Jantarineura serafini gen. et sp. nov. supports biodiversity of Protodikraneurini in Eocene amber forest of Northern Europe (Hemiptera: Cicadellidae: Typhlocybinae)

Abstract

A new genus and species, Jantarineura serafini Gębicki, Walczak and Świerczewski, belonging to the extinct tribe Protodikraneurini of the subfamily Typhlocybinae was described from Baltic amber. The description includes visible external characters based on a single female, especially tegminal venation. Protodikraneurini was classified as a distinctive or at least characteristic element of the fauna inhabiting ecosystems of amber forests.

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Keywords:

• Insecta
• Cicadomorpha
• leafhoppers
• Baltic amber resin
• taxonomy

Introduction

Typhlocybinae are presently one of the two most numerous subfamilies of Cicadellidae (Balme 2007), comprising more than 6000 described extant species, in ca. 300 genera and five tribes (Dietrich et al. 2023), clearly distinguished morphologically from other representatives of Cicadomorpha (Dietrich 2005, 2006; Dietrich et al. 2022). However, the phylogenetic relations as well as the structure of the subfamily still provoke controversy and are widely discussed. The latest research, including also mitogenomes of the main taxa, reveals the presence of only five tribes with a high degree of affinity, i.e. Alebrini and Empoascini together with Typhlocybini, Dikraneurini and Erythroneurini (Yan et al. 2022; Dietrich et al. 2022).

Moreover, molecular data show that the main phylogenetic lineages of Typhlocybinae probably separated from the ancestral one in the mid to late Cretaceous (about 76–112 Ma), and thus in the period of the rapid development of Magnoliophyta (Foster et al. 2016; Dietrich et al. 2017; Yan et al. 2022). The age of amber inclusions is still intensively researched and the age of amber deposits, which are often secondary, does not correspond with the age of the amber itself. Eocene amber forests are probably the primary habitat where the species of the subfamily Typhlocybinae evolved and differentiated ecologically.

Protodikraneurini are evolutionarily one of the two oldest groups of Typhlocybinae known from the Eocene. So far, seven species belonging to five genera have been described: Stareono mirabilis Gębicki and Szwedo, 2006; Protodikraneura cephalica Gębicki and Szwedo, 2006; Protodikraneura ferraria Szwedo and Gębicki, 2008; Protodikraneura nasti Gębicki and Szwedo, 2006; Microelectrona cladara Szwedo and Gębicki, 2010; Retrorsotettix vlaskini Dietrich et al., 2023 and Protoparallaxis clavatus Dietrich et al., 2023 (Gębicki & Szwedo 2006; Szwedo & Gębicki 2008; Szwedo et al. 2010; Dietrich et al. 2023). Recently, also, typical representatives of Dikraneurini tribe have been described, including Eodikraneura obscura Dietrich et al., 2023 and Rovnodikra longipes Dietrich et al., 2023, and the cited source is the first report about the co-occurrence of these two tribes (Dikraneurini and Protodikraneurini) in the Eocene (Dietrich et al. 2023). Four species of Eocene Typhlocybinae described in the 19^th century and the beginning of the 20^th require redescription and reclassification (Germar & Berendt 1856; Bervoets 1910; Cockerell 1920).

The known representatives of Protodikraneurini can be characterized by the following characters: vertex usually deltoid and convex; frontoclypeus trapezoid, widened in upper part, with gibbosity above sutura epistomalis (in lateral view), genae and lora wide; tegmina linear, without appendix in apical portion, with venation similar to that of Dikraneurini and Empoascini; wings with RP and MA veins separated over the whole length, not fused into common stem, connected by r-m transverse veinlet (sometimes strongly shortened), with well-developed marginal vein, reaching costal margin in 1/3 tegmen length (Gębicki & Szwedo 2006; Szwedo & Gębicki 2008; Szwedo et al. 2010).

It is clear that the taxonomic status of the tribe, its phylogenetic affinities and the relationship with extant fauna require further thorough study. In this article, we describe another representative of Protodikraneurini, giving a detailed description of the species and discussing its relation to other hitherto known species.

Material and methods

External structures of the female specimen were examined using an Olympus SZX9 Nikon Eclipse stereoscopic microscope. Photographs were taken with a Canon Eos camera with extension rings. The equipment used is available at the University of Silesia, Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection. All photographs and drawings were digitalized and processed using CorelDRAW software. Morphological terminology, especially that referring to tegmina and wings, follows Gębicki and Szwedo (2006), Szwedo and Gębicki (2008) and Szwedo et al. (2010); apical cell numbering follows Dietrich et al. (2023).

Repository. The examined specimen is deposited in the amber collection of the Institute of Systematics and Evolution of Animals, Polish Academy of Sciences (Kraków, Poland), under number MP/1241. The holotype of Jantarineura serafini Gębicki, Walczak and Świerczewski sp. nov. bears two labels. Below, we quote the specimen labels as follows: “[]” is used to enclose the text of a particular label; “/” is used to separate data written in different rows on the label.

Systematics

Order: Hemiptera Linnaeus, 1758

Suborder: Cicadomorpha Evans, 1946

Superfamily: Membracoidea Rafinesque, 1815

Family: Cicadellidae Latreille, 1802

Subfamily: Typhlocybinae Kirschbaum, 1868

Tribe: Protodikraneurini Gębicki and Szwedo 2006 †

Jantarineura gen. nov. Gębicki, Walczak and Świerczewski

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Type species

Jantarineura serafini sp. nov., by present designation.

Diagnosis

As for the type species.

Etymology

The generic name Jantarineura is an amalgamation of the old Lithuanian word “jantar” meaning amber and the name of the tribe Protodikraneurini, which the new genus belongs to. Gender: feminine.

Jantarineura serafini Gębicki, Walczak and Świerczewski sp. nov.

urn:lsid:zoobank.org:act:53C01423-BBE8-4A45-90B5-65FC92D32C89

Diagnosis

This species differs from other known Protodikraneurini in having the following combination of characters: head with compound eyes wider than pronotum; vertex protruded, almost conical, medially much longer than lateral margins; lateral incision of gena margin beneath eyes very shallow; frontoclypeus lateral sides with two rows of dark stripes; anteclypeus convex, long and narrow, with parallel margins; distal part of CuA₁ vein straight, connected with claval margin of tegmen just above the apex; M vein connected directly with RP vein, r-m transverse veinlet reduced; 4th (external) widest, limited by ScRA i RP veins; transverse veinlet r-m of wing distinctly shortened; abdominal sternite VII trapezoidal and wide.

Description

Head. Head with compound eyes wider than pronotum (Figures 1a, 2b). Vertex protruded, almost conical, medially much longer than lateral margins (Figures 2b). Disc of vertex convex, margin vertex-frons gently rounded. Sutura coronalis short and weakly visible. Frons medially as wide as long (including compound eyes), widest above antennal fossa. Lateral incisions beneath eyes at the level of genae margin very shallow. Lateral margins of genae slightly convex, arcuate, converging at the top of clypeus. Lora oval and long. Maxillary plates rounded at the top, reaching end of anteclypeus (Figure 1b,c). Compound eyes large, length equal to anteclypeus width; upper margin longer than the length of upper margin of frontoclypeus (internal side). Ocelli not visible. Antennae a bit shorter than head, in deep fossa, located below upper margin of eyes. Scapus shorter and wider than cylindrical, a bit narrowed basally, pedicellus. Upper half of pedicellus covered with minute tubercles. Base of flagellum widened and ribbed (7 rings, basal ones with lateral spines), upper half narrow and sharpened (Figure 1b,c). Frontoclypeus convex, with fine-grained texture, forming small gibbosity above upper margin of anteclypeus (sutura epistomalis). Anteclypeus convex, long and narrow, with almost parallel lateral margins, 3 times longer than wide, covered with small, numerous cuticular scales (Figure 1a-c). Rostrum slightly exceeding mesocoxae (Figure 1a).

Figure 1. Morphology of Jantarineura serafini gen. et sp. nov.: (a) head and thorax with legs, ventral side; (b) head, frontal view (reconstruction); (c) head, fronto-lateral view, slightly to the left side (reconstruction).

Figure 2. Morphology of Jantarineura serafini gen. et sp. nov., habitus: (a) latero-ventral view; (b) dorsal view.

Thorax

Disc of pronotum wide and smooth, medially a bit longer than vertex; anterior margin semicircular, posterior margin almost straight. Scutum (mesonotum) shorter than pronotum.

Legs. Protibia interior margin with a row of 6 long and 4 short spines (macrochetae), apex with 2 short conical spines (Figures 3a, 4a); macrochetes a bit curved apically, arising from small tubercles (Figure 4b). Protarsus 2.4 times shorter than tibia; segments short, the same length (Figure 4a). Mesotibia 3.0 times narrower than mesocoxa, with sparse and irregular chaetotaxy. Mesotarsus 2.0 times shorter than tibia, with segments almost the same length (Figures 3b, 4c). Metatibia with posteroventral margin possessing more than 4 spines and a short row of small chaetae, end with crown of spines, laterally marginated with 2 long chaetae (Figures 3c,d, 4d). Metatarsus about 2.4 times shorter than metatibia: basitarsus more than 2.0 times longer than 2nd segment, with 2 short, conical spines on ventral margin; praetarsus 2.0 times shorter than 2nd segment (Figures 3d, 4d).

Figure 3. Morphology of Jantarineura serafini gen. et sp. nov., legs: (a) left fore leg, ventral view; (b) left mid leg, ventral view; (c) right hind leg, ventral view; (d) right hind leg tarsus, ventral view.

Figure 4. Morphology of Jantarineura serafini gen. et sp. nov. legs (reconstruction): (a) left fore leg, ventral view; (b) macrochetes of the fore leg (enlarged); (c) left mid leg, ventral view; (d) right hind leg, ventral view.

Tegmina elongated with long clavus, much exceeding the top of abdomen (level of CuA₂ vein) (Figures 1a, 2a). Apical part of tegmen (with apical cells) about 2.5 times shorter than claval part. Internal apical cells (1^st and 2^nd) almost the same length, 3^rd apical cell triangular, limited by RP and M veins, 4^th apical cell widest, formed by veins ScRA and RP (Figure 5a-c). Transverse veinlet r-m reduced, ScRA vein long and slightly curved towards costal margin. CuA₁ vein almost straight, connected with claval margin near tegmen apex, CuA₂ quite long, only slightly shorter than ScRA. Claval veins invisible. “Wax area” large and strongly elongated, stretching from C vein to M vein. Pterostigma posterior margin with a row of about 7 short spines. Wings poorly visible; RP and M veins distinctly converging in the place of strongly shortened r-m transverse veinlet. MP+CuA vein probably long and forked into separate MP and CuA veins above r-m veinlet.

Figure 5. Morphology of Jantarineura serafini gen. et sp. nov., tegmina: (a) lateral view; (b) dorsal view; (c) tegmen (reconstruction).

Abdomen. Pygofer elongated, both sides with a row of long and sparsely arranged chaetae. VII sternite trapezoidal and wide, with wide median prolongation (Figure 6a,b). Ovipositor arcuate, exceeding the top of abdomen at a distance a bit more than its width (Figure 6b).

Figure 6. Morphology of Jantarineura serafini gen. et sp. nov., abdomen: (a) ventral side; (b) terminal sternites with ovipositor (reconstruction).

Body (especially dorsal side of thorax) uniformly dark coloured (Figure 2b). Frontoclypeus lateral sides with two rows of dark stripes (Figure 1b,c). Tegmina transparent; ends of longitudinal veins and claval margin clearly darkened; dark patch in the shape of horseshoe near costal margin. CuA₂ and basal part of CuA₁ with dark, curved patch (Figure 5a-c). Two oval, dark spots near VII sternite lateral margin (Figure 6a,b).

Body measurements: body length including wings − 4.11 mm; body length excluding wings − 2.26 mm; maximum body width − 1.20 mm; median length of vertex − 0.30 mm; width of head including compound eyes − 0.95 mm; basal width of vertex − unknown; length of frons including anteclypeus − 0.96 mm; width of frons including compound eyes − 0.95 mm; width of frons without compound eyes − 0.47 mm; median length of pronotum − 0.52 mm; basal width of pronotum − 0.90 mm; length of scutum − 0.50 mm; length of tegmen − 3.27 mm; width of tegmen − 0.87 mm; tegmen index (length vs width) − 1:0.27; length of wing − 3.05 mm; length of profemur − 0.64 mm; length of protibia − 0.59 mm; length of protarsus − 0.28 mm; length of mesofemur − 0.47 mm; length of mesotibia − 0.53 mm; length of mesotarsus − 0.26 mm; length of metafemur − 0.97 mm; length of metatibia − 1.44 mm; length of metatarsus − 0.68 mm; length of pygofer − unknown; length of ovipositor − 0.93 mm.

Etymology

The specific epithet is dedicated to Mr Jacek Serafin (1940–2022), a Polish amber and amber inclusions collector, one of the co-founders of the International Amber Association (Societas Succinorum Internationalis), and owner of an extensive collection of amber inclusions, who initiated many scientific studies on this subject.

Type material

Holotype, ♀ Eocene Baltic amber inclusion: 1^st label (white) – [coll. JACEK SERAFIN – AUC 036JS/Hemiptera: Clypaeorrhyncha/Cicadelloidea: Cicadellidae:/Typhlocybinae], 2nd label (red) – [HOLOTYPE ♀/Jantarineura serafini/gen. et sp. nov./Gębicki, Walczak & Świerczewski].

Discussion

The described species, Jantarineura serafini sp. nov., differs from all other representatives of Protodikraneurini tribe by the following unique combination of characters. Wide genae with small incisions beneath the compound eyes distinguish the species from Stareono mirabilis, characterized by a very deep incision and shortened genal part of the head. Fusion of tegminal R and M veins and complete reduction of transversal r-m veinlet as well as widening of the 4^th (external) apical cell clearly distinguish this species from members of the genus Protodikraneura, which possess a well-developed r-m veinlet and in which the 4^th apical cell is equal to or a bit narrower than other cells (Gębicki & Szwedo 2006). Four well-developed apical cells distinguish the newly described species from Protoparallaxis clavata, which has only three wide apical cells. The conical shape of the head in Jantarineura serafini sp. nov. is different from the head of Retrorsotettix vlaskini, with its semicircular vertex margin (Dietrich et al. 2023).

Width of head (including compound eyes) being greater than the width of pronotum is a typical diagnostic character for almost all Protodikraneurini, apart from Microelectrona cladara, which has the head clearly narrower than pronotum (Szwedo et al. 2010).

To date, research on Typhlocybinae has revealed a taxonomically separate and morphologically uniform systematic unit, comprising the probably diverse and speciose tribe Protodikraneurini, which is closely related to the extant tribe Dikraneurini, with the oldest representatives known to date from Oligocene Dominican amber (Dietrich & Vega 1995). However, recent studies provided information on much older Eocene Dikraneurini occurring in the ecosystems of amber forests, represented by two species, Eodikraneura obscura Dietrich, Simutnik & Perkovsky and Rovnodikra longipes Dietrich, Simutnik and Perkovsky (Dietrich et al. 2023). They are characterized by the fusion of R and M veins into one common stem, typical for extant Dikraneurini.

Further studies (Gębicki et al., in prep.) might confirm that Protodikraneurini (as well as fossil Dikraneurini), being fairly common in the pieces of amber resin, are probably a characteristic element of insect communities, which inhabited shrubs and trees (not only resinous) of Eocene amber forests. However, the limited data mean we are still unable to associate particular species of Protodikraneurini with specific biocenoses or to indicate their synecological categories. The shortened piercing-sucking mouthparts, characteristic of most extant Typhlocybinae and also typical for Protodikraneurini, may suggest a similar way of feeding, by the intake of plant sap from mesophyll cells of single and wide leaf blades. There are some examples of interspecific interactions in that group. The first is the case of a typhlocybid male Microelectrona cladara parasitized by the larva of a Pipunculidae fly (Diptera), forming the characteristic thylacium protruding from the body of the leafhopper, known from the middle Eocene (Lutetian − 44 Ma) (Szwedo et al. 2010). Finally, the presence in the sample as a syninclusion of a few trichomes from blossoming flower buds suggests that the examined resin formed in early summer, i.e. at the end of the leafhopper mating season (Larsson 1978). The same can be observed for other previously described representatives of Protodikraneurini; however, the ecology of the tribe is still poorly documented and requires further study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the University of Silesia in Katowice.