Protobaetisca bechlyi Staniczek, 2007

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

Protobaetisca bechlyi Staniczek, 2007

Protobaetisca bechlyi = Protobaetisca bechlyi Staniczek, 2007: The Crato Fossil Beds of Brazil: window into an ancient world, p. 182, fig. 11.6g

Revised diagnosis (Figs 6 - 7 ).

Modified based on Staniczek (2007) and on newly described characters of male nymph [holotype] and putative adult of P. bechlyi . ADULT: (1) body length 7 mm [as preserved]; (2) forewing length of approximately 6 mm, maximum width 3.5 mm [as preserved]; (3) forewing triangular-shaped, width/length ratio approximately 0.58 [as preserved]; (4) longitudinal venation of “posteritornous” condition; (5) MA slightly asymmetrical, fork located at 0.65 of wing length; (6) at least 15 simple and forked cross veins in pterostigma; (7) distinct short intercalary vein between MP2 and CuA; (8) CuP nearly parallel to A1, approaching close to each other; (9) at least five veins going from A1 to basitornal margin; (10) small (ratio of forewing/hind wing length of 1/5) rounded hind wings with prominent costal projection at base; (11) abdominal segment VI enlarged. Nymph: (12) body length 8 mm [without caudal filaments], caudal filaments length 3 mm; (13) genal shelf of head not distinctly projected; (14) femur short, as long as 0.32 of tibia length; tarsus at least 0.50 of tibia length; preserved part of pretarsal claw at least 0.34 of tibia length; (15) notal shield without traces of dorsal or lateral spines; (16) abdominal segment X ventrally covered by well-preserved paired sclerites of triangular shape, rounded apically, markedly separated by narrow V-shaped incision, which may be interpreted either as genital buds (outgrowths of IX) or paraprocts.

Material.

Male nymph, holotype, SMNS 66620 adult, SMF VI 993.

Redescription of holotype (male nymph; Fig. 6A, C, E ).

Length of body 8 mm [without terminal filaments]. Length of cerci 3 mm. The nymph was initially described by Staniczek (2007) as a new species and attributed to a new fossil genus within Baetiscidae . A thorough reinvestigation confirmed that the compressed specimen is visible from its ventral side, which implies an amended description and interpretation as follows: Relatively well-preserved nymph, visible from ventral side (see also Fig. 6 for interpretation). Body stout, nearly ovoid shaped (Fig. 6C ). - Head: Poorly preserved, relatively large, head width at least 0.53 × of head length; lateral portions of head moderately damaged; distinct remnants of frontal and genal projections; frontal projections relatively large, rounded apically, located close to each other; putative remnants of left antenna along left lateral side of head; basal antennal segments better visible; length of antenna at least ⅔ × of head length; genal shelf not distinctly projected, not protruding above anterolateral margin of head. Head in ventrocaudal posture, ventral outer edge of cranium well visible, but labrum and other mouthparts mostly not preserved except of mandibles, maxilla not visible, labium probably lost (Fig. 6A ). - Thorax: Prosternum well separated from head and anterior part of mesothorax, without traces of bispinate projection; prosternum relatively wide, at least 0.30 × its length (Fig. 6A, C ). Base of foreleg large; coxa and trochanter apparently robust; remnants of foreleg located along right side of nymphal body; femur short, about 0.32 × of tibia length; tarsus shorter than tibia, at least 0.50 × of tibia length; pretarsal claw stout and long, with preserved part as long as at least 0.34 × of tibia length (Fig. 6C ). Mesosternum and metasternum mainly lost, distinctly short. Mesonotum posteriorly extended to abdominal segment VI, forming a notal shield (or “carapace”); notal shield well recognizable from ventrally (as anterior abdominal sterna not preserved), with distinct outer margin on right side; notal shield robust, with widest part at half length; near posterior margin slightly narrower than at half length, without traces of dorsal or lateral spines (Fig. 6C ). - Abdomen: Abdominal segments VI-IX with prominent posterolateral projections; no preserved traces of median spines; lateral margins of abdominal segments I-V slightly bent up; abdominal segment VI slightly enlarged, longest, with traces of transversal crest indicating the caudal closure of notal shield; segment VI covered approximately at 1/2 of its length by notal shield (Fig. 6C ). Abdominal segment X ventrally covered by well-preserved paired sclerites of triangular shape (Fig. 6E ), rounded apically, markedly separated by narrow V-shaped incision, which may be interpreted either as genital buds (outgrowths of IX) or paraprocts. Cerci and paracercus stout; swimming setae on both inner sides of cerci and paracercus, denser at half length.

Description of new putative adult (SMF VI993; Fig. 7 ).

Length of body 7 mm; length of forewing approximately 6 mm, maximum width 3.5 mm. Imago of unknown sex. Specimen preserved in right lateral view with both forewings overlapping. Except of forewings, entire body of specimen poorly preserved, first abdominal segments not discernible, only base of cerci preserved. Right forewing is almost complete except of cubital and anal fields with venation poorly distinguishable. Traces of left forewing venation partly overlapping with right forewing venation. Costal brace and basal part of costal field almost destroyed; longitudinal venation mostly preserved and distinguishable; cross veins poorly visible, especially in anal field. Hind wings partially superimposing forewings. Hind wing mostly damaged, with poorly preserved outline and trace of costal projection; venation almost lost. Legs completely missing, except of traces of putative trochanter of right and left foreleg. Because of poor preservation of eyes and lacking gonopods, the sex of this specimen is not determinable (Fig. 7A ). - Head: Relatively small; shape of eyes not distinguishable; preserved part of facial keel relatively short. - Thorax: Prothorax not widened, relatively narrow; m esonotum with trace of elongate medioscutum; putative sharply pointed [? bispinate] projection on ventral side of prothorax, close to pointed projection trace of putative trochanter. Border between pro- and mesothorax poorly recognizable; mesothorax distinctly large; mesonotal sutures poorly preserved; shape of preserved part of MPs and putative MS similar to those in Baetisca (Fig. 5A ); lateral sclerites completely damaged; ventrally with traces of relatively elongate furcasternal projection. Metathorax short (Fig. 7B ). - Wings: Preserved forewing of triangular shape, relatively wide, with width/length ratio approximately 0.58 [as preserved]. Longitudinal venation well recognizable; cross venation well developed, occasionally poorly visible, present in all the fields of forewing. Pterostigma with at least 15 simple and forked cross veins; only simple veins between C and Sc proximally. RP basally forked at 0.30 × of its length; RP2 basally forked at 0.29 × of its length. Longitudinal venation with complete RP, MA and MP triads; RP and MA without common stem, basally approached; posteritornous wing condition: wing tornus situated basally of CuP and A1, A1 nearly parallel and close to CuP throughout remaining length. Furcation of MA slightly asymmetrical, fork located at 0.65 of wing length; iMP slightly closer to MP2 proximally; MP and CuA without common stem; distinct short intercalary vein between MP2 and CuA; traces of short intercalaries in MA and MP fields poorly preserved; MP1 and MP2 without common stem; base of CuP markedly distant from CuA base; at least five veins branching from A1 to basitornal margin; A2, if preserved, most probably visible in basal part of wing (Fig. 7C, D ). Ratio of hind wing / forewing length 1/5. Hind wing length 1 mm; rounded, almost circular appearance, with prominent costal projection near its base, rounded at tip (Fig. 7B ). - Abdomen: All abdominal terga and sterna poorly preserved; borders between segments I-IV poorly preserved, other segments with more or less preserved borders; segments IV-VI partly damaged; distal segments relatively large; segment VI the longest. Gonopods not preserved.

Figures

Figure 5. Baetisca rogersi Berner, 1940. USA, coll. SMNS EPH 009249 A. A-B, F: male imago; C-E: male subimago. A general dorsal view; B general lateral view, inlay: paired right foreclaws enlarged in dorsal view; C mesothorax in dorsal view: MNs - mesonotal suture; LPs - lateroparapsidal suture; MPs - medioparapsidal suture; MLS - medioscutum; SL - scutellum. D thorax in ventral view: AES - anepisternum; KES - katepisternum; BS - basisternum; FSp - fucasternal protuberance, arrows mark bispinate projection of prosternum. E - F genitalia in ventral view: pe - penis; S 1 - segment 1 of forceps; S 2 - segment 2 of forceps.

Figure 6. Nymphs of (A, C, E) Protobaetisca bechlyi Staniczek, 2007 (holotype, Lower Cretaceous, Upper Aptian, Crato Formation, holotype, SMNS 66620) and (B, D, F) Baetisca rogersi Berner, 1940, (USA, coll. SMNS). A - B head and prothorax, ventral view: ant - antenna; cly - clypeus; cx - coxa; cxc - coxal cavity; fr - frons; frp - frontal projections; ge - gena; lbr - labrum; md - mandible; mx - maxilla; prm - prementum; pm - postmentum; pst - prosternum. C - D general ventral view: I-IX - abdominal segments I-IX; cr - head; cl - pretarsal claw; cx - coxa; fe - femur; frp - frontal projections; ns - notal shield; pst - prosternum; ta - tarsus; ti - tibia; tr - trochanter, arrow marks traces of transversal crest. E - F caudal end of abdomen, ventral view: IX-X - abdominal segments IX-X; ce - cerci; gb - genital bud; pp - paraproct; tf - paracercus.

Figure 7. Protobaetisca bechlyi Staniczek, 2007, putative adult specimen, sex unknown, SMF coll., SMF VI 993. A general lateral view; B head, thorax, wing bases and abdominal segments I-III, lateral view. Abbreviations in white colour: cr - head; ThI - prothorax; ThII - mesothorax; ThIII - metathorax; I-III - abdominal segments I-III; FW - forewing; HW - hind wing [wing shape marked by white lines on left half of photo]. Abbreviations in black colour: ALSs - anterolateral scutal suture; ANp - anteronotal protuberance; ANi - anteronotal transverse impression; bp - bispinate projection of prosternum; cb - costal brace; E - eye; fk - frontal keel; fl - foreleg [r - right; l - left]; FSp - furcasternal protuberance; LPs - lateroparapsidal suture; MLs - median longitudinal suture; MNs - mesonotal suture [white line indicates the placement and orientation of MNs / MPs]; MPs - medioparapsidal suture; MS - medioscutum [white lines on right half of photo indicate position of MS]. C right forewing, ventral side; D same with interpretation of venation (for vein abbreviations see Material and Methods).