New Saldidae Enicocorinae (Heteroptera: Leptopodomorpha) from the Lower Cretaceous of Siberia and Mongolia

ISSN 0031-0301, Paleontological Journal, 2015, Vol. 49, No. 2, pp. 153 161. Pleiades Publishing, Ltd., 2015. Original Russian Text O.V. Ryzhkova, 2015, published in Paleontologicheskii Zhurnal, 2015, No. 2, pp. 44 51. New Saldidae Enicocorinae (Heteroptera: Leptopodomorpha) from the Lower Cretaceous of Siberia and Mongolia O. V. Ryzhkova Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Russia 123, Moscow, 117997 Russia e-mail: helgaryzhkova@gmail.com Received December 16, 2013 Abstract Baissotea infanta gen. et sp. nov., B. peregrina sp. nov., and B. popovi sp. nov. from the Lower Cretaceous deposits of the Baisa locality, Eastern Siberia, and the Bon-Tsagan and Shin-Khuduk localities, Mongolia are described. Keywords: Leptopodomorpha, Saldidae, Enicocorinae, fossil insects, true bugs, new taxa, Lower Cretaceous, Siberia, Mongolia DOI: 10.1134/S0031030115020094 INTRODUCTION The subfamily Enicocorinae, viewed until recently as a separate family, is an extinct subfamily of the leptopodomorph family Saldidae. Representatives of this subfamily have been recorded in many Lower Cretaceous localities of China and Mongolia. The first description of a representative of Enicocoridae was published by C. Ping in 1928, who established the genus Mesolygaeus for two species, M. laiyangensis Ping, 1928 and M. rotundocephalus Ping, 1928 and assigned it to the family Lygaeidae. Hong and Wang (1990) described for this genus the monotypic family Mesolygaeidae, subsequently synonymized with Enicocoridae Popov, 1980 (Shcherbakov and Popov, 2002; Zhang et al., 2005; Ryzhkova, 2012). In addition, the family Xishanidae Hong, 1981 also proved synonymous to Enicocoridae (it was also synonymized with Archegocimicidae: Popov, 1988). The family Enicocoridae was originally described in the infraorder Enicocephalomorpha (Popov, 1980); the families Mesolygaeidae and Xishanidae were first considered close to the family Lygaeidae (Lin, 1976, 1982a, 1982b; Hong, 1981, 1984), then, viewed as families of uncertain systematic position (Hong and Ren, 1992; Hong, 1995), and, finally, included in the superfamily Saldoidea (Hong and Wang, 1990; Zhang, 1993). The high similarity in the morphology of pronotum and other body parts as well as in hemelytral venation allowed some authors to include Enicocoridae as a subfamily into the extant family Saldidae, which has a mostly littoral mode of life (Shcherbakov and Popov, 2002; Zhang et al., 2005; Ryzhkova, 2012). The principal differences of enicocorines from other representatives of the subfamily Saldidae are the relatively longer membrane of the hemelytron with apical cells radiating in a fanshaped pattern and the extraordinarily long metatarsi, at least half as long as the metatibia. This peculiar feature is probably associated with the presumable mode of life of the subfamily Enicocorinae: it has been hypothesized that enicocorines lived on floating plant mats typical of Mesozoic water bodies (Zhang et al., 2005; Ponomarenko, 2007, 2010). This hypothesis is indirectly confirmed by the extraordinary abundance of these bugs in some Mongolian localities, in which such abundance is more typical of aquatic insects. The Baisa locality in the Republic of Buryatia is the richest Lower Cretaceous insect locality in Russia. A total of more than 20000 imprints of insects are known from this locality, many of them are very well preserved. The deposits of this locality are considered Lower Cretaceous (Neocomian); more precise dating by different authors ranges from the Upper to Lower Neocomian (Martinson, 1961; Rasnitsyn, 1969, 1975; Zherikhin et al., 1999; Zherikhin, 2002). About 50 imprints of hemelytra and bodies of Leptopodomorpha have been collected in Baisa; they display typical saldoid venation and morphology of pronotum, but are distinguished by very long metatarsi and, therefore, assigned to the subfamily Enicocorinae. The age of the Shin-Khuduk locality in central Mongolia (Dundgovi Aimag) is considered close to Anda-Khuduk, which in turn is of approximately the same age as Baisa (unpublished data of A.G. Ponomarenko, pers. comm.). The representatives of Enicocorinae collected there (over 300 imprints, mostly bodies, but also isolated hemelytra) somewhat differt 153

154 RYZHKOVA Fig. 1. Hemelytron Baissotea infanta sp. nov., specimen PIN, no. 4210/1831. Arrow shows hypocostal carina. Scale bar in all figs., 1 mm. from those collected in Baisa, but have similar length ratios of the metatarsus and metatibia; therefore, I assign the heteropterans collected in these localities to the same genus. It is also interesting that the material collected there includes many specimens of the same heteropterans distinguished by the slightly shorter posterior lobe of the pronotum (measured medially, 0.3 times as long as the width of the anterior lobe of the pronotum, whereas in specimens with fully developed wings, this parameter is 0.35 0.4) and by the narrowed membranes, overlapping only in the area of two internal apical cells (Fig. 5). This type of interspecific variation is rather common among Recent Saldidae (Kerzhner and Yachevskii, 1964; Vinokurov, 1979; Vinokurov and Kanyukova, 1995). The Bon-Tsagan locality in central Mongolia (Bayan Khongor Aimag) is the richest in Mongolia and one of the richest in the world among Mesozoic insect localities, provisionally dated Aptian (Zherikhin et al., 1999). A total of 17 imprints of heteropteran bodies and isolated elytra of the subfamily Enicocorinae have been collected in this locality. These heteropterans are larger than those from Baisa, but have metatibiae of similar length and are assigned here to another species of the same genus. The material studied is stored in the Borissiak Paleontological Institute of the Russian Academy of Sciences, Moscow (PIN). SYSTEMATIC PALEONTOLOGY Genus Baissotea Ryzhkova, gen. nov. E t y m o l o g y. From the Baisa locality. Type species. B. infanta sp. nov. D i a g n o s i s. Medium-sized or large heteropterans (body 5 8 mm long). Length of pronotum and length of mesonotum at most two-thirds of maximum body width. Anterior lobe of pronotum about 3 3.5 times as wide as long. Posterior lobe of pronotum medially about half as long as anterior lobe of pronotum. Hemelytron (without clavus) almost three times as long as wide. Costal space narrow (at least 7 times as long as wide) and long, at least 0.7 0.75 times as long as forewing; relief of hypocostal area very strongly developed, with wide, weakly curved carina reaching anterior margin of wing at distance from wing base equal to one-third to one-fourth of costal space length (Fig. 1). Proboscis reaching bases of metacoxae and base of metaxyphus. Segment III of proboscis approximately thrice as long as segment IV. Antennae rather long, from 1.3 to 1.5 as long as pronotum and mesonotum taken together. Abdomen completely covered by fully developed hemelytra extending beyond abdominal apex. Corium dark with pale spots; large spot at wing base (in distal half of basal cell and in area of costal space adjacent to R+M) and large spot in apical part of costal space near base of costal fracture especially pronounced. Membrane pale. Metatibia at least 1.7 times as long as pronotum and mesonotum taken together. Metatarsus 0.75 0.85 as long as the pronotum and mesonotum taken together and 0.45 0.5 as long as metatibia. Brush on metatibia long, at least 0.6 as long as metatibia. Species composition. B. infanta sp. nov., B. peregrina sp. nov., and B. popovi sp. nov.; Transbaikalia and Mongolia, Lower Cretaceous. C o m p a r i s o n. The new genus differs from the other genera of the subfamily in the longer metatibia and relatively shorter metatarsus as well as in the strongly developed relief of the hypocostal area of the hemelytron. The new genus is similar to the genus Mongolocoris Ryzhkova, 2012 in the presence of a long brush on the metatibia and differs in this character from all other genera of the subfamily. R e m a r k s. The species described below clearly differ in the relative length of antennae and somewhat differ in the length of the metatibia and width of the pronotum, but the equal (within the error) relative length of the metatarsus and overlapping values of most of these characters at present do not allow establishing separate genera for them.

NEW SALDIDAE ENICOCORINAE (HETEROPTERA: LEPTOPODOMORPHA) 155 Fig. 2. Baissotea infanta sp. nov., holotype PIN, no. 4210/2063. Identification Key to Species of the Genus Baissotea gen. nov. 1 (2) Spines on metatibia present......b. peregrina sp. nov. 2 (1) Spines on metatibia absent. 3 (4) Body relatively wide, less than 2.5 times as long as wide; antenna 1.5 times as long as pronotum and mesonotum taken together...b. infanta sp. nov. 4 (3) Body relatively narrow, more than 2.5 times as long as wide; antenna 1.3 times as long as pronotum and mesonotum taken together......b. popovi sp. nov. Baissotea infanta Ryzhkova, sp. nov. Plate 8, fig. 1 Etymology. From the Latin infans (baby, infant). H o l o t y p e. PIN, no. 4210/2063, adult female, part and counterpart of body (counterpart no. 4210/2069); Russia, Republic of Buryatia, Eravninskii District, Upper reaches of the Vitim River, left bank, 20 km downstream from the Zaza River mouth, Baisa locality; Lower Cretaceous (Neocomian), Zaza Formation. D e s c r i p t i o n (Fig. 2). The body is mediumsized; females are larger than males. The body is 2.3 2.4 times as long as wide and about 0.82 0.85 times as wide as the metatibia length. The maximum width of the pronotum is 1.3 1.35 times as great as the length of the pronotum and mesonotum taken together and 3.4 3.5 times as great as its length medially. Antennomere 2 is 2.5 2.8 times as long as antennomere 1, 1.9 times as long as antennomere 3, and 2.3 times as long as antennomere 4. Antennomere 4 has fine setae at most 50 µm long. The antenna is more than 1.5 times as long as the pronotum and mesonotum taken together. The metatibia is at most 1.1 times as long as the antenna, 1.7 times as long as the mesotibia, and 2.9 times as long as the protibia. The mesotarsus is 0.5 times as long as the mesotibia; the protarsus is about 0.55 0.6 times as long as the protibia. Metatarsomere 2 is 7 times as long as metatarsomere 1 and 1.15 times as long as metatarsomere 3. The brush on the metatibia occupies at least 0.8 0.85 of its length. The basal cell measured from the wing base widely varies in length, 0.3 0.42 as long as the hemelytron; the basal and radial cells taken together are 0.6 0.68 as long as the hemelytron; the internal apical cell is 0.4 0.5 as long as the hemelytron. The internal part of the metatibia and all apical tarsomeres are dark; the external surface of the metatibia is pale. Measurements, mm. Body length, 5.3 6.3; width, 2.2 2.5; head length, 0.65 0.85; width, 0.85 1.15; pronotum length, 0.55 0.65; width, 1.9 2.3; length of anterior lobe of pronotum, 0.45; width, 1.45;

156 RYZHKOVA Plate 8 1 3 2 mm 2 mm 2 2 mm 1 mm 4 Explanation of Plate 8 Fig. 1. Baissotea infanta sp. nov., holotype PIN, no. 4210/2063. Fig. 2. Baissotea peregrina sp. nov., holotype PIN, no. 3559/7544. Figs. 3 and 4. Baissotea popovi sp. nov.: (3) holotype PIN, no. 3664/2150; (4) specimen PIN, no. 3664/1928. PALEONTOLOGICAL JOURNAL Vol. 49 No. 2 2015

NEW SALDIDAE ENICOCORINAE (HETEROPTERA: LEPTOPODOMORPHA) 157 Fig. 3. Baissotea peregrina sp. nov., holotype PIN, no. 3559/7544. length of pronotum and mesonotum taken together, 1.65 1.8; length of antenna, at least 2.6 2.85; length of antennomeres (1 4): 0.4 0.5, 1.15, 0.6, 0.5; length of foreleg: femur, 1.2 1.4; tibia, 1.1 1.25; tarsus, 0.65 0.75; length of midleg: femur, 1.6; tibia, 1.7 1.8, tarsus, 0.9 1.0; length of hindleg: femur, 1.4; tibia, 2.3 3.3; tarsus, 1.2 1.55; metatarsomeres (1 3): 0.15 0.2, 0.5 0.8, 0.55 0.65; metatarsal claw, 0.2 0.3; length of brush on metatibia, 2.1 2.5; length of elytra, 4.2 5.6. R e m a r k s. The only imprint of a representative of Saldidae Enicocorinae, PIN, no. 3145/1122, collected in the Anda-Khuduk locality (Mongolia, Övör Khangai Aimag, Ushgiin-Nuru Range, western sources of the Shand-Gol Stream near Anda-Khuduk well) is assigned to the species B. infanta based on the small body size (about 6 mm), but reliable identification of this specimen is difficult because of the absence of legs and because of the poorly preserved antennae. The imprint of an Enicocorinae hemelytron, PIN, no. 3480/246, collected in the Khovur locality (Mongolia, Övör Khangai Aimag, 80 km southeast of Guchin-Us sum along the southern bank of the Arguin-Gol River, southwest from mountains Ikh- Munkh-Ula and Baga-Munkh-Ula) and specimen PIN, no. 4206/127 from the Barun-Suzh locality (Mongolia, Ömnögovi Aimag, 60 km southwest of Bayan-Dalai sum, west of Mount Dzuramtai) are also provisionally assigned to B. infanta based on their size (preserved parts of the elytron are 3.7 and 4.2 mm long, respectively) and strongly developed relief of the hypocostal area. M a t e r i a l. In addition to the holotype, paratypes PIN, nos. 4210/1646, 1905, 2013, 2029, 5731, 5736, 5738, 5740, 6722, and 1655 (imprints of bodies), and about 30 imprints of complete and fragmentary isolated elytra, all from the type locality. Baissotea peregrina Ryzhkova, sp. nov. Plate 8, fig. 2 Etymology. From the Latin peregrinus (foreigner), feminine gender. H o l o t y p e. PIN, no. 3559/7544, adult female, part and counterpart of body; Mongolia, Bayankhongor Aimag, Khulsyn-Gol (Bon-Tsagan) Depression, south of Bon-Tsagan-Nur Lake, Bon-Tsagan locality; Lower Cretaceous (Hauterrivian Barremian or Barremian Aptian), Bon-Tsagan Group. D e s c r i p t i o n (Fig. 3). The body is mediumsized or large; sexual dimorphism in size is absent. The body is 2.3 2.4 times as long as wide and about 0.85 times as wide as the metatibia length. Both sexes have a swollen and concave dilation of the costal margin, appearing in imprints as a dent at the middle of the length of the costal space of the hemelytron (a similar structure has tentatively been recorded in B. infanta, but it is only visible in some imprints). The maximum width of the pronotum is 1.2 1.25 times as great as the length of the pronotum and mesonotum taken

158 RYZHKOVA Fig. 4. Baissotea popovi sp. nov., holotype PIN, no. 3664/2150. together and 3.15 3.2 times as great as its length medially. Antennomere 2 is probably four times as long as antennomere 1, 1.85 times as long as antennomere 3, and 2.2 times as long as antennomere 4. Antennomere 3 is narrowed basally and dilated towards the apex. The antenna is 1.35 1.4 times as long as the pronotum and mesonotum taken together. The metatibia is 1.7 times as long as the mesotibia. Metatarsomere 2 is five times as long as metatarsomere 1 and 2.5 times as long as metatarsomere 3. The brush on the metatibia varies in length, occupying from 0.6 to 0.8 of its length. The external surface of the metatibia bears large spines (poorly preserved and visible only in some imprints): four spines in the proximal part, the first is at a distance of at least 0.1 of the metatibia length from the metatibia base, the first three are at equal distances from each other (equal to the length of one spine), the fourth spine is at the base of the brush; one more spine is present at the base of the upper one-third of the brush. The distal half of the metatibia is slightly curved outwards and flattened. M e a s u r e m e n t s, mm. Body length including genitalia, 6.3 8; width, 2.2 3; head length, 0.75 0.85; width, 0.95 1.15; pronotum length, 0.65 0.8; width, 2 2.7; length of anterior lobe of pronotum, 0.4 0.6; width, 1.1 1.6; length of pronotum and mesonotum, 1.6 2.15; length of antenna, 2.2 3; length of antennomeres (1 4): 0.25 0.45, 0.8 1.05, 0.4 0.55, 0.3 0.35; mesotibia length, 2.1; hindleg length: femur, 1.9; tibia, 2.7 3.8, tarsus, at most 1.4 1.9; metatarsomeres (1 3): 0.2, 0.95, 0.75; metatarsal claw, 0.2; length of brush on metatibia, 2.3 3; length of elytra, 5.5 6.3. C o m p a r i s o n. The new species differs from the above-described species in the shorter antennae, narrower pronotum and mesonotum, presence of spines on the metatibia, somewhat shorter brush on the metatibia, and slightly greater size, as well as, probably, the relatively longer metatarsomeres 1 and 2. R e m a r k s. Material collected in this locality also includes an imprint of a male body, no. 3559/7925, which apparently belongs to B. infanta based on the small size (at most 5 mm long) and the brush on the metatibia occupying about 0.8 of its length. Unfortunately, the antennae of this specimen are preserved incompletely and, therefore, its systematic position cannot be determined with certainty. M a t e r i a l. In addition to the holotype, 12 paratypes, PIN, nos. 3559/3543, 3545, 3600, 7918, 7920, 7923, 7931, 7932, 7933, 7936, 7943, and 7945, and five imprints of isolated elytra not included in the type series, specimens PIN, nos. 3559/ 3550, 3570, 7666, 7667, and 7927, all from the same locality. Baissotea popovi Ryzhkova, sp. nov. Plate 8, figs. 3 and 4 H o l o t y p e. PIN, no. 3664/2150, adult female, part and counterpart of body; Mongolia, Dundgovi Aimag, 40 km southwest of Under-Shil sum, Shin- Khuduk well, Shin-Khuduk locality; Lower Cretaceous, Shin-Khuduk Formation.

NEW SALDIDAE ENICOCORINAE (HETEROPTERA: LEPTOPODOMORPHA) 159 Fig. 5. Baissotea popovi sp. nov, specimen PIN, no. 3664/1928, form with narrowed membranes of hemelytra. D e s c r i p t i o n (Fig. 4). The body is large or medium-sized; females are larger than males. The body is 2.6 2.7 times as long as wide and about 0.75 times as wide as the metatibia length. The maximum width of the pronotum is about 1.3 times as great as the length of the pronotum and mesonotum taken together and 3.4 times as great as its length medially. Antennomere 2 is at least 2.8 times as long as antennomere 1, 1.65 times as long as antennomere 3, and 1.9 times as long as antennomere 4. The antenna is 1.3 times as long as the pronotum and mesonotum taken together. The brush on the metatibia occupies about 0.6 0.65 of its length. At least some females have a convex swelling of the costal margin at the midlength of the costal space of the hemelytron. In addition to pale spots on the hemelytra, common to all representatives of the genus, a small spot is present in the center of the apical part of the clavus. M e a s u r e m e n t s, mm. Body length including genitalia, 5.8 7.4; width, 2.5 2.9; head length, 0.8 1.05; width, 1 1.3; pronotum length, 0.65 0.95; width, 2.5 2.7; length of anterior lobe of pronotum, 0.5; width, 1.4; length of pronotum and mesonotum, 2 2.3; antenna length, 2.85; length of antennomeres (1 4): 0.4, 1.15, 0.7, 0.6; length of hindleg: femur, 1.6 1.7; metatibia, 3 3.5; metatarsus, at least 1.65; length of elytra, 5.3 6.5. C o m p a r i s o n. The new species is distinguished by the narrower body, somewhat shorter antennae, and shorter brush on the metatibia. It differs from B. infanta in the somewhat larger size and from B. peregrina in the absence of spines on the metatibia. M a t e r i a l. In addition to the holotype, paratypes PIN, nos. 3664/1812, 1854, 1876, 1940, 1946, 1948, 1958, 1961, and 2131, four imprints of isolated elytra, specimens PIN, nos. 3664/1813, 1818, 1887, and 1907, and about 20 imprints of bodies with variously preserved underdeveloped elytra, all from the type locality. DISCUSSION The records of the same heteropteran genus in the Baisa, Anda-Khuduk, Shin-Khuduk, and Bon-Tsagan localities probably support the idea that these localities are rather similar in age and make it possible to unite the heteropteran assemblages of these localities into one assemblage. This unity of insects known from Shin-Khuduk, Anda-Khuduk, and Baisa agrees rather well with the data on other insect groups (unpublished data of A.G. Ponomarenko, pers. comm.) and can be tentatively identified with the Shin-Khuduk Assemblage (Ponomarenko, 1990). The record of Baissotea hemelytra in the Khovur

160 RYZHKOVA locality confirms the previously voiced opinion that this locality is similar in age to Anda-Khuduk, and the record of such hemelytra in the Barun-Suzh locality supports the previously noticed similarity of the insect assemblage of Barun-Suzh with the Shin-Khuduk assemblage (unpublished data of A.G. Ponomarenko, pers. comm.). At the same time, the supposed record of the species B. infanta in Bon-Tsagan is rather unusual and contradicts other available data, e.g., on aquatic and terrestrial heteropterans (Popov, 1990) as well as on other insect groups, which make it possible to distinguish between the faunas of Baisa and Bon- Tsagan, which is of a later age (Ponomarenko, 1990; Pritykina, 1990; Rasnitsyn et al., 1998). However, the unity of these faunas agrees rather well with such data as those on the composition of mycetophilid flies, which include eight genera and four species recorded in both Baisa and Bon-Tsagan (Blagoderov, 1998). 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