Triachrysa rusti, Makarkin & Simonsen & Perkovsky, 2025

Makarkin, Vladimir N., Simonsen, Thomas J. & Perkovsky, Evgeny E., 2025, A new genus and species of Nothochrysinae (Neuroptera: Chrysopidae) from the early Eocene Fur Formation, Denmark, Zootaxa 5653 (1), pp. 116-122 : 117-120

Triachrysa rusti sp. nov.

( Figs 1–3 )

Brooksiochrysa jutlandica Rust, 1999: 284, Pl. 23, Fig. f, nomen nudum.

Type material. Holotype MM-14943 (part and counterpart), deposited in the Henrik Madsen collection (number 14M-B2585 ) of the MM; collected by Henrik Madsen on May 27, 1995. An incomplete forewing with the venation indiscernible in the posterior part .

Paratype MM-14944 (part and counterpart), deposited in the Henrik Madsen collection (number HM 5-B2837 ) of the MM; collected by Henrik Madsen on July 12, 1995. An incomplete forewing: the posterior basal part is crumpled and folded, and the distal part of the wing is missing .

Type localities and horizons. Holotype: Denmark: northern Jutland (Region Nordjylland): Mors Island ( Morsø Kommune ): Ejerslev Mo-clay Pit (ash layer +15). Paratype: Mors Island: Sundby Cliff (ash layers +25 – +30). Fur Formation, lower part of Silstrup Member ; earliest Eocene.

Etymology. The specific epithet is a patronym formed from the surname of Jes Rust, a German paleoentomologist, in recognition of his great contributions to the study of Mo-clay insects.

Description. Holotype. Forewing 19 mm long (as preserved; estimated complete length ca. 20.2 mm), 7.2 mm wide. Costal space broad proximally, extremely narrow before pterostigma, then slightly dilated. All subcostal veinlets simple, relatively widely spaced proximally, very dense distally (very poorly preserved). Sc relatively long, poorly discernible distally. RA terminating on margin before wing apex; its veinlets indiscernible distally. Subcostal space narrow; basal subcostal crossveins located opposite origin of RP. RA space broadest medially, with 17 crossveins: basal and distal crossveins perpendicular to RA; medial crossveins with apices slightly inclined to wing apex; one crossvein forked. RP originating relatively close to wing base (at 0.23 length). Anterior trace of RP slightly zigzagged, apically forked; with 21 pectinate branches, mostly preserved only proximally; three distal-most branches simple. Basal crossvein between RP, M (1r-m) long, connecting anterior trace of RP, MA in proximal part of im length. M dividing to MA, MP markedly distad origin of RP. Distal parts of MA, MP not preserved. im broad, pentagonal (length/width ratio 2.1:1). Crossvein between MA, MP (1im) rather long. Psm poorly developed, zigzagged. Crossvein 1m-cu poorly preserved, located proximad origin of CuP; 2m-cu (between im and CuA) short, located in proximal part of im. CuA probably with four simple branches; continuing into well developed, only slightly zigzagged Psc (only its proximal part preserved). CuP deeply forked once; its anterior trace shallowly forked. 1icu long, located near origin of CuP; 2icu connecting CuA and anterior trace of CuP much proximad 2m-cu. 1c: 2c length ratio 0.25:1. 1A fragmentarily preserved; 2A, 3A not preserved. Three gradate series of crossveins: in additional (third) series, four proximal crossveins preserved (between RP3 to RP7); in inner series, three proximal crossveins preserved (between MA to RP3); five distal crossveins (between PR14 to RP20) may belong to either inner or additional series; in outer series, four distal preserved crossveins (between stem of RP to RP18).

Paratype. Forewing 13.9 mm long (as preserved; estimated complete length ca. 17.2 mm), 6.2 mm wide. Costal space broad proximally, very narrow distally. All preserved subcostal veinlets simple, relatively widely spaced proximally, very densely spaced distally. Sc, RA before pterostigma thickened. Subcostal space narrow; basal subcostal crossvein located slightly distad origin of RP. RA space broadened towards apex, with 12 preserved crossveins: proximal crossveins perpendicular to RA; distal crossveins with their apices slightly oblique toward wing apex. Anterior trace of RP zigzagged, with 13 preserved branches; three proximal branches (of five preserved) forked once; distal portions of other branches not preserved. Basal crossvein between RP, M (1r-m) relatively long, connecting anterior trace of RP with MA in proximal part of im length. M dividing to MA, MP markedly distad origin of RP. MA, MP probably forked at Psm; all their branches distad Psc simple. im pentagonal, rather broad (length/ width ratio 2.9:1). Crossvein between MA, MP (1im) long. Psm poorly developed, zigzagged; its proximal-most crossvein (between RP1 , MA) ends just distad im. Crossvein 2m-cu rather long, connecting im, CuA in proximal part of im. CuA probably with three simple branches; continuing into well developed, only slightly zigzagged Psc, which continues into outer gradate series of crossveins. CuP deeply forked once; both branches nearly parallel. 1icu long; 2icu connecting CuA and anterior trace of CuP (much proximad 2m-cu). Anal veins crumpled and forded; presumed 2A simple. Three gradate series of crossveins: additional series going anterior and parallel to inner series possesses four preserved crossveins; preserved part of inner series arranged in straight zigzagged line, with nine preserved crossveins distad MA; two-three proximal crossveins preserved in outer series.

Remarks. This species was described by Rust (1999) as Brooksiochrysa jutlandica Rust, but this is invalid, as it appeared in an unpublished dissertation, and this name is, therefore, unavailable ( ICZN, 1999: Articles 8.1.2 and 8.1.3). We could not locate the Rust’s specimens.

The forewing venation of the holotype and paratype is slightly different, but we consider this as intraspecific variability. The shape of the intramedian cell and the length of crossvein 2m-cu markedly differs in these specimens. The forking of two veins (i.e., one of crossveins between RA and RP, and the anterior branch of CuP) in the holotype are obviously anomalies, often observed in extant species of the family.

Figures

FIGURE 1. Triachrysa rusti gen. et sp. nov., holotype MM-14943. A, part (converted to standard view, with apex to the right); B, counterpart. Scale bars = 2 mm.

FIGURE 2. Triachrysa rusti gen. et sp. nov., paratype MM-14944. A, part; B, counterpart (converted to standard view, with apex to the right). Scale bars = 2 mm.

FIGURE 3. Forewing venation of Triachrysa rusti gen. et sp. nov. A, holotype MM-14943; B, paratype MM-14944. Scale bars = 2 mm (both to same scale).