Non-technical Summary

We describe the first fossil antlion (lacewing order Neuroptera, family Myrmeleontidae) from the Fossil Butte Member of the early Eocene Green River Formation of Wyoming, USA, and name the new genus and species Protopalpares lindgrenae based on it. It is the first reported fossil of the modern antlion subfamily Palparinae. Analysis of its wing venation indicates that Palparinae is closely related to the Cretaceous lacewing family Palaeonleontidae.

Systematic paleontology

Order Neuroptera Linnaeus, Reference Linnaeus1758

Family Myrmeleontidae Latreille, Reference Latreille1802

Subfamily Palparinae Banks, Reference Banks1911

Genus Protopalpares new genus

Remarks

All wings most likely belong to the same specimen, although both forewings and both hind wings are preserved with their apex to the left; we assume that one of each has been folded over (Figs. 1, 2).

Figure 1.

Protopalpares lindgrenae n. gen. n. sp., holotype FOBU 13564 as preserved before preparation. Scale bar = 10 mm.

Figure 2.

Protopalpares lindgrenae n. gen. n. sp., holotype FOBU 13564 after preparation. (1) Both positioned as right wings. (2) Both positioned as left wings. Scale bar = 10 mm.

Figure 2. Long description

Panel 1, located at the top, shows a fossilized wing oriented as a right wing. The wing is elongated and dark brown with a complex network of venation. The proximal end is narrower and more fragmented, while the distal end is rounded and broader. The wing surface is mottled with lighter patches against the dark fossilized tissue.

Panel 2, located at the bottom, shows the fossilized wings oriented as left wings. This specimen appears more fragmented than the first, with two distinct sections of wing material visible. The venation is still apparent, showing a grid-like pattern of longitudinal and cross veins.

A black horizontal scale bar is positioned to the right of the panels, representing 10 mm. The background for both panels is a light gray, textured rock matrix with visible sediment grains.

Protopalpares lindgrenae new genus new species

Figures 1–4

Figure 3.

Wing venation of Protopalpares lindgrenae n. gen. n. sp., holotype FOBU 13564 (all shown in standard right view). (1) Conditionally right forewing. (2) Conditionally right hind wing. (3) Conditionally left forewing. (4) Conditionally left hind wing. A1–A3, first to third anal veins; CuA, anterior cubitus; CuP, posterior cubitus; MA, anterior media; MP, posterior media; RA, anterior radius; RP, posterior radius; Sc, subcosta. Scale bar = 10 mm.

Figure 3. Long description

The four panels show the venation of the right forewing (1), right hind wing (2), left forewing (3), and left hind wing (4). A 10 mm scale bar is provided below panel 1 and panel 4.

* Panel 1 (Right Forewing): Shows a complex network of veins. At the proximal base, labels A 1, A 2, and A 3 identify the anal veins. Moving distally along the posterior edge are C u P, C u A 2, and M P plus C u A 1. The central area contains M A and R P, while the anterior margin shows the C u A and R A regions.

* Panel 2 (Right Hind Wing): Displays a more elongated shape. The anterior margin is marked by S c. The posterior margin includes A 1, C u P, C u A, and M P. The distal interior is dominated by the R P vein network.

* Panel 3 (Left Forewing): Features a dense, reticulated pattern of cross-veins. Labels along the posterior and distal margins include C u P, C u A 2, M P plus C u A 1, M A, and R P. The anterior distal corner is labeled S c plus R A.

* Panel 4 (Left Hind Wing): A partial view of the distal wing section. The anterior margin is labeled S c plus R A, and the distal branching network is labeled R P.

Figure 4.

Preserved venation of Protopalpares lindgrenae n. gen. n. sp. based on all wings. (1) Forewing. (2) Hind wing. Thick arrows show the curvatures of the forewing RP1 (proximalmost branch of RP) and MP+CuA1. 1A–A3, first to third anal veins; M, media; other abbreviations as in Figure 3. Scale bar = 10 mm.

Figure 4. Long description

The drawing consists of two panels labeled 1 and 2. A 10 mm scale bar is located at the bottom left.

Panel 1 shows the forewing. At the proximal base on the left, labels include A 1, C u P, 3 A, 2 A, 1 A, and M. Moving distally toward the center, labels indicate C u A and C u A 2. The anterior margin at the top right is labeled S c plus R A. The distal area contains the R P network, with a specific branch labeled R P 1. Two thick black arrows in the center-right point to the downward curvatures of R P 1 and M P plus C u A 1. The posterior margin is labeled M A and M P plus C u A 1.

Panel 2 shows the hind wing. At the proximal base on the left, labels include A 1 and C u P. Moving toward the center, labels indicate C u A, M A, and M P. The anterior margin at the top right is labeled S c plus R A. The distal region is dominated by the R P branching network. The venation in the hind wing appears less dense than in the forewing.

Subfamily and tribe affinities of the new genus

The venation of Protopalpares is generally similar to that of Palparinae. In Myrmeleontidae, the long and slightly sinuous CuA in the hind wing as found in this genus is present only in five genera of three tribes of Palparinae: Dimarini (Echthromyrmex, Dimares, and Millerleon), Palparidiini (Palparidius), and Pseudimarini (Pseudimares) (see Péringuey, Reference Péringuey1910, pl. 8, fig. 5; Kimmins, Reference Kimmins1933, pl. 6; Markl, Reference Markl1954, fig. 62; Stange, Reference Stange1989, figs. 6–10; 2010, fig. 1; Khrivokhatsky, 1998, fig. 6; Aspöck and Aspöck, Reference Aspöck and Aspöck2009, fig. 8; Tauber et al., Reference Tauber, Simmons and Tauber2019, fig. 89).

A similarly long, sinuous CuA in the hind wing is also characteristic of some Ascalaphinae (i.e., Stilbopterygini, Albardiini, and Ululodini, including one fossil species from the middle Eocene Kishenehn Formation, Montana, USA: Jepson and Makarkin, Reference Jepson and Makarkin2023), and all Palaeoleontidae (see e.g., Ponomarenko, Reference Ponomarenko1992, fig. 5; Heads et al., Reference Heads, Martill and Loveridge2005, fig. 1; Shi et al., Reference Shi, Béthoux, Shih and Ren2012, figs. 2E, F). However, in all ascalaphines, RP originates far from the wing base, there is a short, dark pterostigma (with all pterostigmal veinlets simple), and Sc+RA curves immediately after the fusion of Sc and RA and runs in a straight line. In Protopalpares, these characters are different. In all Palaeoleontidae, RP originates very close to the wing base and presectorial crossveins are absent.

This form of hind wing CuA is probably plesimorphic. We did, however, find a character state of Protopalpares venation that we consider apomorphic. The forewing posterior branch of RP1 and the stem of MP+CuA1 curve toward each other and are connected by two aligned crossveins where they are closest (Fig. 4). This character state is similar to that in most extant Palparinae of three tribes: Palparidini (e.g., Palparidius capicola Péringuey, Reference Péringuey1910); Palparini (e.g., Palpares hispanus Koçak, Reference Koçak1976; Pamares damarus Mansell, Reference Mansell1990); and Dimarini—e.g., Dimares elegans (Perty, Reference Perty1833 [1830–1834]), Echthromyrmex orientalis McLachlan, Reference McLachlan1873—(Mansell, Reference Mansell1990, fig. 43; Krivokhatsky, Reference Krivokhatsky1998, fig. 6; Stange, Reference Stange2010, fig. 1; Khabiev and Krivokhatsky, Reference Khabiev and Krivokhatsky2014, fig. 6; Tauber et al., Reference Tauber, Simmons and Tauber2019, fig. 89). There are no such curvatures in other Myrmeleontidae s.l. (including Cretaceous taxa), and we consider this to be a synapomorphy of Palparinae.

Thus, it is certain that Protopalpares belongs to Palparinae, but what tribe it belongs to remains unresolved due to the incomplete preservation of the specimen. The new genus definitely does not belong to Palparini, in which the hind wing CuA is strongly curved at its junction with the posterior branch of M (e.g., Mansell, Reference Mansell1990, fig. 43; Reference Mansell1992, figs. 1–5; 2018, figs. 2, 3; Krivokhatsky, Reference Krivokhatsky1998, fig. 4; Michel, Reference Michel1999, figs. 13, 14; Hassan et al., Reference Hassan, Akhtar, Zheng and Liu2023, figs. 1, 2, 6, 9, 12, 13).

All three tribes with a long and slightly sinuous CuA in the hind wing (Dimarini, Palparidiini, and Pseudimarini) have rather similar venation. However, the configuration of the forewing CuA (see below) and the presence of numerous crossveins connecting crossveins in the MP+CuA1 space of Protopalpares indicate that this genus might not belong to any of these tribes.

Palparinae and Palaeonleontidae

The myrmeleontid subfamily Palparinae is clearly similar to Palaeonleontidae by wing shape, size, and venation. The wings of all other Cretaceous myrmeleontoids have less dense venation (sometimes much less). Nine genera (15 species) of Palaeonleontidae are known from the Barremian/Aptian of Baissa (Russia: Transbaikalia) and Yixian Formation (China); the late Aptian Crato Formation (Brazil); the Albian/Cenomanian of Redmond (Canada); the Turonian of the Ora Formation (Israel); and the Coniacian of Antibes (Russia: southern Siberia) (Rice, Reference Rice1969; Makarkin, Reference Makarkin and Akimov1990; Martins-Neto, Reference Martins-Neto1992, Reference Martins-Neto1997, Reference Martins-Neto1998; Ponomarenko, Reference Ponomarenko1992; Dobruskina et al., Reference Dobruskina, Ponomarenko and Rasnitsyn1997; Martins-Neto and Vulcano, Reference Martins-Neto and Vulcano1997; Heads et al., Reference Heads, Martill and Loveridge2005; Menon and Makarkin, Reference Menon and Makarkin2008; Martins-Neto and Rodrigues, Reference Martins-Neto and Rodrigues2010; Millet and Nel, Reference Millet and Nel2010; Shi et al., Reference Shi, Béthoux, Shih and Ren2012; Myskowiak and Nel, Reference Myskowiak and Nel2016).

Palaeonleontidae is usually treated as a family (e.g., Dobruskina et al., Reference Dobruskina, Ponomarenko and Rasnitsyn1997; Heads et al., Reference Heads, Martill and Loveridge2005; Menon and Makarkin, Reference Menon and Makarkin2008; Michel et al., Reference Michel, Clamens, Béthoux, Kergoat and Condamine2017; Lu et al., Reference Lu, Wang and Liu2021, Reference Lu, Xu and Liu2022; Bueno et al., 2025a, b) and rarely as a primitive subfamily of Myrmeleontidae (e.g., Martins-Neto, Reference Martins-Neto1997; Stange, Reference Stange2004; Ren and Engel, Reference Ren and Engel2008; Machado et al., Reference Machado, Gillung, Winterton, Garzón‐Orduña, Lemmon, Lemmon and Oswald2019). The venation of its oldest (Early Cretaceous) genera (e.g., Baisopardus Ponomarenko, Reference Ponomarenko1992; Parapalaeoleon Menon and Makarkin, Reference Menon and Makarkin2008; Guyiling Shi et al., Reference Shi, Béthoux, Shih and Ren2012) are more similar to Palparinae than to the youngest (Late Cretaceous) genera (Metahemerobius Makarkin, Reference Makarkin and Akimov1990; Samsonileon Ponomarenko in Dobruskina et al., Reference Dobruskina, Ponomarenko and Rasnitsyn1997), which are clearly more derived (see Makarkin, Reference Makarkin and Akimov1990, fig. 5; Dobruskina et al., Reference Dobruskina, Ponomarenko and Rasnitsyn1997, fig. 4).

The genus Guyiling was described as Myrmeleontiformia insertae sedis (Shi et al., Reference Shi, Béthoux, Shih and Ren2012) but was later classified as belonging to the Palaeonlentidae (e.g., Myskowiak and Nel, Reference Myskowiak and Nel2016; Lu et al., Reference Lu, Wang and Liu2021, Reference Lu, Xu and Liu2022). We agree with this assignment, because the only species of this genus has venation similar to that of other members of the family, especially to Parapalaeoleon, although its antennae are slightly dilated distally.

In addition to the general similarity of venation in these groups, A1 and CuP are separated along their entire length in both Palaeonleontidae and most Palparinae (except Dimarini) (a plesiomorphic character state). In other extant Myrmeleontidae, CuP is short and ends in a fusion with A1; all Cretaceous taxa of antlions also have this plesiomorphic state.

Within the Palparinae, the venation of Protopalpares is most similar to that of the Early Cretaceous genera of Palaeonleontidae (cf. Figs. 4, 5). First, the forewing configuration of CuA2 as found in the new genus is similar to that of most Palaeonleontidae, being clearly pectinate (see e.g., Menon and Makarkin, Reference Menon and Makarkin2008, fig. 4B; Martins-Neto and Rodrigues, Reference Martins-Neto and Rodrigues2010, fig. 3A; Shi et al., Reference Shi, Béthoux, Shih and Ren2012, fig. 2C, D). In other Palparinae, the forewing CuA2 is never so long and clearly pectinate.

Figure 5.

Well-preserved wings of the Early Cretaceous Palaeoleontidae. (1) Forewing of Parapalaeoleon magnus Menon and Makarkin, Reference Menon and Makarkin2008 (holotype SMNS 66000/268) from the Crato Formation, Brazil (redrawn from Menon and Makarkin, Reference Menon and Makarkin2008, with insufficient changes based on photographs). (2) Hind wing of Baisopardus banksianus Ponomarenko, Reference Ponomarenko1992 (holotype PIN 1989/51) from Baissa, Transbaikalian Russia (original drawing based on photographs by A. Khramov). bf, anterior Banksian flexion fold/line; mf, medial (radiomedial) flexion fold/line; other abbreviations as in Figure 3. Scale bars = 10 mm.

Figure 5. Long description

The two-panel illustration displays detailed wing venation.

Panel 1 shows the forewing of Parapalaeoleon magnus. At the proximal base on the left, labels A 3, A 2, and A 1 mark the anal veins. Moving along the posterior margin toward the right, labels include C u P, C u A 2, and M P plus C u A 1. The distal tip is labeled R P and S c plus R A. In the central-proximal region, small arrows point to m f (medial flexion line) and b f (anterior Banksian flexion line). The wing is characterized by a dense network of cross-veins forming a mesh-like pattern. A 10 mm scale bar is located at the bottom right.

Panel 2 shows the hind wing of Baisopardus banksianus. Similar to the first panel, the proximal base on the left is labeled with A 2, A 1, and C u P. Along the posterior margin, labels move from C u A to M P, M A, and R P at the distal end. The anterior margin terminates at S c plus R A. A specific vein in the upper-middle section is labeled R P 1. The venation in this wing appears slightly more elongated than in the forewing. A 10 mm scale bar is positioned at the bottom left.

However, it is unclear yet if this condition is plesiomorphic or apomorphic in Myrmeleontoidea. In all Cretaceous genera of Araripeneuridae (including the oldest), CuA2 is deeply bifurcate and rarely shallowly forked (see e.g., Makarkin et al., Reference Makarkin, Wedmann and Heads2018, figs. 2, 4, 5; Bueno et al., Reference Bueno, Machado, Almeida-Silva and Ribeiro2026, fig. 1). But in a few Cretaceous genera of unclear subfamily position, CuA2 is clearly pectinate, e.g., Blittersdorffia Martins-Neto and Vulcano, Reference Martins-Neto and Vulcano1989 from the late Aptian Crato Formation, and Babinoleon Lu et al., Reference Lu, Wang, Zhuo and Liu2026 from mid-Cretacious Kachin amber (Bueno et al., Reference Bueno, Machado, Martins and Ribeiro2025b, figs. 14, 15; Lu et al., Reference Lu, Wang, Zhuo and Liu2026, fig. 2). In some extant and Cenozoic Ascalaphinae (especially Stilbopterygini) and other Myrmeleontidae (including Epignopholeon sophiae from the Green River Formation), CuA2 is also clearly pectinate (see e.g., Kimmins, Reference Kimmins1940, fig. 3; Makarkin, Reference Makarkin2017, figs. 5A, B; designated as CuA1).

Secondly, RP originates more proximally in Protopalpares than in other Palparinae, with only one presectrial crossvein (between R and M proximad the origin of RP).

In general, the venation of Palaeonleontidae differs from that of Myrmeleontidae s. str. (without the vast majority of Cretaceous genera) only by RP originating very close to the wing base, leaving no room for presectrial crossveins; by the absence of a long hypostigmal cell (between RA and RP below the pterostigmal area); and the presence of a medial flexion fold/line.

All of these character states are plesiomorphic. The origin of RP very close to the wing base is never found in other Myrmeleontidae s.l. (i.e., including all Cretaceous taxa), but is shared with Nymphidae, the only group of Myrmeleontoidea known in the Jurassic. Also, in the Myrmeleontoidea, the medial flexion fold/line occurs only in Palaeonleontidae (see Fig. 5.1; Menon and Makarkin, Reference Menon and Makarkin2008); it is not detected even in Nymphidae. But in other Neuroptera, this is detected in the basal Jurassic Kalligrammatidae and Parakseneuridae, and in the Hemerobiidae (Yang et al., Reference Yang, Makarkin, Winterton, Khramov and Ren2012, fig. 13; Makarkin and Perkovsky, Reference Makarkin and Perkovsky2020, fig. 2A).

All extant and Cenozoic taxa of Myrmeleontidae (including the new genus) have presectrial crossveins. The absence of these crossveins is characteristic of the vast majority of Cretaceous taxa, including all Palaeonleontidae and most Araripeneuridae.

A long hypostigmatic cell is characteristic of Myrmeleontidae s.l., i.e., including Araripeneurinae (Stange, Reference Stange2004), but also Nymphidae, some Nemopteridae, and Mesochrysopidae. Its absence occurs not only in Palaeonleontidae, but also in Ascalaphinae, most Mesochrysopidae, and some Nemopteridae. We assume that this characteristic is of little significance.

The anterior Banksian flexion fold/line is absent in Palparinae, but present in most Palaeoleontidae, with the exception of the Coniacian Metahemerobius kalligrammus Makarkin, Reference Makarkin and Akimov1990, the Aptian Araripeleon alphonsei Millet and Nel, Reference Millet and Nel2010, and an undescribed species from the Crato Formation (unpublished data, Makarkin, 2018). In other Myrmeleontidae this fold is often present (e.g., Zheng et al., Reference Zheng, Badano, Aspöck, Aspöck, Hayashi and Liu2025, fig. 12A).

The discovery of Protopalpares supports Palparinae as more similar to Palaeonleontidae. Given this, should Palaeonleontidae be considered a subfamily of Myrmeleontidae?

Palaeonleontidae species do not have diagnostic features of Myrmeleontidae, even considering Myrmeleontidae s.l. (i.e., with Cretaceous taxa and including Ascalaphidae). Unfortunately, recent studies of the phylogenetic relationships within Myrmeleontoidea based on molecular data usually do not recognize synaphomorphies or other morphological characteristics of Myrmeleontidae (e.g., Haring and Aspöck, Reference Haring and Aspöck2004; Winterton et al., Reference Winterton, Hardy and Wiegmann2010, Reference Winterton, Lemmon, Gillung, Garzon and Badano2018; Wang et al., Reference Wang, Liu, Garzón-Orduña, Winterton, Yan, Aspöck, Aspöck and Yang2017; Machado et al., Reference Machado, Gillung, Winterton, Garzón‐Orduña, Lemmon, Lemmon and Oswald2019; Vasilikopoulos et al., Reference Vasilikopoulos, Misof, Meusemann, Lieberz and Flouri2020).

Lu et al. (Reference Lu, Wang, Zhuo and Liu2026) stated that the monophyly of Myrmeleontidae s.l. (i.e., including Ascalaphidae) is supported by: (1) antennae strongly dilated distally; (2) RP originating distad the wing base, and (3) elongated tibial spurs. Previously, Stange (Reference Stange1994) identified as synapomophies of Myrmeleontidae s.l.: (4) the presence of the pilula axillaris (‘Eltringham’s organ’: a projection at the base of hind wings in males) as an autapomorphy of Myrmeleontidae (including Stilbopteryginae); and (5) the absence of the basal subcostal crossvein in both wings.

Palaeonleontidae does not conform to any of (1–4) and possibly (5): (1) the antennae are not dilated distally (except in Guyiling, in which they are slightly dilated); (2) RP originates very close to the wing base; (3) tibial spurs are relatively short and straight in the Cretaceous Parapalaeoleon magnus Menon and Makarkin, Reference Menon and Makarkin2008 and Guyiling jianboni Shi et al., Reference Shi, Béthoux, Shih and Ren2012 (Menon and Makarkin, Reference Menon and Makarkin2008, fig. 4A; Shi et al., Reference Shi, Béthoux, Shih and Ren2012, fig. 2B). These are quite similar to those of Ascalaphinae (see e.g., Tjeder, Reference Tjeder1992, fig. 32). In most extant Myrmeleontidae, the spurs are longer and usually curved (see e.g., Vshivkova and Makarkin, Reference Vshivkova, Makarkin, Devetak, Lipovšek and Arnett2010, fig. 40). Such spurs were also detected in the mid-Cretaceous Babinoleon jinmingae Lu et al., Reference Lu, Wang, Zhuo and Liu2026; Nanoleon wangae Hu, Lu, and Liu in Lu et al., Reference Lu, Hu, Wang, Zhang, Ohl and Liu2019; Xiaoleon amoena Lu and Liu, Reference Lu and Liu2022 (Lu and Liu, Reference Lu, Xu and Liu2022, fig. 1C; Lu et al., Reference Lu, Hu, Wang, Zhang, Ohl and Liu2019; fig. 9B; 2026, fig. 1D). Thus, the shape of the tibial spurs in Palaeoleontidae is more plesiomorphic than in most Myrmeleontidae. Their presence is generally normal in all Neuroptera, but are usually short. (4) A pilula axillaris is not detected; and (5) the absence of the basal subcostal crossvein is difficult to establish with certainty due to preservation, but numerous subcostal crossveins are present at least in Metahemerobius (Makarkin, Reference Makarkin and Akimov1990, fig. 5).

There are other character states considered diagnostic by Aspöck et al. (Reference Aspöck, Plant and Nemeschkal2001), Zimmermann et al. (Reference Zimmermann, Randolf, Metscher and Aspock2011), and Randolf et al. (Reference Randolf, Zimmermann and Aspöck2014), but these are difficult identify in fossils. For example, tergite 9 divided ventrolaterally, closed anterior tentorial pits, and the anterior tentorial arms as flat tubes were considered by these authors to be synapomorphies of Myrmeleontidae+Ascalaphidae.

Therefore, we agree that the genera of Palaeonleontidae constitute a distinct family, although they do not possess any known synapomorphies. However, judging by their strong similarity to Palparinae, it can be assumed that Palparinae had a close relationship with Early Cretaceous Palaeonleontidae.