A new Gondwanan mayfly family from the Lower Cretaceous Crato Formation, Brazil (Ephemeroptera: Siphlonuroidea: Astraeopteridae fam. nov.)

The adult holotype of the fossil mayfly Astraeoptera cretacica Brandão et al. 2021 from the Cretaceous Crato Formation, Brazil, is reviewed and attributed to a new family Astraeopteridae fam. nov. Based on alate specimens, we also describe further new representatives of Astraeopteridae fam. nov., namely Astraeoptera vitrea sp. nov. and Astraeoptera oligovenata sp. nov., as well as the new genus and species Eosophobia acuta gen. et sp. nov. A subsequent character analysis of the new material suggests systematic affinities of Astraeopteridae fam. nov. with those extant families of Siphlonuroidea distributed in the Southern Hemisphere. These newly described fossil Siphlonuroidea from the Cretaceous of Brazil thus add to the biogeography and systematics of mayflies.

www.nature.com/scientificreports/shortened; MP2 straight at entire length; a pair of elongated, basally free intercalaries between MP2 and CuA, alternating with a few short intercalary veins.Cubital field relatively wide, with at least eight intercalary veins running probably from CuA towards posterior margin of wing; distal half of iCu1-iCu2 nearly subparallel to CuA, and putative ?iCu3-?iCu4 nearly subparallel to CuP; shorter free intercalaries alternating with iCu1-iCu4; CuP poorly visible; anal field not preserved, except of short fragment of putative [intercalary?]anal vein close to distal end of CuP (Fig. 2b).Hind wing fragmentarily preserved, incomplete, shape and character of venation not visible; preserved part of hind wing as long as approximately 0.37 of forewing (1.93 mm) (Fig. 2a).Foreleg partly preserved; coxa as long as trochanter; forefemur as long as 0.5 of preserved part of foretibia; preserved part of foretarsus slightly shorter than foretibia; tarsomeres and pretarsal claw poorly discernible.Measurements for preserved parts of forelegs: femur-1.60 mm; tibia-3.00mm; tarsus-1.55mm.Middle legs shorter than foreleg, with partly preserved trochanters and relatively short femora.Hind femur partly preserved, with visible distal end; remnants of patellotibial suture poorly visualized on hind tibia basally; fragments of putative tarsus and pretarsal claw partly preserved; first tarsal segments of preserved legs not shortened (Fig. 2a).
Abdomen with relatively tall segments (possibly the result of fossilization); abdominal segments VII and VIII are the tallest and widest; remnants of relatively large subgenital plate posteriorly on sternum VIII; segment X smallest, details poorly visible.Only one terminal filament (either paracercus or cercus) partly preserved, fragmented, approximately 6.70 mm in length (Fig. 2a).
For a summary of morphological characters of A. cretacica compared to other representatives of Astraeopteridae fam.nov., see Supplementary Table 1.
Etymology.Species epithet derived from the Latin adjective vitreus for glassy, as the preserved forewing of the holotype resembles shiny glass.
Diagnosis.Body length 10.40 mm.Forewing length 8.40 mm; costal brace arched and only slightly pronounced; fork of RP slightly distant from base, at 0.23 of forewing length; RP2 forked at 0.48 of forewing length; two intercalaries between MP2 and CuA (one long and one short); cubital field with seven longitudinal veins subparallel to CuA.Hind wing as long as 0.45 of forewing length.
Generalities.Specimen preserved in lateral left view, with partly preserved head, thorax and abdomen.Head and thorax damaged; details of mesopleuron not discernible; mesonotum poorly preserved; thoracic sterna mostly missing.Left forewing with almost completely preserved longitudinal and cross venation, except parts of iMP and MP2, and proximal half of cubital venation.Hind wings present, but shape and venation not discernible.Femur, tibia and part of putative tarsus of [? left] hind leg preserved; remnants [? femur and tibia] of putative [? right] hind leg partly preserved; remnants of putative middle leg preserved, separated from body.Abdominal terga V-X damaged or partly missing; genitalia damaged, incomplete.One incomplete terminal filament [? left cercus] preserved (Fig. 3a,b).
Description.Adult male with robust body embedded in lateral aspect.Body length approximately 10.4 mm.Head preserved but mostly damaged, with visible remnants of vertex, frons and clypeus; frontal and coronal sutures well distinguishable.Remnants of putative left eye mostly preserved, relatively small; right eye damaged; remnants of frontal ocellus relatively large.Antennae and ocelli missing.Facial keel relatively narrow (Fig. 3c).For measurements see Supplementary Table 1.
Preserved left forewing elongated and wide; length of preserved part 8.45 mm, width of preserved part 4.53 mm; forewing width/length ratio-0.54.Longitudinal venation mostly well visible; cross venation moderately developed.Costal brace partly preserved basally, slightly pronounced, clearly arched; costal field between C and Sc narrow, with regular row of at least 17 simple cross veins, interspersed with about five forked cross veins in distal half; venation of pterostigma poorly preserved.Sc and RA straight at entire length; subcostal field narrower than costal field, with at least 13, sparsely scattered simple cross veins; Sc and RA reaching wing apex.Solitary intercalaries between RA and MA2 basally connected to main longitudinal veins by cross veins; between MP1 and CuA also solitary and paired intercalaries.RP fork slightly distant from base after 0.23 of RP length; RP2 forked near midlength.Fork of MA nearly symmetrical at about midlength (0.46); iMA is at least 0.57 of MA2 length; short solitary intercalary veins on each side of iMA.MP1-iMP-MP2 bent centrally; MP fork slightly asymmetrical; at least one short intercalary vein between MP1and iMP, and at least two of such intercalaries are between iMP and MP2; proximally iMP seems to be approximated to MP1, not shortened; MP2 straight at entire length; one elongated intercalary vein between MP2 and CuA, alternating with a pair of shorter intercalaries.Cubital field relatively narrow, with at least seven iCuA of different length, with iCu1-iCu4 nearly subparallel to CuA centrally and distally; putative CuP moderately bent distally.Anal field with one or two veins, moderately bent centrally.Hind wings preserved, but details of shape and venation are poorly distinguishable; preserved part of hind wing approximately 3.72 mm in length, as long as 0.44 of forewing (Fig. 3b,d).
Hind legs fragmentarily preserved, with indistinct margins between segments; distal end of [? left] hind leg reaches out to the middle of abdominal segment VI (Fig. 3a).
Abdomen relatively large, with moderately tall segments (possibly the result of fossilization); abdominal segment VII is the tallest and widest; remnants of putative male genitalia on segment X are present, but poorly preserved.Only one terminal filament [? left cercus] partly preserved, fragmented, with approximately 3.00 mm in length (Fig. 3a,e).Etymology.Species epithet named after its fewer numbers of cubital intercalary veins compared to its congeners, from Latin oligo for few and venatus for veined.
Diagnosis.Body length 13.20 mm.Basisternum of mesothorax relatively short.Forewing length 11.40 mm; RP fork basally at 0.15 of RP length; RP2 fork basally at 0.26 of RP2 length; one intercalary between RP3 + 4 and MA; two intercalaries between MP2 and CuA (one short and one long); cubital field with at least three longitudinal veins subparallel to CuA.
Generalities.Incomplete specimen embedded in left lateral position, with damaged head and thorax.Left forewing partly preserved; venation poorly distinguishable; hind wings and all legs missing; abdominal segments without details, only traces preserved; only margins of segments I-IV visible; caudal filaments missing (Fig. 4a,b).
Description.Adult, sex cannot be determined.Body length approximately 13.20 mm.Head fragmentarily preserved, eyes relatively large, at least 0.33 of head length; facial keel elongated and relatively wide proximally; antennal segments not preserved (Fig. 4a).For measurements, see Supplementary Table 1.
Thorax in lateral view expanded above head, poorly preserved.Prothorax relatively large, about 0.80 mm in length.Pterothorax well developed, robust, with poorly preserved pleuron and partly damaged metathorax; preserved part of pterothorax at least 5.00 mm in length.Mesothorax largest, with elongated mesonotum; structure and shape of MNs poorly visible, apparently stretched backward medially; putative LPs seems to be elongated and curved inward distally; PcxsA and PLsS well developed, elongated and complete; posterior arc of prealar bridge [PAB:PA] neither shortened nor reduced.Lateral and ventral aspect of thorax poorly visible; basisternum relatively short; putative furcasternal protuberance with indistinct shape and structure (Fig. 4c).
Forewing short and wide, length of preserved part 11.40 mm, width of preserved part at least 6.30 mm; width/ length ratio of forewing is 0.55.Longitudinal and cross venation poorly preserved; cubital venation mostly missing; only distal ends of several cubital intercalaries preserved.Costal brace covered by matrix and not visible; costal field between C and Sc moderately widened centrally, lost distally; pterostigmatic area mostly missing; in preserved part of costal area at least six simple cross veins; Sc and RA nearly subparallel proximally, moderately bent distally; subcostal field centrally slightly wider than costal field.Sc reaching wing apex; RA terminating close to RP1.Intercalary veins between RP1 and CuA poorly visible and fragmented; their cross venation mostly missing; solitary or paired intercalaries preserved between RP1 and CuA.RP symmetrically forked after 0.15 of its length; RP2 slightly asymmetrical, forked after 0.26 of its length.MA nearly symmetrically forked at 0.58 of its length; MA1 moderately bent centrally and basally, MA2 slightly bent centrally; iMA poorly distinguishable, with preserved part of less than 1/3 of MA2 length; cross venation not visible.MP fork is covered by matrix; MP1 and MP2 moderately bent centrally; proximal part of MP2 missing; at least one elongated intercalary vein between MP1 and iMP, no visible intercalaries between iMP and MP2; cross venation of MP field mostly missing; two short intercalary veins between MP2 and CuA.Cubital field relatively narrow, with at least three veins running from CuA towards posterior margin of wing [the length of these veins cannot be determined]; remaining cubital field damaged; CuP fragmentary, preserved part straight.Anal field damaged, with a single preserved vein A1 clearly bent distally.Outline of one hind wing fragmentarily preserved, incomplete, at least 1/3 of forewing length; shape and structure of hind wing venation not visible (Fig. 4b,d).
All legs are missing.Abdominal segments I-IV nearly subequal in length.Caudal filaments missing (Fig. 4a).
Comments.The general similarities between Astraeoptera oligovenata sp.nov.and A. cretacica (apart from diagnostic characters of Astraeopteridae fam.nov.and Astraeoptera) are the positions of RP and MA forks and the shape of vein A1, which are strongly bent distally.General similarities between A. oligovenata sp.nov.and A. vitrea sp.nov.concern the forewing width/length ratio; the nearly symmetrical fork of MA; and the presence of two intercalaries between MP2 and CuA, one being short and one long (see Supplementary Table 1).Also important to note is that the cubital field of specimen SMF VI 743 is not entirely preserved, so the number of longitudinal veins of the cubital field is probably higher than only the three discernible ones.For a summary of morphological characters of A. oligovenata sp.nov.compared to other representatives of Astraeopteridae fam.nov., see Supplementary Table 1.
Eosophobia gen.nov.Urn:lsid:zoobank.org:act:F1CC23ED-862E-43E2-9FB1-89997BF00969Etymology.The generic name Eosophobia gen.nov. is a compound noun of female gender, deriving from Eos (Greek: Ἠώς), the Greek goddess of dawn, and phobia (Greek: φοβία), the Greek word for fear.Eos was the wife of titan Astraeus, the Greek god of dusk, after whom the related mayfly genus Astraeoptera was named.Eosophobia is also a common medical term describing the fear of dawn or daylight.It is also the name of a song by American musician Jack White III on the record "Fear of Dawn", released in 2022, which was in heavy rotation when describing this genus.
Diagnosis.Body length 7.60 mm; forewing length 7.70 mm.Thorax elongated, as long as 0.82 of abdomen.Costal brace strongly arched, more than in Astraeoptera; relatively fewer cross veins than in Astraeoptera; RP fork at 0.22 of its length; RP2 fork at 0.20 of its length; distal half of MA + MA1 strongly approximated to RP3 + 4 (at least four times closer than in Astraeoptera); three long intercalaries between MP1 and MP2; one short intercalary between MP2 and CuA, instead of two as in Astraeoptera; cubital field with at least eight longitudinal veins in an acute angle of CuA, not subparallel as in Astraeoptera, only one vein nearly subparallel to CuA.Largest abdominal segments of abdomen are V and VI (unlike VII and VIII in Astraeoptera).
Etymology.The specific epithet is of female gender and derived from the Latin adjective acutus (sharp), referring to the posterior veins of the cubital field of forewing, which are arranged in an acute angle to CuA, compared to the respective subparallel orientation of these veins in the cubital fields of its congeners.At the same time, acuta refers to an acute condition of eosophobia.
Generalities.Well-preserved specimen visible in lateral view, with an almost complete body.Head with preserved eye and putative frontal ocellus.Thorax almost complete, with pleuron relatively well visible.Longitudinal venation relatively well preserved; pattern of forewing venation hardly distinguishable due to overlapping of veins in both forewings.Distal end of preserved right forewing partly damaged or lost.Hind wing preserved, but detailed shape and venation pattern not discernible.Right fore-and hind legs fragmentarily preserved; tarsi and pretarsal claws missing.Abdominal segments completely preserved, with putative subgenital plate ventrally on segment VII partly damaged; abdominal segments IX-X damaged, subanal plate not discernible; traces of both putative cerci preserved; putative paracercus probably vestigial (Figs. 5 and 6).
Description.Adult of putative female with body well visible in lateral view.Body length approximately 7.6 mm.Head mostly damaged; preserved trace of eye relatively large, at least 0.40× of head length; relatively wide trace of frontal ocellus.Antennae and ocelli missing.Facial keel slightly elongated, distally hooked, pointed, and strongly bent inwardly (Fig. 5a).For measurements see Supplementary Table 1.
Preserved right forewing relatively narrow; tip of forewing damaged; length of preserved part 7.7 mm, width of preserved part 3.7 mm.Longitudinal venation mostly well recognizable; cross venation moderately developed, poorly visible.Cubital brace well preserved, strongly arched; costal area narrow, with relatively dense row of at least 13 simple cross veins proximally and centrally; sparse, forked veins spread distally, including pterostigma; details of pterostigma venation poorly recognizable.Sc and RA straight at entire length and nearly subparallel proximally and centrally, divergent distally, reaching wing apex; subcostal area relatively narrow; cross venation poorly preserved, at least eight simple cross veins hardly distinguishable.RP nearly symmetrical, fork clearly distant from base; RP forked after 0.22 of its length; RP2 nearly symmetrical, forked at about 0.20 of its length.RP3 + 4 approximated to MA1 distally.Several long and short solitary intercalaries between RP and CuA.Fork of MA nearly symmetrical, situated distally, forked after 0.65 of its length; iMA as long as 0.66 of MA2 length.MP1-iMP-MP2 slightly bent distally; MP fork seems to be asymmetrical and situated close to vein base; MP forked at least after 0.07 of its length; iMP not shortened, approximated MP2 basally; paired intercalary veins on each side of iMP; MP2 and CuA not convergent basally, straight at entire length; one short intercalary vein between MP2 and CuA.Cubital field relatively narrow, with at least seven iCuA of different length running from CuA towards posterior margin of wing, terminating at basitornal margin; iCu3 and iCu6 longest; cross venation in cubital field poorly preserved; CuP distinctly bent.Anal field with at least two moderately bent veins; A1 basally approximating CuP (Fig. 6).Hind wings preserved, but details of shape and venation poorly distinguishable; preserved part of hind wing as long as approximately 0.44 of forewing; traces of hind right wing of 3.40 mm in length.
Right foreleg fragmentarily preserved, with relatively wide femur; preserved part of tibia longer than femur.Preserved part of hind right femur relatively wide centrally; longer tibia (Fig. 5a).
Abdomen relatively short and robust, segments moderately tall (possibly the result of fossilization); abdominal segments V-VIIII approximately of same width, segments V-VI largest; segment X partly damaged, subanal plate missing; structure of putative subgenital plate indistinct, its distal half lost.Fragmented remnants of putative cerci shorter than body; putative remnant of non-segmented paracercus terminates at abdominal segment X (Fig. 5a).

Discussion
When Brandão et al. 8 described Astraeoptera cretacica as a new genus and species, they refrained from placing it in an existing or new mayfly family, stating that the specimen lacked crucial characters for a proper assignment and thus leaving its systematic position in limbo.Now, with several additional specimens available, which could be placed in four different species and two genera, it is possible to narrow down the systematic affinities of these mayflies.
Several characters clearly indicate that the new taxon belongs to the crown-group Ephemeroptera.All specimens have a significantly reduced size of hind wing, whereas the forewing shows the characteristic, apomorphic type of costal brace, which is basally fused with the costal vein (unlike the unfused condition as seen in Paleozoic and Mesozoic Ephemerida, see 10 ).
Within the Ephemeroptera, Astraeopteridae fam.nov.clearly form a monophyletic group.Unlike all other mayflies, adult Astraeopteridae fam.nov.have an autapomorphic, robust thorax.Unlike the humped pterothorax in all other mayflies, the entire thorax of Astraeopteridae fam.nov. is markedly ascending above the head in a straight angle posteriad, giving the thorax a unique appearance in lateral view (Figs. 2, 3, 4 and 5).
Otherwise, most of the characters visible are plesiomorphic within Ephemeroptera, so it is on the one hand difficult to find synapomorphic characters, which would place Astraeopteridae fam.nov.as sister group to another monophyletic group within Ephemeroptera.On the other hand, it is actually easy to preclude their systematic placement within several of the traditional superfamilies or other higher taxa (see below).
The anteritornous wing shape precludes a placement within Prosopistomatoidea.The first tarsomere, which is not shortened in the imaginal stage (preserved in the type species A. cretacica, Fig. 2a), precludes a placement within the superfamilies Ephemerelloidea, Caenoidea, Leptophlebioidea, and Ephemeroidea (all united as Furcatergalia sensu Kluge 11 ).Likewise, Astraeopteridae fam.nov.cannot be placed within Heptagenioidea (i.e.Branchitergalia sensu Kluge 11 ), or Setisura (sensu McCafferty 12 ) due to their well-developed posterior arc of the prealar bridge (PAB:PA, see Figs. 2a, 4c and 5b), which is neither shortened nor reduced in both genera like it is in the Heptagenioidea.Finally, Astraeopteridae fam.nov.probably have also no closer relationship with Baetoidea.While it is not possible to evaluate the numbers of tarsomeres in the legs of the two genera of Astraeopteridae fam.nov.due to their poor preservation, the combination of a well-developed transverse mesonotal suture and the basal approximation of CuA to CuP in the forewing still precludes the inclusion of Astraeopteridae fam.nov.into Baetoidea.
While Astraeopteridae fam.nov.obviously cannot be placed within most of the superfamilies of Ephemeroptera as discussed above, their forewings resemble in many ways the plesiomorphic forewings present in Siphlonuroidea, with whom they have in common the characteristic cubital field containing a series of sinusoid, long, intercalary veins, occasionally forked towards the hind margin of the forewing.Together with the typical, probably plesiomorphic swimming setation of the tail filaments in the nymphs as already seen in Mesozoic Protereismatidae, this common plesiomorphic wing feature together with the lack of other apomorphic characters has been regarded as the main defining character for Siphlonuroidea 13 .It is obvious that Siphlonuroidea are an artificial, paraphyletic assemblage of different lineages, which only share symplesiomorphic characters, also molecular analyses did not support Siphlonuroidea as monophyletic 14,15 .However, Astraeopteridae fam.nov. on the one hand is a distinct phylogenetic lineage with autapomorphic characters, namely the unique shape of the thorax.On the other hand, it is lacking any obvious synapomorphic characters to place it within any other superfamily.Consequently, we place the new taxon provisionally as a separate family within Siphlonuroidea, knowing that the lack of many key characters, used in Ephemeroptera systematics, on the few specimens of Astraeopteridae fam.nov.precludes a thorough cladistic analysis at this time.
Kluge et al. 13 distinguished within Siphlonuroidea a group of families distributed in the Northern Hemisphere and another group in the Southern Hemisphere.In the Northern Hemisphere group, the mesofurcasternal protuberances are contiguous over their entire length, while in the Southern Hemisphere group, the mesofurcasternal protuberances are separated by a median invagination at least in their posterior part to give space to the metathoracic ganglion, which has shifted anteriorly in these taxa.However, the enigmatic family Siphluriscidae, only known from the single species Siphluriscus chinensis Ulmer, 1920, was not considered by Kluge et al. 13 , although it likewise fulfills the formal criteria for placement within Siphlonuroidea.While distributed in the Northern Hemisphere, namely in Southern China and Vietnam 16 , it still shows separated mesofurcasternal protruberances, at least in their posterior parts.It is difficult to evaluate this character in Astraeopteridae fam.nov., because all species described here are preserved in lateral position and only a small part of the thoracic sterna is recognizable.Only in Eosophobia gen.nov.we can confirm the presence of a relatively large mesofurcasternal protuberance, which is tapering anteriorly and apparently not contiguous, as in Siphluriscidae Zhou and Peters, 2003 and the siphlonuroid families of the Southern Hemisphere 11,13 .However, this character in any case is of limited phylogenetic significance, as an anteriorad shift of the metathoracic ganglion has taken place several times in different groups of Ephemeroptera 11 .
For a broad taxonomic and paleoecological comprehension of Siphlonuroidea placement in the Cretaceous of Brazil, it is also paramount to re-evaluate McCafferty's 17 unnamed putative records of adult Siphlonuridae.Based on the descriptions and illustrations provided, it is difficult to judge the precise systematic position of the material.It is only certain that all specimens are located within Anteritorna.However, at least the alate specimen preserved laterally and depicted in his figure 13  Finally, the base of most veins of the forewing, including MP2 and CuA, appears to be poorly preserved or covered by the matrix in all discussed specimens.Therefore, it is difficult to establish the presence/absence of bending of MP2 and CuA veins posteriorly at the base.McCafferty 17 already even discussed that siphlonurids presence in Brazil was predictable since the group crossed the equator at least twice and probably through West Gondwana.
Fossil Gondwanan representatives of Siphlonuroidea are the bottom-dwelling larvae Australurus plexus Jell and Duncan, 1986; Dulcimanna sculptor Jell and Duncan, 1986; and Promirara cephalota Jell and Duncan, 1986, which were all described as Siphlonuridae. A. plexus is considered a common species and part of the autochthonous fauna of the Koonwarra beds, just as the hexagenitid larvae Protoligoneuria limai is considered for the Crato Formation 4 .However, the Koonwarra paleolake, unlike Crato, is hypothesized as a shallow, cold, and freshwater water setting 18 .In the Crato Formation, Astraeopteridae fam.nov.may have prospered in opening phases of periodic floodings in larger distant depressed areas, as already assumed as more humid phases of the Crato system 33 .
Siphlonuroidea, despite their nymphs having a morphotype typical of lentic settings, do not usually inhabit equatorial regions but are distributed in more temperate climates 17,32 .It is important to point to the hypothesized arid paleoclimate of the Crato Formation in its main member Nova Olinda 33 , and also the physical features of most of the water body phases in the deposition paleolake itself (closed system) 34,35 .The former was probably favourable for the Hexagenitidae, as evidenced by an autochthony of this group 4,5 , but harsh for other groups such as the Oligoneuriidae 36 , Euthyplociidae 6 , and most certainly also Astraeopteridae fam.nov.These, as part of a significant allochthonous fauna, apart from being rare in this deposit, are more commonly found as adults that must have reached the depositional site through flight, and their rarer larvae washed out during wetter and open periods 6 .Here, we hypothesize powered flight for Astraeopteridae fam.nov., since they present a robust thorax with putative strong flight muscles, as well as wings with strong, complete venation in the radial and cubital field, which may have been also important for dispersal ability.

Material and methods
The holotype of Astraeoptera cretacica is housed in the fossil collection of the Laboratório de Paleontologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil under the accession no.LPRP/USP 0504, but was physically not accessible to us, so we relied solely on the documentation of Brandão et al. 8 for our redescription.The remaining material was studied between 2016 and 2019 as a part of the fossil collection of Senckenberg Naturmuseum, Frankfurt/Main, Germany [SMF], who had acquired it in 2004 from Fossils Worldwide, Sulzbachtal, Germany, and later kindly made it available to us for investigation.Due to an exchange of specimens under the framework of an ongoing cooperation of the Senckenberg Gesellschaft für Naturforschung, Frankfurt/ Main, Germany (SMF), with the Universidade Regional do Cariri (URCA), Crato, Brazil, the following holo- The material was examined in dry condition, as well as under a layer of ethanol using stereomicroscopes Olympus SZX7 and Leica M205 C. Photographs were taken through a Leica Z16 APO Macroscope equipped with a Leica DFC450 Digital Camera using Leica Application Suite v. 3.1.8.Resulting photo stacks were processed with Helicon Focus Pro 6.4.1 to obtain combined photographs with extended depth of field.Photographs were sharpened, and contrast and tonality were adjusted using Adobe Photoshop™ version 23.1.1 (Adobe Systems Incorporated, San Jose, USA).All drawings were made using a Wacom tablet and the software Autodesk Version 8.6.1.
Measurements were taken either by using an ocular grid or inferred from the photographs taken with a calibration scale (see Supplementary Table 1).
The descriptive morphological terminology mainly follows Kluge 11,37 , for the systematic classification we followed Kluge 11,13 .

Conclusion
A new extinct mayfly family, Astraeopteridae fam.nov., is described from the Lower Cretaceous Crato Formation.This new taxon comprises two genera, the genus Astraeoptera 8 , and the monospecific genus Eosophobia gen.nov., assigned in the present study.The type genus of the new family, Astraeoptera, is composed of three species, the type species Astraeoptera cretacica Brandão et al., 2021, and the two newly described Astraeoptera vitrea sp.nov., and Astraeoptera oligovenata sp.nov.After comparison and addition of new specimens to the taxon, we place Astraeopteridae fam.nov.within the basal, putatively paraphyletic Siphlonuroidea.So far, only adult forms were described for the group, but even though Astraeopteridae fam.nov.were most certainly living at distance to the depositional site of the Crato, it might not be impossible to discover their immatures after investigation of many unstudied larvae in numerous collections or in new material from new excavations at this Lagerstätte.A thorough review that includes first-hand investigation of putative Siphlonuridae specimens described by McCafferty 17 is also paramount to clarify the occurrence of further Siphlonuroidea among the Crato mayfly fauna and broadly in the Gondwana, as well as the possibility of association of these specimens within Astraeopteridae fam.nov.

Data availability
All data generated or analysed during this study are included in this published article and its Supplementary Information files.All relevant data are available from the authors.The datasets generated during and/or analysed during the current study are available from the corresponding author upon reasonable request.All fossil specimens newly described in this study are housed in the institutional collection of Museu de Paleontologia Plácido Cidade Nuvens, Santana do Cariri, Brazil (MPSC), as specified in the Section "Material and methods".Respective inventory numbers of studied specimens are listed in this published article.Requests for access to the fossil materials should be addressed to the curator of the collection.This work has been registered online at zoobank.org under LSID urn:lsid:zoobank.org:pub:1A5D1BE4-2B49-4D36-8745-9D9A1A700D92.The new taxa are registered in zoobank.org.
[AMNH 43477] does not possess the autapomorphic markedly elevated thorax.The head and thorax of two other putative adult siphlonurids discussed by McCafferty 17 are either missing [AMNH 44313] or very damaged [AMNH 44306].