Balticobaetisca bispinata, Staniczek & Storari & Godunko, 2022

Staniczek, Arnold H., Storari, Arianny P. & Godunko, Roman J., 2022, Revised systematics, phylogeny, and paleontology of the mayfly family Baetiscidae (Insecta: Ephemeroptera), Arthropod Systematics & amp; Phylogeny 80, pp. 389-409 : 389

publication ID	https://dx.doi.org/10.3897/asp.80.e82845
publication LSID	lsid:zoobank.org:pub:2046ADA5-5456-45D8-AA27-4328496DAD5B
persistent identifier	https://treatment.plazi.org/id/DDFF50E6-178E-43E7-B451-0BA19EF9DF89
taxon LSID	lsid:zoobank.org:act:DDFF50E6-178E-43E7-B451-0BA19EF9DF89
treatment provided by	Arthropod Systematics & Phylogeny by Pensoft
scientific name	Balticobaetisca bispinata
status	sp. nov.

Treatment

Balticobaetisca bispinata sp. nov.

Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4; Table S1 View Figure 4

Balticobaetisca bispinata “Eintagsfliege”, p 15, fig. 5, W. Struve (1960): Die Eroberung der Luft, in: Schmidt H. (ed.): Der Flug der Tiere. Verlag Waldemar Kramer, Frankfurt am Main: 9-40 [figured specimen herein designated as paratype of the new species].

Material.

Holotype: BaB 1373/ 1 in coll. CCHH. Paratype: SMF Be 411 in coll. SMF (see also Supplementary Material 1, Fig. S1).

Etymology.

The species epithet refers to the shape of the paired subapical process of the penis, which is sharply pointed at the tip.

Diagnosis.

Male subimago (Figs 1A-D View Figure 1 , 2A-D View Figure 2 ): (1) body length 6.80-7.50 mm; (2) from vein A1, 8-9 veins going to basitornal margin of forewing; (3) costal projection of hind wings distinctly prominent, widely rounded apically; (4) numerous simple and forked cross veins between C and Sc of hind wings; (5) forceps segment I with widely rounded hump on inner margin.

Description of holotype.

Male subimago (Figs 1 View Figure 1 - 3 View Figure 3 ). Well preserved specimen visible in dorsoventral aspect. Head, thorax and abdomen covered by a whitish cloud of turbidity or so-called “Verlumung”, a milky emulsion surrounding the embedded carcass due to leaking gases and fluids during decomposition ( Schlüter and Kühne 1975). Body completely preserved. Left forewing partly damaged, twisted centrally, covered by streaks and overlaying cracks of amber. Rest of body also surrounded by darkened bands and cracks. The subimaginal stage is indicated by the presence of microtrichia covering the wings and by a fringe of microtrichia along posterior wing margin. Additionally, the wings are not translucent, but markedly frosted (Fig. 2 View Figure 2 ). For complete measurements see Table S1.

Colouration relatively pale, dirty yellow to light brown, except of fore- and hind wings distinctly darker, coloured brown to dark brown; distal half of left forewing intensively dark brown to blackish. Due to “Verlumung”, body colouration slightly frosted. Femora relatively pale, yellow to yellowish-brown; tibiae and tarsi darker than femora, up to brown, with blackish maculation irregularly scattered. Abdominal segments unicoloured, dirty brown to greyish brown, segments VII-X fully covered by “Verlumung”. Genitalia only visible ventrally, due to streaks and cracks of amber mainly from dorsal side; natural colouration of genitalia most probably not preserved.

Head. Eyes large, well developed, indistinctly separated into two portions; medially contiguous at short distance, flattened laterally; hexagonal ommatidia of upper portion of eyes well distinguishable; no preserved bands or strips on eyes laterally; ocelli poorly visible due to streaks and cracks, relatively small; antennae short, not longer than length of head; facial keel relatively large (Fig. 1C View Figure 1 and D View Figure 1 ). - Thorax: Prothorax mostly covered by “Verlumung”, relatively short; prosternum medially with strong bispinate projection between bases of forelegs (Fig. 1B View Figure 1 and D View Figure 1 ). Mesothorax covered by “Verlumung”; details of lateral mesothorax not visible; mesonotum massive, with elongate medioscutum; sutures of mesonotum poorly recognizable; mesonotal suture [MNs] nearly transverse, laterally stretched backwards; medioparapsidal suture [MPs] slightly curved medially; lateroparapsidal suture [LPs] not elongate, curved outward distally, not reaching posterior scutal protuberance; mesobasisternum [BS] elongate; furcasternal protuberances [FSp] contiguous, without median impression. Metathorax short; metanotum reduced (Fig. 1C View Figure 1 and D View Figure 1 ). - Wings: Forewing. Opaque, not translucent (Figs 1A View Figure 1 , 1B View Figure 1 ; 2A View Figure 2 ; 3A View Figure 3 , 3B View Figure 3 ), relatively narrow, with posterior margin slightly scalloped. Pterostigma with 11-13 simple veins only. Longitudinal veins well recognizable, including short marginal intercalaries; cross venation well developed. Venation of “posteritornous” condition, i.e. CuP and A1 end distally of wing tornus; RS, MA and MP triads well developed; RS field complete, with RSa2 diverting from RSa; RS and MA without common stem, basally approached; MA furcation nearly symmetrical, forked after 0.56-0.58 of its length; MP1 and MP2 without common stem; MA-CuA arise from the same point; base of CuP distant from CuA base; CuA and CuP nearly parallel centrally, slightly divergent distally, no cubital intercalaries; 6-7 simple veins going from A1 to basitornal margin; four cross veins between A1 and A2; anal veins except of A1 short, ending distally near wing base. Numerous free short intercalaries along of tornoapical margin of forewing, and a smaller number of short marginal intercalary veins connected to longitudinal veins (Fig. 3 View Figure 3 ). - Hind wings: Opaque, not translucent, nearly round, as long as 0.26 × forewing length (Fig. 1A View Figure 1 and B View Figure 1 ). Costal projection well developed, situated strongly proximally; widely rounded apically; numerous simple and forked cross veins between C and Sc, densely grouped in costal area; MA not forked, thus lacking MA triad; MP triad complete, MP fork situated nearly middle of vein length; CuA and CuP nearly parallel; at least three longitudinal veins and a few intercalaries in anal field. Cross venation well developed; numerous short and elongatemarginal intercalaries between RA and A1 (Fig. 3 View Figure 3 ). - Legs. Subimaginal forelegs shorter than body. Patellotibial suture vestigial, present on middle and hind legs, absent on forelegs. Tarsi five-segmented; first tarsomere longest, well separated from foretibia, but fused with tibia in middle and hind legs. Tarsi of forelegs with paired blunt pretarsal claws, in each pair one foreclaw smaller than the other; middle and hind legs with one hooked and one blunt claw (Figs 1D View Figure 1 , 2B View Figure 2 , 2C View Figure 2 ). - Abdomen: Abdomen relatively short and massive, moderately tapered distally. Segment I shortest, fused with metathorax; segments II-V relatively short, segments VI-VII enlarged and robust; segment VI largest; tergum VI without middorsal transverse evaluation; segment IX markedly enlarged, wider than adjacent segments. Cerci completely preserved, approximately two times shorter than body; paracercus very short, segmentation not recognizable (Fig. 1A View Figure 1 and B View Figure 1 ).

Genitalia.

Penis lobes partly covered by “Verlumung”. Two-segmented forceps well preserved. Segment I long, moderately expanding distally, with widely rounded hump on inner margin; apically of hump indented, superficially giving the appearance of segmentation; after this indentation, segment I distinctly bent inwards at half-length, so forcipes tilted towards each other. Distal segment short, as long as 0.22-0.24 of segment I length, only laterobasally with clear segment border towards segment 1, tapering apically, with widely rounded tip. Penis lobes well separated by wide, V-shaped cleft; each lobe moderately tapered apically, rounded at tip; both lobes with prominent subapical process, sharply pointed at the tip (Figs 2D View Figure 2 , 3C View Figure 3 ).

Description of paratype.

Male subimago (Figs 3D View Figure 3 , 4 View Figure 4 ). Well preserved and almost complete specimen visible in dorsoventral aspect. Piece of amber with numerous cracks and streaks. Head, thorax and abdomen covered with thin layer of “Verlumung”. Dense layer of “Verlumung” on posterior half of abdomen, so details of genitalia poorly visible; shape of styliger basally not recognizable. Right forewing and both hind wings well preserved, complete; distal half of left forewing missing. A dense row of microtrichia along of posterior margin of wings. Wings not translucent, frosted. Legs well preserved, complete. Most part of cerci missing. For complete measurements see Table S1.

Remarks.

Despite some differences in body size of the specimens (see Table S1), we attribute both male subimagines described here to the single species B. bispinata sp. nov., based on similarities in wings venation and shape of genitalia. It should however be noted that, unlike in the holotype, the upper portion of compound eyes in the paratype specimen is not contiguous dorsally, but separated by a narrow gap. Although genitalia are mostly covered by “Verlumung” in the paratype, the shape of the apical portion of the penis lobes and forceps resemble those of the holotype.

The new species described herein can be undoubtedly assigned to the genus Balticobaetisca Staniczek and Bechly, 2002 within Baetiscidae . In contrast to extant representatives of the subgenus Balticobaetisca Fascioculus Pescador and Berner, 1981 (genus Baetisca ) ( Pescador and Berner 1981), the upper portion of compound eyes is unicolorous and without stripes. The same character state is observed in the two other known species of Balticobaetisca , as well as in representatives of Baetisca s. str.

Like other taxa of Baetiscidae , B. bispinata sp. nov. has a prominent bispinate prosternal projection located between the bases of forelegs (Fig. 1D View Figure 1 ) and characteristically rounded hind wings (see also Kluge 2004, Staniczek and Bechly 2002). It is further characterized by the presence of (1) forewings with fully developed RS, MA and MP triads, and numerous intercalaries between RS and CuP (see Kluge 2004: 68, fig. 17B); (2) foretarsus with each of both paired claws blunt apically, similar to males of Balticobaetisca stuttgardia and extant species of Baetisca , both claws of one pair with different length to each other (see also Fig. 5B View Figure 5 , inlay); (3) tergum VI of abdomen without mid-dorsal transverse evaluation (see also Staniczek and Bechly 2002: 127, fig. 2) and (4) vestigial, not segmented paracercus (see Staniczek and Bechly 2002; Kluge 2004: 68-69, fig. 17).

Balticobaetisca bispinata sp. nov. can be distinguished from other representatives of the genus by (1) its smaller general size; (2) by having tarsomere I as the longest (tarsomere V is the longest in Balticobaetisca velteni and Balticobaetisca stuttgardia ); (3) having shorter caudal filaments (half the length of B. velteni and B. stuttgardia ); (4) shorter intercalaries between longitudinal veins (at least 3) compared to other Balticobaetisca representatives, and (5) lacking forked veins in the anal field unlike the other two species.

Up to now there was only a single male specimen of Balticobaetisca known: B. stuttgardia was established based on a specimen with complete genitalia that have well separated penis lobes, which are blunt at the tip ( Godunko and Krzemiński 2009: 130). A similar shape of penis is described for B. bispinata sp. nov. (Fig. 2D View Figure 2 ), but the new species can be clearly separated from B. stuttgardia (Fig. 2F View Figure 2 ) by the first segment of forceps, which lacks the distinct triangular inner projection of segment I, as well as the general shape of both forceps segments (Fig. 2F View Figure 2 , Godunko and Krzemiński 2009: 130).

A comparison of B Balticobaetisca bispinata sp. nov. with B. velteni is limited, as only the opposite sex is described in both species ( Staniczek and Bechly 2002). The female holotype of B. velteni however differs by the pattern of venation, especially of forewings, with a rich cross venation and numerous veins, mostly forked, going from A1 to the basitornal margin. The hind wings of B. velteni also have a less prominent costal projection and fewer cross veins in the costal field [in contrast to the costal projection of B. bispinata sp. nov., which is markedly protruding and proximally in the costal field with rich cross venation] (Staniczek and Bechly 2009: 7-8, figs 3-7). It also differs in the foreclaws, which are dissimilar (one hooked, one blunt) in B. velteni (Fig. 2E View Figure 2 ), but this may be a generic character, which is only present in the female sex (as also in females of extant Baetisca ).

Regarding body size, there remains the possibility that the described female of B. velteni and male of B. bispinata sp. nov. belong to the same species ( Staniczek and Bechly 2002: 7-8). On the other hand, a clear difference in the venation of fore- and hind wings between B. velteni and B. bispinata sp. nov. rather points to the presence of two different fossil species. Table 2 View Table 2 lists a detailed comparison of characters between Balticobaetisca representatives.