TANYTARSINI Zavřel, 1916

Baranov, Viktor A., Haug, Joachim T., Greenwalt, Dale E. & Harbach, Ralph, 2022, Diversity of culicomorphan dipterans in the Eocene Kishenehn Konservat-Lagerstätte (Montana, USA) and its palaeoecological implications, Palaeontologia Electronica (a 4) 25 (1), pp. 1-30 : 9-19

TANYTARSINI Zavřel, 1916 [in Thienemann and Zavřel, 1916]

TANYTARSUS van der Wulp, 1874 cf. TANYTARSUS

Figure 10 A-E

Material. This morphotype of Chironomidae is represented by a single adult male and several probably related pupae on a single slab of shale (specimen USNM 722523). As we could not ascertain the state of some important characters, most notably wing venation, we have refrained from a formal description of this morphotype.

Remarks. Medium-sized fly with midge-shaped body, long legs and long abdomen ending with prominent external genitalia. Wings lost in the only preserved adult male, Holotype: USNM 722523. Specimen preserved mostly in dorsolateral aspect. Body length 4.8 mm.

Adult male. Ocular segment and post-ocular segments 1–5 (presumably) forming distinct capsule (head capsule) ( Figure 10 A-E). Ocular segment recognizable by a pair of large compound eyes. Eyes without micro- or macrotrichia. Labrum and clypeus not preserved. Post-ocular segment 1 recognizable by its appendages, antennae [antennulae]. Each antenna bears a dense plumage of long setae. Lengths of the individual elements of the antenna as follows (n = 1, USNM 722523): first and second flagellomeres only partially visible/ obscured, third 50 µm, fourth 40 µm, fifth 45 µm, sixth 25 µm, seventh 40 µm, eighth 35 µm, ninth 40 µm, tenth 40 µm, eleventh 40 µm, twelfth 48 µm, and thirteenth 825 µm. Frons (frontal sclerite) of post-ocular segment 1 impossible to examine as it is embedded in matrix. Post-ocular segment 2 (intercalary segment) without externally recognizable structures. Post-ocular segment 3 bears no recognizable appendages (mandibles). Post-ocular segment 4 recognizable by its appendage, maxilla [maxillula]. Maxilla recognizable by maxillary palpi, which normally consist of five elements (palpomeres), with palpomeres 1 and 2 hidden behind the head; lengths of elements 3 and 4 (n = 1) 160 µm and 180 µm, respectively. Palpomere 5 not preserved. Post-ocular segment 5 recognizable by its appendages, forming the labium [conjoined left and right maxillae]. Labium mostly obscured on all specimens, no details visible. Thorax ( Figure 10A ) bears three pairs of the ambulatory appendages (fore-, mid- and hindlegs) on the pro-, meso- and metathorax, respectively. Each leg consists of coxa, trochanter, femur, tibia and tarsomeres 1–5. Wings not preserved. Prothorax horseshoe-shaped (with arms of ‘horseshoe’ facing ventrally), narrow. Prothorax bears first thoracic appendages (forelegs). Lengths of foreleg elements: femur 870 µm (n m = 1), tibia 640 µm (n = 1), tarsomere 1 1000 µm (n = 1), tarsomere 2 530 µm (n = 1), tarsomere 3 440 µm (n = 1), tarsomere 4 280 µm (n = 1). Mesothorax with wing not preserved. Lengths of midleg elements as following: femur 670 µm (n = 1), tibia 1300 µm (n = 1); other elements not preserved. Metathorax bears a pair of ambulatory appendages (hindlegs). Lengths of hindleg elements as following: femur 1200 µm (n = 1), tibia 1400 µm (n = 1), tarsomere 1 670 µm (n = 1), tarsomere 2 400 µm (n = 1), tarsomere 3 300 µm (n = 1), tarsomere 4 320 µm (n = 1). Tibia with two separate combs ( Figure 10B ).

Abdomen (posterior trunk) comprised of 10 units, only 8 of which are represented as fully developed abdominal segments. Units 9 and 10 incorporated into hypopygium. Abdominal units 1–8 roughly rectangular in shape. No setae preserved on specimen ( Figure 10 C-E). Abdominal unit 9 together with hypopygium forms the male copulatory apparatus.

Male genitalia (hypopygium) (appendages of abdominal unit 8 and following units): unit 9 broadly rounded posteriorly, trapezoidal in shape ( Figure 10 C-E). Unit 10 represented by anal point, poorly preserved, seemingly parallel-sided, with two prominent rows of spinulae (eight in two rows of four). Gonocoxite (2) cylindrical, 170 µm long. Superior volsella of gonocoxite (lateral protrusion of gonocoxite) oval, elongate with a row of setal tecae. Gonocoxite and gonostylus without a flexible articulation, conjoined ( Figure 10 C-E). Gonostylus narrow, curved, with pointed distal end, 220 µm long ( Figure 10 C-E).

Taxonomic attribution. Males of this morphotype can be recognized as representatives of Chironomidae based on a specific combination of characters: overall similar habitus, body slender, antennae with more than six elongated elements (flagellomeres), second element of antenna (pedicellus) conspicuously larger than the rest of the antennal elements, antenna with strong plumage, ocelli absent, head without functional mouthparts, thorax without distinct pre-halter lobe at the base of the true halter, scutum without distinct V-shaped suture, tarsomere 1 on all (preserved) legs is considerably longer than tarsomere 2, tergite of abdominal unit 1 without fringe of strong lateral setae ( Marshall et al., 2017). Within Chironomidae , this morphotype is an ingroup of Chironominae , due to a specific combination of characters: gonocoxite and gonostylus conjoined rigidly, no articulation visible (Wiederholm, 1989). Although the available specimen lacks wings, and therefore crucial diagnostic characters are missing, we can assume that this midge is a representative of Tanytarsini . This assumption is based on the combination of a prominent oval superior volsella and anal point with spinulae arranged in longitudinal rows (Wiederholm, 1989) ( Figure 10E ). Within the Tanytarsini , this morphotype is most similar to Tanytarsus van der Wulp, 1874 , based on the following combination of characters: maxillary palpus elements are considerably longer than wide, mid- and hindtibiae with separated combs, anal point without two anteriorly directed processes and with a group of spines ( Langton and Pinder, 2007). General shape of the superior volsella and characteristic spinulae of the anal point arranged into two longitudinal rows are reminiscent of the condition in extant representatives of Tanytarsus , such as T. gracilentus Holmgren, 1883 [in Homgren and Aurivillius, 1883] ( Giłka, 2011a). Numerous fossil adult representatives of Tanytarsus are known from amber, but differences in amber taphonomy from that of the Kishenehn Formation makes them difficult to compare to the specimens discussed here ( Giłka, 2010; 2011b; Giłka, et al. 2013; Zakrzewska and Giłka, 2015; Zakrzewska, et al. 2020). Pupae on the same slab as the adult male appear to be representatives of Tanytarsini based on the armament of the abdominal tergites and can potentially represent the same morphotype as the male. Unfortunately, these pupae are too poorly preserved to able to ascertain if they represent the same species.

RHEOTANYTARSUS Thienemann and Bause, 1913 [in Bause 1913]

RHEOTANYTARSUS LACUSTRIS Baranov and Haug , sp. nov.

Figures 11 A-E, 12A-E zoobank.org/ D0CBCF87-28EF-41B5-A812-CA8D5DFAF245

Diagnosis (based on adult males and pupal exuviae). This new species can be easily distinguished from all other species of Rheotanytarsus based on the specific combination of characters of adult males and pupae: adult male with extremely short medium volsella (lateral protrusion of gonocoxite) and blunt gonostylus. Pupae associated with the adults are well preserved with thoracic horn parallel-sided and bare; tergites 2–5 of abdominal units with paired, circular patches of spinules present; tergite 2 with shagreen split into two groups; comb of abdominal unit 8 with four strong, thorn-like, strongly sclerotized spurs.

Etymology. Named lacustris after the lake deposits of the Kishenehn Formation the specimens were found in.

Type material. Holotype: USNM 717577 adult male and its pupal exuvium; paratypes, pupae: USNM 722460 , USNM722479 , USNM624824 and USNM 623669 . Additional material: 76 additional pupae were examined; see Appendix Table 1 for additional material.

Pupa. Habitus. Medium-size, with flattened, comma-shaped body (in lateral aspect). Body length, 5.1–7.0 mm (n = 17); length of head and thorax combined, 0.9–1.7 mm (n = 17); abdomen length, 4.0– 5.5 mm (n = 17). Body differentiated into presumably 20 segments, ocular segment plus 19 post-ocular segments ( Figure 11 A-C); anterior part of the body composed of head and thorax, visible as a single globose structure; thorax bears wings and ambulatory appendages (legs) ( Figure 11 A-C). Ocular segment and post-ocular segments 1–5 (presumably) forming a distinct capsule (head capsule); antennae missing or incomplete on the available specimens; frons of the pupae with a pair of small cephalic tubercles; mouthparts located ventrally, short, ending before attachment of the fore ambulatory appendages ( Figure 11 A-C). Only three specimens of Rheotanytarsus lacustris have well-preserved thoracic horns ( USNM 722460, 722479 and 624824). Thoracic horn long (0.6–2.0 mm, n = 3), with parallel-sided base, tapering towards the apical end. Thoracic horns smooth, without spikes or setae. Wings reaching beyond the thorax to the abdomen. Legs not preserved in the available specimens ( Figure 11 A-C).

Abdomen (posterior trunk). Comprised of 10 units, only eight of which are represented as fully developed abdominal segments; units 9 and 10 incorporated into hypopygium. Tergites of abdominal units 2–5 with paired circular patches of spinules at anterior margin ( Figure 11 D-E). Tergite 2 with a rectangular field of shagreen on posterior margin, split by an area of smooth cuticle medially. Tergites of the units 6–9 without visible armament. Combs at the posterolateral edge of tergite 8 with four strong, wide spurs ( Figure 11E ). Anal lobes with a dense fringe of setae although setae not preserved per se, rather only their tecae at the edge of the lobe.

Adult male. Medium-sized midge, with long legs and long abdomen ending with prominent external genitalia. Wings are lost in the only preserved adult male, Holotype: USNM 717577 ( Figure 12 A-E). The specimen preserved mostly in dorsolateral aspect. Body length 4.8 mm.

Ocular segment and post-ocular segments 1–5 (presumably) forming distinct capsule (head capsule) ( Figure 12 A-E). Ocular segment recognizable by pair of large compound eyes. Eyes without micro- or microtrichia, with well-preserved ommatidia. Frons (frontal sclerite) of post-ocular segment 1 impossible to examine as it is embedded in matrix. Labrum and clypeus 240 µm long, rectangular. Post-ocular segment 1 recognizable by its appendages, antennae [antennulae]. Antenna 1200 µm in length, impossible to distinguish the borders between the antennal elements (flagellomeres). Each antenna bears dense plumage of long setae. Post-ocular segment 2 (intercalary segment) without externally recognizable structures. Post-ocular segment 3 bears no recognizable appendages (mandibles) ( Figure 12 A-E). Post-ocular segment 4 recognizable by its appendage, maxilla [maxillula]. Maxilla recognizable by maxillary palpi. Maxillary palpus consists of five elements (palpomeres) with palpomeres 1 and 2 hidden behind the labrum; lengths of elements 3 through 5: 140–150 µm (n = 2), 200 µm (n = 1) and 170 µm (n = 1), respectively. Post-ocular segment 5 recognizable by its appendages, forming the labium [conjoined left and right maxillae]. Labium mostly obscured on holotype, with details not visible ( Figure 12A ). Thorax ( Figure 12A ) bears three pairs of the ambulatory appendages (fore-, mid- and hindlegs) on the pro-, meso-, and metathorax, respectively. Each leg consists of the following elements (proximal to distal): coxa, trochanter, femur, tibia, tarsomeres 1–5. Wings lost ( Figure 12A ). Prothorax horseshoe-shaped in frontal view (with arms of ‘horseshoe’ facing ventrally), narrow. Prothorax bears first thoracic appendages (forelegs). Lengths of foreleg elements as follow (n = 2): femur 1120–1130 µm, tibia 890–1130 µm, tarsomere 1 1120–1280 µm, tarsomere 2 760–790 µm, tarsomere 3 550–650 µm, tarsomere 4 300– 490 µm, and tarsomere 5 410 µm (n = 1). Mesothorax with wings poorly preserved, 2.6 mm long, venation not distinguishable. Lengths of midleg elements as follow (n = 1): femur 1250 µm, tibia 1040 µm. Other elements have not been preserved. Metathorax bears a pair of ambulatory appendages (hindlegs). Lengths of hindleg elements as follow (n = 1): femur 770 µm, tibia 1150 µm, tarsomere 1 700 µm, tarsomere 2 480 µm, tarsomere 3 220 µm, and tarsomere 4 240 µm ( Figure 12A ).

Abdomen (posterior trunk). Comprised of 10 segments (abdominal units), only eight of which are represented as fully developed abdominal segments; units 9 and 10 incorporated into male genitalia (hypopygium). Abdominal units 1–8 roughly rectangular in shape. Only a few setae, visible in the lateral aspect, preserved on the abdomen ( Figure 12 A-D). Abdominal unit 9 together with hypopygium forms male copulatory apparatus ( Figure 12 B-D).

Male genitalia (hypopygium) (male genitalia, appendages of abdominal unit 8 and following units). Unit 9 broadly rounded posteriorly ( Figure 12 B-D). Unit 10 represented by strong, parallel-sided anal point, with two parallel crests running atop of it. Gonocoxite (2) cylindrical, 220 µm long. Inferior volsella (lateral protrusion of gonocoxite) of the gonocoxite relatively long (230 µm) and curved outwards, towards gonostylus. Medium volsella is visible as a short stump at the base of the gonocoxite. Gonocoxite and gonostylus without a flexible articulation, conjoined ( Figure 12 B-D). Gonostylus narrow, curved, with blunt, rounded, distal end, 230 µm long ( Figure 12 B-D).

Remarks. Pupa and adult of the new species are directly associated with each other on the slab with the holotype, where the adult male can be seen eclosing from the pupal exuviae. The adult male of this morphotype is a representative of Chironomidae based on the following combination of characters: overall similar habitus, body slender, antennae with> 6 elongate elements (flagellomeres), second element of antennae (pedicellus) conspicuously larger than the rest of antennal elements, antennae with strong plumage, ocelli absent, head without functional mouthparts, thorax without distinct pre-halter lobe at the base of the true halter, scutum without distinct V-shaped suture, tarsomere 1 on all (preserved) legs is considerably longer than tarsomere 2, tergite of abdominal unit 1 without fringe of strong lateral setae ( Marshall et al., 2017). Within Chironomidae , this morphotype is a representative of the ingroup Chironominae , due to the following combination of characters: gonostylus and gonocoxite are conjoined rigidly, no articulation visible (Wiederholm, 1989). While the specimen lacks wings, and therefore crucial diagnostic characters are missing, we can assume that this midge is a representative of Tanytarsini . This assumption is based on prominent oval superior and medium volsellae (lateral protrusions of gonocoxite), and anal point with prominent spinules arranged in longitudinal rows (Wiederholm, 1989; Figure 12B ). Within the group Tanytarsini , this morphotype is most similar too Rheotanytarsus Thienemann and Bause, 1913 , based on the following combination of characters: maxillary palpal elements are considerably longer than wide, mid- and hindtibiae with double combs, anal point without rows of spines (Langton and Pin- der, 2007).

The new species has a peculiar combination of characters of the male genitalia (hypopygium), such as a gonostylus with a broadly rounded apical end (similar to R. buculicaudus Kyerematen and Saether, 2000 ) and a very short median volsella (similar to R. verticillus Kyerematen, Andersen and Saether, 2000 ) and a relatively parallel-sided anal point (similar to R. pallidus Kyerematen, Andersen and Saether, 2000 ). In general, the combination of the hypopygial characters exhibited by the new species is somewhat reminiscent of R. barrengaryensis Cranston, 1997 , particularly in terms of the parallel-sided anal point, and bluntly rounded gonostylus. In contrast to R. barrengaryensis , however, the new species has an outwardly bending inferior volsella and a very short medium volsella ( Cranston, 1997).

Pupae of the new species are similar to the pupa of R. barrengaryensis in the following aspects: thoracic horn bare with a medial bend; tergites of abdominal units 2–5 with circular anterior patches of spinules; shagreen of the tergite 2 medially divided by a stretch of smooth cuticle; tergite 6 without anterior patch of spinules; anal lobe with more than 20 setae in fringe ( Cranston, 1997; Kyerematen and Saether, 2000).

Numerous species of Rheotanytarsus are known from amber, but differences in amber taphonomy relative to that of the Kishenehn Formation makes them hard to compare to the specimens discussed here (Zakrzewska and Giłka, 2015; Zakrzewska et al., 2020).

DIPTERA Linnaeus, 1758

CERATOPOGONIDAE Newmann, 1834

ALLUAUDOMYIA Kieffer, 1913 cf. ALLUAUDOMYIA

Figures 13 A-B, 14A-F

Material. This morphotype is represented by numerous early and late pupae (pharate adults) (see list in Table 1).

Taxonomic attribution. This morphotype is an ingroup of Ceratopogonidae based on a specific combination of characters: antennae extended posteriorly from the head; maxillary palpus directed posteriorly; thoracic horns without transverse striation (‘undivided’), with two rows of pores; end of the abdomen without articulated terminal paddles, end of abdomen bearing two spine-like protrusions ( Figures 13 A-B, 14A-F). It is difficult to further interpret the morphotype within Ceratopogonidae due to the poor preservation of the thorax and armament of the abdominal units. Nevertheless, a thoracic horn with two parallel rows of pores ( Figure 14 C-D) and a slightly bifid distal end indicates that this morphotype is like Alluaudomyia Kieffer, 1913 (Art Borkent, pers comm.; Borkent, 2014a).

DIPTERA Linnaeus, 1758

CHAOBORIDAE Edwards, 1912

CHAOBORUS Lichtenstein, 1800

CHAOBORUS KISHENEHNICUS Baranov and Haug sp. nov.

Figures 15 A-B, 16A-F, 17A-D, 18A-D, 19A-D, 20A- D, 21A-B, 22A-D zoobank.org/ B03B0A39-FDA2-4AF4-A5E7-EF6C15F9E9FC

Etymology. The name ‘ kishenehnicus ’, meaning of or pertaining to Kishenehn, refers to the geological formation in which the species was found.

Diagnosis (based on adult males). This species is easily distinguished from all other species of Chaoborus based on a specific combination of characters ( Figures 15 A-B, 16A-F, 17A-D, 18A-E, 19A-D, 20A-D, 21A-B, 22A-D): adult male without lobe or paired, strong setae on the inner surface of the apical part of the gonocoxite; pulvilli absent or very minute, and thus invisible in the fossil specimens; legs with at least the proximal part of the femur much lighter than the rest of the leg (Figures 18A-E, 19A-E, 20A-D).

Type material. Holotype: USNM 626053 , adult male; paratypes: USNM 623065 , USNM 717303 ; adult female USNM 624863 ; USNM 595142 (pupa) . Additional material consisting of 140 adult or pharate males and pupae and seven females are listed in Appendix Table 1.

Pupa. Habitus. Medium-sized, with flattened, comma-shaped body (in lateral aspect). Body length 2.6–3.9 mm (n = 28); abdomen length 1.9– 3.1 mm (n = 28); length of thorax 0.8–1.3 mm (n = 28), body differentiated into presumably 20 segments, ocular segment plus 19 post-ocular segments ( Figures 15 A-B, 16A-F, 17A-D); anterior part of the body composed of head and thorax, visible as a single globose structure; thorax bears wings and ambulatory appendages (legs) ( Figures 15 AB, 16A-F, 17-D); ocular segment and post-ocular segments 1–5 (presumably) forming a distinct capsule (head capsule); mouthparts located ventrally and short, ending before attachment of the first ambulatory appendages (forelegs) ( Figures 15 A-B, 16A-F, 17A-D). Ocular segment recognizable by its appendage derivative, clypeo-labral complex, and a pair of large compound eyes. Labrum and clypeus are present, but their shape is obscured by deformation of the specimens, since most of the pupae are preserved in lateral aspect ( Figures 15 A-B, 16A-F, 17A-D). Post-ocular segment 1 recognizable by its appendages, antennae (antennulae). Antennae curved around the head, ending beneath the head, at about mid-length to 0.8 of the length of the wings. Antennae attached to the massive, rounded pedicellus (antennal element 2) ( Figure 16 A-B). Post-ocular segment 2 (intercalary segment) without externally recognizable structures. Post-ocular segment 3 bears no recognizable appendages (mandibles) ( Figure 16 A-B). Post-ocular segment 4 recognizable by its appendage, maxilla [maxillula]. Maxilla recognizable by maxillary palpus. Palpi are poorly preserved on the available specimens. Post-ocular segment 5 is recognizable by its appendages, forming the labium [conjoined left and right maxillae]. Labium mostly obscured on all specimens, with no details visible ( Figure 16 A-B). Thorax bears three pairs of ambulatory appendages (fore-, mid- and hindlegs) on the pro-, meso-, and metathorax, respectively. Thoracic segments forming a single semi-globose structure, closely enveloping the head of the pupa. Ambulatory appendages of the thorax folded around and under the wings ( Figure 15 A-B). Prothorax bears thoracic horns (modified first spiracle). Thoracic horns spindle-shaped, widest at mid-length, tapering apically into a short tube (300–650 µm, n = 13) ( Figures 16 A-B, 17A-B). Thoracic horn with a honeycomb-shaped surface texture and small apical opening ( Figures 16 A-B, 17A-B). Prothorax bears first thoracic appendages (forelegs). Forelegs running posteriorly, upwards anteriorly to the upper edge of the eye and then downward to the apical edge of the wing ( Figure 17B ). Mesothorax bears a pair of wings and a pair of ambulatory appendages (midlegs). Midlegs situated medially to foreleg. Midlegs are also looping around the wing, distal part of the loop lying on the abdomen, beyond the distal end of the wing. Distal parts of the midlegs loop again under the wing ( Figures 15 A-B, 16A-F). Metathorax bears a pair of ambulatory appendages (hindlegs); halteres not visible in the fossils. Hindlegs almost entirely hidden behind the coxae of the fore- and midlegs and wings ( Figure 17 A-B).

Abdomen (posterior trunk). Abdominal units 1–8 with setae of the pharate adult tergites visible through the pupal cuticle. Setae radiating from the abdominal midline, outwards, forming pointed FIGURE 18. Chaoborus kishenehnicus sp. nov. ( Chaoboridae ). Adult males. Holotype: USNM 626053 (A–B) and paratype USNM 623065 (C–E). A, C, Habitus, unmarked. B, Schematic drawing of the male genitalia (hypopygium). D, Wing. E, Wing, schematic drawing. Abbreviations: Cu1, cubital vein one; gc, gonocoxite ( II); gs, gonostylus; M 1 -M 3+4, median veins one through three+four; m-cu, crossvein median-cubital; R 1 - R 4+5, radial veins one through four+five; Sc, subcostal vein; a9, abdominal unit IX.

ends, at the dorso-posterior part of each abdominal unit ( Figures 15 A-B, 16D-E, 17C-D). Trunk end (abdominal unit 9 plus remnants of abdominal unit 10) bears genitalia and remnants of two anal lobes (paddles). Anal lobes of all studied specimens consist only of a single, medial rib, membranous parts of the terminal paddles and rest of the ribs seem to have been lost. Genitalia (appendages of abdominal unit 8) present as well as a tight cluster of gonocoxal setae ( Figures 16 D-E, 17C-D).

Adult male. Medium-sized fly with midge-shaped body, long legs, and long abdomen ending with prominent external genitalia. Wings are relatively well preserved in Holotype. USNM 626053 and paratype USNM 623065 males (Figures 18A-E, 19A-D). Wings with poorer preservation are relatively frequent in the available material. The specimens are preserved mostly in dorsolateral aspect, but some midges are preserved in mostly lateral aspect (Figures 18A-E, 19A-D). This orientation gave us the opportunity to examine different characters. Ocular segment and post-ocular segments 1–5 (presumably) forming distinct capsule (Figures 18A, C, 19A). Ocular segment recognizable by a pair of large compound eyes. Eyes without micro- or macrotrichia, with long, wedge-shaped dorso-medial extension (six ommatidia long and four ommatidia across). Eyes well preserved with individual ommatidia visible (Figure 18A, C), Frons (frontal sclerite) of post-ocular segment one impossible to examine as it is embedded in the matrix. Labrum rectangular, longer than wide, as evident from observation of specimens USNM 622981 and USNM 624754 (labrum 176–276 µm long). Post-ocular segment 1 recognizable by its appendages, antennae (antennulae). Each antenna with two proximal elements (scape and pedicellus) and 13 additional elements (flagellomeres). Pedicellus donut-shaped (squashed sphere with invagination on the top), 130–240 µm in diameter (n = 5). Flagellomeres widest at mid-length, tapering apically (Figures 18A, C, 19A). Each flagellomere with a whorl of setae at its ‘equator’ (Figures 18A, C, 19A). Each whorl contains at least 12 setae. Lengths of individual elements of the antenna as follow (n = 3): first flagellomere 35–88 µm, second 26–68 µm, third 27–74 µm, fourth 26–70 µm, fifth 39–65 µm, sixth 29–63 µm, seventh 43–77 µm, eighth 47–77 µm, ninth 40–66 µm, tenth 45–61 µm, eleventh 56–91 µm, twelfth 57 µm (n = 1), two specimens ( USNM 626083, USNM 624754) with flagellomere 13 preserved, but the border between it and flagellomere 12 is unclear, length of two flagellomeres together 192–317 µm (Figures 18A, C, 19A). Post-ocular segment 2 (intercalary segment) without externally recognizable structures. Post-ocular segment 3 bears no recognizable appendages (mandibles) (Figures 18A, C, 19A). Post-ocular segment 4 recognizable by its appendage, maxilla [maxillula]. Maxilla recognizable by maxillary palpi. Maxillary palpus consists of five elements (palpomeres), with palpomeres 1 and 2 hidden behind the labrum and clypeus; lengths of elements 3 through 5 (n = 2): 123–146 µm, 113– 167 µm and 116–125 µm, respectively. Post-ocular segment 5 recognizable by its appendages, forming the labium [conjoined left and right maxillae]. Labium mostly obscured on all specimens, no details visible (Figures 18A, C, 19A). Thorax (Figures 18A, C, 19A) bears three pairs of the ambulatory appendages (fore-, mid-, and hindlegs) on the pro-, meso-, and metathorax, respectively. Each leg consists of the following elements (proximal to distal): coxa, trochanter, femur, tibia, tarsomeres 1–5. Prothorax horseshoe-shaped in lateral view (with arms of ‘horseshoe’ facing ventrally), narrow. Prothorax bears the first pair of thoracic appendages (forelegs). Lengths of foreleg elements as follow: femur 550–860 µm (n = 3), tibia 930–1240 µm (n = 4), tarsomere 300–440 µm (n = 3), tarsomere 2 175–345 µm (n = 3), tarsomere 3 140–230 µm (n = 3), tarsomere 4 280 µm (n = 1), tarsomere 5 370 µm (n = 1) (Figures 18A, C, 19A). Mesothorax of several specimens have wings relatively well preserved, but complete venation was only preserved in specimen USNM 623065. Even for this specimen, it is impossible to trace where exactly the vein reaches the edge of the wing (Figure 18D, E). Wing length (tip to arculus) 1.7–2.5 mm (n = 13). Radial 1 vein is long, terminating closer to radial 2 vein than to the subcostal vein (Figure 18D, E). R 4 +5 ending at the level with M 1 and M 2. Cu 1 is slightly bent at the distal third. Crossveins barely visible.

Lengths of midleg elements as follows: femur 740–1280 µm (n = 3), tibia 730–1220 µm (n = 3), tarsomere 1 400–460 µm (n = 2), tarsomere 2 350 µm (n = 1). Other elements have not been preserved in any of the available specimens (Figures 18A, C, 19A). Metathorax bears a pair of altered wings (halteres) and a pair of ambulatory appendages (hindlegs). Lengths of hindleg elements as follow: femur 550 – 860 µm (n = 3), tibia 930–1240 µm (n = 4), tarsomere 1 300–440 µm (n = 3), tarsomere 2 175–345 µm (n = 3), tarsomere 3 140– 230 µm (n = 3), tarsomere 4 280 µm (n = 1), tarsomere 5 370 µm (n = 1). Posterior trunk consisted of 10 units, only eight of which are represented as fully developed abdominal segments; units 9 and 10 incorporated into hypopygium. Abdominal units 1–8 roughly rectangular in shape. No setae preserved on a specimen (Figures 18B, 19B-D). Abdominal unit 9 together with hypopygial structures, forming a male copulatory apparatus.

Male genitalia (hypopygium) (appendages of abdominal unit 9 and following units). Unit 9 broadly rounded posteriorly, trapezoidal in shape (Figures 18B, 19B-D). Gonocoxite (2) cylindrical 320–450 µm long. Phalapodemae can be seen impressed on unit 9 (Figures 18B, 19B-D). Gonocoxite and gonostylus with a mobile articulation (Figures 18B, 19B-D). No penis valve preserved. Gonostylus narrow, parallel-sided, with pointed, narrow, distal end, 230–315 µm long (Figures 18B, 19B-D).

Adult female (probable association). Medium-sized fly, with midge-shaped body, long legs and long abdomen ending with a prominent cercus. Body length 2.5–3.5 mm (n = 5). Wings with poorer preservation are relatively frequent in the available material. The specimens are preserved mostly in dorsolateral aspect, but some midges are preserved in mostly lateral aspect ( Figure 20 A-D).

Ocular segment and post-ocular segments 1– 5 (presumably) forming distinct head capsule ( Figure 20 A-D). Ocular segment recognizable by pair of large compound eyes. Eyes without micro- or macrotrichia, with long, wedge-shaped dorsomedial extension (6 ommatidia long and 4 ommatidia across). Eyes well preserved with individual ommatidia structure visible ( Figure 20A , C-D). Post-ocular segment 1 recognizable by its appendages, antennae [antennulae]. Each antenna with one proximal element (pedicellus) and 11 additional elements (flagellomeres) still visible. Pedicellus around 50–70 µm in diameter (n = 2), while flagellomeres are widest at mid-length, tapering apically. Lengths of individual elements of the antenna are as follow (n = 4): first flagellomere 35–70 µm, second 30–55 µm, third 45–70 µm, fourth 50–65 µm, fifth 40–50 µm, sixth 45–60 µm, seventh 40–65 µm, eighth 50–65 µm, ninth 45–86 µm, tenth 87– 190 µm, eleventh 115–125 µm (n = 2). Labrum rectangular, longer than wide, 220–240 µm long (n = 2). Post-ocular segment 2 (intercalary segment) without externally recognizable structures. Post-ocular segment 3 bears no recognizable appendages (mandibles) ( Figure 20A ). Post-ocular segment 4 recognizable by its appendage, maxilla [maxillula]. Maxilla recognizable by maxillary palpi. Maxillary palpus consists of five elements (palpomeres), with palpomeres 1 and 2 hidden behind the labrum and clypeus; lengths of elements three through five (n = 1): 145 µm, 160 µm, and 160 µm, respectively. Post-ocular segment 5 recognizable by its appendages, forming the labium [conjoined left and right maxillae]. Labium mostly obscured on all specimens, no details visible.

Thorax ( Figure 20A , C-D) bears three pairs of the ambulatory appendages (fore-, mid-, and hindlegs) on the pro-, meso-, and metathorax, respectively. Each leg consists of the following elements (proximal to distal): coxa, trochanter, femur, tibia, tarsomeres 1–5. None of the females have well-preserved legs fit for proper measurements. Prothorax horseshoe-shaped (with arms of ‘horseshoe’ facing ventrally), narrow, bears first pair of thoracic appendages (forelegs). Mesothorax of several specimens have wings relatively well preserved but complete venation is not visible on any of them. Wing length (tip to arculus) 2.0– 2.7 mm (n = 7). Metathorax bears a pair of altered wings (halteres, both well visible) and a pair of ambulatory appendages (hindlegs).

Posterior trunk consists of 10 segments (abdominal units), only nine of which are represented as fully developed abdominal segments. Abdominal units 1–8 roughly rectangular in shape ( Figure 20A ). Abdominal units 9 and 10 are reduced, forming the copulatory apparatus of the female. Paired cerci attached to the end of abdomen, but they are poorly or not at all preserved in most of the available specimens. Most complete cerci can be seen in specimen USNM 623071. A triple spermatheca, situated within abdominal unit 8, well visible in many specimens through the outer cuticle due to its strong sclerotization ( Figures 20B , 21 A-B).

Egg clutches (probable association). We have found a number of the fossilized structures resembling euarthropodan eggs ( Figure 22 A-D). Large cclusters of such eggs are arranged in a spiral pattern, characteristic for the eggs of extant representatives of Chaoborus (Strickman, 1980) . Therefore, we hypothesize that these fossils might represent egg clutches of C. kishenehnicus sp. nov.

Remarks. We interpret this new species as an ingroup of Chaoboridae based on a specific combination of characters. Pupa: end of abdomen with a pair of large, articulated paddles, supported by a sclerotized area of cuticle, called the medial rib; mouthparts short, not reaching beyond coxae of anterior legs; bundles of the diagonally oriented setae visible on the tergites of the abdominal units ( Borkent, 2012). Adult male: with radial 1 vein long, terminating closer to radial 2 vein, longer than to the subcostal vein. Pupae associated with the adults by the genitalia of the pharate specimens visible via the pupal cuticle ( Figures 15-17) and by the direct association of the eclosing male with the pupa ( Figure 21A ). Pupae associated with the adults are mostly well preserved, but are always missing some crucial characters, most notably the mesal and lateral longitudinal ribs of the terminal paddle. Therefore, pupae cannot be used for a differential diagnosis. Pupae can be associated with adult males by the virtue of genitalia of pharate males' genitalia. Adult females are poorly preserved, but wing venation similar to that of males, can indicate that they are also representatives of C. kishenehnicus sp. nov. ( Figure 21B ).

Within Chaoboridae , the new species is an ingroup of Chaoborus , based on a specific combination of characters (listed separately for each life stage). Pupa: with spindle-shaped thoracic horns, more than three times longer than wide, terminal paddles with prominent median rib almost reaching the edge of the lobe. It is notable that pupae have their terminal paddles only partially preserved, with most of the ribs and membrane absent from all available specimens. This type of preservation is apparently common in pupae of the fossil pupae of Chaoborus , as it is also the common type of anal paddle preservation in the Oligocene Chaoborus tertiarius von Heyden, 1862 ( Borkent, 1978; 1A-C, 2A-C). Chaoborus kishenehnicus is the second formal record of a fossil species of Chaoboridae in the United States, after the record of Chaoborus pupae from the Middle Eocene Tallahatta Formation ( Johnston and Borkent, 1998; Borkent, 2014b).

This new species is highly reminiscent of many modern representatives of Chaoborus ( Cook, 1956) . The lack of crucial characters, such as well-preserved pulvilli or coloration, does not allow the identification of the new species as a representative of any of the ingroups of Chaoborus (‘subgenera’) ( Cook, 1956; Saether, 1970).

DIPTERA Linnaeus, 1758

CULICIDAE Meigen, 1818

CULICINAE Meigen, 1818

CULICINI Meigen, 1818

CULEX Linnaeus, 1758

Figures

FIGURE 10. Representatives of Chironomidae cf. Tanytarsus, specimen USNM 722523. Adult male. A, Habitus of the adult male and remnants of a water boatmen nymph (Corixidae). B, Hindtibial combs. C, Male genitalia (hypopygium), unmarked. D, Male genitalia (hypopygium), marked. E, Male genitalia (hypopygium), schematic drawing. Abbreviations: a8–a9, abdominal units (segments) eight and nine; an, antenna; ap, anal point (abdominal unit X remnants); gs, gonostylus; sv, superior volsella (lateral protrusion of gonocoxite).

FIGURE 11. Rheotanytarsus lacustris sp. nov. (Chironomidae). Pupa. Paratypes USNM 722460 (A–B) and USNM 623669 (C–E). A, Habitus, unmarked. B, Habitus, marked. C, Habitus, unmarked. D, Abdominal tergite III with armament of shagreen. E, Anal lobes and posterolateral comb of abdominal unit 8. Abbreviations: a2–a7, abdominal units (segments) two to seven; al, terminal lobes; tc, thorax; th, thoracic horn (respiratory organ); wg, wing.

FIGURE 12. Rheotanytarsus lacustris sp. nov. (Chironomidae). Adult male and pupa. Holotype USNM 717577 (A–E). A, Habitus, unmarked. B, Schematic drawing of male genitalia (hypopygium). C, Male genitalia (hypopygium), unmarked. D, Male genitalia (hypopygium), marked. E, Abdominal tergite II with armament of shagreen. Abbreviations: a8–a9, abdominal units (segments) eight and nine; ap, anal point (remnants of tergite X); gc, gonocoxite (II); gs, gonostylus; iv, inferior volsella (lateral protrusion of gonocoxite); mv, median volsella (lateral protrusion of gonocoxite); tb, tergal bands; ts, shagreen of tergites.

FIGURE 13. Representatives of Ceratopogonidae cf. Alluaudomyia. Pupa. USNM 623317. A, Habitus, unmarked. B, Habitus, marked. Abbreviations: a2–a8, abdominal units (segments) two to eight; tc, thorax; th, thoracic horn (respiratory organ); wg, wing.

FIGURE 14. Representatives of Ceratopogonidae cf. Alluaudomyia. Pupa. USNM 623317 (A–B), USNM 623326 (C), USNM 624879 (D–F). A, Thorax, unmarked. B, Thorax, marked. C, Thoracic horns. D, Thoracic horns. E, End of abdomen. F, Male genitalia (hypopygium). Abbreviations: an, antenna; ey, compound eyes; p1, forelegs; p2, midlegs; p3, hindlegs; th, thoracic horn (respiratory organ).

FIGURE 16. Chaoborus kishenehnicus sp. nov. (Chaoboridae). Pupa. USNM 623080(A, D), USNM 624863 (B, E), USNM 623356 (C, F). A–C, Habitus, unmarked. D– E, Genitals. F, Thoracic horn (respiratory organs).

FIGURE 17. Chaoborus kishenehnicus sp. nov. (Chaoboridae). Pupa. USNM 595142. A, Thorax, unmarked. B, Thorax, marked. C, Male genitalia (hypopygium) unmarked. D, Male genitalia (hypopygium), marked. Abbreviations: an, antenna; ey, compound eyes; fc, forecoxa; gc, gonocoxite; gs, genitals; mc, midcoxa; mr, medial rib of the anal paddle; p1, forelegs; p2, midlegs; p3, hindlegs; pd, pedicellus; sc, scutum; su, scutellum; th, thoracic horn (respiratory organ); wg, wing.

FIGURE 20. Chaoborus kishenehnicus sp. nov. (Chaoboridae). Probably associated females. USNM 624863 (A, B), USNM 623071 (C), USNM 717284 (D). A, C, D, Habitus. B, Spermathecae.

FIGURE 21. Chaoborus kishenehnicus sp. nov. (Chaoboridae). A, Adult male eclosing from the pupa (USNM622875). B, Male and probably associated female side-by-side, with additional female present (USNM623038).

FIGURE 22. Chaoborus kishenehnicus sp. nov. Probably associated egg masses and individual eggs. A, USNM 623795, egg mass. B, USNM 624281, egg. C, USNM 624174, eggs. D, USNM 624230, eggs.