A world checklist of extant and extinct species of Megaloptera (Insecta: Neuropterida)

. A global synonymical checklist of the species and higher taxa of the insect order Megaloptera is provided. The checklist includes both extant and extinct taxa, and recognizes 2 families, 4 subfamilies, 48 genera, 425 species, and 6 subspecies. Both families (Corydalidae and Sialidae), and three of the four subfamilies (Corydalinae, Chauliodinae, and Sialinae) are known from both extant and extinct species; the Sharasialinae (Sialidae) is entirely extinct. Country-level geographic distribution data are provided for all species and subspecies. Synoptic type data are provided for taxa in the family and genus groups. Summary data are given for the numbers of megalopteran species currently known to occur in each of the major biogeographical regions of the world, and for the world fauna. Increase of knowledge about the diversity of the world Megaloptera fauna is summarized in counts of valid species described per decade and in a global taxonomic description curve. An updated set of keys to the world families, subfamilies, and genera of the Megaloptera is also provided.


Introduction
Megaloptera Latreille, 1802 -commonly known in English as dobsonflies, fishflies, and alderflies -is a low-diversity but widespread group of holometabolous insects with terrestrial adults and predaceous aquatic larvae. Eggs of Megaloptera are oviposited in masses that are typically deposited on tree trunks, leaves, rocks and other surfaces near or over freshwater. The masses can contain up to several thousand eggs -especially in Corydalidae Leach in Brewster, 1815, and may be uncovered and one-layered (Sialidae Leach in Brewster, 1815), or covered with a white or yellowish substance and multi-layered (Corydalidae Leach in Brewster, 1815) (New & Theischinger 1993;Rasmussen & Pescador 2002;Bentes et al. 2014;Ardila-Camacho & Contreras-Ramos 2018a). Megaloptera larvae range in size from small (0.8-12 mm body length -Sialidae) to large (20-90 mm body length -Corydalidae), and are generalist predators predominantly associated with perennial or (less commonly) intermittent lotic habitats, but some also inhabit lentic environments. The larvae are characterized by a dorsoventrally flattened body with 7-8 pairs of lateral abdominal filaments, a well-developed head capsule with six stemmata (per side), large chewing mouthparts, and short antennae. Adult megalopterans range from small to very large (7-100 mm forewing length), with an enlarged hind wing anal area and a prognathous head (New & Theischinger 1993;Contreras-Ramos & Harris 1998;Beutel & Friedrich 2008;Liu et al. 2015bLiu et al. , 2015cArdila-Camacho & Contreras-Ramos 2018a). Because of the impressive size of their larger species, megalopterans have attracted the attention of entomologists since the early days of scientific entomology in the 18 th century. Nowadays, megalopterans have continued to attract attention as aquatic insects that generally inhabit clean freshwaters, and are often useful as indicator species for environmental impact studies (Bowles & Contreras-Ramos 2019). Megalopterans ( Fig. 1) belong to an ancient neuropteroid lineage of the holometabolous insects (Theischinger 1991), with its oldest known fossils dating back to the Early Jurassic of Europe, †Dobbertinia reticulata Handlirsch in Schröder, 1920 (Sialidae: Sialinae) and †Nematophlebia plicata Cockerell, 1915 (Family incertae sedis). Recent time-calibrated phylogenies suggest that the ancestors of the Megaloptera comprised a lineage distinct from other extant insect orders prior to the end of the Permian period (ca 250 Ma), and that among extant insect orders the Megaloptera form the sister group to the Neuroptera (Misoft et al. 2014;Y. Wang et al. 2017;Winterton et al. 2018;Vasilikopoulos et al. 2020). The monophyly of crown-group Megaloptera is widely accepted and supported by both morphological and molecular phylogenetic analyses (Y. Wang et al. 2017;Winterton et al. 2018;Vasilikopoulos et al. 2020). Some of the proposed morphological synapomorphies of Megaloptera include: a special sensillum on the antepenultimate larval antennomere, the presence of lateral abdominal filaments in all larval stages, absence of the male gonapophyses 9, absence of the male hypandrium internum, and the paired female ectoprocts (Hennig 1981;Ax 2000;Aspöck & Aspöck 2008;Beutel & Friedrich 2008;Beutel et al. 2014;. The episodic publication of comprehensive global checklists like the current work is a vital and enabling step for the continued advancement of biodiversity research on individual higher taxa, and provides important faunistic data to support ecological assessments at local and regional scales (Ohl 2004). In the last two decades when the taxonomic studies of Megaloptera were rapidly increasing, a notable earlier world checklist of Megaloptera was provided by Yang & Liu (2010), and a world catalogue of Sialidae was presented in Liu et al. (2015d), although further updates are needed at present. In the current work, we recognize a total of 425 megalopteran species (400 extant, 25 extinct; also 6 extant subspecies) and 47 genera (28 extant only, 13 extinct only, and 6 with both extant and extinct species), which are placed in two families and four subfamilies (Corydalidae: Corydalinae and Chauliodinae; Sialidae: Sialinae and †Sharasialinae) (Fig. 1). Relatively recent reviews of the general biology and/or higher-level systematics of the Megaloptera on a global scale are available in New & Theischinger (1993), Cover & Resh (2008), Liu et al. (2012b, , Liu (2019a) and Jiang et al. (2021). Much of the remaining literatures on the group focused on the systematics of more restricted taxa, typically genera or intrageneric species groups (Hazard 1960;Flint 1964Flint , 1965Penny & Flint 1982;Glorioso & Flint 1984;Contreras-Ramos 1995, 1998Liu & D. Yang 2004, 2005a, 2005b, 2005c, 2005d, 2006a, 2006b, 2006c, 2006d, 2006e, 2006f, 2006g, 2006h, 2007Liu et al. 2005Liu et al. , 2006Liu et al. , 2007aLiu et al. , 2007bLiu et al. , 2007cLiu et al. , 2007dLiu et al. , 2008aLiu et al. , 2008bLiu et al. , 2008cLiu et al. , 2008dLiu et al. , 2009aLiu et al. , 2009bLiu et al. , 2009cLiu et al. , 2010aLiu et al. , 2010bLiu et al. , 2010cLiu et al. , 2010dLiu et al. , 2011aLiu et al. , 2011bLiu et al. , 2011cLiu et al. , 2012aLiu et al. , 2012bLiu et al. , 2013aLiu et al. , 2013bLiu et al. , 2013cLiu et al. , 2013dLiu et al. , 2015aLiu et al. , 2015bLiu et al. , 2015cLiu et al. , 2015dPrice et al. 2012;Jiang et al. 2020), or on regional geographic faunas (Davis 1903;Ross 1937;Banks 1943;Flint 1970Flint , 1973Flint , 1992Flint , 2008Evans 1972;Penny 1981Penny , 1982Theischinger 1983Theischinger , 1999Geijskes 1984;Hayashi & Suda 1995;Contreras-Ramos 1997Rasmussen & Pescador 2002;Azevêdo & Hamada 2008Thouvenot 2008;Letardi et al. 2012 To further enhance the usefulness of this work we have included an updated suite of keys to the higher taxa of world Megaloptera down to genus (for adults) or subfamily (for larvae). We also provide summary data on the distribution of megalopteran diversity at the broad level of biogeographic region, and historical data on the decadal rate of description of valid megalopteran species, including a global taxonomic description curve for the order.

Checklist of Megaloptera species and subspecies
Checklist entries are formatted as follows. All entries for valid taxa are arranged alphabetically within the next-higher valid taxon. All valid taxon entries include the scientific name of the taxon, followed by its author(s) and date. Entries for family-and genus-group taxa contain citations to the page on which the name was established, and information on associated nomenclatural types (including designation kind).
Each species entry includes the currently recognized valid combination, followed by a list of all known synonymous invalid combinations (if any). Invalid synonyms are listed in approximately the chronological order in which they appeared in the literature. Species-level distribution data are reported by biogeographic region(s) and country(ies); uncertain records are flagged with a question mark (?). Chronostratigraphic ages for extinct species are reported in standard International Commission on Stratigraphy units (Gradstein et al. 2020).
Corydalus peruvianus (Davis, 1903) Corydalis peruviana Davis, 1903 Corydalus primitivus var. ferus Navás, 1927a Corydalus primitivus ferus Navás, 1927a Neotropical ( Taxonomic notes This species was originally described within Corydalis; however, it is probably an error because this genus is known only from the New World. This species has not been recorded since its original description, so it is not possible to confirm its actual identity.

Nomenclatural notes
Oswald & Penny (1991) identified Archichauliodes as a genus name based on a misidentified type species and a name whose type species had yet to be validly fixed.  (Walker, 1853)], which was misidentified as Archichauliodes dubitatus (Walker, 1853) [Hermes] in the original designation of van der Weele (1909).

Taxonomic notes
Austrochauliodes, whose type species is fixed below, is formally established here as a new junior subjective synonym of Protochauliodes.

Nomenclatural notes
Oswald & Penny (1991) identified Austrochauliodes as a genus name based on a misidentified type species and a name whose type species had yet to be validly fixed. They noted that the case (at that time) required referral to the Commission for type species fixation under Art. 70b of the Code (3 rd edition, ICZN 1985). We are not aware of any nomenclatural acts published since 1991 that have validly fixed the type species of Austrochauliodes under either the 3 rd or 4 th editions of the Code. To resolve this long-standing issue, we act here to formally fix the type species of Austrochauliodes under Art. 70.3 (4 th edition, ICZN 1999) in a manner that is in accordance with currently-accepted usage. Riek (1954) originally included a single valid nominal species in Austrochauliodes -Hermes dubitatus Walker,

Nomenclatural notes
Taeniochauliodes. The genus name Taeniochauliodes has priority over the concurrently-published name Leptochauliodes based on the First Reviser action of Liu et al. (2013d), who treated Taeniochauliodes as valid and Leptochauliodes as its invalid synonym.
Leptochauliodes. Oswald & Penny (1991) identified Leptochauliodes as a genus name based on a misidentified type species and a name whose type species had yet to be validly fixed.

Taxonomic notes
In addition to the two named extant species listed below, Lambkin (1992) reported an unnamed Austrosialis species from the Paleocene of Australia.

Taxonomic notes
The extinct genus †Chauliosialis contains one species - †Chauliosialis sukatshevae -which is known only from a single early instar larva preserved in Late Cretaceous Taymyr amber. Ponomarenko's (1976) original description noted that the larval structure of †Chauliosialis differed significantly from that of all other known megalopteran larvae, for instance in possessing the smallest number of lateral abdominal filaments in the order Megaloptera. We treat †Chauliosialis here as Megaloptera incertae sedis, rather than as Corydalidae: Chauliodinae, as it has sometimes been treated in prior literature. Ponomarenko, 1976 Palaearctic (Russia) [Late Cretaceous].
Taxonomic notes †Nematophlebia is an extinct genus known only from one Early Jurassic species, †Nematophlebia plicata, from Gloucestershire or Warwickshire, England (without further locality). The original species description reports only a few general venational characteristics, which are not enough to confidently include this species in any specific megalopteran family. Cockerell, 1915 Palaearctic (England) [Early Jurassic].

Taxa excluded from the Megaloptera
In addition to the species above, which we recognize here as belonging to the order Megaloptera, several other taxa have been placed in the order by some authors. We list below the taxa that are known to us that have previously been included in the Megaloptera by one or more previous authors, but which are now excluded. For each taxon we provide brief taxonomic notes about its current placement. In the synonymical listings in this section we make no attempt to be comprehensive. We present only enough synonymy to document original taxon placements, prominent intermediate placements (in some cases), and current placements (outside Megaloptera). Because our primary intent is to document the exclusion of certain taxa from Megaloptera, we make no attempt to provide comprehensive sub-taxon listings (e.g., of genera within families, or species within genera) of the higher taxa included in the list below.

Taxonomic notes
Navás (1927c) described a new extant genus and species from Argentina -Brucheiser argentinus -which he placed in a new family, Brucheiseridae, in the order Megaloptera. Riek (1975) described a second species of this same genus and transferred Brucheiseridae to the order Neuroptera. New (1989) demoted Brucheiseridae to a subfamily of Coniopterygidae, a placement that was adopted in Meinander's (1990) world catalogue of the Coniopterygidae, and subsequently by all later authors. Brucheiserinae currently contains two genera -Brucheiser and Flintoconis Sziráki, 2007 -both extant, and only the first of which has ever been placed in Megaloptera.  Wichard et al. (2005) described the family †Corydasialidae in Megaloptera based on a single species, †Corydasialis inexspectata, from the Baltic amber of Kaliningrad, Russia (Eocene). Corydasialids have been treated as belonging to either the Megaloptera (e.g., Wichard et al. 2005) or the Neuroptera (e.g., . In the present work, we follow  in treating corydasialids as chrysopoid neuropterans. Currently †Corydasialidae contains four extinct genera, †Cratochrysa Martins Neto, 1994, †Megalopteroneura Liu, Lu & Zhang, 2017, †Corydasialis Wichard, Chatterton & Ross, 2005, and †Ypresioneura Archibald & Makarkin, 2015, but only the two later have ever been placed in Megaloptera.

Discussion
The extant species of Megaloptera are present in all of the major biogeographical regions of the world (Table 1), but they are more than twice as speciose in northern regions (Nearctic + Palearctic + Oriental; 282 species) than they are in southern regions (Neotropical + Afrotropical + Australian; 124 species) and are particularly depauperate in the Australian (27 species) and Afrotropical (19) regions. Although present in cool-temperate latitudes (particularly in the Northern Hemisphere), megalopterans are absent from the more extreme near-polar regions of the Arctic and Antarctic, and are also absent from oceanic islands that lie distant from continental source areas. Among the six biogeographic regions, the Oriental region possesses the largest number of recorded extant species, 205, slightly more than half (51%) of the total number of extant megalopteran species (400). The Neotropical region has the second-most diverse fauna with 78 extant species, followed by the Nearctic (49), Palearctic (36), Australian (27), and Afrotropical (19) regions.
Extant corydalid diversity displays a pattern similar to that of total-order extant diversity, but the Australian, rather than the Palaearctic, has the fourth-largest number of species, and the Palearctic and Afrotropical faunas are both small (less than 15 species). With respect to extant sialid diversity, the Palearctic region possesses the largest number of species (26), followed by the Nearctic (24), Oriental (17), Neotropical (11), Australian (4), and Afrotropical (4) regions. The extant megalopteran faunas of four biogeographic regions are strongly dominated by corydalid species: Oriental (92% of species), Neotropical (86%), Australian (85%), Afrotropical (79%); one region is dominated by sialid species: Palearctic (69% Sialidae, 31% Corydalidae); and one region contains approximately equal numbers of species in both families: Nearctic (51% Sialidae, 49% Corydalidae). In the Palearctic, extant Corydalidae are restricted to eastern Asia and are notably absent from Europe. As insects with aquatic larvae, megalopterans are rare or absent in most arid areas of the world, including northern Africa and most of Australia. Anomalously, no megalopteran species have yet been reported from the wet tropical areas of western and central Africa.
Extinct megalopteran species, summarized in Table 2, are known from the Early Jurassic through the Miocene from fossils found on the continents of Europe (15 species), Asia (7), North America (2), and South America (2); no fossil megalopterans are currently known from Africa, and an unnamed Austrosialis species is reported to from the Paleocene of Australia (Lambkin 1992). For convenience and consistency of numerical treatment, we include extinct megalopterans within the Holocene biogeographic framework in Table 1, but it is understood that the recent factors responsible for delimiting those regions are not applicable to the extinct species. Of the 25 extinct megalopteran species known: 13 are Cenozoic Table 1 (continued on next two pages). Megaloptera species counts by family, subfamily, genus, and biogeograhic region ( † = taxon known only from extinct species; * = genus placement questionable).  The ca 40-period since 1980 is notable for its increased focus on previously under-studied areas of the globe, particularly the neotropics and southeastern Asia. More than half of the currently-known extant megalopteran species, and approximately two-thirds of its known extinct species, have been described since 1980. During this period the megalopteran fauna of the New World was studied by several entomologists, especially Oliver S. Flint Jr (1931-2019) †, Michael J. Glorioso (1956Glorioso ( -1980 †, Norman D. Penny (1946Penny ( -2016 †, Elwin D. Evans, and Atilano Contreras-Ramos. Southeastern Asia has proven to contain an unexpectedly rich and diverse fauna of megalopterans (particularly corydalids), which has been described by several workers including Fumio Hayashi, Ding Yang, and Xingyue Liu. Several other workers have described species of other biogeographic regions, notably Günther Theischinger for the Australian region.

Genus
Despite the comparatively large size and ecological importance of Megaloptera immatures, the taxonomy of the order is based principally upon adult characters, and relatively few species (only ca 20%) are known from one or more immature stages. No immature stages are known for five (of 35) extant and seven (of 13) fossil genera (Table 3). Only 34 species (8%) are known from eggs, and even fewer, Table 2 (continued on next page). Extinct Megaloptera: a summary by taxon, life stage, preservation, distribution, and chronostratigraphic age.   An unknown fossil species of Austrosialis is recorded for Paleocene Redbank Plains Formation of Queensland, Australia (see Lambkin 1992), nevertheless it is not added in this table.

Fig. 2.
Valid extant and extinct species of world Megaloptera established by decade; each species is attributed to the decade in which its currently valid species group-name was established. Subspecies are excluded. Fig. 3. Taxonomic description curve for valid extant, extinct, and total species of world Megaloptera by decade (based on data in Fig. 2). Table 3 (continued in next two pages). Known Megaloptera immatures: species counts by family, subfamily, genus, biogeographic region, and known life stage ( † = taxon known only from extinct species; * = taxon identified to genus only, species unknown).  Table 3 (continued). Known Megaloptera immatures: species counts by family, subfamily, genus, biogeographic region, and known life stage ( † = taxon known only from extinct species; * = taxon identified to genus only, species unknown).  Table 3 (continued). Known Megaloptera immatures: species counts by family, subfamily, genus, biogeograhic region, and known life stage ( † = taxon known only from extinct species; * = taxon identified to genus only, species unknown). 25 (6%), have described pupae. The number of species known from described larvae, 87 (20%), is somewhat greater, but well below the level of completeness necessary to permit the group to fullfill its potential for use in ecological studies and environmental impact assessment. Perhaps predictably, the number of described immature stages varies among the biogeographic regions, with knowledge best for species found in the Nearctic and Paleartic, less knowledge for species in the Neotropical and Oriental regions, and virtually nothing known of the immature stages for Afrotropical and Australian species (Table 3), especially their eggs and pupae.

Genus
This work provides detailed, species-level, information on the diversity and distribution of world Megaloptera. We hope that its taxonomic synopsis, keys, and assessment of the known immature stages will provide part of the foundation needed to support and broaden research on this group of charismatic insects in the decades to come.