New Chironomidae (Diptera) with elongate proboscises from the Late Jurassic of Mongolia

Abstract Four new species of Chironomidae with well-developed elongate proboscises are described from a Late Jurassic site Shar Teg in SW Mongolia. These are named Cretaenne rasnicyni sp. n., Podonomius blepharis sp. n., Podonomius macromastix sp. n., ?Podonomius robustus sp. n.


Introduction
The present paper continues a series of articles with descriptions of Diptera from the Late Jurassic Shar Teg site (e.g. Kalugina 1992, Lukashevich 2009). The Upper Jurassic lacustrine deposits of Shar Teg Beds outcrop at Ulan Malgait Mt., 4-5 km west of Shar Teg Mt., 100 km ESE of Altai Somon, Gobi-Altai Aimag, SW Mongolia. The fossil assemblage of Shar Teg includes a diverse and abundant complex of flora and fauna (Gubin and Sinitza 1996).

systematics
Family Chironomidae Newman, 1834 Subfamily ?Aenneinae Ansorge, 1999 Genus Cretaenne Azar, Veltz & Nel, 2008 http://species-id.net/wiki/Cretaenne Cretaenne Azar et al. 2008: 688. Type species Cretaenne kobeyssii Azar et al. 2008: 689. The genus was established based on two species from Early Cretaceous Lebanese amber. The specimens under description are assigned to this genus due to functional blade-like laciniae and mandibles in females, postnotum with a longitudinal groove, reduced hind tibial comb, and peculiarities of wing venation (vein C long and reaching wing tip; Sc not terminating in wing margin; R 2 present; cell between divergent R 2+3 and R 4+5 very broad; R 4+5 almost straight; bM 3+4 present; r-m, bM 3+4 and m-cu aligned; m-cu connecting CuA proximal to r-m). In the new species, tibial spurs are probably present; however, their structure remains unclear due to the state of preservation. The structure of claws is important for the determination of Lebanese species, but claws are not visible in the Mongolian specimens as well as the details of chaetotaxy (e.g., on pedicel) and therefore not mentioned in the description.
Diagnosis. The new species is distinguished from both known species of Cretaenne by the longer proboscis (more than half of the head height and about twice the clypeus height) and the longer Rs stem.
Remarks. The pattern of the female mouthparts is poorly visible in the holotype and unknown in paratype PIN 4270/2459; paratype PIN 4270/2367 has a well-preserved proboscis and its wing venation is very pale and incomplete; the setae at the tibial apices are distinctly visible only in paratype PIN 4270/2459; in both paratypes the spermathecae are not visible. Hence it is possible that these specimens are not conspecific. However, we suggest that all these specimens belong to the same species due to visible peculiarities of venation (particularly the long Rs stem and R 2 position).
The genus Cretaenne was described in the subfamily Aenneinae with reservations, due to the vein Sc not terminating in the wing margin and short Rs stem, as distinct from the type genus of the subfamily, Aenne Ansorge, 1999 from the Late Triassic and Early Jurassic of Europe (Krzeminski andJarzembowski 1999, Azar et al. 2008). In the new species from Shar Teg, the stem Rs is long without doubt but Sc is clear only to the level of the first Rs bifurcation, then sharply thins out and possibly does not terminate in C, as seen in Cretaenne. We did not reexamine the type material of Aenne and Cretaenne, but according to the published data, Rs length can vary within species: in Aenne liasina Ansorge, 1999, the relatively long Rs is longer or shorter than r-m (Ansorge 1999: figs 6-7), whereas the distal thinning of Sc is not recorded. Consequently, the new species is described here as a member of Cretaenne due to several features unknown for Aenne (described from isolated wings only), viz. a reduced hind tibial comb, the postnotum with a longitudinal groove, the structure of well-developed extended proboscis, and, probably, spurs on middle and hind tibia. Actually, biting mandibles were reported for the Mesozoic Aenne with reference to unpublished data of Cranston (Grimaldi and Engel 2005: 504).
The genus was described for six species from the Early and Middle Jurassic of Siberia, with only two species being attributed with certainty. Later, one more species from the Early Jurassic of Germany was tentatively included (Ansorge 1996). The specimens under description are assigned to this genus due to their broad head, large reniform eyes with dorsomedial projection, short thorax (no longer than its height), narrow scutellum, short postnotum, three rounded sclerotized spermathecae, and peculiarities of venation (vein C long, reaching R 4+5 tip; Sc not terminating in wing margin; R 2+3 absent; R 1 long, not thickened distally in female; R 4+5 straight or only slightly curved down distally; bR 4+5 and m-cu inclined to long wing axis; r-m, bM 3+4 and m-cu aligned; r-m much longer than bM 3+4 ; cell ba and bp not symmetrical; m-cu connecting Cu proximal to r-m; costal and radial veins, stem M and CuA, r-m, bM 3+4 and m-cu thickened, other veins very thin and pale; wings without spots). We re-examined the type material of the six species described by Kalugina (1985) from Siberia ( Fig. 2i) but did not examine ?P. tumidus Ansorge, 1996 from Grimmen. A postnotum without longitudinal median groove was recorded in the original diagnosis of Podonomius (for German species, such information was absent; Ansorge 1996). This feature is known only in Aphroteniinae and Podonominae and unknown in Tanypodinae and Buchonomyiinae (Brundin 1966, Murray and Fittkau 1989, Saether 1989). Unfortunately it is impossible to see this important character in the new specimens, in particular, due to the lateral position of impressions. Pubescence and setae of their bodies are also not visible on any specimens described here. Podonomius blepharis sp. n. urn:lsid:zoobank.org:act:EE993F1F-6B84-4BA7-80B6-9905C90DA6B2 http://species-id.net/wiki/Podonomius_blepharis Etymology. From Greek "blepharis" for eyelash, after the pattern of the tibial comb.
Diagnosis. The new species is distinguished by its small size (wing length l.4 mm), well-developed elongate proboscis, weakly convex scutum without a hump, wing with broad cell c, and pale legs with darker junction of femur with trochanter and tibia, and with combs of dark closely-spaced spiniform setae at tibial apices.
Remarks. The new species is similar to P. splendidus Kalugina, 1985 (J 1/2 , Novospasskoye, Transbaikalia) in its venation (C length, ratio R 1 / R 4+5 ), colour pattern of legs and elongated mouthparts, which are visible on paratype PIN 3000/1857 (in the other type specimens of Podonomius from Siberia, the mouthparts are not visible due to the state of preservation). Podonomius blepharis sp. n. differs from P. splendidus in broader cell c and smaller size. As for tibial combs, Kalugina noted (1985) that in P. tugnuicus and P. splendidus the tibial apices are darkened but without mentioning combs. According to our re-examination of the type material of P. splendidus, the hind tibia has a reduced comb consisting of a row of separate dark points, which may be minute setae or possibly bases of missing long bristles (these seem to be visible near the tibial apex in the holotype). In the latter case, a well-developed tibial comb is not unique for P. blepharis.
Diagnosis. The new species is distinguished by its small size (wing length 1.9), well-developed elongate proboscis, strongly convex scutum with a hump, comparatively long wings with R 1 with arched tip and broad cell r 5 , and pale legs with darker junction of femur with trochanter and tibia.
Remarks. The new species is similar to ?P. rotundatus Kalugina, 1985 (J 2 , Kubekovo, South Siberia, Fig. 2i) in its venation (length of C, R 1 /R 4+5 ratio, cells r 1 /r 5 ratio) and size, but is distinguished by the arched tip of R 1 . The new species differs from P. blepharis sp. n. in the longer wings with broader cell r 5 and thoracic shape.
Diagnosis. The new species is distinguished by its medium size (wing length 3.7 mm), well-developed, strongly elongate proboscis, wing with C produced beyond R 4+5 and reaching wing tip, strongly sclerotized abdomen and legs, and one spermatheca situated proximally of other two.
Remarks. Adults of this new species are the largest among Podonomius (wing length is similar only in ?P. simplex Kalugina, 1985 (J 2 , Kubekovo, South Siberia), but in the Siberian species R 1 is curved up distally). ?Podonomius robustus sp. n. differs from other species from Shar Teg also in the longer costal extension. Such a long costa extending to the wing tip is an important plesiomorphic character (Brundin 1976) and may be a character of generic value. Thus, the new species is only tentatively placed in Podonomius.

Subfamily Tanypodinae Skuze, 1889
Among fifty adult chironomids from Shar Teg, only two incomplete females (PIN 4270/2324±, 4270/2431) and one male (PIN 4270/2384) can be determined as members of this subfamily (all from the same 443/1 outcrop) due to the typical venation on partly preserved wings (Fig. 1о). The poor state of their preservation does not allow us to place the specimens within a genus.

Discussion
The four new species of Chironomidae described in this paper are characterized by the elongate proboscis with well-developed (probably sclerotized) mandibles and/or maxillae. To date, a well-developed piercing proboscis has been described only in two recent and no less than four extinct genera of the Chironomidae (Azar et al. 2008). Among the recent Chironomidae, strongly elongate mouthparts are known also in some Orthocladiinae, namely, in both sexes of the North American species Pseudorthocladius macrostomus Soponis, 1980 andRhinocladius Edwards, 1931 (all three species;distributed in South America and Australia). Their proboscis, superficially resembling that of a mosquito, is formed entirely of the extremely elongated labellae, devoid of stylets and presumably used for sipping nectar, not for piercing (Edwards 1931, Freeman 1961, Soponis 1980. Possibly, a poorly described species Camptocladius nigripectus Bigot 1888 has a similar type of the proboscis (Edwards 1931).
The proboscises of Cretaenne rasnicyni sp. n. and ?Podonomius robustus sp. n. are much longer than in any other fossil Chironomidae described to date (possibly except for an undeterminable culicomorphan from the Triassic Cow Branch Formation; Blagoderov et al. 2007). Among the Chironomoidea, similar strongly elongate mouthparts are known in a number of recent species in many genera of Ceratopogonidae belonging to different lineages of this family, such as Culicoides Latreille, 1809, Echinohelea Macfie, 1940, Atrichopogon Kieffer, 1906, Forcipomyia Meigen, 1818, Leptoconops Skuse, 1889, as well as in extinct species such as the Lower Cretaceous Protoculicoides skalskii Szadziewski, Arillo, 1998, P. punctus Borkent, 2000, and the Upper Cretaceous Culicoides filipalpus Remm, 1976(e.g. Borkent 2000, Borkent et al. 2009). In nearly all Ceratopogonidae with such mouthparts, females are either insectivorous predators, or blood-suckers on vertebrates, or haemolymph-suckers on insects. However, haemolymph-sucking is restricted to Forcipomyiinae and considered derived feeding mode which appeared in the Cenozoic (Borkent 2000). Nectar-feeding ceratopogonids usually have the stylets more or less reduced, but Forcipomyia (F.) brevipennis (Macquart, 1826) considered nectarophagous retains the sclerotized, distinctly toothed mandibles subequal in size to piercing mandibles of its insectivorous congeners (Glukhova 1981). By analogy with Ceratopogonidae we assume that the females of the new chironomid species were entomophagous or haematophagous but secondary nectarophagy cannot be excluded. It is impossible to argue for one of these feeding types, because the fine details of the mouthparts are not discernible in our fossils.
In the general appearance (very long and strong proboscis, body size, shape and proportions; pattern and degree of sclerotization, e.g. strongly sclerotized abdomen and legs) ?P. robustus differs from "typical" Chironomidae as well as from other species assigned to the genus Podonomius and resembles some "robust" Ceratopogonidae, especially many Palpomyiini, but this advanced tribe is unknown from the Mesozoic (Szadziewski 1996). Unfortunately, the posterior part of the wing is not visible in the holotype of ?P. robustus, as well as in the holotype of P. blepharis sp. n., and the presence of a forked M 1+2 (characteristic of Ceratopogonidae) cannot be excluded. Thus, the position of these two species seems to be somewhat uncertain. Similar female wings bare of macrotrichia, with well-developed single radial cell, costal ratio more than 0.9 and vein C produced beyond R 4+5 and almost reaching wing tip, are known in several Cretaceous species of the ceratopogonid genus Protoculicoides Boesel, 1937, such as P. schleei (Szadziewski, 1996) and P. unus Borkent, 2000 from Lebanese amber (Borkent 2000).
However, in the holotype of ?P. robustus the partly visible transverse vein under r-m is undoubtedly coloured, that is not recorded for the basal part of vein M 2 in ceratopogonid wing, but typical for bM 3+4 in podonomine wing (Figs 2h-i). In addition, the venation pattern of the anterior part of the wing is more similar to Podonominae than to Ceratopogonidae (vein R 1 long, cell r 1 long and not narrow) and the vertex of P. blepharis as well as ?P. robustus possesses a coronal suture, which is a feature of the Chironomidae, absent in Ceratopogonidae (Saether 2000). Moreover, ?P. robustus has a well-developed elongate notum of gonapophysis IX, whereas its absence has been considered as a synapomorphy of the Ceratopogonidae (Saether 2000), and only some early lineages of Ceratopogonidae have a differently-shaped, short squat notum (vaginal apodeme in Borkent et al. 1987). So we exclude ceratopogonid affinity for both discussed species in spite of the incomplete state of preservation and the strong resemblance to insectivorous predatory or bloodsucking ceratopogonids in the general appearance and consider them as members of Podonominae.
The subfamily Podonominae is shown to be a dominant one in specimen abundance and diversity in the Jurassic deposits of Siberia (Kalugina and Kovalev 1985). No relevant data are available for the other regions. Kalugina stressed the difficulties in differentiation of the Mesozoic Podonominae and Tanypodinae and suggested that often it was possible to classify new taxa with certainty only as members of Tanypodoinae (Tanypodinae + Aphroteniinae + Podonominae) (Kalugina and Kovalev 1985: 82). However, she assigned new genera to subfamilies and explained her choice at every turn. At the same time, Kalugina assumed that some taxa she described in the Podonominae might actually belong to the Tanypodinae, considering that these two subfamilies were less clearly distinguished morphologically in the Jurassic.
Recently, Veltz et al. (2007) have concluded that subfamily identification of Jurassic Chironomidae is impossible and all Podonominae described by Kalugina are Chironomidae incertae sedis. Their only argument was rather methodical: Veltz and coauthors found it impossible to assign the different life stages to the same species as well as different species known only as pupae, to the same genus. Veltz and coauthors did not discuss the arguments proposed by Kalugina, e.g. that the larvae with translucent thoracic horns and pupae with translucent male genitalia were found among the numerous Jurassic impressions of Oryctochlus Kalugina, 1985, so the association of larvae with pupae was made with certainty and those of pupae and imago, with some doubts. Kalugina compared every life stage of Oryctochlus with those of recent Trichotanypus Kieffer, 1906 and drew a conclusion about an undoubted affinity of these two genera of Podonominae (e.g. in pupae of both genera, segment VIII is deeply emarginated posteriorly, which is remarkably similar to segment IX in shape and segment IX with 3 lateral setae, 2 of which are close together in mid-section). According to the time-calibrated molecular data (Cranston et al. 2010), Trichotanypus is one of the oldest genera of the subfamily, which split from Parochlini in the Early Cretaceous. The French authors did not discuss substantially any genus described by Kalugina. However, they considered that Podonominae may not be recorded in the Mesozoic (Azar et al. 2008), but that hardly can be true. A transfer of Libanochlites Brundin, 1976 (К 1 , Lebanese amber) from Podonominae to Tanypodinae made by these authors based on their new data was not supported by other specialists (Cranston et al. 2010).