The Achilidae Stål, Reference Stål1866 is one of the smaller families of planthoppers (Hemiptera: Fulgoromorpha), known from both extant and extinct taxa, and appeared in the fossil record in the Early Cretaceous. Due to their cryptic lifestyle and scarcity, it is one of the least known and least understood group of planthoppers. Currently, the family Achilidae comprises over 160 genera and about 550 species (Bourgoin Reference Bourgoin2016), divided into three subfamilies (Achilixinae Muir, Reference Muir1923a, Bebaiotinae Emeljanov, Reference Emeljanov1991 and Achilinae Stål, Reference Stål1866), the latter with 11 Recent and two extinct tribes. Many of these tribes are poorly represented, often with just 1–2 specimens preserved in collections, often belonging to only one sex. There are still discussions on the classification and composition of the Achilidae (Emeljanov Reference Emeljanov1991, Reference Emeljanov1992; Urban & Cryan Reference Urban and Cryan2007; Bartlett et al. Reference Bartlett, O'Brien and Wilson2014).
The Achilidae are distributed worldwide, mainly in the tropical and subtropical zones (Metcalf Reference Metcalf1948; Fennah Reference Fennah1950; O'Brien & M. R. Wilson Reference O'Brien, Wilson, Nault and Rodriguez1985; O'Brien Reference O'Brien and Holzinger2002); however, representatives of this family can range to high latitudes in the Northern Hemisphere, to the taiga zone, such as Cixidia (Epiptera) lapponica Zetterstedt, Reference Zetterstedt1828, C. (E.) slossonae (Van Duzee, Reference Van Duzee1908) and C. (E.). woodworthi (Van Duzee, Reference Van Duzee1916) (Bartlett et al. Reference Bartlett, O'Brien and Wilson2014; Asche Reference Asche2015). According to the biogeographical division of Holt et al. (Reference Holt, Lessard, Borregaard, Fritz, Araujo, Dimitrov, Fabre, Graham, Graves, Jønsson, Nogues-Bravo, Wang, Whittaker, Fjeldsa and Rahbek2013), Achilixinae are known from the Oriental Region (the Philippines, Borneo, Celebes) and Bebaiotinae from the Panamanian Region (Ecuador, Guiana, Panama); whilst Achilinae are, in general, distributed worldwide, with a more limited distribution of particular tribes (e.g., Achilini in Africa, Australia and South America with a fossil record in Europe; Achillini from Africa with a fossil record in European deposits; Ilvini from Africa, Sevini from the Panamanian Region and Tropiphlepsini from Australia), with only Plectoderini widely dispersed from tropical to mild temperate zones of the world (Bourgoin Reference Bourgoin2017).
All Achilidae are phytophagous terrestrial insects. The biology of the group is insufficiently known; immatures are fungus feeders and are most easily found under the bark of dead logs (O'Brien Reference O'Brien1971). Adults feed on woody plants, mostly they are reported as polyphagous (Wilson et al. Reference Wilson, Mitter, Denno, Wilson, Denno and Perfect1994), but the degree of host specificity of adults is still not clear (O'Brien Reference O'Brien1971; Asche Reference Asche2015); they mainly feed on phloem of the host plants belonging to the gymnosperm families Pinaceae and Cupressaceae, and to the angiosperm orders Arecales, Asparagales, Asterales, Boraginales, Cupressales, Ericales, Fabales, Fagales, Hamamelidales, Lamiales, Laurales, Malpighiales, Malvales, Myrtales, Pinales, Poales, Rosales, Sapindales and Vitales (Wilson et al. Reference Wilson, Mitter, Denno, Wilson, Denno and Perfect1994; Asche Reference Asche2015; Bourgoin Reference Bourgoin2017).
1 Fossil Achilidae
1.1. Family characters
Diagnostic features of Achilidae are: body usually dorsoventrally flattened, with tegmina held flat or tectiform, with their tips overlapped; clavus open, with claval veins Pcu+A1 running into CuP at the apex of clavus; head small, antennal pedicel globose; the second hind tarsomere with a row of spines (a feature shared with Cixiidae Spinola, Reference Spinola1839 and Kinnaridae Muir, Reference Muir1925, which are the most similar families); in the male genitalia, the pygofer is flattened horizontally, often with median lobe, styles usually subquadrate, with aedeagal complex bilaterally symmetrical, consisting of periandrium surrounding an elongate paired rod-like penis, a connective is usually present between aedeagal base and the genital styles and inner walls of the pygofer; female genitalia modified to raking-kneading device enabling female to attach the eggs to particles of soil, decaying wood, or bark, with anterior connective lamina of gonapohyses VIII bearing sturdy teeth, membranous endogonocoxal process and sclerotized endogonocoxal lobe; gonapophyses IX broadly fused basally, with distal tips pointed and gonoplacs with dorsal and ventral lobes, the latter bearing several sturdy bristles, exposed caudally.
The Achilidae is usually included amongst the group of Fulgoromorpha families referred to as ‘Cixiid-like'. Often, genera and species of Achilidae were mistaken for cixiid taxa. Though overlapping tegmina occurs in some representatives of other families (e.g., some Derbidae), it is generally a good way to recognise an achilid. The head capsule has vertex usually broader than long, with anterior margin more-or-less angulate or convex, and the disc slightly depressed, while the median carina is often obsolete or incomplete. The border between vertex and frons is sometimes callused. The frons, together with the postclypeus is, in most cases, elongate–ovate in outline, with lateral margins being carinate to foliate. Disc of frons is slightly convex to flattened, with median carina developed to various extent. The postclypeus is subtriangular, more-or-less flattened in profile, with the disk flattened or slightly convex. Median carina of postclypeus usually present, lateral margins carinate. However, many modifications and departures of this basic plan are observed. Antennae are typical for Fulgoromorpha, with enlarged, globular to suboval pedicel, with flattened star-shaped sensory plates, and thin flagellum. There are two ocelli located beneath the compound eyes, but achilids lack the third, median ocellus. Pronotum in general is little wider than head with compound eyes, short medially, usually with median disc, bounded laterally by carinae and with median carina. Lateral portions of pronotum variable, sloping down and anteriad of median disc. Mesonotum generally slightly broader than long in mid-line, more-or-less distinctly tricarinate. The tegulae are moderately large and bent through almost a right angle, sometimes carinate at line of flexure. Pro- and mesolegs bear no abnormal features in this family. Metatibiae usually bear lateral spine or spines and row of apical teeth; basimetatarsus is elongate, longer than middle one, middle metatarsus distinctly longer than broad, both with rows of apical teeth, sometimes with subapical setae; apical metatarsus with arolium well developed, a pair of wide dorsolateral sclerites and distinct tarsal claws. Tegmina usually with membrane widened, overlapping at repose, membranous to slightly coriaceous. In the majority, the costal area not developed and pterostigma absent. Stem ScP+R+MP in most taxa leaving basal cell with a common stalk; stem ScP+R forked on corium; stem MP forked usually at level of nodal line, stem CuA forked on corium, basad of stem MP forking, branches CuA1 and CuA2 usually forked (at least one of them) subapically; long perpendicular to branch CuA2 veinlet icu connecting CuA2 and tornus (postclaval margin) present in majority of taxa. Clavus with apex obtuse and line of CuP prolonged as furrow on membrane. Hind wings usually wide, with venation developed variably, with basal cell present or absent, and variable venation of anal area (characters of taxonomic importance). Abdomen, in both males and females, is usually relatively short and depressed. Anal tube in most cases short and rounded (Fennah Reference Fennah1950; Anufriev & Emeljanov Reference Anufriev, Emeljanov and Ler1988; Asche Reference Asche2015).
1.2. Taxonomic history and early fossil discoveries
The family Achilidae was erected by Stål in Reference Stål1866 in his Hemiptera Africana under the name ‘Achilida' (as a subfamily of the family ‘Fulgorida'), to include the 13 genera known at that time. The group was erected to the family level by Muir (Reference Muir1923b), although the spelling ‘Achilidae' was first used by White (Reference White1879) as a subfamily of Fulgoridae. Muir (Reference Muir1923a) also established Achilixiidae, as a separate family. The first subdivision of Achilidae into subfamilies (Apatesoninae and Achilinae) was proposed by Metcalf (Reference Metcalf1948), in his catalogue of the Hemiptera, with two and 76 genera included in the subfamilies respectively. The first author to attempt a full revision of this group was Fennah (Reference Fennah1950), who divided the family into seven tribes: Rhotalini, Plectoderini, Myconini, Breddiniolini, Elidipterini, Achilini and Apatesonini. However, the current classification of Achilidae (Fig. 1) is mainly the result of major works by Emeljanov (Reference Emeljanov1991, Reference Emeljanov1992), with subsequent updates (Emeljanov & Fletcher Reference Emeljanov and Fletcher2004), but these papers did not include fossils.
Figure 1 Relationships of tribes in the subfamily Achilinae (after Emeljanov Reference Emeljanov1992 and Emeljanov & Fletcher Reference Emeljanov and Fletcher2004).
The first Achilidae fossils to be named were described by Germar & Berendt (Reference Germar, Berendt and Berendt1856); however, they were placed with other unrelated taxa in the family Cixiidae, all under the genus Cixius Latreille, Reference Latreille1807. It must be noted that these taxa (i.e., the genus Cixius and family Cixiidae), were a convenient ‘basket' to place fossils without addressing classification or evolutionary issues, when they were described in the 19th and the beginning of the 20th centuries. Subsequent fossils (originally placed in the families Delphacidae and Derbidae) were described by Cockerell (Reference Cockerell1917, Reference Emeljanov1922). The first taxon to be placed in the family Achilidae was described from late Eocene deposits of Florissant (Scudder Reference Scudder1890) and the first extinct genus was described by Usinger (Reference Usinger1939), from Baltic amber. Over the next 50 years, there were no descriptions of fossil achilids, nor any discussions or revisionary studies on them.
1.3. Renaissance of studies on Baltic amber and other fossils of Achilidae
Recent studies on fossil Achilidae commenced in 1990, when Emeljanov (Reference Emeljanov1990) described a new genus and two species, representing a new extinct tribe of Achilidae from Baltic amber and Hamilton (Reference Hamilton and Grimaldi1990) described a new extinct genus and two species from Lower Cretaceous deposits of the Crato Formation in Brazil. A few years later, Emeljanov (Reference Emeljanov1994) transferred the genus Hooleya Cockerell, Reference Emeljanov1922 from the Derbidae to the Achilidae. Another fossil that was originally described by Cockerell (Reference Cockerell1917) from Burmese amber was transferred to the Achilidae as a new genus, Niryasaburnia Szwedo, Reference Szwedo2004. The fossils of the family were critically reviewed, catalogued and discussed by Szwedo et al. (Reference Szwedo2004). A new fossil tribe from Baltic amber was described by Szwedo (Reference Szwedo2006) and several new genera and species from Baltic amber were described by Lefebvre et al. (Reference Lefebvre, Bourgoin and Nel2007) and Emeljanov & Shcherbakov (Reference Emeljanov and Shcherbakov2009).
2. Fossil achilid genera and species
An annotated checklist (in alphabetical order) of the fossil Achilidae (Figs 2, 3), with some comments, is given below. This list complements Szwedo et al. (Reference Szwedo2004). The open nomenclature principles as proposed by Matthews (Reference Matthews1973) and Bengston (Reference Bengston1988) are used.
Figure 2 The fossil record of Achilidae subfamilies and tribes, and their presumed relatives.
Figure 3 (A–C) Fossil Achilidae from Baltic amber: (A) Angustachilus sp., NHMUK In.18899, tribe Achilini; (B) Ptychoptilum sp., coll. Carsten Gröhn 5032, tribe Ptychoptilini; (C) Waghilde baltica, MNHN-LP-R AUF 061JS, tribe Waghildini. (D) Fossil Achilidae from Burmese amber: Achilinae, NIGPAS BA 04-16306, genus and tribe not yet identified.
Genus Acixiites Hamilton, Reference Hamilton and Grimaldi1990
*1990 Acixiites Hamilton, p. 97.
.1992 Acixiites Hamilton; Hamilton, p. 429.
.2004 Acixiites Hamilton, Reference Hamilton and Grimaldi1990; Szwedo et al., p. 41.
.2006 Acixiites Hamilton, Reference Hamilton and Grimaldi1990; Szwedo, p. 173.
.2007 Acixiites Hamilton, Reference Hamilton and Grimaldi1990; Szwedo, pp 298, 300.
Type species. Aciixites immodesta Hamilton, Reference Hamilton and Grimaldi1990, p. 97, by original designation.
Remarks. This genus belongs to subfamily Achilinae as tribe incertae sedis, as it cannot be placed in any of the currently recognized Achilinae tribes. With relatively simple venation, it is similar to some modern representatives of Plectoderini Fennah, Reference Fennah1950.
Acixiites costalis Hamilton, Reference Hamilton and Grimaldi1990
*1990 Acixiites costalis: Hamilton, p. 97, Figs. 39, 42, 108, 109.
.2004 Acixiites costalis Hamilton, Reference Hamilton and Grimaldi1990; Szwedo et al., p. 41.
.2006 Acixiites costalis Hamilton, Reference Hamilton and Grimaldi1990; Szwedo, p. 167.
.2007 Acixiites costalis Hamilton, Reference Hamilton and Grimaldi1990; Szwedo, p. 300, fig. 11.48.a.
Occurrence. Lower Cretaceous, late Aptian (c.114 Ma; Martill et al. Reference Martill, Bechly and Loveridge2007), Crato Formation, Céara State, Brazil.
Acixiites immodesa Hamilton, Reference Hamilton and Grimaldi1990
*1990 Acixiites immodesta Hamilton, p. 97, figs 37, 38, 40, 41, 107.
.2004 Acixiites immodesta Hamilton, Reference Hamilton and Grimaldi1990; Szwedo et al., p. 41, fig. 3.
.2006 Acixiites immodesta Hamilton, Reference Hamilton and Grimaldi1990; Szwedo, p. 167.
.2007 Acixiites immodesta Hamilton, Reference Hamilton and Grimaldi1990; Szwedo, p. 300, fig. 11.48.c.
Occurrence. Lower Cretaceous, Aptian (c.114 Ma), Crato Formation, Céara State, Brazil.
Genus Angustachilus
*2007 Angustachilus Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007, p. 41.
.2009 Angustachilus Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007; Emeljanov & Shcherbakov, pp 1008, 1009.
Type species. Angustachilus longirostris Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007, p. 41, by original designation.
Remark. The genus is placed in subtribe Cixidiina Emeljanov, Reference Emeljanov1992 of the tribe Achilini Stål, Reference Stål1866.
Angustachilus longirostris Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007
*v2007 Angustachilus longirostris Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007, p. 42, figs 21–27.
2015 Angustachilus longirostris Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, Baltic coast, Poland.
Remarks. The age of Baltic amber is a subject of continuous debates (see Szwedo & Drohojowska Reference Szwedo and Drohojowska2016; Wolfe et al. Reference Wolfe, McKellar, Tappert, Sodhi and Muehlenbachs2016; Grimaldi & Ross Reference Grimaldi, Ross, Fraser and Sues2017). The glauconites from ‘blue earth' amberiferous Prussian Formation (the most productive mined horizon) were aged radiometrically by Ritzkowski (Reference Ritzkowski1997) as Lutetian. However, the reliability of this glauconite chronometer was argued by Clauer et al. (Reference Clauer, Huggett and Hillier2005). Perkovsky et al. (Reference Perkovsky, Rasnitsyn, Vlaskin and Taraschuk2007) suggested a Bartonian/Priabonian age for the Prussian Formation, and this is also supported by the interpretations of Aleksandrova & Zaporozhets (Reference Aleksandrova and Zaporozhets2008) and Bogdasarov (Reference Bogdasarov2010). Grimaldi & Ross (Reference Grimaldi, Ross, Fraser and Sues2017), discussing the age of Baltic amber, concluded that the amber that comes from the ‘blue earth' is most likely to be Priabonian in age. On the other hand, Ritzkowski (Reference Ritzkowski, Kosmowska-Ceranowicz and Paner1999), Erichson & Weitschat (Reference Erichson and Weitschat2008) and Matuszewska (Reference Matuszewska2010) pointed out that Baltic amber is deposited in a marine environment, and that after the removal from the forest, the floating resin was transported south and redeposited together with fine-grained sands. Ritzkowski (Reference Ritzkowski, Kosmowska-Ceranowicz and Paner1999) and Weitschat & Wichard (Reference Weitschat, Wichard and Penney2010) mentioned that two additional amber-bearing horizons in the underlying beds of ‘blue earth' indicate that amber had already been transported to secondary deposits about 50 million years ago. These statements for a Middle Eocene age of Baltic amber resin and its inclusions are supported by faunal links to the Middle Eocene Eckfeld Maar deposits of Germany (Wappler Reference Wappler2003; Wappler & Engel Reference Wappler and Engel2003); Pleuarthropterus (Balticarthropterus) Nagel, Reference Nagel1987 (Coleoptera: Carabidae: Paussinae) and the extinct bees (Hymenoptera: Apidae): Protobombus Cockerell, Reference Cockerell1908 and Electrapis Cockerell, Reference Cockerell1908 are taxa that have so far been found only in Baltic amber. Accordingly, we consider the age of fossils from the Baltic amber to be 48–38 Ma.
Genus Elidiptera Spinola, Reference Spinola1839
1966 Elidiptera Spinola, Reference Spinola1839; Metcalf & Wade, p. 100.
1992 Elidiptera Spinola, Reference Spinola1839; Carpenter, p. 238.
2004 Elidiptera Spinola, Reference Spinola1839; Szwedo et al., p. 42.
Type species. Elidiptera callosa Spinola, Reference Spinola1839, p. 305, pl. 15, fig. 2; by monotypy.
Remark. The genus was placed in the tribe Achilini Stål, Reference Stål1866, subtribe Elidipterina Fennah, Reference Fennah1950.
Elidiptera regularis Scudder, Reference Scudder1890
*1890 Elidiptera regularis Scudder, Reference Scudder1890, p. 297, l. XIX, fig. 13.
.1906 Elidiptera regularis Scudder, Reference Scudder1890; Handlirsch Reference Handlirsch1906–08, p. 1068.
.1939 Elidiptera regularis Scudder, Reference Scudder1890; Usinger, p. 65.
.1966 Elidiptera regularis Scudder, Reference Scudder1890; Metcalf & Wade, p. 100.
.1991 Elidiptera regularis Scudder, Reference Scudder1890; Lewis & Hikes, p. 220.
.2003 Elidiptera regularis Scudder, Reference Scudder1890; Meyer, p. 207.
.2004 Elidiptera regularis Scudder, Reference Scudder1890; Szwedo et al., p. 42.
.2006 Elidiptera regularis Scudder, Reference Scudder1890; Szwedo, p. 167.
Occurrence. Upper Eocene, Priabonian (c.34 Ma), Florissant, Teller County, Colorado, USA.
Remark. Only tentatively placed in this genus. The figure in Scudder (Reference Scudder1890) is too unclear to resolve the placement.
Genus Hooleya Cockerell, Reference Cockerell1922
*v1922 Hooleya Cockerell, Reference Cockerell1922, p. 160.
.1992 Hooleya Cockerell, Reference Cockerell1922; Carpenter, p. 256.
.1994 Hooleya Cockerell, Reference Cockerell1922; Emeljanov, p. 76.
.2004 Hooleya Cockerell, Reference Cockerell1922; Szwedo et al., p. 42.
Type species. Hooleya indecisa Cockerell, Reference Cockerell1922, p. 160, by monotypy.
Hooleya indecisa Cockerell, Reference Cockerell1922
*v1922 Hooleya indecisa Cockerell, Reference Cockerell1922, p. 160, fig. 2.
.1992 Hooleya indecisa Cockerell, Reference Cockerell1922; Carpenter, p. 256
.1994 Hooleya indecisa Cockerell, Reference Cockerell1922; Emeljanov, p. 77, fig. 1a; pl. VII, figs. 1a, b.
.2004 Hooleya indecisa Cockerell, Reference Cockerell1922; Szwedo et al., p. 42.
.2004 Hooleya indecisa Cockerell, Reference Cockerell1922; Szwedo, p. 105.
.2006 Hooleya indecisa Cockerell, Reference Cockerell1922; Szwedo, p. 167.
Occurrence. Upper Eocene, Priabonian (c.34 Ma), Insect Limestone, Solent Group, Isle of Wight, UK.
Remark. The genus and species were originally placed in family Derbidae, but transferred to Achilidae, subfamily Achilinae and tribe Achillini Cockerell, Reference Cockerell1922, by Emeljanov (Reference Emeljanov1994). In the original description, the type locality is given as ‘Gurnet Bay' (Cockerell Reference Cockerell1922, p. 160). It is an old name for Gurnard Bay, but this was probably not where the specimen was found. The specimen probably came from Thorness Bay instead (Ross & Self Reference Ross and Self2014).
Genus Niryasaburnia Szwedo, 2004
.1992 Liburnia Stål, Reference Stål1866; Carpenter, p. 240.
.2004 Liburnia Stål, Reference Stål1866; Szwedo et al., p. 94.
Type species. Liburnia burmitina Cockerell, Reference Cockerell1917, p. 105, by original designation by Szwedo Reference Szwedo2004, p. 105.
Remark. This genus belongs to the subfamily Achilinae as taxon incertae sedis, as it cannot be placed in any of the currently recognised Achilinae tribes.
Niryasaburnia burmitina (Cockerell, Reference Cockerell1917)
*v1917 Liburnia (s. lat.) burmitina Cockerell, Reference Cockerell1917, p. 329, figs 8, 9.
.1920 Liburnia burmitina Cockerell, Reference Cockerell1917; Fletcher, p. 988, pl. 166, figs 21, 22.
.1966 Liburnia burmitina Cockerell, Reference Cockerell1917; Metcalf & Wade, p. 113.
.1982 Liburnia s. lat. burmitina Cockerell, Reference Cockerell1917; Keilbach, p. 230.
.1988 Liburnia s. lat. burmitina Cockerell, Reference Cockerell1917; Spahr, pp 19, 48.
.1990a Liburnia burmitina Cockerell, Reference Emeljanov1917; Lewis, p. 5.
.1992 Liburnia burmitina Cockerell, Reference Emeljanov1917; Poinar, p. 125.
.2000 ‘Liburnia' burmitina Cockerell, Reference Cockerell1917; Ross & York: 12, Fig. 7.
.2000 ‘Liburnia' burmitina Cockerell, Reference Cockerell1917; Shcherbakov, p. 36.
.2002 Liburnia (s. lat) burmitinia [sic] Cockerell, Reference Cockerell1917; Szwedo, p. 52.
.2004 Liburnia burmitina Cockerell, Reference Cockerell1917; Szwedo et al., p. 94.
.2004 Niryasaburnia burmitina (Cockerell, Reference Cockerell1917); Szwedo, p.106, fig. 1; pl. 1, fig. 4.
.2006 Niryasaburnia burmitina (Cockerell, Reference Cockerell1917); Szwedo, pp 167, 173.
.2007 Niryasaburnia burmitina (Cockerell, Reference Cockerell1917); Szwedo, p. 298.
.2010 Niryasaburnia burmitina (Cockerell, Reference Cockerell1917); Ross et al., p. 232.
Occurrence. Upper Cretaceous, Cenomanian (c.99 Ma), Burmese amber, Hukawng Valley, Kachin State, Myanmar.
Remarks. The species was originally place in the Recent Delphacidae genus Liburnia Stål, Reference Stål1866. It was transferred to Achilidae by Shcherbakov (Reference Shcherbakov2000), but without a detailed redescription. The venation of this species is plesiomorphic and similar to that of Plectoderini Fennah, Reference Fennah1950 and Mycarini Emeljanov, Reference Emeljanov1991; however, the presence of platellae on the basi- and middle metatarsomeres excludes it from a close relationship with any representatives of these tribes. Double rows of subapical setae are to be found in Achilini Stål, Reference Stål1866 and similar, platella-like structures are present in Tropiphlepsiini Emeljanov, Reference Emeljanov1991.
Genus Paratesum Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009
Type species. Paratesum rasnitsyni Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009, p. 1009, by original designation.
Remark. The genus was placed in the tribe Achilini s.l., without subtribal assignation.
Paratesum rasnitsyni Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009
*2009 Paratesum rasnitsyni Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009, p. 1011, l. 1, fig. 1, text-fig. 1a.
2015 Paratesum rasnitsyni Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, Gulf of Gdańsk deposit.
Protepiptera Usinger, Reference Usinger1939
*1939 Protepiptera Usinger, Reference Usinger1939, p. 66.
.1950 Protepiptera Usinger, Reference Usinger1939; Neave, p. 223.
.1966 Protepiptera Usinger, Reference Usinger1939; Metcalf & Wade, p. 100.
1982 Oliarius [sic]; Keilbach, p. 230.
.1990b Proterpiptera [sic]; Lewis, p. 54.
1992 Protepiptera Usinger, Reference Usinger1939; Poinar, p. 124.
.1992 Protepiptera Usinger, Reference Usinger1939; Carpenter, p. 238.
.2004 Protepiptera Usinger, Reference Usinger1939; Szwedo et al., p. 43.
2007 Protepiptera Usinger, Reference Usinger1939; Lefebvre, Bourgoin & Nel, pp 41, 43.
.2009 Protepiptera Usinger, Reference Usinger1939; Emeljanov & Shcherbakov, p. 1008.
.2009 Protepiptera Usinger, Reference Usinger1939; Emeljanov & Shcherbakov, pp 1008, 1009.
Type species. Protepiptera kaweckii Usinger, Reference Usinger1939, p. 66, by original designation.
Comment. The genus is placed in the tribe Achilini s.l., without subtribal assignation.
Protepiptera kaweckii Usinger, Reference Usinger1939
(?)*1856 Cixius longirostris Germar & Berendt, p. 15, pl. I, fig. 22
(?)1891 Cixius longirostris Germar & Berendt, Reference Germar, Berendt and Berendt1856; Buckton, p. 182, pl. G, fig. 22.
(?)1906 Cixius longirostris Germar & Berendt, Reference Germar, Berendt and Berendt1856; Handlirsch, p. 1068.
(?)*1910 Oliarus oligocenus Cockerell, Reference Cockerell1910, p. 153.
(?)1938 Oliarus oligocenus Reference CockerellCockerell, 1910; Rodeck, p. 285.
*1939 Protepiptera kaweckii Usinger, Reference Usinger1939, p. 66.
(?)1966 Cixius longirostris Germar & Berendt, Reference Germar, Berendt and Berendt1856; Metcalf & Wade, p. 121.
(?)1966 Oliarus oligocenus Cockerell, Reference Cockerell1910; Metcalf & Wade, p. 123.
(?)1982 Cixius longorostris Germar, Reference Germar, Berendt and Berendt1856 [sic]; Keilbach, p. 230.
(?)1982 Cixius longirostris Germar & Berendt, Reference Germar, Berendt and Berendt1856; Keilbach, p. 230.
(?)1982 Oliarius oligocenicus [sic] Cockerell, Reference Cockerell1910; Keilbach, p. 230.
(?)1988 Oliarus oligocenus Cockerell, Reference Cockerell1910; Spahr, p. 22.
.1990b Protepiptera kaweckii Usinger, Reference Usinger1939; Lewis, p. 54.
.1992 Protepiptera kaweckii Usinger, Reference Usinger1939; Carpenter, p. 238.
.2001 Protepiptera kaweckii Usinger, Reference Usinger1939; Szwedo & Stroiński, p. 95.
(?)2001 “Cixius” longirostris Germar & Berendt, 1856; Szwedo & Stroiński, p. 101.
2002 Cixius longirostris Germar & Berendt, 1856; Szwedo, p. 52.
2002 Oliarus oligocenus Cockerell, Reference Cockerell1910; Szwedo, pp 45, 52.
.2002 Protepiptera kawecki i Usinger, Reference Usinger1939; Szwedo, p. 52.
?2004 Cixius longirostris Germar & Berendt, 1856; Szwedo et al., p. 86.
*v.2007 Cixidia christinae Lefebvre, Bourgoin & Nel, p. 39, figs. 10–20.
2007 Protepiptera kaweckii Usinger, Reference Usinger1939; Lefebvre, Bourgoin & Nel, p. 41.
.2009 Protepiptera kaweckii Usinger, Reference Usinger1939; Emeljanov & Shcherbakov, p. 1008.
2009 “Cixius” longirostris Germar & Berendt, 1856; Emeljanov & Shcherbakov, p. 1008.
2009 “Oliarus” oligocenus Cockerell, Reference Cockerell1910; Emeljanov & Shcherbakov, p. 1008.
2009 Cixidia christinae Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007; Emeljanov & Shcherbakov, p. 1008.
2009? “Cixius” longirostris Germar & Berendt, 1856; Emeljanov & Shcherbakov, p. 1015.
2009? “Oliarus” oligocenus Cockerell, Reference Cockerell1910; Emeljanov & Shcherbakov, p. 1015.
.2009 Protepiptera kaweckii Usinger, Reference Usinger1939; Emeljanov & Shcherbakov, pp 1015, 1016, pl. 2, figs. 1-3, text-fig. 2a–g.
2009 Cixidia christinae Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007; Emeljanov & Shcherbakov, p. 1015.
2015 Protepiptera kaweckii (Usinger, Reference Usinger1939) [sic]; Gröhn, p. 231.
2015 Cixidia christinae Lefebvre, Bourgoin & Nel, Reference Lefebvre, Bourgoin and Nel2007; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, ‘East Prussia' [?], Sambia Peninsula: Kaliningrad Region, Russia; Gulf of Gdańsk, Poland.
Protepiptera reticulata (Germar & Berendt, 1856)
*p1856 Pseudophana reticulate Germar & Berendt, 1856, p. 16, pl. II, fig. 4 (pupa).
p.1906 Pseudophana reticulata Germar & Berendt, 1856; Handlirsch Reference Handlirsch1906–08, p. 1070.
p.1966 Dictyophara reticulata (Germar & Berendt, 1856); Metcalf & Wade, p. 126.
p.1982 Pseudophana reticulata Germar, 1856; Keilbach, p. 229.
p.1982 Pseudophana reticulata Germar in Berendt 1856; Keilbach, p. 229.
p.1983 Cixidia reticulata (Germar & Berendt, 1856); Emeljanov, p. 79.
p.1988 Dictyophara (Pseudophana) reticulata (Germar & Berendt, 1856); Spahr, p. 23
p.2002 ‘Pseudophana' reticulata Germar & Berendt, 1856; Szwedo, p. 48.
p.2002 Pseudophana reticulata Germar & Berendt, 1856; Szwedo, p. 52.
p.2004 ‘Cixidia' reticulata (Germar & Berendt, 1856); Szwedo et al., pp 41–42.
p.2009 “Dictyophara (= Pseudophana)” reticulata (Germar & Berendt, 1856; Emeljanov & Shcherbakov, p. 1008.
2011 Protepiptera reticulata (Germar & Berendt, 1856); Emeljanov & Shcherbakov, p. 177.
2015 Protepiptera reticulata (Germar & Berendt, 1856); Gröhn, p. 231.
2015 Cixidia reticulata (Germar & Berendt, 1856); Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma); Baltic amber, ‘East Prussia' [?], Sambia Peninsula: Russia.
Remarks. On the basis of the original figures, Emeljanov (Reference Emeljanov1983) argued that the “nymph” (Germar & Berendt 1856, pl. II, fig. 3) of Pseudophana reticulata Germar & Berendt, 1856 resembles nymphs of representatives of Tropiduchidae; whilst the “pupa” (Germar & Berendt 1856, pl. II, fig. 4) is similar to the nymphs of the genus Cixidia Fieber, Reference Fieber1866 species. The type material was probably lost during World War II, as it was sent to Königsberg in 1937. In the collection of Paläontologisches Institut Humboldt-Universität in Berlin, there is a single specimen labelled as ‘Pseudophana reticulata', and its taxonomic status is under consideration. A lectotype for this species was designated by Emeljanov & Shcherbakov (Reference Emeljanov and Shcherbakov2011, p. 177). These authors suggested that Protepiptera reticulata (Germar & Berendt, 1856) could possibly be a senior synonym of P. kaweckii Usinger, Reference Usinger1939.
Genus Protomenocria Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009
Type species. Protomenocria notata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009, p. 1011; by original designation.
Remarks. The genus was originally placed in the tribe Achilini s.l., without subtribal assignment (Emeljanov & Shcherbakov Reference Emeljanov and Shcherbakov2009). Another species, originally described under the name Cixius testudinarius by Germar & Berendt (1856, p. 13, pl. I, fig. 19a, b), later moved to Achilidae by Usinger (Reference Usinger1939), should probably be placed in this genus (Emeljanov & Shcherbakov Reference Emeljanov and Shcherbakov2009).
Protomenocria notata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009
*2009 Protomenocria notata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009, p. 1014, pl. 2, fig. 4, text-fig. 1b–d.
2015 Protomenocria notata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, Gulf of Gdańsk deposit.
Remark. Emeljanov & Shcherbakov (Reference Emeljanov and Shcherbakov2009) noted that in analysed specimens, a variability in venation is observed, which could result in synonymisation of this species under ‘Cixius' testudinarius Germar & Berendt, 1856.
Genus Psycheona Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009
Type species. Psycheona variegata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009, p. 1016; by original designation.
Remark. The genus was originally placed in the tribe Achilini s.l., without subtribal assignation (Emeljanov & Shcherbakov Reference Emeljanov and Shcherbakov2009).
Psycheona striata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009
*2009 Psycheona striata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009, p. 1018, pl. 1, fig. 4, text-fig. 3c.
2015 Psycheona striata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c. 48–38 Ma); Baltic amber, Gulf of Gdańsk deposit.
Psycheona variegata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009
*2009 Psycheona variegate Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009, p. 1017; pl. 2, figs. 2–3; text-fig. 3a–b.
2015 Psycheona variegata Emeljanov & Shcherbakov, Reference Emeljanov and Shcherbakov2009; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, Gulf of Gdańsk deposit.
Genus Ptychogroehnia Szwedo & Stroiński, Reference Szwedo and Stroiński2001
*2001 Ptychogroehnia Szwedo & Stroiński, Reference Szwedo and Stroiński2001, pp 95, 98.
.2004 Ptychogroehnia Szwedo & Stroiński, Reference Szwedo and Stroiński2001; Szwedo et al., p. 43.
.2009 Ptychogroehnia Szwedo & Stroiński, Reference Szwedo and Stroiński2001; Emeljanov & Shcherbakov, p. 1009.
Type species. Ptychogroenia reducta Szwedo & Stroiński, Reference Szwedo and Stroiński2001, pp 95, 98; by original designation.
Remark. This genus is placed in the extinct tribe Ptychoptilini Emeljanov, Reference Emeljanov1990 (Szwedo & Stroiński Reference Szwedo and Stroiński2001).
Ptychogroehnia reducta Szwedo & Stroiński, Reference Szwedo and Stroiński2001
*v2001 Ptychogroehnia reducta Szwedo & Stroiński, Reference Szwedo and Stroiński2001, p. 98, figs. 5–10, 14–15.
.2002 Ptychogroehnia reducta Szwedo & Stroiński, Reference Szwedo and Stroiński2001; Szwedo, p. 52.
.2004 Ptychogroehnia reducta Szwedo & Stroiński, Reference Szwedo and Stroiński2001; Szwedo et al., p. 3, fig. 4.
.2015 Ptychogroehnia reducta Szwedo & Stroiński, Reference Szwedo and Stroiński2001; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c. 48–38 Ma); Baltic amber, Gulf of Gdańsk deposit.
Genus Ptychoptilum Emeljanov, Reference Emeljanov1990
*1990 Ptychoptilum Emeljanov, Reference Emeljanov1990, p. 7.
.2001 Ptychoptilum Emeljanov, Reference Emeljanov1990; Szwedo & Stroiński, p. 95.
.2004 Ptychoptilum Emeljanov, Reference Emeljanov1990; Szwedo et al., p. 43.
.2009 Ptychoptilum Emeljanov, Reference Emeljanov1990; Emeljanov & Shcherbakov, pp 1008, 1009.
Type species. Ptychoptilum major Emeljanov Reference Emeljanov1990, p. 7; by original designation.
Remark. It is the type genus of the extinct tribe Ptychoptilini Emeljanov, Reference Emeljanov1990, so far known only from Eocene Baltic amber (Emeljanov Reference Emeljanov1990).
Ptychoptilum major Emeljanov, Reference Emeljanov1990
*1990 Ptychoptilum major Emeljanov, Reference Emeljanov1990, p. 10, fig. 1.
.2001 Ptychoptilum major Emeljanov, Reference Emeljanov1990; Szwedo & Stroiński, p. 95, figs 1–3.
.2002 Ptychoptilum major Emeljanov, Reference Emeljanov1990; Szwedo, p. 52.
.2004 Ptychoptilum major Emeljanov, Reference Emeljanov1990; Szwedo et al., p. 43.
.2015 Ptychoptilum major Emeljanov, Reference Emeljanov1990; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, Gulf of Gdańsk deposit.
Ptychoptilum minor Emeljanov, Reference Emeljanov1990
*1990 Ptychoptilum minor Emeljanov, Reference Emeljanov1990, p. 9, fig. 2.
.2001 Ptychoptilum minor Emeljanov, Reference Emeljanov1990; Szwedo & Stroiński, p. 95, fig. 4.
.2002 Ptychoptilum minor Emeljanov, Reference Emeljanov1990; Szwedo, p. 52.
.2004 Ptychoptilum minor Emeljanov, Reference Emeljanov1990; Szwedo et al., p. 43.
.2015 Ptychoptilum minor Emeljanov, Reference Emeljanov1990; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, Gulf of Gdańsk deposit.
Genus Waghilde Szwedo, Reference Szwedo2006
*2006 Waghilde Szwedo, Reference Szwedo2006, p. 168.
.2009 Waghilde Szwedo, Reference Szwedo2006; Emeljanov & Shcherbakov, p. 1009.
Type species. Waghilde baltica Szwedo, Reference Szwedo2006, p. 168; by original designation.
Remark. It is the type genus for the extinct tribe Waghildini Szwedo, Reference Szwedo2006, known exclusively, so far, from Eocene Baltic amber (Szwedo Reference Szwedo2006).
Waghilde baltica Szwedo, Reference Szwedo2006
*v2006 Waghilde baltica: Szwedo, Reference Szwedo2006, p. 169, figs 1–13, 15–27.
.2015 Waghilde baltica Szwedo, Reference Szwedo2006; Gröhn, p. 231.
Occurrence. Eocene, Lutetian–Bartonian (c.48–38 Ma), Baltic amber, Gulf of Gdańsk deposit.
3. Summary – taxonomic issues and challenges
The investigation of Achilidae inclusions in Baltic amber has been going on for 160 years, but the group still is very challenging. There are several taxa already described which require revision; for example, some taxa described by Germar & Berendt (1856), placed formally in the genus ‘Cixius' (Szwedo et al. Reference Szwedo2004). The other challenge is the placement of the known fossil taxa into a phylogenetic context and classification scheme for the Achilidae. The question of the position and relationships of extinct tribes remains open. Despite new findings of fossils, analysis of relationships of the family and within the family, including fossil material, still awaits. Former studies on taxonomic diversity and morphological disparity of Baltic amber Achilidae revealed several unique forms, not present amongst Recent representatives of the family (such as the presence of the extinct tribes Ptychoptilini Emeljanov, Reference Emeljanov1990 and Waghildini Szwedo, Reference Szwedo2006), or ascribable to taxa of low diversity. Surprisingly, most fossils from Baltic amber can be placed in the tribe Achilini. This tribe, in the Recent fauna, is represented by three subtribes (Elidipterina Fennah, Reference Fennah1950 (with 13 extant genera); Achilina Stål, Reference Stål1866 (with four extant genera); and Cixidiina Emeljanov, Reference Emeljanov1992 (single extant genus, subdivided into two subgenera)) and nine extant genera unplaced to tribes (Asche Reference Asche2015; Bourgoin Reference Bourgoin2017).
Precise biological data on Achilidae are scarce (O'Brien Reference O'Brien1971; Bartlett et al. Reference Bartlett, O'Brien and Wilson2014; Wilson et al. Reference Wilson, Mitter, Denno, Wilson, Denno and Perfect1994; Asche Reference Asche2015; Bourgoin 2016), but it seems that at least some Recent species of the tribe Achilini have a close association with Fagaceae (Quercus spp., Fagus spp.) and Pinaceae (Pinus spp, Abies spp.) (Asche Reference Asche2015), which could be an old association, possibly explaining their relative abundance amongst large Baltic amber inclusions. The trees of families and genera recognised as host plants of Achilidae were present in the Eocene amberiferous forests (Szwedo Reference Szwedo2012). The Baltic amber forests were rich in decaying logs and twigs, creating suitable environments for the development of Achilidae nymphs. The trophic relationships of immatures, and partly of adults as sap-suckers, on the hyphae of fungi belonging to the Basidiomycota: Polyporales could be another reason for the incidence of these planthoppers in Baltic amber. These factors combined could result in a high taxonomic and morphological diversity of Achilidae, accounting for their frequent findings amongst large Baltic amber inclusions.
New efforts in collecting and studying specimens of Achilidae enclosed in Baltic amber are an essential prerequisite for any future analyses. The Achilidae seems to be a relic in the Recent fauna, and their taxonomic diversity is a result of a long evolutionary history. This hypothesis could be tested with detailed studies of the inclusions in Baltic amber and other Eocene deposits, the probable time of the Achilidae heyday. There are many unanswered questions on Recent Achilidae and many challenging issues regarding extinct Achilidae. This could be frustrating on the one hand, but on the other hand it makes studies on this group of insects very interesting.
4. Acknowledgements
We would like to cordially thank Professor Thierry Bourgoin (Muséum national d'Histoire naturelle) and Dr Manfred Asche (Museum für Naturkunde, Berlin) for their constructive reviews; and we also thank Dr Andrew J. Ross (National Museums Scotland, Edinburgh) and Mrs Vicki Hammond (Journals & Archive Officer, RSE) for their valuable comments and corrections.
