Neuroptera are uncommon insects in nearly all Cenozoic lacustrine deposits, usually comprising less than 1% (and never more than 5%) of the insects found (Archibald & Makarkin Reference Archibald and Makarkin2006). This is also the case for the late Eocene lagoon setting of the Isle of Wight where this order is represented by nine species distributed in four families in the Insect Bed (Bembridge Marls: Jarzembowski Reference Jarzembowski1980). The family Hemerobiidae (brown lacewings) is represented by ‘Megalomus' tinctus (Jarzembowski Reference Jarzembowski1980, pp. 254, 257, 259, fig. 31; Makarkin Reference Makarkin1991, pp. 57, 60), two unnamed ?Neuronema species (Jarzembowski Reference Jarzembowski1980, pp. 258–259, figs 39, 40) and three species in undetermined genera. Furthermore, Mantispidae (mantis flies) are represented by Vectispa relicta (Cockerell Reference Cockerell1921, pp. 477–478, fig. 46; Jarzembowski Reference Jarzembowski1980, pp. 254–255, 257, fig. 29; Lambkin Reference Lambkin1986, pp. 16, 23; Wedmann & Makarkin Reference Wedmann and Makarkin2007), Sisyridae (spongilla flies) by unnamed Species A (Jarzembowski Reference Jarzembowski1980, pp. 254, 261, fig. 27) and Chrysopidae (green lacewings) by another Species A (Jarzembowski Reference Jarzembowski1980, pp. 258, 260–261, fig. 42). This could appear a rather low count, but it is higher than what has been found in the fossiliferous Oligocene deposits of the palaeolake Céreste: one ascalaphid and one undescribed chrysopid (Nel Reference Nel1991). New acquisitions at the Isle of Wight County Museum and Natural History Museum have added the family Nemopteridae (spoon-winged lacewings), another species of Chrysopidae and a new species of Hemerobiidae to the Isle of Wight Eocene entomofauna and are described herein. Nemopterids are weakly flying insects no longer found in the UK, with distinctly elongate hindwings used in courtship display. The adults rest on flowers where they feed on small insects and pollen, whereas the larvae are ground predators.
The insects are preserved in concretions or tabular bands of very fine-grained micrite, known as Insect Limestone. The unit in which these concretions/bands occur is known as the Insect Bed, which lies towards the base of the Bembridge Marls Member (Solent Group: Bouldnor Formation). The Bembridge Marls are currently considered to be late Eocene in age (Ross & Self Reference Ross and Self2014). The specimens described herein are from the coastal outcrop on the W of Burnt Wood behind Saltmead Ledge (National Grid Reference SZ 439928). Repositories of specimens are the Natural History Museum, London (NHMUK) and the Isle of Wight County Museum Service (IWCMS).
1. Systematic palaeontology
Order Neuroptera von Linnaeus, Reference von Linnaeus1758
Family Nemopteridae Burmeister, Reference Burmeister1839
(spoon-winged lacewings)
Subfamily Nemopterinae Burmeister, Reference Burmeister1839
Tribe Stenonemiini Orfila, Reference Orfila1954
Genus and species undetermined A (Figs 1, 2a, b)
Figure 1 Nemopteridae Stenonemiini species A, specimen IWCMS.2006.102a, b (field no. 28a, b), drawing of forewing. Scale bar=4mm.
Figure 2 (A) Nemopterinae Stenonemiini genus and species undetermined A, no. IWCMS.2006.102a (part). (B) Counterpart of (A). (C) Chrysopidae genus undetermined species B, no. IWCMS.2006.103a (part). (D) Sympherobius yulei sp. nov., holotype NHM II.2973a (print), left wings. (E) Counterpart of (D). (F) Part of (D), general habitus. (G, H) Specimen NHMUK II.2979b, part and counterpart of the base of a forewing, coll. Andy Yule, NHM. Scale bars=4mm (A, B, D, E); 5mm (C); 3.5mm (F); 4mm (G, H).
Material. Specimen no. IWCMS.2006.102a,b (Yule 28a, b). Insect Bed, NW Isle of Wight. A. Yule collection.
Taphonomy. Incomplete wing in a fossiliferous parting associated with other insect remains (Odonata, formicid Hymenoptera and Diptera inc. Dixa-like species), ostracods and a seed.
Description. Part and counterpart of the costo-basal one-third of a hyaline forewing, 23.6mm long, 7.7mm wide; costal area narrow, 0.8mm wide with 30 preserved simple crossveins; subcosta posterior (ScP) and radius anterior (RA) very close, straight and parallel; radial sector (Rs)+media anterior (MA) emerges from radius (R) 19.5mm from wing base; area between R and media posterior (MP)1 narrow with more than 22 simple crossveins basal of Rs+MA; area between MP1 and MP2+cubitus anterior (CuA)1 very narrow with about 28 preserved crossveins; CuA2 and CuA1 separating 4.6mm from wing base; area between MP2+CuA1 and CuA2 very broad, with more than 13 parallel branches of MP2+CuA1; area between CuA2 and cubitus posterior (CuP) very narrow distally; 1A short, 5.3mm long, with only two posterior branches; 2A very short, 2.6mm long.
Discussion. This fragment belongs to the Nemopteridae in the tribe Stenonemiini (=Stenorrhachiini sensu Tjeder Reference Tjeder1967) because of the following typical features: MP1 and MP2 + CuA1 closely parallel, very long and nearly straight; area between MP2+CuA1 and CuA2 very broad, with more than 13 parallel branches of MP2+CuA1; base of Rs+MA in a very distal position; and 1A short with only two posterior branches (Orfila Reference Orfila1954).
Affinities with the Cretaceous family Roeslerianidae Martins-Neto are excluded because the costal crossveins are simple and not dichotomous (Martins-Neto Reference Martins-Neto2000). The Mesozoic nemopterid genus Cratonemopteryx Martins-Neto, Reference Martins-Neto1992 differs from the Bembridge Marls fossil in having a narrower area between MP2+CuA1 and CuA2 and the base of Rs+MA in a more basal position (Martins-Neto Reference Martins-Neto1992).
The forewing venations of numerous genera of the extant tribe Stenonemiini are very similar to that of this fossil, viz. Nemopistha Navás, Reference Navas1910; Sicyoptera Navás, Reference Navas1910, Nemeura Navás, Reference Navas1910, Brevistoma Tjeder, Reference Tjeder1967, Semirhynchia Tjeder, Reference Tjeder1967, etc. (Tjeder Reference Tjeder1967; Navás Reference Navás1912). Thus, it is not possible to attribute this fossil to an extant genus.
Fossil Nemopteridae belonging to the same tribe are also represented by the fossil genus Marquettia Navás, Reference Navas1913, with two species – M. americana (Cockerell, Reference Cockerell1907) and M. metzeli Pierce & Kirkby, Reference Pierce and Kirkby1959 – from the late Eocene of the USA (Carpenter Reference Carpenter1960). Our fossil differs from Marquettia in the organisation of the veins in the area between MP2+CuA1 and CuA2; that is, the branches of MP2+CuA1 are more regularly spaced. Nel (Reference Nel1991) described a unnamed fossil belonging to the same tribe from the early Oligocene of the ‘Potasse d'Alsace', Haut-Rhin, France, which could well belong to the same genus, if not the same species as our one, based on the similar wing proportions and venation.
The UK fossil is the second record of this tribe in the European Cenozoic. Recent Stenonemiini are known from Africa, South America and Asia, and are represented by one species in Europe (from Bulgaria). The new find confirms the previous inference of a rather warm palaeoclimate in Western Europe during the late Eocene (Nel Reference Nel1991) corresponding to the cooling associated with the 33.5 mya ‘Oi-1 Glaciation' (sensu Van Simaeys et al. Reference Van Simaeys, Brinkhuis, Pross, Williams and Zachos2005). This cooling is perceptible through the proportions of the bibionid genera in the Insect Bed (Collomb et al. Reference Collomb, Nel and Waller2008; Krzeminski et al. Reference Krzemiński, Blagoderov, Azar, Lukashevich, Szadziewski, Wedmann, Nel, Collomb, Waller and Nicholson2019), but it did not affect several taxa whose recent relatives live in warm climates, e.g., these Nemopteridae, the Isoptera: Mastotermitidae and the leaf-mimicking Orthoptera: Tettigoniidae: Pseudophyllinae (Nel et al. Reference Nel, Prokop and Ross2008).
Family Chrysopidae Schneider, 1851
Genus undetermined species B (Figs 2c, 3)
Figure 3 Chrysopidae species B, specimen IWCMS.2006.103a,vb. (A) Drawing of forewing costal area. (B) Drawing of left hindwing. (C) Drawing of right hindwing. Scale bars=2mm.
Material. Specimen no. IWCMS.2006.103a, b. Insect Bed, NW Isle of Wight.
Taphonomy. Specimen preserved in weathered ‘rind' of the insect limestone.
Description. A body with the fore- and hindwings preserved but twisted and deformed. Forewing only partly preserved and only the basal part of the costal area is clearly visible and rather broad, up to 1.1mm wide; hindwing 14.5mm long, width unknown; costal area narrow, 0.4mm wide, with about 14 simple crossveins; pterostigmal area not well preserved; veins subcosta (Sc) and RA fused apically; vein pseudo-median vein (psm) straight with five branches of Rs+MA ending on it; Rs+MA with eight branches ending on the posterior wing margin; six inner gradate veins regularly spaced; only the apical outer gradate veins are preserved.
Discussion. Jarzembowski (Reference Jarzembowski1980) has already recorded the family Chrysopidae from the Insect Bed. The new fossil confirms the presence of this family supported by the characteristic vein psm, and inner gradate (i.g.) and outer gradate (o.g.) crossveins (Brooks & Barnard Reference Brooks and Barnard1990; Nel et al. Reference Nel, Martinez-Declos and Hutin2005). Like the previous records, affinities with the Apochrysinae seem unlikely because the o.g. veins are few and not well aligned, and this fossil could well be related to Chrysopinae sensu stricto or Nothochrysinae. It is not possible to give a more precise attribution because the forewing intramedian cell is not preserved.
Jarzembowski's chrysopid species A is based on a small fragment of wing apex (specimen NHMUK I.8643). The new find differs from it in that Sc and RA are fused distally, suggesting a generic difference. The new fossil is more intact, also suggesting less transportation than the previous record. Chrysopidae are well known from the Palaeogene of continental Europe (Nel et al. Reference Nel, Martinez-Declos and Hutin2005); future fieldwork may well yield critical material.
Remark. Another specimen (NHMUK II.2989a, b, A. Yule collection) could be attributed to the Chrysopidae on the basis of the apparent presence of a straight vein psm, but this is uncertain (Fig. 4a). This last fossil is remarkable by its very long antennae, a character present in Chrysopidae but also in some other neuropteran families, e.g., Osmylidae.
Figure 4 (A) ?Chrysopidae genus and species undetermined, NHMUK II.2989a, A. Yule collection. (B) Hemerobiidae genus and species undetermined, NHMUK II.2988, A. Yule collection. (C, D) NHMUK II.2981a, b part and counterpart of Neuroptera family, genus and species undetermined, II2981a, A. Yule collection. Scale bars=4mm.
Family Hemerobiidae Latreille, Reference Latreille1802
Genus Sympherobius Banks, Reference Banks1904
Sympherobius yulei sp. nov. (Figs 2d–f, 5)
Figure 5 Sympherobius yulei sp. nov. Holotype, NHMUK II.2973a, b, drawing of forewing. Scale bar = 4 mm.
Holotype. NHMUK II.2973a, b. Insect Bed, Saltmead Ledge, Isle of Wight. A. Yule collection.
Diagnosis. Fossil species of Sympherobius with forewing crossvein 3 intercalary radial vein (ir) just distal of first fork of branches of radial sector (ORB) 3; ORB3 with only one fork; 1 median-cubital (m-cu) crossvein nearly aligned with base of CuP.
Etymology. Named after Andy Yule who found and donated the type specimen to the NHM.
Taphonomy. Part and counterpart of a body, a forewing with apical fifth missing, base of the opposite forewing and fragments of a hindwing; legs and antennae not visible; spider on same bedding plane.
Description. We follow the wing venation nomenclature of Oswald (Reference Oswald1993a). The body is probably complete, but shows no taxonomically useful characters, unlike the forewing. Forewing 4.4mm long (the complete length of the wing was certainly only slightly longer than what is preserved), 2.3mm wide as preserved; costal area very broad near its base, 0.5mm wide, trichosors of anterior wing margin present; humeral marginal silhouette convex; prestigmal width of subcostal space narrow but broader than adjacent Sc throughout; subcostal crossvein 2 subcosta-radial (sc-r) present; radial vein with three ORBs and ORB1 shallowly forked; ORB3 with only one fork; radial veins straight, not sinuate; pre-3ir1 intraradial crossveins absent; crossvein 3ir1 just distal of first fork of ORB3; posterodistal marginal silhouette convex; anterior border of third intercalary radial-median cell (c3r-m) straight; radiomedial crossvein 3 radial-median crossvein (r-m) present, 3r-m connecting ORB1 and MA; intersection of 2m-cu with MP located more than the crossvein's length distal to fork MA/MP; cell c2m-cu narrow distally; intramedial crossvein 2 intercalary median cell (im) absent; three mediocubital crossveins present; mediocubital flexion line present; intercubital crossvein 1 cubital crossvein (cua-cup) absent; proximal forks of CuP and A1 absent.
Discussion. Based on the phylogenetic analysis of the hemerobiid genera by Oswald (Reference Oswald1993a, Reference Oswaldb), the pre-3ir1 intraradial crossvein is a synapomorphy of the Hemerobiidae, even if reversed in the two genera Neuronema and Gayomyia. Sympherobius yulei sp. nov. differs strongly from the ‘basal' subfamily Adelphomerobiinae Oswald, Reference Oswald1994 in the structure of the radial sector (Oswald Reference Oswald1994). Following the key to genera of Oswald (Reference Oswald1993a), it would fall near the genera Hemerobiella, Hemerobius, Wesmaelius or Sympherobius (in part), because of the presence of three prestigmal ‘radial sectors', forewing humeral vein narrow and forewing with three m-cu veins. Wesmaelius differs from Sympherobius yulei sp. nov. in ORB3 possessing three forks and 2r-m displaced proximad of crossvein 2m-cu; the latter feature is an apomorphy of Hemerobius. Also, the anterior border of cell c3r-m being straight and the radial veins not sinuate exclude the fossil from Hemerobiella. S. yulei sp. nov. differs from the extant Hemerobius species in the position of the crossvein 3ir1, just distal of the first fork of ORB3 (Aspöck et al. Reference Aspöck, Aspöck and Holzel1980). Also in Hemerobius, 2r-m is either lost or located much proximal to the fork of median vein (M) and ORB1. The fossil shows more similarities with Sympherobius (Oswald Reference Oswald1988). Thus, we tentatively place the fossil in this genus, even if the absence of the body and hindwing characters renders its attribution uncertain.
Among the fossil Sympherobius species, Sympherobius yulei sp. nov. differs from the Baltic amber Sympherobius completus Makarkin & Wedmann, Reference Makarkin and Wedmann2009 in its ORB3 with only one fork (although some uncertainty remains about this character as the wings are not completely preserved), and more proximal position of crossvein 1m-cu (Makarkin & Wedmann Reference Makarkin and Wedmann2009). Sympherobius yulei sp. nov. differs from the Baltic amber Sympherobius siriae Jepson et al., Reference Jepson, Penney and Green2010 in the shorter forewing (ca.4.4mm instead of 5.9mm long; Jepson et al. Reference Jepson, Penney and Green2010). The Sympherobius sp. described by Engel & Grimaldi (Reference Engel and Grimaldi2007) from the Dominican amber has retained the crossvein 4m-cu.
Sympherobius yulei sp. nov. differs from all fossil Hemerobiidae already described and figured from the Isle of Wight, except Hemerobiidae species B in the few branches of Rs separated by broad intercalary areas (Jarzembowski Reference Jarzembowski1980); the latter is based on a rather fragmentary specimen but is possibly congeneric with the new fossil, even if they are not conspecific, S. yulei having an ORB3 with a distinct angle near its base while this vein is straight in species B. Sympherobius yulei sp. nov. also differs from ‘Hemerobius' tinctus Jarzembowski, Reference Jarzembowski1980, from the Isle of Wight Eocene – later transferred to the genus Megalomus by Makarkin (Reference Makarkin1991) – in the presence of the crossvein 2r-m, simple ORB1 and only two forks of ORB3. We agree with Oswald (Reference Oswald1993a), who considered that the wing venation of ‘Megalomus' tinctus resembles more that of Psychobiella than Hemerobius and Megalomus, especially in the structure of the radial sector.
Among the fossil hemerobiid genera, Sympherobius yulei differs from the Early Eocene Cretomerobius Makarkin et al., Reference Makarkin and Archibald2003 in the organisation of the radial sector (Makarkin et al. Reference Makarkin and Archibald2003). Sympherobius yulei sp. nov. also differs from the enigmatic Baltic amber Prolachlanius Krüger, Reference Krüger1923 and Prophlebonema Krüger, Reference Krüger1923 in the position of the crossvein 1r-m, and from Prospadobius Krüger, Reference Krüger1923 and Promegalomus Panfilov, Reference Panfilov, Dolin, Panfilov, Ponomarenko and Pritykina1980 in the organisation of the radial sector (Pictet & Hagen Reference Pictet De La Rive, Hagen and Berendt1856; Krüger Reference Krüger1923; Panfilov Reference Panfilov, Dolin, Panfilov, Ponomarenko and Pritykina1980; Oswald Reference Oswald1993a). The forewing venation of the Canadian genus Bothromicromus Scudder, Reference Scudder1878 resembles that of Drepanepteryx (Scudder Reference Scudder1890; Oswald Reference Oswald1993a). Mesohemerobius Ping, Reference Ping1928 is a very enigmatic and incomplete wing differing from S. yulei sp. nov. in its very numerous radial branches (Ping Reference Ping1928).
In addition, Rumbucker (Reference Rumbucher1995) described two Lower Cretaceous genera Brasilopsychopsis and Cratopsychopsis, but Makarkin et al. (Reference Makarkin and Archibald2003) indicated that they should be revised.
Remark. A new specimen (NHMUK II.2979a, b, part and counterpart of the base of a forewing, A. Yule collection) has its preserved veins similar to those of the type specimen of Sympherobius yulei. It is larger than this fossil, and has five dark coloured bands in the subcostal space (Fig. 2g, h), not present in the type specimen of S. yulei, but this could be due to variation or a problem of taphonomy, or it could be a different species, maybe in the same genus.
A further specimen (NHMUK II.2988, A. Yule collection) can also be attributed to the Hemerobiidae, but as only the basal part of costal area is preserved with traces of dark bands, it is impossible to attribute it to a precise genus or subfamily, although the dense venation would suggest some similarities with the ?Neuronema species already known from the same bed. We consider it as a Genus undetermined species C (Fig. 4b).
For another Neuroptera specimen (NHMUK II2981a,b, A. Yule collection), it is impossible to suggest a family attribution because the organisation of the radial area is not preserved, although an aberrant osmylid affinity cannot be ruled out, due to the long distal fusion of R and Sc with a series of long, parallel, anterior branches (Fig. 4c, d).
Note. Makarkin (Reference Makarkin1998) described the Oligocene–Miocene genus Oligogetes and attributed it to the Jurassic family Solenoptilidae Handlirsch, 1906. However, Oligogetes relictum Makarkin, Reference Makarkin1998 is based on fragments of wing apices that do not show any character, which is typical of Neuroptera. In particular, the holotype specimen (PIN 3429/305) is much more likely to be a hindwing apex of an orthopteran (cf. Carpenter Reference Carpenter, Moore and Kaesler1992; Makarkin Reference Makarkin1998, text-fig. 4a; Makarkin & Archibald Reference Makarkin and Archibald2003). The attribution of Oligogetes to the Solenoptilidae is very doubtful.
2. Acknowledgements
We sincerely thank Andy Yule and the staff of the Dinosaur Isle Museum and Isle of Wight County Museum Service for their kind help. We also acknowledge an anonymous referee and Dr Andrew Ross for comments on the first version of the paper. We also thank Phil Crabb and Andrew Ross for the photographs of the material in the Natural History Museum. This study was supported by the INTAS Project 03-51-4367, ‘The terrestrial fauna and flora of the Insect bed, Isle of Wight: interpreting the climate near the Eocene/Oligocene boundary'.
