Diagnosis of the extinct Nevrorthidae in Baltic amber:

Head: Ocelli absent; filiform antennae with slightly enlarged scapus, smaller pedicellus and uniform cylindrical flagellomeres, with about 25 (Rophalis relicta) or about 35 or more flagellomeres (all other extinct species). Maxillary palps 5-segmented, labial palps 3-segmented, their terminal segments pointed.

Wings: Forewing lengths 4.5–9.5 mm, about oval, apically rounded, translucent, small setae in rows along on veins. Costal cross-veins simple (Rophalis, Electroneurothus, Palaeoneurothus) or partly branched (Proberotha, Balticoneurorthus), in hindwings always all simple. In fore- and hindwings subcosta (Sc) and radius anterior (RA) running parallel each other distantly and connected distally by a short crossvein. The area between RA and RP interrupted by usually three crossveins: 2ra-rp, 3ra-rp and 4ra-rp, in Balticoneurothus some more crossveins present, similar to some extant nevrorthids: e.g. Austroneurorthus. Cross-vein 2ra-rp participates in the inner crossvein gradate series, crossvein 3ra-rp in the middle crossvein gradate series and crossvein 4ra-rp in the outer crossvein gradate series (Fig. 1). In forewings radius posterior pectinate, 3-branched in the subordinate branches RP1, RP2, RP3+4 (Rophalis, Electroneurothus, Palaeoneurothus, Proberotha prisca) or dichotomus, 4-branched in the subordinate branches RP1, RP2, RP3, RP4 (Balticoneurorthus, Proberotha eocaenus). In hindwings RP always 3-branched. In forewing crossvein 3rp3+4 — rp2 absent in Rophalis and present in all other genera. MA usually simple and MP with dichotomous branch in MP1+2 and MP3+4. The longitudinal veins in fore- and hindwings, e.g. R and M, always divided apically into small terminal branches at margin. CuA running parallel to margin with terminal branches; CuP simple. Anal veins simple, running separately to anal margin.

Male and female genitalia of extinct species often incompletely visible, but of extant nevrorthid species described and analysed by Aspöck & Aspöck (2008).

Type species: Sisyra (Rophalis) relicta Hagen, 1856 in Berendt 1856: 87, pl. 8, fig. 19.

Neotype: Rophalis relicta Hagen, 1856, designated in Wichard et al. 2009: 96–100, figs. 7.10–7.12.

Diagnosis: Rophalis differs definitely from all extant and extinct Nevrorthidae in Baltic amber by the low number of 25 flagellomeres and by the absence of crossvein “3rp3+4 — rp2″ in forewings.

1856 Sisyra (Rophalis) relicta Hagen, 1856. — Berendt: 87, pl. 8, fig. 19.

2009 Rophalis relicta (Hagen, 1856). — Makarkin & Perkovsky: 137–144.

2009 Rophalis relicta Hagen, 1856. — Wichard et al.: 96–100.

Holotypeis lost, neotype illustrated in Fig. 2 (designated by Wichard et al. 2009: 96–100, figs. 7.10–7.12.): Female from the amber collection of Helm (1826–1902) and Menge (1808–1880) originally kept in the “Westpreussisches Provinzialmuseum” of Danzig, now partially kept in the “Westpreussisches Landesmuseum” in Münster-Wolbeck, Inv.-Nr. 467, formerly no. 398.

Diagnosis: In addition to family-traits of the Nevrorthidae Rophalis relicta is characterised by filiform antennae with about 25 flagellomeres including slightly enlarged scapus and pedicellus. In fore- and hindwings the crossvein “3rp3+4 - rp2″ is absent. Furthermore the males bearing distally of the 6^th and 7^th abdominal segments at most 6 extruded and eversible tubes which can be probably interpreted as androconial glands. Extant males, e.g. Nevrorthus, possess also these eversible tubes (Aspöck & Aspöck 1983). Similar analogical organs are found in some amphiesmenopteran insects as well as in some males of fossil Trich optera in Baltic amber (Wichard 2013). In Rophalis relicta two tubes located lateroventral between 6^th and 7^th abdominal segments and respectively between 7^th and 8^th abdominal segments two tubes lateroventral and two tubes laterodorsal (Fig. 3). Forewing length 4.5–5.5 mm.

Male genitalia (Fig. 3c, d): The 9^th sternite rectangular and almost square-cut; the four edges being nearly equally in lengths and slightly rounded at the corners; the lateral edges touching the 9^th tergite, forming together the closed ring of the 9^th segment. The distal margin of the quadrate sternite medially bears a small lobe, probably the pseudoapex derived from the 10^th segment (sensu Aspöck & Aspöck 2008). Two strong and elongate appendages protrude at the laterodistal margin of 9^th sternite; probably belonging to the 10^th segment. They extended to the cavity of the gonocoxite, where the elongate appendage distally expanded into a tetrahedral, rounded structure. Each gonocoxite of the 9^th segment, basally broad, curved, changing distally into curved, sinusoidal gonostyli running to the middle. At the base of each 9^th gonocoxite a gonapophyses, sinusoidal and denticulate, running parallel to the gonostylus. Dorsally the genital is covered by a broad and pre-bulged ectoproct (compare Wichard et al. 2009: 108, fig. 7.17 b).

Female genitalia : Most often “verlumt”, therefore the outer genitalia often not visible; exceptionally the typical nevrorthid female genital structures are partly shown in lateral view in Fig. 2c.

Remarks : Rophalis relicta is the most common nevrorthid species in Baltic amber; single adults are also found in the Eocene Rovno amber (Makarkin & Perkovsky 2009) and in the Bitterfeld amber (Wichard et al. 2009; Rappsilber 2016).

Type species: Electroneurorthus malickyi Wichard et al., 2010: 447–449, figs. 3–4.

Diagnosis: The extinct genus Electroneurorthus is closely related to the extinct genus Palaeoneurorthus. They coincide with the antennae consisting of about 34–36 segments including a larger scapus and a smaller pedicellus. In forewings crossveins 3rp3+4 — rp2 present, in hindwings absent. Electroneurorthus differs from Palaeoneurorthus in the male genitalia by the absence of needle-shaped gonapophyses of the 9^th gonocoxites. Moreover 9^th sternite is elongate, compactly stickshaped and apically slightly forked, whereas 9^th sternite in Palaeoneurorthus dorsoventrally flattened, apically with a small tongue. In forewings Electroneurorthus and Palaeoneurorthus differ from the genera Balticoneurorthus n. gen. and from Proberotha by the absence of some branched crossveins between costa and subcosta.

Holotype: Male embedded in Baltic amber, GPIMH (ex coll. Gröhn 7078).

Diagnosis: As for the genus. Adults of small body size; male forewing length 6–7 mm.

Male genitalia : The 9^th abdominal ring segment is ventrally interrupted by the derived 9^th sternite orientated mediad to the genital centre. The 9^th sternite is much longer than wide, elongate and stick-shaped, apically slightly forked. The forked apex and/or the bulbous structures at both sides of the basal 9^th sternite are probably elements of 10^th segment. Basally broad gonocoxites of the 9^th segment as a pair of robust claspers terminally with gonostyli bend mediad. The gonapophyses of the 9^th gonocoxites not visible basoventrally.

Type species: Palaeoneurorthus hoffeinsorum Wichard, 2009 in Wichard et al. 2009: 101–105, figs. 7.13–7.14.

Diagnosis: Adults of small body size; male forewing length 5.5–7 mm, body light brown, wings translucent.

Head: Ocelli absent. Filiform antennae with slightly enlarged scapus, smaller pedicellus and 34 — 36 following uniform flagellomeres. 5-segmented maxillary palps and the 3-segmented labial palps terminate in a pointed final segment.

Wings: Costal crossveins are simple in both wings. Sc and radius RA approximated each other distally, connected apically by a short crossvein. Fore- and hindwings characterized by 4 rows of crossveins (Fig. 1). In forewings the crossvein 3rp3+4- rp2 present; in hindwings crossvein 3rp3+4 — rp2 absent.

Male genitalia : The 9^th abdominal ring segment ventrally interrupted by the modified sternite. The 9^th sternite much longer than wide, elongate, folded down and often dorsoventrally flattened; the tongue-shaped apex of the 9^th sternite probably derived from the 10^th segment (interpreted as pseudoapex of 9^th sternite sensu Aspöck & Aspöck 2008). Gonocoxites of the 9^th segment as a pair of basally broad claspers terminally with gonostyli bend mediad, claw-like in most Palaeoneurorthus. Basoventrally the gonocoxites bearing gonapophyses with a set of two or three pointed needles or two thorns. The ectoproct (10^th tergite) distally modified to a broad, curved sclerite (compare Wichard et al. 2013: 108, fig. 7.17c).

Comparisons: The genus Palaeoneurorthus differs from Electroneurorthus by the male genital, from Balticoneurorthus n. gen. and Proberotha by the simple, unbranched crossveins between costa and subcosta in the forewings. Palaeoneurorthus differs from genus Rophalis by the number of flagellomeres (Rophalis: 25, Palaeoneurorthus: ca. 35) and the crossveins between subordinate branches of radius posterior in forewings (in Rophalis crossvein 3rp3+4 — rp2 absent).

Holotype: Male embedded in Baltic amber, GPIMH 4523 (ex coll. Gröhn 7076).

Diagnosis: Male forewing length 5 mm. Palaeoneurorthus bifurcatus differs from all other Palaeoneurorthus species by the modified gonocoxites of 9^th segment bearing basally gonapophyses consisting of a pair of distinct thorns instead of the set of two or three needles, present in other extinct Palaeoneurorthus species.

Male genitalia : The 9^th sternite long, slender and bearing a terminal membranous tongue-shaped lobe, probably as pseudoapex derived from 10^th segment. The gonocoxites of the 9^th segment broad at their base bent distad into digitiform structures. At apex each gonocoxite bearing a gonostylus consisting of a short and pointed cone, beaked. A pair of thornsshaped gonapophyses orginates at base of the gonocoxite, in lateral view subtriangular and apically bent dorsad and pointed. 10^th tergite dorsally slightly bulging forming the curved ectoproct.

Holotype: Male embedded in Baltic amber, SDEI (ex coll. Hoffeins 1124-3).

Diagnosis: Male forewing length 5.0–6.0 mm. Palaeoneurorthus hoffeinsorum differs from all other fossil species of genus Palaeoneurorthus in the set of three straight needlesshaped gonapophyses of 9^th gonocoxites.

Male genitalia : The 9^th abdominal segment separating the genitalia from the abdomen by a closed small ring consisting of a small border of the 9^th tergite and a short basal part of the slender 9^th sternite. The 9^th sternite long, flattened, narrows dorsad and bearing a conical, membranous extension at its end, probably pseudapex, a derivate of 10^th segment. The robust 9^th gonocoxites with terminal gonostyli running mediad. Each 9^th gonocoxite bearing basoventrally bizarre gonapophyses, consisting of a set of three dark and pointed needles arranged in a row of decreasing length, the ventral one longest. Ectoproct broad and bulging.

Holotype: Male embedded in Baltic amber, GPIMH (ex coll. Gröhn 7081).

Diagnosis: Male forewing length 5.5–6.5 mm. Palaeoneurorthus groehni differs clearly from all other fossil species of Palaeoneurorthus by the modification of a baggy 9^th gonapophyses bearing two needles.

Male genitalia : The abdominal 9^th segment ring ventrally interrupted by the flattened 9^th sternite, folded down to the genital center. Gonocoxites of 9^th segment present as a pair of strong claspers, terminally with gonostyli, bent and running towards each other until touching medially. Baggy gonapophyses on each 9^th gonocoxite bearing two needles; the ventral (outer) one a long needle, in distal part slightly ampullate, enlarged and pointed, the dorsal (inner) one a small needle with one third of the length of the dorsal needle. Ectoproct broad and bulging.

Holotype: Male embedded in Baltic amber, kept in the Staatliches Museum für Naturkunde Stuttgart, SMNS no. BB-2817 (ex coll. Wichard). Forewings cover partly hindwings and abdomen; male genitalia visible in ventral and lateral view; head, antennae and the legs well preserved.

Etymology: The species eocaenus is named after the Eocene period of the Baltic amber.

Diagnosis: The male genitalia of Palaeoneurorthus eocaenus n. sp. is similar to the genital structure of Palaeoneurorthus groehni. They differ strongly in the gonapopyhses of the 9^th gonocoxites. In the new species (P. eocaenus n. sp.) the basal baggy part of the gonapophyses is missing, but the apical two neddles are present in both species. However, in a further different way from P. groehni, the ventrally orientated (outer) needle is much smaller as in P. groehni, the dorsally orientated (inner) needle is longer than in P. groehni and about 5 × longer than the ventral one of P. eocaenus n. sp.. The needles are not ampullate enlarged as in P. groehni.

Description: Male forewing length 5.5 mm, wings and body light brown, wings ovoid, apically rounded, hindwing with 4.5 mm length smaller than forewing.

Head: Ocelli absent. Filiform antennae with enlarged scapus, smaller pedicellus and 34 uniform flagellomeres. The 5-segmented maxillary palps and the 3-segmented labial palps terminate in a pointed final segment.

Wings: Costal crossveins are simple in both wings. SC and RA running parallel to margin and connected apically by a short crossvein, RP 3-branched. In both wings crossvein gradate series present. In forewings the crossvein 3rp3+4 — rp2 present; in hindwings crossvein 3rp3+4 — rp2 absent.

Male genitalia : The modified 9^th sternite is basally moderately broad, dorsoventrally flattened, folded down, mediad; the pseudoapex not visible. The gonocoxites of the 9^th segment broad at their base, apically the gonostyli claw-like, pointed. Basoventrally the 9^th gonocoxites bearing gonapophyses each with a set of two fine needles, a long one dorsally orientated and a smaller one ventrally orientated, about 1/5 in length of the inner dorsad needle. The broad, curved ectoproct distally modified of the 10^th segment visible in ventral and lateral view.

Type species: Balticoneurorthus elegans n. sp., monotypic.

Diagnosis: Balticoneurorthus with its type species Balticoneurorthus elegans n. sp. differs from all extinct Baltic amber Nevrorthidae in the forewing length of 9.5 mm, in the forewing venation with partially forked subcostal crossveins and numerous irregular crossveins (Fig. 7c), and moreover in the male genitalia showing ventrally a pair of long sclerotized rods (Fig. 7b).

Holotype: Male embedded in Baltic amber, kept in Staatliches Museum für Naturkunde Stuttgart, SMNS no. BB-2818 (ex coll. Wichard). Well preserved, forewings and hindwings visible. Male genitalia visible in posterior and partly lateral view. Head, antennae and legs are present.

Etymology: The new species bears the Latin name “elegans”, a beautiful and exclusive species and the largest nevrorthid adult in Eocene Baltic amber.

Diagnosis: See diagnosis of genus Balticoneurorthus.

Description: Adults of relatively large body size; forewing length 9.5 mm and hindwing length 8mm. Wings light brown, translucent, apical margin rounded.

Head: Ocelli absent. Antennae filiform, half as long as forewings, consisting of a strong scapus, approximately twice the length of the short pedicellus, following 39 flagellomeres, each slightly ovoid, surrounded by fine setae. Maxillary palps 5-segmented, labial palps 3-segmented, their terminal segments pointed.

Forewings (Fig. 7c): Wing venation conspicuous by numerous crossveins, more common than usually in the crossvein gradate series 1–4 of other extinct Nevrorthidae. (Two extant nevrorthid species of genus Austroneurorthus: A. horstaspoecki and A. brunneipennis with similar numerous crossveins.) Costal crossveins at least partially forked, others simple and unbranched. (Branched crossveins between costa and subcosta present in the extinct genus Proberotha and the extant genera Nipponeurothus and Austroneurorthus.) Radius anterior running straight to the apical margin, parallel to Sc; RA and Sc bridged apically by a short crossvein. Radius posterior dichotomous 4-branched in subordinate branches RP1, RP2, RP3, RP4. MA simple, MP branched in MP1+2 and MP3+4. CuA running parallel to posterior wing margin with some terminal branches; CuP simple. Anal veins 1–3 running separate to anal margin.

Hindwings (Fig. 7c): All crossveins between costa and subcosta simple, unbranched; 9 crossveins between RA and RP1; 4 crossveins between MA and MP1+2. Outer gradate crossvein series present. RP pectinate, 3-branched in subordinate branches RP1, RP2, RP3+4. MA simple, MP branched in MP1+2 and MP3+4. CuA running parallel to posterior wing margin with some terminal branches; CuP simple. Anal veins 1–3 running separate to anal margin. In fore- and hindwings all longitudinal veins ramified apically in a last step into small terminal branching.

Male genitalia (Fig. 7a, b): Genital structure with dominant ectoproct and coxopodite of 9^th segment. Ectoproct strong and broad, concaved medially on posterior margin, posterolateral corner little amplified and rounded. 9^th coxopodite present as robust claw, in ventral view basally broad, convex, trapeziform, terminally with a thorn-shaped gonostylus curved mediad, in lateral view the distal end tapered, in posterior view the distal end forming a small edge. Ectoproct and gonostylus densely covered with fine setae. Ventrally a pair of long sclerotised rods drawing a bow, running parallel about 1 mm in length, mediad and spread afterwards apart. The two ventral rods originate a deep furcation, probably distal of the 9^th sternite or of a modification of 10^th segment present as a pair of widely protruding rods.

Remarks : The pair of the long sclerotized rods in the male genitalia of Balticoneurorthus elegans n. sp. is extremely distinct and unknown in all other extinct nevrorthids in Baltic amber. Clarifying details about the origin of the furcated rods are not visible in the embedded fossil.

Aspöck et al. (1980), Monserrat & Gavira (2014) illustrated the variable 9^th sternites of the five species of the genus Nevrorthus; N. apatelios possesses terminally a rounded lobe whereas the other species show a tendency to furcation and N. iridipennis bears a branched apex, but in Balticoneurorthus elegans n. sp. the furcation is much longer and its genesis unknown.

Type species: Proberotha prisca Krüger, 1923: 81–83.

Neotype: Proberotha prisca Krüger, 1923, designated M. S. Engel, NHM I.15997 BMNH, Natural History Museum, London.

Diagnosis: The genus Proberotha was established by Krüger (1923) on the base of wing venations in fore- and hindwings (however, not illustrated), originally placed in the family Berothidae. In Proberotha the fore- and hindwing venations concur with the wing venations of the known extinct nevrorthid species in Baltic amber. In forewings Sc and RA running parallel to apical wing margin and connected apically by a crossvein as in all other nevrothids. Radius posterior 3-branched in subordinate branches RP1, RP2, RP3+4 (Proberotha prisca) or dichotomus, 4-branched in subordinate branches RP1, RP2, RP3, RP4 (Proberotha dichotoma). Media M 3-branched, MA simple, unbranched, MP branched in the subordinate branches MP1+2 and MP3+4. CuA running to margin with 9 terminal branches; CuP simple. Furthermore the middle and outer crossvein gradate series are present in Proberotha and in all extinct Nevrorthidae.

Remarks : The genus Proberotha belongs to the family Nevrorthidae Nakahara, 1958. In forewings the costal crossveins partially forked as in the extinct Balticoneurorthus gen. nov. Proberotha differs from the extinct genera Rophalis, Electroneurothus and Palaeoneurorthus by the partially branched costal crossvein.

Holotype is lost, neotype designated by M. S. Engel, unpublished, NHM I.15997, BMNH, Natural History Museum, London.

Material:

Four adults in clear Baltic amber. Fore- and hindwing, antennae, maxillary palps, labial palps, legs as well as male and female genitalia visible, however, partially “verlumt”.

The old amber inclusions of Natural History Museum, London, NHM I.15997, originally from “Museum Stantin & Becker”, and of Geoscience Centre, University of Göttingen, GZG.BST.05230, originally from “B.S. d. Univers Königsberg i.Ps.” are mounted on standard microscope slides, embedded probably in Damar resin (Tornquist 1911; Neumann 2010) and covered by a thin cover slip (Fig. 8).

Re-description: Small adult male and female, forewing length 7 mm. Wings ovalness, apical rounded, hindwings smaller than forewings.

Head: Ocelli absent; filiform antennae with slightly enlarged scapus, smaller pedicellus and about 35 flagellomeres in male neotype and apparently 33 in female. Maxillary palps 5-segmented, labial palps 3-segmented, their terminal segments pointed.

Forewing (Fig. 9c, d): Costal cross-veins partially branched. Subcosta (Sc) and radius anterior (RA) running parallel to wing margin, apically connected by a short crossveins. The area between RA and RP interrupted by usually three crossveins: 2ra-rp, 3ra-rp and 4ra-rp. The gradate series of crossveins present. Radius posterior (RP) pectinate, 3-branched in subordinate branches RP1, RP2, RP3+4. Crossvein 3rp3+4 — rp2 present. Media MA simple and MP with dichotomous branch in MP1+2 and MP3+4. CuA running parallel to margin with terminal branches; CuP simple. Anal veins (1A, 2A, 3A) simple, running separately to anal margin.

Hindwing: Costal cross veins all simple; in subcostal area Sc and RA running separately and parallel to margin, connected only by a basal and a distal cross vein. Between RA and RP three crossveins: 2ra-rp, 3ra-rp and 4ra-rp. RP pectinate, usually 3-branched; crossvein 3rp3+4 — rp2 absent. MA unusually simple, MP with dichotomous branch in MP1+2 and MP3+4, apically divided into small terminal branches at margin. CuA running parallel to margin with terminal branches; CuP simple.

Genitalia: Male genitalia of the neotype (Fig. 9b) in part “verlumt”, in ventral view the ectoproct (e) broad, curved, concaved medially; the gonocoxites (gx9) basally abundant, bulged, inside concave, the apical part (gonostylus gst9) small, distad tapered and pointed. Female genitalia in part strong shrunken (together with the abdomen) and verlumt, compare Fig. 10.

Holotype: Female embedded in Baltic amber, deposited in the Geologisch-Paläontologisches Institut und Museum, University of Hamburg, GPIMH (ex coll. Gröhn 7156). Well preserved in Baltic amber but body partially “verlumt”, left forewing absent.

Etymology: The name is derived from the Latin and pointed to the dichotomous venation of the subordinate branches of radius posterior in forewings.

Diagnosis: The new species differs from Proberotha prisca by the forewing venation. Radius posterior branched dichotomous and forming four subordinate branches of equal lengths RP1, RP2, RP3, and RP4, instead of the pectinate 3-branched RP in Proberotha prisca. The dichotomous branching is also known from the extinct Balticoneurorthus elegans n. gen. n. sp. and from the extant nevrorthid Sinoneurorthus yunnanicus Liu, H. Aspöck & U. Aspöck, 2012.

Description: Small adult female, forewing length 7 mm. In fore- and hindwings rows of setae along the wing veins; crossveins often indistinct, but the crossvein gradate series present.

Head: Ocelli absent; filiform antennae with slightly enlarged scapus, smaller pedicellus about 35 segments. Maxillary palps 5-segmented, labial palps 3-segmented, their terminal segments pointed.

Forewing : Costal cross veins partially branched. Sc and RA running parallel and connected distally by a short crossvein. The area between RA and RP interrupted by usually three crossveins: 2ra-rp, 3ra-rp and 4ra-rp. The gradate series of cross-veins can be discerned. Radius posterior dichotomous, 4-branched in subordinate branches RP1, RP2, RP3, RP4. Crossvein between 3rp3 and 3rp2 present (3rp3-rp2). MA simple and MP with dichotomous branch in MP1+2 and MP3+4. Longitudinal veins apically divided into small terminal branches at margin. CuA running parallel to margin with terminal branches; CuP simple. Anal veins simple, running separately to anal margin.

Hindwing: Costal cross veins all simple; so far visible, in subcostal area Sc and RA running separately and parallel to margin, connected by a basal crossvein, digital part not visible. RP pectinate, usually 3-branched; crossvein 3rp3+4 - rp2 absent. MA simple, MP with dichotomous branch in MP1+2 and MP3+4. CuA running parallel to margin with terminal branches; CuP simple. Anal veins (1A, 2A, 3A) simple, running separately to anal margin.