark positions of detailed figures. Abbreviations: ant - antenna, cl - clypeus, e - compound eye, lb - labrum, sap - subanal plate, sgp - subgenital plate. Roman numbers indicate abdominal segments. Scale bars: 5 mm (A, B, F, H), 3 mm (G), 1 mm (C - E).