The earliest fully brachypterous auchenorrhynchan from Cretaceous Burmese amber (Homoptera: Fulgoroidea: Jubisentidae)

Abstract

Psilargus anufrievi gen. et sp.n. (Psilarginae subfam.n.) from mid-Cretaceous Burmese amber is assigned to the family Jubisentidae in basal (pre-cixioid) Fulgoroidea. The two formerly known genera of this family are placed in Jubisentinae stat.n. The only known specimen of the new species is a minute female with extremely shortened wings. It is the earliest recorded instance of extreme brachyptery in Auchenorrhyncha. All known Jubisentidae were flightless, camouflaged, and likely associated with herbs in the Burmese Cretaceous tropics. РЕЗЮМЕ. Psilargus anufrievi gen. et sp.n. (Psilarginae subfam.n.) из среднемелового бирманского янтаря отнесён к семейству Jubisentidae среди примитивных (до-циксиоидных) Fulgoroidea. Два ранее известных рода этого семейства помещены в Jubisentinae stat.n. Единственный известный экземпляр нового вида — мелкая самка с сильно укороченными крыльями. Это древнейший отмеченный случай резкой короткокрылости у Auchenorrhyncha. Все известные Jubisentidae были нелетающими, обладали маскировкой и, вероятно, обитали на травах в бирманских меловых тропиках. The mid-Cretaceous Burmese amber (ca. 100 Ma) is a real Aladdin’s cave for paleoentomologists. This fossil resin was produced by araucarian trees in a rainforest [Poinar et al., 2007; Poinar, Buckley, 2008] on an island in the tropical Tethys Ocean between Gondwana and Laurasia [Westerweel et al., 2019], far from other Cretaceous Lagerstätten. Among many wonderful and unexpected insect taxa, three endemic planthopper families have recently been discovered in Burmese amber — Dorytocidae, Yetkhatidae and Jubisentidae [Emeljanov, Shcherbakov, 2018; Song et al., 2019; Zhang et al., 2019]. In the Burmese amber fauna these groups coexist with widespread Cretaceous families, such as Perforissidae [Shcherbakov, 2007a; Zhang et al., 2017] and Mimarachnidae [Shcherbakov, 2007b, 2017; Luo et al., 2020; etc.], and several extant families, such as Cixiidae and Achilidae [Shcherbakov, 2000; Szwedo, 2004] making up a rich and diverse planthopper assemblage [Perkovsky et al., 2019]. The latest find, recently offered on eBay, is an unusual brachypterous female planthopper described below as a new genus and subfamily of Jubisentidae. The two Cretaceous planthopper families known from adults, Perforissidae and Mimarachnidae [Shcherbakov, 2007a, b] are referred to the basal, precixioid Fulgoroidea on account of having setigerous hind tibial pectens and the proximal CuA fork in the tegmen. The two other Cretaceous families based on nymphs with asetigerous hind tibial pectens, Neazoniidae [Szwedo, 2007] and Dorytocidae [Emeljanov, Shcherbakov, 2018] show other features in common with perforissids and mimarachnids. Subbrachypterous flightless Jubisentidae were described as related to Perforissidae [Zhang et al., 2019]. The new subfamily combines characters of typical jubisentids with a few perforissid characters and so bridges the gap between the two families. 7 Earliest brachypterous Auchenorrhyncha in Burmese amber The holotype female of the new species is extremely brachypterous, with tegmina covering only the mesoand metanotum. Such advanced brachyptery is common in planthoppers (Delphacidae, Dictyopharidae Orgeriinae, Caliscelidae) and leafhoppers, as well as in some groups of true bugs [Schuh, Slater, 1995], occurs as a rare exception in froghoppers [Fennah, 1966], and is unknown in cicadas, treehoppers and Sternorrhyncha. Brachypterous leafhoppers and planthoppers have been reported from Eocene Baltic amber (Szwedo, 2002, fig. 24; Szwedo, Stroiński, 2013; Dietrich, Gonçalves, 2014), but appear to remain unknown from pre-Cenozoic strata. Therefore, the discovery of a strongly brachypterous planthopper in Cretaceous amber is of considerable interest. It seems to be the first record of a brachypterous Auchenorrhyncha from as far back as the Mesozoic. In its general habitus, short veinless tegmina, and foliaceous fore and mid legs the new genus is similar to some Caliscelidae, especially Caliscelis de Laporte, 1833. Caliscelids sometimes show striking sexual dimorphism, with males mimicking jumping spiders [O'Brien, 1967] or ants [Gnezdilov, 2019]. Perforissidae also share many traits with Caliscelidae, though these two families are not closely related [Shcherbakov, 2007a]. Wing reduction occurs in Auchenorrhyncha feeding on herbs and forbs, but not in their arboreal relatives [Waloff, 1983]. Among grass feeding Auchenorrhyncha, flightless brachypterous forms are common in permanent habitats and rare in temporary ones [Denno et al., 1991; Novotný, 1994]. Caliscelidae and Delphacidae largely feed on grasses and often display wing dimorphism; the macropterous form can be very rare, for example, in Caliscelidae. The new species may be wing dimorphic as well. Its hypothetical macropterous form is expected to retain such diagnostic characters of the new subfamily as sensory pits, reduced setation, and modified head structure to be easily distinguishable from Jubisentinae, which are currently known by two subbrachypterous flightless species. Flightless Jubisentidae presumably fed on some herbaceous host plants, such as grass-like monocots of the Burmese amber flora [Poinar, 2004]. The new genus may be one of the earliest planthoppers associated with grasses, and its extreme brachyptery agrees with the assumption that some permanent grassy patches already existed in the mid-Cretaceous. Plants with vegetative morphology of grasses (Graminophyllum) are known since the Neocomian [Krassilov, 1982]. Nymphs of most planthopper families have sensory pits, forming rows and groups associated with carinae [Bräunig et al., 2012] and homologous to setigerous pits of Cicadomorpha [Emeljanov, 2001]. The sensory pits, supposed to be receptors of atmospheric humidity [Šulc, 1928], persist in adults of some planthopper taxa, especially in xerophiles or hygrophiles. The numerous sensory pits of adult perforissids suggest that they have lived in habitats with highly variable and/or extreme humidity [Shcherbakov, 2007a], like littoral environments with xeromorphic bennettite-brachyphyll communities, rich in proangiosperms and considered to have been the cradle of angiosperms [Krassilov, 1997]. The new genus of Jubisentidae, similar to perforissids in having numerous sensory pits, could also have inhabited herbaceous vegetation near the sea coast, on river banks, rocky outcrops, etc. Various examples of camouflage and mimicry in insects from Burmese and other Cretaceous ambers indicate widespread occurrence of these phenomena in the Mesozoic tropics [Wang et al., 2016; Chen et al., 2019; Vršanský et al., 2019; etc.]. Some Mesozoic hoppers showing such camouflage elements as bizarre outgrowths, long head processes, foliaceous legs fringed with setae, or undulating margins of tegmina supposedly mimicked buds, strobiles or thorns of their host plants [Shcherbakov, 2011; Emeljanov, Shcherbakov, 2018], or adhered closely to the bark of host trees [Jiang et al., 2019]. Jubisentids also display elements of cryptic appearance [Zhang et al., 2019]. Some present-day hoppers, especially flightless, are masters of camouflage. Ground-dwelling subbrachypterous Myerslopiidae leafhoppers encrust their strangely shaped, ridged bodies with soil particles to blend into their environment [Rakitov, 2015]. Some brachypterous planthoppers, such as Risius Stål, 1859 (e.g. R. gibbus Fennah, 1967, R. palamedes Fennah, 1967, Fulgoridae) and Kazerunia Dlabola, 1974 (e.g. K. leguaniforma Dlabola, 1977, Tropiduchidae), have dorsal humps, ridges and lobes and resemble small lumps of dirt. The flattened and slender forms of Dorycephalini and Hecalini leafhoppers imitate grass seeds or twigs [Hamilton, 2000]. Brachypterous Orgeriinae planthoppers (Dictyopharidae) taking an unusual upright posture with their long legs stretched out [Ball, 1909] supposedly mimic the achenes of Asteraceae [Oshanin, 1913: 9] or salticid spiders [Emeljanov, 1980: 44]. The new apterous Burmese amber jubisentid appears camouflaged due to its serrated dorsal outline with transverse ridges, long foliaceous fore and mid legs fringed with setae, and brown colouration. On account of its long legs, it was likely mimicking spiders, seeds or plant debris rather than soil. A camouflage of this kind can be effective both on the host plant and near the ground. The holotype of the new species is deposited at Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow (PIN). Photographs were taken using a Leica M165C stereomicroscope with a Leica DFC425 digital camera and z-stacked with Helicon Focus 7.0. Nomenclature of the planthopper cranium is given after Anufriev and Emeljanov [1988]. Family Jubisentidae Zhang et al., 2019 REVISED DIAGNOSIS. Small and compact planthoppers, at least legs with long setae. Eumetope and clypeus with median carina; clypeus strongly raised, without lateral carinae; rostrum extending beyond hind coxae, apical segment longer than wide. Ocelli absent. Pronotum with anterior margin produced beyond eye midlength, lateral margin posterior to eyes very short, posterior margin shallowly incised. Subbrachypterous or brachypterous, venation of tegmina