Aneurus sp. from the early Miocene Foulden Maar, New Zealand: the first Southern Hemisphere record of fossil Aradidae (Insecta: Hemiptera: Heteroptera)

Abstract

The first specimen of fossil Heteroptera (Aradidae, Aneurinae) from New Zealand is figured and described. The ventrally preserved specimen from early Miocene lake sediments at Foulden Maar, Otago is assigned to Aneurus, a flat-bug genus that is represented by six species in the modern New Zealand fauna. Aneurus sp. from Foulden Maar represents the first Southern Hemisphere fossil record of the family Aradidae. Its occurrence at Foulden Maar indicates that the genus has been present in the Australasian region at least since the early Miocene and supports previous suggestions of a long evolutionary history of New Zealand aradids closely linked to rainforest habitats.

Keywords:

• fossil Heteroptera
• Aradidae
• Aneurus
• Miocene
• Foulden Maar
• Otago

Introduction

Aradidae (also known as flat-bugs) is a large family within Heteroptera comprising about 2000 species in more than 200 genera that occur in all major zoogeographic regions (Schuh & Slater 1995). New Zealand is clearly a centre of aradid diversity as it contains species of all eight aradid subfamilies (Aneurinae, Aradinae, Calisiinae, Carventinae, Chinamyersiinae, Isoderminae, Mezirinae, Prosympiestinae), the majority of which are endemic (Larivière 1997; Larivière & Larochelle 2004, 2006). The subfamily Aneurinae is represented by two genera in New Zealand, the monotypic Aneuraptera Usinger & Matsuda 1959, and Aneurus Curtis 1825. For the latter, Heiss (1998) revised the three known species A. brouni White 1876, A. salmoni Pendergast 1965 and A. prominens Pendergast 1965, and described three new species as A. zealandensis, A. maoricus, and A. brevipennis. Due to consistent morphological differences between Aneurus from New Zealand and from the Palearctic Region, and taking into account biogeographical considerations, Heiss (1998) proposed a new subgenus, Aneurodellus, for the six endemic species occurring in New Zealand.

The fossil record of Aradidae is rather scarce, with 39 taxa in one extinct subfamily (Archearadinae) and four extant subfamilies,1 mainly described from Baltic amber and other amber deposits (e.g. Froeschner 1992; Heiss 2000, 2002a, b, c,). The oldest aradid fossil is Archearadus burmensis Heiss & Grimaldi 2001 (Archearadinae) from mid-Cretaceous (Turonian/Cenomanian, 90–100 Ma) Burmese amber (Heiss & Grimaldi 2001, 2002; Grimaldi et al. 2002). Fossils of the subfamily Aneurinae comprise the sole genus Aneurus (subgenera Aneurodes and Neaneurosoma) with three species from Eocene Baltic amber, A. ancestralis, A. (Neaneurosoma) kotashevichi and A. (Aneurodes) groehni (Heiss 1997, 2001) and one species, A. opertus, from the Miocene Shangwang Formation in China (Zhang et al. 1994). To date, no fossil Aradidae has been described from the Southern Hemisphere.

Fossil collecting at the early Miocene Foulden Maar, Otago, southern New Zealand, has yielded a diverse micro- and macroflora and galaxiid fish in the past decades (Pole 1996; Lee et al. 2007; Bannister et al. 2009). Recently, several spiders and insects from at least five orders have been found (Kaulfuss & Lee 2010) which are of special interest for reconstructing the largely unknown Cenozoic arthropod fauna of Zealandia, and hence the history of the modern arthropod fauna in New Zealand. Previously described Cenozoic insects include the exuviae of an Eocene bibionid fly larva from North Otago (Harris 1983), a late Eocene lepidopteran wing scale from the Waikato Coal Measures (Evans 1931) as well as female scale insects (Diaspididae) attached to an angiosperm leaf (Harris et al. 2007) and a wet-wood termite from Foulden Maar (Kaulfuss et al. 2010). The aim of this paper is to describe Aneurus sp. from Foulden Maar as the first representative of Heteroptera from New Zealand and the first Southern Hemisphere fossil record of the family Aradidae.

Locality and age

Foulden Maar near Middlemarch (45.5271°S, 170.2218°E; Fig. 1) is a partly eroded maar-diatreme volcano that preserves sediments deposited in a small (diameter c. 1500 m) but deep (c. 200 m) freshwater lake that formerly filled the maar crater. The Aneurus specimen was found in finely laminated diatomite of the uppermost part of the preserved sedimentary sequence which is exposed in small surface mining pits near the centre of the crater. The geological setting and sedimentological description of the outcropping maar lake sediments were given by Lindqvist and Lee (2009) and the paleoenvironmental setting of the maar lake is described in Bannister et al. (2005).

Figure 1  Map of the Otago region showing the fossil locality Foulden Maar near Middlemarch.

The fossil flora from Foulden Maar comprises diatoms and other algae, saprophytic and epiphyllous fungi, leaves with cuticle-preservation, flowers with pollen, various types of fruits and seeds, and fern fronds with in situ spores (e.g. Pole 1993, 1996; Bannister et al. 2005, 2009; Conran et al. 2009, Conran et al. 2010). The fauna includes freshwater sponges, insects, spiders, and at least three different types of fish (Lee et al. 2007; Lindqvist & Lee 2009; unpubl. data). The fossil insect fauna is dominated by members of Coleoptera and Hymenoptera, but representatives of Diptera, Isoptera, and Hemiptera are also present (Kaulfuss & Lee 2010; Kaulfuss et al. 2010).

Foulden Maar is considered to be of early Miocene age from pollen analysis (Bannister et al. 2005), and from radiometric dating of nearby basalts (23.2±0.2 Ma, Lindqvist & Lee 2009). The locality is registered as I43/f8503 in the New Zealand Fossil Record File administered by the Geoscience Society of New Zealand and GNS Science.

Methods

The fossil was cleaned using a fine needle and a paint-brush. Microphotographs were taken with a Nikon Coolpix 4500 camera attached to a Leica Wild MZ8 binocular microscope and measurements of anatomical structures were taken with a measurement-eyepiece. The morphological details given in the description and the reconstruction in Fig. 3 are based on microphotographs and were double-checked with the original specimen that is stored in a plastic sample-bag in a fridge in order to prevent drying and disintegration of the diatomite matrix. The fossil is held in the Department of Geology, University of Otago, catalogue number OU44555.

Systematic paleontology

Class Insecta Linnaeus, 1758

Sub-class Pterygota Gegenbaur, 1878

Order Hemiptera Linnaeus, 1758

Suborder Heteroptera Latreille, 1810

Infraorder Pentatomomorpha Leston, Pendergrast & Southwood, 1954

Superfamily Aradoidea Brullé, 1836

Family Aradidae Brullé, 1836

Subfamily Aneurinae Douglas & Scott, 1865

Genus Aneurus Curtis, 1825

Aneurus sp. (Figs. 2, 3)

Figure 2  Compression of Aneurus sp. from Foulden Maar, photomicrograph (OU44555); scale bar = 1 mm.

Figure 3  Reconstruction of Aneurus sp. from Foulden Maar, ventral view; scale bar = 1 mm.

Material examined

Preserved is a nearly complete, ventro-dorsally compressed specimen with body outline and most appendages discernible. The morphology of the abdominal apex suggests the specimen may be female. The entirely visible trochanters, middle and hind femora, and the transverse sutures of the abdomen indicate that the preserved compression shows the ventral side of the animal, which is also considered in the reconstruction (Fig. 3).

Measurements

(in mm as preserved): body length 3.94 (4.79 including antennae); length of antennae 0.85 (I, 0.20; II, 0.17; III, 0.22; IV, 0.26); maximal width of head 0.60; maximal length of head 0.57; width of pronotum 0.66; width of abdomen 1.15.

Description

Body elongate-oval, abdomen wider than pronotum. Head about as long as wide across eyes (0.57 mm/0.60 mm); antennae about 1.42×the width of the head; antennal segment I thick, II–IV slender, with IV the longest; clypeus, in ventral view, shorter than antennal segment I; antenniferous tubercles subacute; postocular lobes rounded, not exceeding beyond outer margin of eyes. Prothorax trapezoidal; lateral margins converging anteriorly. Abdomen with lateral margins evenly rounded in apical half; transverse sutures of sternites III–VII visible; ventral laterotergites clearly delimited by longitudinal sutures. Legs; middle and hind femora incrassate; hind tibiae cylindrical; forelegs not preserved.

Remarks

The habitus and body outline of the preserved compression are typical of members of the aradid subfamilies Aneurinae or Mezirinae. The Mezirinae of New Zealand comprise two genera, Woodwardiessa (one species) and Ctenoneurus (four species). Affiliation of the fossil with either genus is excluded on the following basis. Woodwardiessa is much larger (8–10 mm) than the fossil, has a subquadrate body outline, a shorter antennal segment IV (shorter in length than III), femora only moderately inflated and no transverse carina anteriorly on sternites IV–VI, and well delimited ventral laterotergites on the abdomen. Ctenoneurus is also much larger than the fossil (6–9 mm), has a subparallel body outline, clypeus longer than antennal segment I, a relatively short antennal segment IV (subequal in length to III), femora only moderately inflated, a transverse carina anteriorly on sternites IV–VI (character shared with Aneurus), and lacks well delimited ventral laterotergites on the abdomen.

The subfamily Aneurinae is represented by Aneurus (Aneurodellus) with six species and the monotypic, micropterous Aneuraptera (Heiss 1998; Larivière & Larochelle 2006). The fossil appears congeneric with Aneurus based on the following characteristics shared with extant members of this genus in New Zealand: rather small size (around 5 mm), elongate-oval body outline, head with clypeus shorter than antennal segment I, the latter thickest and IV longest, postocular lobes rounded, femora incrassate, a transverse carina anteriorly on sternite IV–VI, and ventral laterotergites well delimited by longitudinal sutures. However, it is not possible to determine whether the fossil represents the subgenus Aneurodellus characterized mainly by patterns of rugulose areas on the abdomen and an area of glabrous cuticle (contergite) on the inner side of the fused connexival segments II + III (Heiss 1998) as these characters are not visible in the ventral preservation.

Discussion

Concerning the New Zealand Aradidae, Larivière & Larochelle (2006, p. 209) stated: ‘From what is known of their geographic distribution, habits, and affinities with taxa of neighbouring land masses, there is little doubt New Zealand aradids have had a long evolutionary history closely linked to that of rainforest habitats, in particular, old Gondwanan elements such as podocarps (“conifers”) and Nothofagus (beech) that occurred widely and were shared with other parts of Gondwana.’ Fossil evidence is mostly lacking but this view can be supported here with the discovery of the new Aneurus sp. fossil, which represents the first Southern Hemisphere fossil record for Aradidae with a presence in lake sediments at Foulden Maar, suggesting that the subfamily Aneurinae has been present in Zealandia at least since the early Miocene (23 Ma).

The ventral preservation of Aneurus sp. from Foulden Maar does not allow definitive comparisons with the fossil species from the Palearctic Region or modern species from New Zealand or elsewhere, until further material becomes available.

The extant subgenus Aneurus (Aneurodellus) occurs throughout New Zealand, living under tree bark in both evergreen broadleaf-podocarp and beech (Nothofagus) forests in lowland to subalpine regions. Anerus species are not generally host-specific and can be found on several tree species, sometimes in association with other aradids (Heiss 1998; Larivière & Larochelle 2004, 2006). Miocene Foulden Maar was a small lake surrounded by a warm temperate to subtropical evergreen forest dominated by Lauraceae, but also including Araliaceae, Cunoniaceae, Elaeocarpaceae, Euphorbiaceae, Menispermaceae, Myrsinaceae, Myrtaceae, Proteaceae, Sapindaceae and Sterculiaceae (Bannister et al. 2009). The palynoflora and macroflora from Foulden Maar indicate that two species of podocarps grew nearby (Pole 1993; J.M. Bannister, pers. comm. 2010) and that one species of Nothofagus, N. cranwelliae (Couper) Mildenhall & Pocknall 1989, probably also grew in the vicinity of the lake (Mildenhall & Pocknall 1989; Pole 1993; see discussion in Bannister et al. 2005). However, both podocarps and Nothofagus were only accessory components in the forest surrounding Foulden Maar. In this regard, the habitat of the fossil Aneurus sp. may perhaps be more appropriately compared to modern rainforests in south-east Queensland and northern New South Wales, Australia (Webb 1959; J.G. Conran pers. comm. 2010), where Aneurus is represented by five extant species: A. angulatus Kormilev 1965, A. androphymus Bergroth 1914, A. australicus Stål 1873, A. crenulatus Kormilev 1957, and A. robustus Kormilev 1957. This also supports a long evolutionary history of New Zealand aradids closely linked to rainforest habitats that were shared with other parts of Gondwana as proposed by Larivière and Larochelle (2006).

Acknowledgements

The authors are grateful to Featherston Resources Ltd and the Gibson family for kindly allowing access to the fossil site. We also wish to thank D.E. Lee (Department of Geology, University of Otago) for helpful comments on an earlier version of the manuscript, J.M. Bannister (Department of Botany, University of Otago) and J.G. Conran (School of Earth and Environmental Sciences, University of Adelaide) for botanical information, and two reviewers for their helpful comments. The Department of Botany, University of Otago, provided photographic equipment. Research at Foulden Maar is financed by the Marsden Fund (awarded to D.E. Lee) and this study has been supported by a Postgraduate Scholarship (Division of Science, University of Otago), and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) project No. WA 1492/4–1.

Notes

¹Aneurinae, Aradidae, Calisiinae, and Mezirinae. Cretopiesma suukyiae Grimaldi & Engel 2008 from mid-Cretaceous Burmese amber was described as a member of Piesmatidae (Grimaldi & Engel 2008) but might instead belong to Aradidae as shown by recent cladistic analyses by Cassis & Schuh (2010).