﻿The Nereididae (Annelida) – diagnoses, descriptions, and a key to the genera

﻿Abstract Nereididae is among the most familiar of marine annelid families, common and well-studied in most marine environments but paradoxically no recent key or identification guide exists to the world’s genera. Here updated generic descriptions, a list of characters, a linear key to genera, and minimal diagnoses that distinguish each genus from all others in the family are provided. This information is generated from a Delta database of 186 morphological characters and a link is provided to downloadable software allowing the same data to be interrogated using the open-source Delta program Intkey – a nonlinear multiple entry point computerised interactive key. For each genus the recent literature is also summarised, comments on taxonomic status provided, and published keys to species cited. Nexus format matrices are provided for all 45 genera and 158 Nereididae species, representing all genera, scored for 146 multistate characters from the same character list to facilitate future phylogenetic studies.


Introduction
The Nereididae is probably the best-known of all the families of marine annelids ("polychaetes") -the family includes many species that are commonly encountered world-wide, intertidally, and also in diverse habitats from ephemeral freshwaters to abyssal depths (Bakken et al. 2022;Rouse et al. 2022). Nereididae are also frequent study subjects in teaching laboratories, and some species are commonly studied as laboratory animals (Fischer et al. 2010) (although now known to comprise complexes of multiple species; see Systematic account of Nereididae genera). Nereididae are almost invariably used as exemplars of marine Annelida in invertebrate zoology textbooks (Marshall and Williams 1972;Ruppert et al. 1994;Rouse and Giribet 2016). Nereididae are significant ecologically especially in intertidal flats (Compton et al. 2013;Choi et al. 2014) where they form significant components to the diet of fish and shorebirds (Iwamatsu et al. 2007;Alves et al. 2013;Duijns et al. 2013) and are aquaculture species of importance for fish bait and for aquaculture species for human consumption (Yoshida 1984;Olive 1994;Lim et al. 2021). A number of nereidid species are accidental introductions, or their introduced status is cryptic (Einfeldt et al. 2014;Villalobos-Guerrero and Carrera-Parra 2015;Tosuji et al. 2019;Kurt et al. 2021).
Taxonomic research on Nereididae is active, with nearly 100 papers published in the past decade, and the family currently comprises 45 genera and 719 species (Read and Fauchald 2023). Prominent among recent studies are investigations using molecular evidence leading to discovery of cryptic species Villalobos-Guerrero and Bakken 2018;Tosuji et al. 2019;Teixeira et al. 2022aTeixeira et al. , 2022b and new phylogenetic hypotheses (Tosuji et al. 2018;Alves et al. 2020Alves et al. , 2023Villalobos-Guerrero et al. 2022b). The past decade has also seen description of 40 new species, revision of eight genera and a review of the diversity, biology, anatomy, and ecology of the family Bakken et al. (2022).
Despite this recent taxonomic progress, identification of nereidid specimens remains a challenge, especially to non-specialists. Genus-level identification is difficult because no key to genera has been published since Fauchald (1977) and our own interactive key, now 20 years out of date (Wilson et al. 2003). Identification difficulties are compounded by the wide recognition that several of the most species-rich genera are assemblages of unrelated species (Bakken and Wilson 2005;Bakken et al. 2022;Rouse et al. 2022). It is clear that a number of genera will be revised when further molecular systematic studies are completed. But it is also clear that achieving sufficient taxon sampling in those molecular studies is a significant challenge and that the composition of many genera and identity of many species is likely to remain doubtful for a significant number of years. Yet the need for identification tools is widespread, not least by those conducting new molecular systematics studies to resolve problematic taxa. For these reasons we provide this review with the following aims: • to provide updated descriptions of all genera; these correct one error in Bakken et al. (2022) and also include additional characters (see Systematic account of genera); • to provide a dichotomous key to genera (see Key to genera of Nereididae) and a downloadable interactive identification tool (= Taxonomic Information System) using the Delta Intkey software (Wilson et al. 2023); • to discriminate all genera based on minimal diagnoses (see Systematic account of genera); • to provide a character list (see Nereididae characters) and Nexus format data matrices (Wilson et al. 2023) for inclusion in future phylogenetic studies requiring morphological evidence.

Methods
We used the Delta (Descriptive Language for Taxonomy) suite of programs to create and manage taxonomic data to support objective and quantitative description and discrimination of Nereididae taxa (Dallwitz 1974(Dallwitz , 1980Dallwitz et al. 1993;Dallwitz and Paine 2015). The original implementation of the Delta software by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) is still available as Windows only software via Dallwitz (2020). The Delta software was ported to Java by the Atlas of Living Australia as Open-Delta (Atlas of Living Australia 2014) as Windows/Mac OS/Linux software and this is the version we use. A third implementation of Delta, although lacking interactive identification software, is Cavalcanti (2022). The implementation of Delta is approximately identical in Dallwitz (2020) and Atlas of Living Australia (2014) so the guide of Coleman et al. (2010), although based on Windows software, is a very useful introduction for any Delta installation. Delta comprises several separate applications: the Delta Editor manages taxon by character data and generates outputs via scripts (called Action Sets). For the purposes of this paper, principal outputs are natural language descriptions and diagnoses of taxa (see below and Systematic account of Nereididae genera), linear keys (see below and Key to genera of Nereididae), interactive keys and Nexus files (Wilson et al. 2023) and annotated character lists (see Nereididae characters, below).
For each genus we include two Delta outputs: a description and a diagnosis -terms that have been used loosely in much of the taxonomic literature, where typically "diagnoses" are merely descriptions. Our descriptions are Delta-generated natural language outputs, use all character states known for a genus based on the sources we list as interpreted against our character list. These are concatenations of character states recorded for each taxon.
We concur with Borkent (2021) that diagnoses should be minimal statements that precisely distinguish taxa -typically from other taxa of the same rank -and ours do so. Borkent (2021) did not identify tools for the non-trivial task of generating such diagnoses but the Delta system has that capability: the DiagLevel setting specifies the minimum number of characters for which the diagnostic description should differ from all the other taxa (Dallwitz 1989). The diagnoses provided below include, for all genera, 'minimal diagnoses' which as the name implies, are a list of those characters which alone are sufficient to distinguish the given genus from all others. These minimal diagnoses were generated using the Intkey setting DiagLevel=1. For many genera, the setting could be increased to DiagLevel=2, thus generating additional characters which, for those genera, can be used to verify a 'minimal diagnosis' that may have been tentatively achieved by the user (perhaps when viewing damaged specimens, or when interpreting some characters was uncertain). These additional diagnostic characters providing an additional secondary level of verification are termed 'secondary diagnosis' in the generic accounts below. Our intended use of the diagnosis is to verify identifications by detecting errors that may have been made while using a key (Borkent 2021; also see comment below at the beginning of Key to genera of Nereididae).
The key was generated by the Delta Confor program with the following settings: RBASE = 2.00 ABASE = 1.00 REUSE = 1.01 VARYWT = 0.80; Number of confirmatory characters = 2. Following the recommendation of Dallwitz and Paine (2015) these settings were arrived at by iterative modification: balancing length of key (RBASE), evenness of subdivisions based on abundance indices, (ABASE, not used here), minimising re-use of characters (REUSE) and treatment of variable characters (VARYWT); Dallwitz (1974) provides further details.
Characters and character states are described and illustrated in the following section. The downloadable Intkey interactive key associated with this paper includes a more comprehensive set of character state illustrations. Two Nexus files are provided as Suppl. materials 1, 2 and as part of Wilson et al. (2023). One Nexus file contains all 45 genera, the second contains 158 species representing all nereidid genera (these are the 158 species for which we have the most complete data). Delta truncates character and character state labels in Nexus outputs to 30 characters; these truncated labels were replaced with full names from original Delta text files using shell scripts provided by Buz Wilson (pers. comm. 2 September 2023) and subsequent manual editing. Both Nexus files use the same 146 unordered multistate characters; both exclude meristic characters since their coding for phylogenetic analyses requires additional data and assumptions (e.g., Lawing et al. 2008) and was beyond the scope of this project. All these information sources are generated from the same Delta database that was used for the diagnoses and descriptions.
Interactive keys are implemented in the Delta suite by the Intkey application (Dallwitz et al. 1995;Coleman et al. 2010) which requires binary files generated from the Delta Editor (Penev et al. 2009). Our Intkey files for Nereididae are available as a separate download (Wilson et al. 2023) and require prior installation of the (recommended) Open-Delta software (Atlas of Living Australia 2014) or the original Delta programs (Dallwitz 2020). This paper serves as an alternative for those unable to install the Delta software.

Annotated characters of Nereididae
We identified 186 morphological characters to characterise nereidid taxa. Characters are given as they are described in the Delta Editor with annotations and illustrations as required, elaborating features in more detail. We have illustrated characters that we consider the most useful for identification using specimens lodged with the Museum & Art Gallery of the Northern Territory (NTM) and Museum Victoria (NMV), or derived from the literature as credited in the figure captions. Some characters are included even though their potential to inform higher level relationships are not yet tested, for example: palpophore surface (character 4), and prostomium longitudinal groove (character 9). We have also included some characters useful for distinguishing species (principally counts of papillae and paragnaths on the eversible pharynx). Meristic characters, in particular paragnath counts, are thus far rarely used to characterise nereidid genera -typically such characters require data from large numbers of specimens if they are to be the basis of robust taxonomic conclusions (Wilson 1993;Wilson and Glasby 1993).
This character list is also the basis of the Nexus format files provided by Wilson et al. (2023). That Nexus file excludes meristic characters for the reasons set out above, thus the 186 characters listed below are reduced to 146 multistate characters in Nexus outputs. Nexus file labels of character descriptions in some are abbreviated for convenience in phylogenetic software; all Nexus character labels are provided below in square brackets.
All Nereididae have a pair of antennae excepting Unanereis Day, 1962 in which a single antenna is present as illustrated in Day (1962: fig. 3a) (Unanereis macgregori) and Ben Amor (1980: fig. A) (Unanereis zghali). Bakken et al. (2022) discussed the possibility that presence of a single antenna is a developmental anomaly seen occasionally in Nereididae specimens, in which case both species of Unanereis may be referable to Ceratonereis or Solomononereis.  Glasby (1999) E modified after Hutchings and Reid (1990) G Leon Altoff photograph L, O, P R. Wilson drawings. Not to scale; body widths of these example specimens are in the range 2-5 mm wide excluding parapodia.
In most nereidids the palps are anteriorly directed and both palpophore and palpostyles are typically easily seen in dorsal view e.g., Villalobos-Guerrero et al. (2022b: fig. 5b, c) for Nereis agulhana. However, in some taxa, e.g., Micronereis and some Kainonereis and Platynereis species, the palps are distinctly ventrally directed and not fully visible in dorsal view. Examples of ventrally directed palps are Paxton (1983: fig. 15) for Micronereis bansei, Conde-Vela et al. (2018: fig. 3b, c) for Kainonereis alata and Read (2007: fig. 6a, b) for Platynereis australis. Caution is required utilising this character alone for identification since, at least in Kainonereis and Platynereis, this condition seems to be expressed in epitokes and not always confirmed for atokes. Furthermore, it is plausible that palps which may have been ventrally directed in live epitokes may be distorted into an anteriorly directed palps orientation as an artefact caused by preservation with pharynx extended (Read 2007: figs 2a, 3a); Read (2007) did not make use of this character to separate New Zealand species of Platynereis.
Although palpophore shape has been considered in recent revisionary works at the generic and species group levels, there has been no convincing arguments identifying particular shapes. At least four characteristic shapes have been documented: oval (Perinereis species complex) sub-ovoid (Composetia, Leonnates), obtusely conical (Leonnates, Parasetia, Potamonereis), and subconical (Parasetia, Neanthes) (Villalobos-Guerrero 2019; . However, some genera were found to be polymorphic for the states recognised and the states themselves can be difficult to distinguish, especially if specimens are preserved in a distorted condition. Other authors have distinguished palpophores on the basis of size: e.g., the palpophores of Potamonereis have been referred to as massive (as in Potamonereis kumensenis (Sato, 2020)). The present 2-state system is an attempt to describe more effectively the variation in the family. Thus, barrel-shaped palpophores (most genera) have an approximately equal width from base to palpostyle. They are not overly large compared to the size of the palpostyle, and in some cases may be of similar length and usually they have a transverse groove (Fig. 1A). Variability in length of barrel-shaped palpophores may be an indication that this character needs to be further divided into additional states. Subconical, dorso-ventrally flattened palpophores (Alitta, Hediste, Leonnates, Neanthes micromma, Neanthes glandicincta; Fig. 1B) tend to be massive compared to the size of the palpostyle, have a maximum width at mid to mid-end of palp, and usually have longitudinal striae. Neanthes is polymorphic for this character and Dendronereis is uncertain.
The presence of a transverse groove (Fig. 1A, open arrow) or multiple striae (Fig. 1B, filled arrows) on the palpophore, as noted by  is present in many nereid genera with biarticulated palps. The depth of the groove is variable depending on how extended the palps were on fixation. Sometimes many finer transverse grooves (striae) are visible although they may be faint if the palps are extended. In general, we observed that barrel-shaped forms have a single transverse groove which is perpendicular to the long axis of the palpophore, and that subconical, flattened forms possess multiple striae which are at an oblique angle.
A biarticulate palp with a distinct distal palpostyle is present in all Nereididae except members of the genus Micronereis which have an undivided roughly spherical palp that is also ventrally located on the anterior prostomium; see Paxton (1983: fig. 15; Micronereis bansei).
Two pairs of eyes are present in most Nereididae but they are absent in a number of species found at bathyal and abyssal depths and subterranean and cave-dwelling Namanereidinae. Examples of the former are illustrated by Hartman and Fauchald (1971: pl. 4 fig. a; Ceratocephale abyssorum, as Pisionura abyssorum) and Hartmann-Schröder (1975: fig. 22; Neanthes bioculata).
Terminology for characters 10 and 11 follows Villalobos-Guerrero et al. (2022a) who as part of a revision of Composetia showed that the body part referred to widely in the literature as "tentacular segment", "achaetigerous segment" and "apodous segment" comprises two segments plus the peristomium. While some genera are polymorphic for this character, others consistently have one or the other state. A short tentacular belt (state 1) distinguishes Namalycastis and Namanereis from most other nereidids. 14. Tentacular cirri extending to chaetiger (number) Small variations in the length of these cirri on the tentacular belt is often not a useful statistic, but may assist in recognising taxa which have very long tentacular cirri (e.g., Ceratonereis spp. and Platynereis spp.). Generally the posterodorsal pair is the longest.
2. with rows of tubercles extending to the base of each neuropodium (Fig. 1M).

absent.
Oesophageal caeca (equivalent terms are caecal glands, oesophageal pouches) are a pair of organs that are prominent and easily visible if present, but only by dissection. The oesophageal caeca are located immediately posterior to the muscular pharynx. at the start of the oesophagus. Their utility in taxonomy was first suggested by Savigny (1822) but Khlebovich (2001) was the first to use these structures in the taxonomy of Nereididae.
Variation in jaw morphology is as yet not well understood. Some taxa have jaws with smooth or faintly crenulate cutting edge, while others have distinctly or indistinctly toothed jaws. In some taxa the jaws are robust and dark (e.g., Neanthes spp., Perinereis spp.), while others have finer, translucent jaws (e.g., Ceratocephale spp., some Simplisetia spp.). However, many taxa are intermediate between these conditions, and abrasion may falsely result in the appearance of "smooth" jaws. Differences in the chemical composition of nereidid jaws may offer the best opportunity to distinguish taxa, but these studies have yet to be undertaken systematically.
This character was introduced by Villalobos-Guerrero et al. (2021) using the term "frustrum-shaped" however we prefer simpler language (and frustrum can also refer to a truncate pyramid).

Maxillary ring of pharynx with papillae number
A count of the total number of papillae on the maxillary ring helps to discriminate taxa and is practical even when the arrangement in discrete Areas is unclear, as is often the case in Gymnonereidinae.

Undivided maxillary ring -total number of paragnaths present
Micronereis is the only nereidid genus with paragnaths present on an undivided maxillary ring. In this genus the pharynx is not fully eversible and specimens are small -the number of paragnaths present can only be recorded as a single number, if it can be determined at all. These are the smooth bar paragnaths of Bakken et al. (2009) and are not formed by fusion of separate conical paragnaths but are apparently present throughout development in the form of smooth bars in all those taxa in which they occur. When they occur on Area IV, cones are also usually present (sometimes lacking, see Tosuji et al. 2019), as illustrated in Hutchings et al. (1991: fig. 3B; Perinereis amblyodonta) and Villalobos-Guerrero et al. (2022b: fig. 4B; Neanthes capensis).
Thus, bar-like paragnaths are distinct from "melted paragnaths" described and illustrated by Bakken et al. (2009: fig. 2c) which are formed by partial fusion of distinct paragnaths and occur most often in epitokes and are not considered to have taxonomic value. Glasby et al. (2011) clarified that the term "melted" should apply only to conical paragnaths mounted on a plate-like basement while Conde-Vela and Salazar-Vallejo (2015) introduced the term "merged paragnaths" for forms where a basement is not present. We have not used merged or melted paragnaths here since their intra-specific variability is incompletely understood.

Area IV smooth bar-like paragnaths: number
Paragnaths on Area IV are typically roughly conical in shape, though variations range from flattened domes of irregular shape to tooth-like paragnaths. In some taxa, particularly species of Neanthes and Perinereis, in addition to cones a separate patch of bar-shaped paragnaths occurs at the maxillary end of Area IV; these bars are counted separately. In Ceratocephale spp., Area V and VI contain up to three papillae in total; these are here interpreted as all occurring in Area V, with VI = 0,0. Typically the paragnaths on Areas VII-VIII comprise a variety of sizes irregularly arranged. However, in some taxa there is differentiation into an anterior band of paragnaths similar in size to elsewhere on the proboscis, and a separate band of minute paragnaths.
79. Areas VII-VIII P-bar paragnaths ( Fig. 2A)  It has been shown by Blake (1985) and Hilbig (1997) (for Ceratocephale loveni) and by Hylleberg and Nateewathana (1988) (for Ceratocephale andaman) that presence/absence of mid-dorsal papilla is variable and likely to be related to size or sexual maturity. However, the description of Ceratocephale papillata de León-González & Góngora-Garza, 1992  The prechaetal notopodial lobe is here defined as a digitiform process that is anterior to the acicular notopodial lobe and is not supported by the notopodial acicula (see character 100 Notopodial acicular process).   evidence of absence. It is necessary to manipulate the parapodia with transmitted light, or, preferably in small specimens, to remove and mount parapodia on slides. In Ceratonereis mirabilis and related species, notoaciculae of chaetigers 1 and 2 are present, but are short and translucent even though those of subsequent chaetigers are dark and extend to the tip of the acicular ligule. Namalycastis and Namanereis have notoacicula in chaetigers 1 and 2, although like notoaciculae in remaining chaetigers, they sit just above the neuroaciculae in the upper part of the neuropodium.  Chaetal shaft with sesquigomph articulation is illustrated in Fig. 4C. Despite the advance in quantifying chaetal articulation by Conde-Vela (2021) we retain the terms homogomph/ heterogomph/ sesquigomph due to their near-universal usage in the literature over the near-equivalents proposed by Conde-Vela (2021). It would also be desirable to compare inter-and intra-specific variation between verified Nereididae species before adopting new terms and a revised assessment of their taxonomic significance. 1. tapering, with straight margin (Fig. 4G). 2. bowed, with convex margin (Fig. 4H).

Prechaetal
This character was introduced by Villalobos-Guerrero et al. (2022a: fig. 1e, f) and is valuable for distinguishing Composetia and similar taxa. Other Nereididae, for example many species illustrated in Pettibone (1971) appear intermediate between bowed and straight-bladed forms or appear to be variable depending on which chaetiger is examined and are difficult to score.  (2005) depending on length of the free margin of the blade relative to the part within the articulation (Fig. 4D-F) but has not been widely adopted. Here we use simpler terms; "long blades" is equivalent to "Type 0" of Bakken and Wilson (2005). The term "extra-long blades" is equivalent to "Type 1" of Bakken and Wilson (2005). The term "short blades" is equivalent to "Type 2" of Bakken and Wilson (2005).

Pygidium and appendages -character 179
A trilobate pygidium is present in Namanereis while other Namanereidinae, and some Nicon species, have a bilobate pygidium. Other nereidids are commonly described as having a funnel-shaped pygidium, which may be crenulated or multi-incised (perhaps indicating specimens approaching epitoky). For the majority of Nereididae the form of the pygidium is unknown, often because specimens were incomplete posteriorly. Thus, we have not included a character describing the form of the pygidium.  Bakken and Wilson (2005)) E heterogomph falcigers with extra-long blades (2× a < b; = Type 1 of Bakken and Wilson (2005)) F heterogomph falcigers with short blades (a ≥ b; = Type 2 of Bakken and Wilson (2005)) G heterogomph falciger blade with straight margin H heterogomph falciger blade with bowed margin I fused heterogomph falciger chaetiger 70 Hediste diversicolor complex AHF, Gilleleje, Denmark J fused falciger chaetiger 40 Simplisetia aequisetis NMV F53970 K homogomph falciger with terminal tendon (filled arrow) and with terminal secondary tooth (open arrow; = bifid) Platynereis antipoda notopodial falciger chaetiger 66 NMV F50116 L sesquigomph falciger with terminal tendon absent but bifid with secondary terminal tooth (open arrow) and boss (filled arrow) Ceratonereis mirabilis median chaetiger M homogomph falciger with smooth blade Nereis cirriseta chaetiger 74 N homogomph falcigers with bidentate blade and large adjacent terminal and subterminal teeth Nereis bifida chaetiger 71 O homogomph falciger with bidentate blade and large widely-separated terminal and subterminal teeth Nereis triangularis chaetiger 24 P homogomph falciger with multidentate blade with ≥ 2 large lateral teeth, first lateral tooth subequal to terminal tooth, subsequent teeth decreasing in size Nereis denhamensis anterior chaetiger Q homogomph falciger with multidentate blade with ≥ 2 small lateral teeth, first and subsequent lateral teeth much smaller than terminal tooth Nereis apalie chaetiger 74. Sources: A-F, I-K, M-J R. Wilson drawings G, H edited after   fig. 1e, f) L after Perkins (1980: fig. 1d) M-P redrawn after Hutchings and Turvey (1982) Q after Wilson (1985: fig. 1E). Not to scale; maximum widths of chaetal shafts (at articulation) are in the range 0.01-0.03 mm.

Epitokal modifications and reproduction -characters 180-186
Although some epitokal features may be diagnostic at the genus level (Pamungkas and Glasby 2015), they are too poorly known across the family to be used in the present keys. Read (2007), Pamungkas and Glasby (2015) and Conde-Vela et al. (2018) demonstrated their utility in discriminating species across several genera. The seven characters presented below represent the basic characters for documenting epitokal reproductive forms. Oocytes are typically spherical in Nereididae but in many Namanereis species they are ovoid.

Key to genera of Nereididae
It is easy to reach an incorrect identification using a linear (usually dichotomous) key -one always reaches a name, irrespective of errors that may have been made. Thus, it is wise to doubt, and some form of verification is highly desirable. Our recommendation is that after reaching a genus determination using the key below, the next step should be to compare the specimen at hand with the diagnosis of the genus that has been tentatively identified; if specimen and diagnosis match, the user can have increased confidence in the identification. See Methods above for further discussion. As discussed in the Introduction, several Nereididae genera are widely rec-ognised as likely para-or polyphyletic groups. They are polymorphic for characters which distinguish other nereidid genera and therefore key out in more than one couplet.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present (absent occasionally in some specimens of A. virens species complex); II conical paragnaths present; III conical paragnaths present; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV smooth bar-like paragnaths absent. Oral ring papillae absent. Oral ring paragnaths present; with Areas V, VI, and VII-VIII discrete. Oral ring pyramidal paragnaths absent, or present. Area V conical paragnaths present, or absent; arranged in a longitudinal line, or irregularly. Area VI paragnaths present; paragnaths arranged in a roughly circular group, or in lines or arcs; conical paragnaths present. Areas VII-VIII paragnaths present; conical paragnaths present; P-bar paragnaths absent, or present.
Dorsal notopodial ligule markedly elongate on posterior chaetigers, or not markedly elongate on posterior chaetigers; markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly, or approximately equal to length of dorsal notopodial ligule at least on anterior chaetigers (thus notopodium of three similar sized ligules/lobes); present on all chaetigers. Notopodial acicular process absent. Dorsal cirrus sub-terminally attached to dorsal margin of dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers.
Remarks. The modern concept of Alitta is due to Khlebovich (1996) but the generic description and the species included have been emended by Villalobos-Guerrero and Carrera-Parra (2015) and Villalobos-Guerrero and Bakken (2018); the description here is based on that of the latter two studies. Alitta now contains eight species all occurring in either the North Pacific or North Atlantic Oceans. Alitta succinea (Leuckart, 1847) has been reported as a supposed introduced species from numerous cosmopolitan localities but as summarised by Villalobos-Guerrero and Carrera-Parra (2015: 165-166) many of these represent misidentifications of related species.
There is no identification guide for all species of Alitta but the four species in the A. virens species complex can be identified using the keys to atokes and to epitokes in Villalobos-Guerrero and Bakken (2018).
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Ventrum of anterior chaetigers with rows of tubercles extending to the base of each neuropodium.
Maxillary ring of pharynx with papillae present (sometimes with horny tips); solitary; 50-110 papillae in total. Maxillary ring paragnaths absent. Oral ring papillae absent. Oral ring paragnaths absent. Dorsal notopodial ligule present; commences chaetiger 1; not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Anal cirri form cirriform or conical. Remarks. Australonereis is a monotypic genus. The single species A. ehlersi (Augener, 1913) occurs only in southern Australian estuaries where these large and often locally abundant worms are instantly recognisable by the conspicuous rows of tuberculae on the ventral surface; living specimens are also much more fragile than those belonging to other genera of Nereididae and readily fragment in the field.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpostyles subconical, or acutely conical. Eyes present, or absent. Prostomium anterior margin indented. Tentacular belt equal to or less than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V three papillae present (close together); VI papillae present, or absent; VII-VIII seven papillae present, arranged in a single row. Oral ring paragnaths absent. In Ceratocephale spp., Areas V and VI contain up to three papillae in total; these are here interpreted as all occurring in Area V, with VI = 0,0.
Remarks. The definition of Ceratocephale used here follows Santos (2007). Bakken et al. (2022) noted the possible synonymy of Tambalagamia Pillai, 1961 and suggested that a revision was required. Further evidence of morphological diversity of key characters also suggests that Ceratocephale as presently constituted may not be a natural group: according to Santos et al. (2005), in Ceratocephale the tentacular belt is shorter than the subsequent chaetigers however this is not so for all species: e.g. Ceratocephale papillata de León-González & Góngora-Garza, 1992, nor in C. loveni Malmgren, 1867 or C. pacifica (Hartman, 1960) based on Hilbig (1997); and C. bansei Khlebovich, 1966 may be the only species of Ceratocephale with papillae on Area VI of the pharynx.
Ceratocephale currently includes 12 accepted species recorded from all oceans except the Arctic Ocean and from intertidal to abyssal depths (Read and Fauchald 2023). There is no identification guide to all species although Hylleberg and Nateewathana (1988) have a key to the six species then known. Hutchings and Reid (1990) allow identification of the three Australian species currently described although we know of two additional undescribed Australian Ceratocephale species.
Maxillary ring of pharynx with papillae absent. Area I conical paragnaths absent; II conical paragnaths present; III conical paragnaths present; IV paragnaths present; IV conical paragnaths present. Oral ring papillae absent. Oral ring paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers, or not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe absent. Notopodial acicular process absent. Dorsal cirrus sub-terminally attached to dorsal margin of dorsal notopodial ligule on posterior chaetigers; arising from basal cirrophore; cirrophore of dorsal cirrus short, at most as long as ventral notopodial ligule, or much longer than ventral notopodial ligule; cirrophore of dorsal cirrus not enlarged and vascularised; cirrophore of dorsal cirrus cylindrical throughout.
Neuropodial postchaetal lobe present; projecting beyond end of the acicular ligule; restricted to anterior chaetigers; digitiform or flattened. Ventral neuropodial ligule of anterior chaetigers present. Ventral neuropodial ligule of anterior chaetigers approx. as long as acicular neuropodial ligule, or short, up to half length of acicular neuropodial ligule. Ventral neuropodial ligule on posterior chaetigers present. Ventral neuropodial ligule on posterior chaetigers similar to length of acicular neuropodial ligule, or short, up to half length of acicular neuropodial ligule.
Anal cirri form cirriform or conical. Remarks. Ceratonereis as currently defined follows the concept of Perkins (1980) and Hartmann-Schröder (1985). Previously the genus ("Ceratonereis sensu lato") had included unrelated nereidid species with superficially similar paragnath configuration. Those disparate species (none of which have the indented prostomium characteristic of Ceratonereis sensu stricto) are now moved to genera Composetia Hartmann-Schröder (1985) and Simplisetia Hartmann-Schröder (1985). This restricted definition of Ceratonereis is probably monophyletic (Bakken and Wilson 2005) and comprises 43 species which are known from all oceans (Read and Fauchald 2023).
There is no identification guide to the species of Ceratonereis and many nominal species are poorly known and some still may belong to other genera. Distinguishing species relies heavily on differences in chaetae and in parapodial structures; pigmentation pattern in living specimens is often distinctive and would probably be most helpful.
Conde-Vela (2021) includes a key to American species of Ceratonereis. Glasby (2015) provides a key that includes four species of Ceratonereis known from tropical Australia. Sources. Bakken et al. (2022). Diagnosis. Ventral peristomial flap present (minimal diagnosis). Areas VII-VIII conical paragnaths differentiated, with a separate band of minute paragnaths also present; dorsal notopodial ligule markedly broader on posterior chaetigers (secondary diagnosis).
Oesophageal caeca present. Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present; II conical paragnaths present; IV paragnaths present; IV conical paragnaths present. Oral ring papillae absent. Oral ring paragnaths present; with Areas V, VI and VII-VIII discrete; on Area V and VI form distinct groups. Area V conical paragnaths absent. Area VI paragnaths present; paragnaths arranged in a roughly circular group; conical paragnaths present; smooth bars absent. Areas VII-VIII paragnaths present; conical; arranged in isolated patches, or in one or more irregular lines forming a continuous band; conical paragnaths differentiated, with a separate band of minute paragnaths also present (present as patches in C. peristomialis).
Dorsal notopodial ligule markedly elongate on posterior chaetigers; markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Dorsal cirrus sub-terminally attached to dorsal margin of dorsal notopodial ligule on posterior chaetigers.
Oesophageal caeca present. Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present; II conical paragnaths present; III conical paragnaths present; IV paragnaths present; IV conical paragnaths present. Oral ring papillae absent. Oral ring paragnaths absent.
Dorsal notopodial ligule not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; present on all chaetigers, or restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers. Neuropodial postchaetal lobe present; projecting beyond end of the acicular ligule; restricted to anterior chaetigers. Ventral neuropodial ligule of anterior chaetigers present. Ventral neuropodial ligule of anterior chaetigers approx. as long as acicular neuropodial ligule. Ventral neuropodial ligule on posterior chaetigers present. Ventral neuropodial ligule on posterior chaetigers similar to length of acicular neuropodial ligule.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed).
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae present; solitary. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae present; VI papillae present; VII-VIII papillae present. Oral ring paragnaths absent.
Dorsal notopodial ligule present. Dorsal notopodial ligule divided into numerous branchial filaments. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Remarks. Dendronereides is the only nereidid genus in which the dorsal notopodial ligule is transformed into "branchial" filaments; the genus contains three species which occur in tropical estuaries of the Indo-Pacific. There is no taxonomic review or identification guide for the species of Dendronereides.
Maxillary ring of pharynx with papillae present, or absent. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly. Dorsal cirrus divided into numerous branchial filaments. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Ventral neuropodial ligule of anterior chaetigers present. Ventral neuropodial ligule of anterior chaetigers approx. as long as acicular neuropodial ligule. Ventral neuropodial ligule on posterior chaetigers absent. Neuropodia of branchial chaetigers divided into five lobes, plus ventral cirrus, plus two smaller cirri on ventral neuropodial lobe (not arising from same location as ventral cirri). Posteriorly becoming simpler, eventually with a single neuropodial lobe and ventral cirrus.
Remarks. Species belonging to Dendronereis are easily recognised as this is the only genus of Nereididae in which the dorsal cirrus is transformed into branchial filaments. Bakken et al. (2022) incorrectly stated that maxillary ring paragnaths may be present or absent; they are always absent as per the corrected description and diagnosis above.
Five species of Dendronereis are known, all occurring in shallow waters of the Indo-Pacific. Hsueh (2019b) provides a key to all known species.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae present, or absent. Oral ring paragnaths present; with Areas V, VI, and VII-VIII discrete, or comprising a continuous ring dorsally and ventrally, discrete groups not recognisable; on Areas V and VI form distinct groups. Area V conical paragnaths present, or absent. Area VI paragnaths present; arranged in a roughly circular group; conical paragnaths present, or absent; smooth bars present, or absent. Areas VII-VIII paragnaths present, or absent; conical paragnaths present; conical paragnaths arranged in isolated patches, or in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band; rod-shaped paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers, or not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present, or absent; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process present, or absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers; simple, lacking basal cirrophore.
Remarks. The description here follows Hsueh (2018) with additional information on the straight/bowed blade falcigers character introduced (for Composetia) by Villalobos-Guerrero et al. (2022a).
Eunereis is the only Nereididae genus with paragnaths present only on the oral ring. Eunereis includes species which in other respects, especially chaetal characters, are similar to either of the genera Neanthes or Nereis suggesting a review is necessary.
Eunereis includes ten accepted species which encompass wide geographic and bathymetric distributions. There is no published identification guide to all species.
Jaws with smooth or slightly crenulate cutting edge or with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae present; VI papillae present; VII-VIII papillae present. Oral ring paragnaths absent.
Transverse dorsal lamellae absent, or present. Dorsal notopodial ligule present; commences chaetiger 1; not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers (but cirrophore of dorsal cirrus is expanded and looks like an expanded notopodial lobe unless progressive change is noted over many chaetigers). Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; present on all chaetigers. Notopodial acicular process present. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers; arising from basal cirrophore.
Anal cirri form cirriform or conical. Remarks. The genus Gymnonereis is diagnosed by the presence of accessory dorsal and ventral cirri and notochaetae comprising sesquigomph spinigers (although as discussed by Darbyshire 2014 it is not clear that these chaetae are alike in all species). Gymnonereis is most similar to Tambalagamia and the two have been combined by some authors, Gymnonereis being the senior synonym (Pettibone 1970;Hylleberg and Nateewathana 1988).
Gymnonereis is a genus of seven species, predominantly occurring in the southern hemisphere and the tropical Indo-Pacific and from shallow water (~ 60 m or less). There is no published key to all species although several regional keys exist (Hylleberg and Nateewathana 1988;Hutchings and Reid 1990).
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Area I conical paragnaths present; II conical paragnaths present; III conical paragnaths present; III rodlike paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV rod-like paragnaths absent. Oral ring papillae absent. Oral ring paragnaths present; with Areas V, VI, and VII-VIII discrete; on Areas V and VI form distinct groups. Area V conical paragnaths absent. Area VI paragnaths present; paragnaths arranged in a roughly circular group, or in lines or arcs; conical paragnaths present; smooth bars absent. Area VII-VIII paragnaths present; conical paragnaths present; conical paragnaths arranged in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band; rod-shaped paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Remarks. Hediste species are characterised by the "simple" neuropodial falcigers (with fused articulation) which are present in posterior chaetigers and by having paragnaths on both rings of the pharynx. The most recent taxonomic treatments are Sato and Nakashima (2003) and Teixeira et al. (2022a) who described a total of four new species, broadened the generic diagnosis, and demonstrated the power of morphometric methods to discriminate cryptic species.
Hediste is a genus of estuarine nereidids which occur in the northern hemisphere. Seven species of Hediste are currently described but despite recent publications, the most widespread species, H. diversicolor (O.F. Müller, 1776) still contains cryptic species not yet described (Tosuji et al. 2018;Teixeira et al. 2022a). A key to Asian species of Hediste is provided by Sato and Nakashima (2003) and Teixeira et al. (2022a) provide a key to European species.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Tentacular belt greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Area I conical paragnaths present; II conical paragnaths present; III conical paragnaths present; III rodlike paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV rod-like paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae absent; VI papillae absent; VII-VIII papillae present. Oral ring paragnaths present; with Areas V, VI, and VII-VIII discrete; on Areas V and VI form distinct groups. Area V conical paragnaths absent. Area VI paragnaths present; paragnaths arranged in a roughly circular group; conical paragnaths present; smooth bars absent. Areas VII-VIII paragnaths present; conical paragnaths present; conical paragnaths arranged in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band; rod-shaped paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Remarks. Imajimainereis contains a single species, I. pacifica de León-González & Solís-Weiss, 2000, which differs from all other Nereididae by having both papillae and paragnaths on the oral ring and neurochaetae including heterogomph spinigers.

Kainonereis
Description. Palps anteriorly directed, or ventrally directed. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Prostomium the antennae are separate but sometimes basally fused in male epitokes. Tentacular cirri articulated.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring paragnaths absent.
Remarks. Kainonereis was originally described for an epitokous specimen in which dorsal cirri of chaetigers 5-7 were expanded into elytra-like structures.
Jaws with dentate cutting edge, 20 teeth. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae number two in total; arrangement solitary. Area V papillae absent; VI papillae present, one papilla (a single fleshy nob on each side); VII-VIII papillae absent. Oral ring paragnaths absent.
Dorsal notopodial ligule present; markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; approximately equal to length of dorsal notopodial ligule at least on anterior chaetigers (thus notopodium of three similar sized ligules/lobes); present on all chaetigers. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers.
Remarks. The most recent taxonomic treatment of Kinberginereis is the original description of Pettibone (1971). Kinberginereis is most similar to Kainonereis, atokes differing only in that Kinberginereis has an indented prostomium but the prostomium of Kainonereis is entire. Epitokes of Kainonereis are distinctive in having elytriform expansion of dorsal cirrophores of chaetigers 5-7 but epitokes of Kinberginereis are unknown.
Kinberginereis includes a single species, K. inermis (Hoagland, 1920) described from a single specimen from shallow water in the Philippines; the only subsequent reports are unverified occurrence records now in the Smithsonian National Museum of Natural History from the Gulf of Mexico.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Prostomium anterior margin indented; longitudinal groove present. Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae present; in tufts. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae absent; VI papillae present; VII-VIII papillae present or absent (may be absent in juveniles). Oral ring paragnaths absent. Papillae triangular or conical on Area VI, rounded on Areas VII-VIII. Dorsal notopodial ligule present; commences chaetiger 1; not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Remarks. The description and diagnosis of Laeonereis here is derived from the revision of Conde-Vela (2021) which is only slightly modified from that of Pettibone (1971) who recognised a single species of Laeonereis. Simultaneously with the publication of the morphological revision of Laeonereis by Conde-Vela (2021), Sampieri et al. (2021) published a molecular study of Laeonereis (but with no morphological component) and revealed seven or nine molecular OTUs. It is tantalising that Sampieri et al. (2021) and Conde-Vela (2021) discovered very similar species-level diversity from within the same geographic range but frustrating that neither apparently was aware of the others' research.
Currently eight species of Laeonereis are recognised, largely confined to the Atlantic coasts of North and South America; they can be identified using the key of Conde-Vela (2021).
Oesophageal caeca absent. Jaws with smooth or slightly crenulate cutting edge or with dentate cutting edge. Maxillary ring of pharynx with papillae present, or absent; solitary. Maxillary ring paragnaths present. Area I conical paragnaths present, or absent; II conical paragnaths present; III conical paragnaths present, or absent; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV smooth bar-like paragnaths present, or absent; IV rod-like paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae present, or absent; VI papillae present; VII-VIII papillae present. Oral ring paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly, or approximately equal to length of dorsal notopodial ligule at least on anterior chaetigers (thus notopodium of three similarly sized ligules/lobes); present on all chaetigers, or restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Anal cirri form cirriform or conical. (2000) and emendments by Villalobos-Guerrero et al. (2022a). Original descriptions sometimes report the presence of sesquigomph falcigers and spinigers but as noted by Qiu and Qian (2000) some of these interpretations are inconsistent, with the same chaetal forms being given different names by some authors. However Qiu and Qian (2000) also do not interpret these terms consistently: they do not use the term sesquigomph yet their figures 3B and 3E (Leonnates indicus Kinberg, 1865), 5E (L. nierstraszi Horst, 1924), 7B (L. decipiens Fauvel, 1929), 9D (L. persicus Wesenberg-Lund, 1949, and14D (L. crinitus Hutchings &Reid, 1991, albeit  Leonnates includes 13 species with the greatest diversity in the tropical Indo-Pacific. Qiu and Qian (2000) provide a key to the seven species known at that time.

Type species. Leptonereis laevis
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle).
Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae absent. Oral ring paragnaths absent. Dorsal notopodial ligule present; markedly elongate on posterior chaetigers; markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Remarks. The description of Leptonereis given here follows the most recent treatment (Pettibone 1971) which in turn was based on new descriptions and figures of the type by Kinberg (1910) and Hartman (1945). However, many characters including articulation of the chaetae remain unverified.
Leptonereis includes a single species, L. laevis Kinberg, 1865, based on a single specimen from Guayaquil, Ecuador and now recorded from tropical east Pacific coasts of North and South America.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed). Prostomium anterior margin entire. Tentacular belt greater than length of chaetiger 1. Tentacular cirri three pairs. Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae present. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae absent; VI papillae present; VII-VIII papillae present, arranged in a single row. Oral ring paragnaths absent.
Dorsal notopodial ligule markedly reduced or absent on posterior chaetigers. Prechaetal notopodial lobe present; restricted to a limited number of anterior chaetigers.
Remarks. This easily diagnosed genus from estuaries in India includes a single species. Conde-Vela (2019a) provides a redescription based on non-type material which is topotypic and shares the unusual morphological characters of the original description including the presence of only three pairs of tentacular cirri. Conde-Vela (2019a) also clarified the surname of the author, which is Rao, not 'Nageswara- Rao' or 'Nageswara Rao' as stated in much of the literature. Although the double surname is a more precise authority name, we follow Conde-Vela (2019a) because Rao appears to be an uncommon name among polychaete taxon authors and thus not easily confused.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Eyes absent. Prostomium with eyes, if not absent, indistinct and likely to be missed. Tentacular belt equal to or less than length of chaetiger 1; represented by two distinct segments each carrying a pair of tentacular cirri.
Jaws with dentate cutting edge, seven teeth. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae absent. Oral ring paragnaths absent.
Remarks. Micronereides was erected to contain M. capensis Day, 1963 a small nereidid lacking pharyngeal papillae or paragnaths and in which tentacular cirri arise from two distinct anterior segments (unique among Nereididae). A revised diagnosis was provided by Banse (1977) including the observation that accessory ventral cirri are present on anterior segments thus placing the genus in Gymnonereidinae.
The genus is still only known from a single species, M. capensis, recorded from shelf depths in the South Atlantic Ocean.
Jaws with dentate cutting edge. Maxillary ring of pharynx undivided. Maxillary ring of pharynx with papillae absent; undivided maxillary ring with two paragnaths in total. Oral ring papillae absent. Oral ring paragnaths present; on Areas V and VI not recognisably distinct. Crown-shaped oral ring paragnaths present. Area V conical paragnaths absent.

Remarks.
Micronereis is a genus of small nereidids generally associated with algal turfs in intertidal and shallow (to ~ 30 m) marine waters. Micronereis species differ from other Nereididae in lacking antennae and having a pharynx that is not fully eversible. They are sexually dimorphic and males have distinctive neurochaetae that function as copulatory hooks not found in other Nereididae.
Micronereis currently includes ten accepted species which collectively have a wide global distribution. Paxton (1983) revised the genus and included a key to males but three more species have since been recognised.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface without grooves or striae (palps short, compact) or with a single transverse groove (palpophores well developed); palpostyles spherical. Prostomium anterior margin indented; longitudinal groove present. Tentacular belt equal to or less than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae absent. Oral ring paragnaths absent.
Pygidium with three incisions marking lateral and dorsal lobes. Anal cirri form cirriform or conical, or flattened, resembling posterior dorsal cirri.
Reproductive characters. Oocyte spherical. Remarks. Namalycastis currently includes 33 accepted species recorded mainly from intertidal and supralittoral areas, including freshwater, of the tropics and subtropics. Together with sister-group Namanereis, they are one of only a few polychaetes to be found in association with riparian vegetation. Because they have an unadorned pharynx and a simplified parapodia, distinguishing species relies heavily on differences in chaetae, form of sensory organs of the head, and pigmentation patterns in living specimens. The modern concept of the subfamily and genus was introduced by Hartman (1959) and later reviewed by Glasby (1999), who included a key to all known species at the time. Since Glasby (1999) there have been five species described: Namalycastis caetensis Alves & Santos, 2016, Namalycastis glasbyi Fernando & Rajasekaran, 2007, Namalycastis jaya Magesh, Kvist & Glasby, 2012, Namalycastis occulta Conde-Vela, 2013 and Namalycastis rhodochorde Glasby, Miura, Nishi & Junardi, 2007;however, Namalycastis occulta Conde-Vela, 2013 is now accepted as Namanereis occulta (Conde-Vela, 2013). Magesh et al. (2013) provided a key to Indian species and Conde-Vela (2013) provided a key to Caribbean species.
Description. Antennae present, or absent (rarely). Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface without grooves or striae (most species; palps short, compact) or with a single transverse groove (palpophores well developed); palpostyles spherical. Eyes present, or absent. Tentacular belt equal to or less than length of chaetiger 1. Tentacular cirri four pairs, or three pairs. Jaws forms with a crenulate cutting edge have 2 teeth proximally, with smooth or slightly crenulate cutting edge or with dentate cutting edge.
Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae absent. Oral ring paragnaths absent.
Pygidium with three incisions marking lateral and dorsal lobes. Anal cirri form cirriform or conical, or short, stout and appearing as an extension of the pygidium.
Reproductive characters. Oocyte spherical (rarely), or ovoid. Remarks. Namanereis currently includes 27 accepted species recorded mainly from intertidal, supralittoral and terrestrial areas, including the freshwaters of streams, caves, and underground aquifers. Although mainly found in the tropics and subtropics one species, Namanereis quadraticeps (Blanchard in Gay 1849), has a circum-subantarctic/temperate distribution. Together with sister-group Namalycastis, they are one of only a few polychaetes to be found in association with riparian vegetation. Because they have an unadorned pharynx and a simplified parapodia, distinguishing species relies heavily on differences in chaetae and form of sensory organs of the head. The modern concept of the subfamily and genus was introduced by Hartman (1959) and reviewed by Glasby (1999), the latter who included a key to all known species at the time. Since Glasby (1999) there have been seven species described: Namanereis canariarum Núñez, Glasby & Naranjo, 2020, Namanereis christopheri Conde-Vela, 2017, Namanereis gesae Fiege & Van Damme, 2002, Namanereis llanetensis Núñez, Glasby & Naranjo, 2020, Namanereis occulta (Conde-Vela, 2013, Namanereis pilbarensis Glasby, Fiege & Van Damme, 2014, and Namanereis socotrensis Glasby, Fiege & Van Damme, 2014, making this genus one of the most studied in the last 20 or so years. As noted by Alves et al. (2018) in a morphological phylogenetic study of the subfamily, Lycastoides alticola Johnson, 1903 is also part of the Namanereis clade, but the species cannot take the name Namanereis, as Lycastoides is the senior genus (Read and Fauchald 2023). Conde-Vela (2017) provides an updated key to Namanereis species of the World.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle), or massive subconical, flattened (palpostyle is minute by comparison) (rarely). Palpophore surface without grooves or striae or with a single transverse groove (palpophores well developed) or with several oblique grooves or striae (palpophores well developed). Eyes present, or absent. Tentacular belt greater than length of chaetiger 1.
Oesophageal caeca present, or absent. Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present; II conical paragnaths present, or absent; III conical paragnaths present, or absent; III rod-like paragnaths absent; IV paragnaths present, or absent; IV conical paragnaths present, or absent; IV smooth bar-like paragnaths present, or absent; IV rod-like paragnaths absent. Oral ring papillae absent. Oral ring paragnaths present, or absent; with Areas V, VI, and VII-VIII discrete, or comprising a continuous ring dorsally and ventrally, discrete groups not recognisable; on Areas V and VI form distinct groups, or not recognisably distinct. Area V conical paragnaths present, or absent. Area VI paragnaths present, or absent; paragnaths arranged in a roughly circular group, or in lines or arcs; conical paragnaths present; smooth bars absent. Areas VII-VIII paragnaths present, or absent; conical paragnaths present; conical paragnaths arranged in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band, or differentiated, with a separate band of minute paragnaths also present; rod-shaped paragnaths absent.
Dorsal notopodial ligule markedly elongate on anterior chaetigers, or not markedly elongate on anterior chaetigers; markedly elongate on posterior chaetigers, or not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers, or not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present, or absent; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly, or approximately equal to length of dorsal notopodial ligule at least on anterior chaetigers (thus notopodium of three similar sized ligules/lobes); present on all chaetigers, or restricted to a limited number of anterior chaetigers. Notopodial acicular process present, or absent; reducing in size posteriorly, last present on chaetiger 5-25. Dorsal cirrus sub-terminally attached to dorsal margin of dorsal notopodial ligule on posterior chaetigers, or not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Neuropodial prechaetal lobe absent. Neuropodial postchaetal lobe absent, or present; projecting beyond end of the acicular ligule, or not projecting beyond end of the acicular ligule; present throughout all chaetigers, or restricted to anterior chaetigers; digitiform. Ventral neuropodial ligule of anterior chaetigers present. Ventral neuropodial ligule of anterior chaetigers approx. as long as acicular neuropodial ligule, or short, up to half length of acicular neuropodial ligule. Ventral neuropodial ligule on posterior chaetigers present, or absent. Ventral neuropodial ligule on posterior chaetigers similar to length of acicular neuropodial ligule, or short, up to half length of acicular neuropodial ligule.
Anal cirri form cirriform or conical. Remarks. Neanthes, even after removing some species to Alitta and Pseudonereis, was found by Bakken and Wilson (2005) to contain morphologically dissimilar species. Our diagnosis here compounds the problem since the description is expanded to include species with variable palpophore morphology (N. gisserana (Horst, 1924) and N. glandicincta (Southern, 1921)) and with elongate dorsal notopodial lobe on all chaetigers (N. articulata Knox, 1960, N. crucifera (Grube, 1878, and N. mossambica Day, 1957) or only on posterior chaetigers (N. mancorae Berkeley &Berkeley, 1961 andN. noodti Hartmann-Schröder, 1962). Furthermore, Neanthes includes a subset of species having well-developed prechaetal notopodial lobes, giving the notopodia a tri-lobed appearance, which differs from the majority of bilobed species (Bakken 2006). However, the genus must still comprise several unrelated groups. Neanthes currently includes 88 species. There are no comprehensive keys or identification guides but there are several tabular comparisons of subsets of species, for example Asian species (Hsueh 2019a; Villalobos-Guerrero and Idris 2021) and deep-sea species (Shimabukuro et al. 2017).
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Area I conical paragnaths present; II conical paragnaths present; III conical paragnaths present; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV rod-like paragnaths absent. Oral ring paragnaths present; with Areas V, VI and VII-VIII discrete; on Areas V and VI form distinct groups. Area V conical paragnaths present. Area VI paragnaths present; paragnaths arranged in a roughly circular group; conical paragnaths present; smooth bars absent. Areas VII-VIII paragnaths present; conical paragnaths present; conical paragnaths arranged in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band; rod-shaped paragnaths absent.
Dorsal notopodial ligule markedly elongate on posterior chaetigers; markedly broader on posterior chaetigers. Prechaetal notopodial lobe present; approximately equal to length of dorsal notopodial ligule at least on anterior chaetigers (thus notopodium of three similar sized ligules/lobes); present on all chaetigers. Dorsal cirrus sub-terminally attached to dorsal margin of dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on anterior or posterior chaetigers.

Remarks.
Nectoneanthes was treated as a synonym of Neanthes by Wilson (1988) and Bakken and Wilson (2005). Sato (2013) showed Wilson (1988) to be incorrect in treating Nectoneanthes oxypoda (Marenzeller, 1879) as an epitokal form and resurrected Nectoneanthes and described a second species for the genus. The description by Sato (2013) is followed here. Sato (2013) provided a key to the two species of Nectoneanthes; both species occur on the north-west Pacific coast, with N. oxypoda also recorded by Sato (2013) from southern Australia and the Persian Gulf.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed). Eyes present, or absent. Tentacular belt greater than length of chaetiger 1.
Oesophageal caeca present, or absent. Jaws with smooth or slightly crenulate cutting edge or with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present, or absent; II conical paragnaths present, or absent; III conical paragnaths present, or absent; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV smooth bar-like paragnaths present, or absent; IV rod-like paragnaths absent. Oral ring papillae absent. Oral ring paragnaths present, or absent; Areas V, VI, and VII-VIII discrete, forming distinct groups. Area V conical paragnaths present, or absent; arranged in a triangle, or in a longitudinal line. Area VI paragnaths present, or absent; paragnaths arranged in a roughly circular group; conical paragnaths present; smooth bars absent. Areas VII-VIII paragnaths present, or absent; conical paragnaths present; conical paragnaths arranged in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band; rodshaped paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers, or not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present, or absent; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.

Remarks.
Nereis is the type taxon of the family Nereididae. It is a large assemblage of species, currently with 226 species attributed to the genus, many that probably belong in other genera. There are no revisions of the genus, or parts of it, or any that delineate species into informal subgroups. The description here follows Bakken et al. (2022). Some species are treated as part of revisions of single species or of several similar species (e.g., Salazar-Vallejo et al. 2021), or in treatments of species belonging to the genus in a regional perspective (e.g., Hsueh 2020).
Species of Nereis have been found from the littoral zone to abyssal areas, and from a wide range of habitats.
No complete identification guide to species is available but several useful keys of restricted scope have been published: Ramírez-Hernández et al. (2015) has a key to 22 species occurring in the Grand Caribbean, Hsueh (2020) includes a key to 32 species reported from East Asia, and Salazar-Vallejo et al.
(2021) has a key to the 11 species previously confused with N. falsa de Quatrefages, 1866.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed). Eyes present, or absent. Tentacular belt greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae and paragnaths absent. Oral ring papillae and paragnaths absent.
Dorsal notopodial ligule present, or absent; not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present, or absent; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Pygidium bilobate. Anal cirri form cirriform or conical. Remarks. Nicon is not a species-rich genus: of the 700+ species of Nereididae, only ten belong to the genus Nicon and those ten species are from diverse habitats and widespread regions (Read and Fauchald 2023). Nicon species exhibit more morphologically diversity than seen in many genera of Nereididae and with only a single species included in the most recent study (Wang et al. 2021), both their phylogenetic placement within Nereididae and their monophyly are doubtful.
The two most recent studies describing new Nicon species, de León-González and Trovant (2013) and Wang et al. (2021), both also provided keys to the then-known species.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Tentacular belt greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae present; solitary. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae absent; VI papillae present; VII-VIII papillae present. Oral ring paragnaths absent. Dorsal notopodial ligule present; commences chaetiger 3; not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers.
Anal cirri form cirriform or conical. Remarks. Ceratocephala edmondsi Hartman, 1954 (misspelling for Ceratocephale) was separated into the new genus Olganereis by Hartmann-Schröder (1977) because of the lack of accessory ventral cirri and presence of papillae on both oral and maxillary rings of the pharynx (characters present in Ceratocephale species).
Olganereis is monotypic and the sole species O. edmondsi (Hartman, 1954) occurs in estuaries in southern Australia. The only other Australian nereidid with papillae on both rings of the pharynx is Dendronereides heteropoda Southern, 1921 from tropical estuaries and in which the dorsal notopodial ligule is divided into 'branchial' filaments.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed).
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present, or absent; II conical paragnaths present; III conical paragnaths present; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV rod-like paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae present, or absent; VI papillae present; VII-VIII papillae present. Oral ring paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; approximately equal to length of dorsal notopodial ligule at least on anterior chaetigers (thus notopodium of three similar sized ligules/lobes). Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Remarks. The most recent taxonomic treatments of Paraleonnates are those of Hong et al. (2012) and Conde-Vela (2019a) which form the basis of the description and diagnosis provided here. Paraleonnates is a genus of four species which occur in shallow muddy habitats, typically estuaries and mangroves, in the Indo-Pacific.
Oesophageal caeca absent. Jaws with smooth or slightly crenulate cutting edge. Everted pharynx a truncate cone, tapering, greatest width at margin of tentacular belt.
Dorsal notopodial ligule not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; restricted to a limited number of anterior chaetigers. Notopodial acicular process present, or absent.
Jaws with smooth or slightly crenulate cutting edge or with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present or absent; II conical paragnaths present or absent; III conical paragnaths present; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present or absent; IV smooth barlike paragnaths present, or absent; IV rod-like paragnaths absent. Oral ring papillae absent. Oral ring paragnaths present; with Areas V, VI, and VII-VIII discrete; on Areas V and VI form distinct groups. Area V conical paragnaths present, or absent; arranged in a triangle, or in a longitudinal line. Area VI paragnaths present, arranged in lines or arcs; conical paragnaths present, or absent; smooth bars present. Areas VII-VIII paragnaths present, or absent; conical paragnaths present; conical paragnaths arranged in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band; rod-shaped paragnaths absent.
Dorsal notopodial ligule markedly elongate on posterior chaetigers, or not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present, or absent; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Dorsal cirrus sub-terminally attached to dorsal margin of dorsal notopodial ligule on posterior chaetigers, or not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Neuropodial prechaetal lobe absent. Neuropodial postchaetal lobe absent, or present; projecting beyond end of the acicular ligule; present throughout all chae-tigers, or restricted to anterior chaetigers. Ventral neuropodial ligule of anterior chaetigers present. Ventral neuropodial ligule of anterior chaetigers approx. as long as acicular neuropodial ligule. Ventral neuropodial ligule on posterior chaetigers present. Ventral neuropodial ligule on posterior chaetigers similar to length of acicular neuropodial ligule, or short, up to half length of acicular neuropodial ligule.
Remarks. The genus Perinereis contains 97 species and is thus one of the most species-rich in the family (Elgetany et al. 2022). Species of Perinereis are recorded from global locations but are most common in shallow water, particularly where algae occur. There is much morphological diversity within the genus, notably in respect of the form of Area VI paragnaths and of notopodial lobes, so for practical identification purposes informal groupings of species have been proposed (Hutchings et al. 1991). One such grouping, the Perinereis nuntia species complex, has been the subject of several recent studies combing morphological and molecular evidence and is probably not monophyletic (Tosuji et al. 2019;Villalobos-Guerrero 2019;Elgetany et al. 2022). The monophyly of the other informal groupings remains untested. Glasby (2015) provides a key to Nereididae from tropical eastern Australia and Villalobos-Guerrero (2019) presents a key to 20 species then known in the Perinereis nuntia species complex. Most other keys to species of Perinereis are now of limited use since they predate the most recent 20 or so papers which add significantly to knowledge of diversity within the genus.
Description. Palps anteriorly directed, or ventrally directed. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed). Tentacular belt greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area II rod-like paragnaths present; III conical paragnaths absent; III rod-like paragnaths present; IV paragnaths present; IV conical paragnaths absent; IV rod-like paragnaths present. Oral ring papillae present, or absent. Oral ring paragnaths present; on Area V and VI form distinct groups. Area V conical paragnaths absent. Area VI paragnaths present; conical paragnaths absent; rod-shaped paragnaths present. Areas VII-VIII paragnaths present; conical paragnaths absent; conical paragnaths arranged in isolated patches, or in one or more irregular lines forming a continuous band; rod-shaped paragnaths present.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Dorsal cirrus sub-terminally attached to dorsal margin of dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Notoaciculae on chaetigers 1 and 2 absent. Notochaetae: homogomph spinigers present; homogomph falcigers present; with terminal tendon present; articulation fused on some chaetigers (present as a simple chaeta), or with blade free throughout. Neurochaetae dorsal fascicle: heterogomph spinigers absent; homogomph spinigers present; heterogomph falcigers in anterior chaetigers present; on posterior chaetigers present; blades serrated; blades with teeth only slightly longer proximally than distally. Neurochaetae ventral fascicle: heterogomph spinigers present; spinigers in anterior chaetigers with blades evenly serrated throughout; on posterior chaetigers with blades finely serrated proximally; homogomph spinigers absent; heterogomph falcigers present; anterior chaetigers heterogomph falcigers with long blades absent; anterior chaetigers heterogomph falcigers with extra-long blades present; anterior chaetigers heterogomph falcigers with short blades absent; heterogomph falcigers blade lacking distinct tendon on terminal tooth. Anal cirri form cirriform or conical. Remarks. Species belonging to Platynereis are easily recognised by the small rod-like paragnaths in tight rows on the pharynx; 36 species are rec-ognised. No revisions have been published, but regional studies using molecular data to revise species to resolve the complex taxonomy, and taxonomic history of this genus have been appearing (Wäge et al. 2017;Kara et al. 2020;Teixeira et al. 2022b). Morphological characters from reproductive specimens (epitokes) may be important to distinguish species (Read 2007 Diagnosis. Maxillary ring paragnaths present; neuropodial postchaetal lobe not projecting beyond end of the acicular ligule; notoaciculae on chaetigers 1 and 2 present; prostomium anterior margin entire (minimal diagnosis; secondary diagnosis not attained).
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Prostomium longitudinal groove present; anterior region entire, hemispherical, longitudinal groove present; prostomial posterior region shorter than anterior region. Tentacular belt greater than length of chaetiger 1.
Oesophageal caeca absent. Jaws with dentate cutting edge. Everted pharynx a truncate cone, tapering, greatest width at margin of tentacular belt.

Remarks. Potamonereis
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed). Tentacular belt greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present; of pharynx with P-bar paragnaths present, usually in regular comb-like rows. Area I conical paragnaths present; II conical paragnaths present; III conical paragnaths present; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV rod-like paragnaths absent. Oral ring papillae absent. Oral ring paragnaths present; with Areas V, VI and VII-VIII discrete; on Area V and VI form distinct groups. Area V conical paragnaths present, or absent. Area VI paragnaths present; paragnaths arranged in lines or arcs; conical paragnaths present, or absent; smooth bars present, or absent; shield-shaped bars present. Areas VII-VIII paragnaths present; conical paragnaths present; conical paragnaths arranged in one or more irregular lines forming a continuous band; conical paragnaths similar in size, or irregular mix of large and small paragnaths in a single band; P-bar paragnaths absent, or present.
Notoaciculae on chaetigers 1 and 2 absent. Notochaetae: homogomph spinigers present; homogomph falcigers present, or absent. Neurochaetae dorsal fascicle: heterogomph spinigers present, or absent; homogomph spinigers present, or absent; heterogomph falcigers in anterior chaetigers present; on posterior chaetigers present; blades serrated; blades with teeth only slightly longer proximally than distally. Neurochaetae ventral fascicle: homogomph spinigers absent; heterogomph falcigers present; heterogomph falcigers blade lacking distinct tendon on terminal tooth. Anal cirri form cirriform or conical. Remarks. Pseudonereis species are characterised by presence of both P-bars and comb-like rows of paragnaths in Areas II-IV (Villalobos-Guerrero and Idris 2020). The genus was found to be a monophyletic group and could be diagnosed from morphological characters (Bakken and Wilson 2005;Bakken 2007). More species have been described in recent years, and the genus description has been emended (Glasby 2015; Conde-Vela 2018; Villalobos-Guerrero and Idris 2020). The description used here follows Villalobos-Guerrero and Idris (2020). Kara et al. (2018) investigated relationships between several species using molecular data.
Species in this genus are primarily found in tropical and subtropical waters, in shallow depths. Following the last work including revised species, the genus includes 19 species (Villalobos-Guerrero and Idris 2020).
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Tentacular belt greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae present, or absent. Oral ring paragnaths absent. Dorsal notopodial ligule present; commences chaetiger 3; not markedly elongate on posterior chaetigers (and may be fused with dorsal cirri); not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.

Remarks.
Rullierinereis is a genus with similarities to Nicon and Typhlonereis but differing in having notopodial homogomph falcigers (Tanaka and Sato 2017). Fifteen species of Rullierinereis are recognised and they occur widely around the world from shallow water to abyssal depths (4800 m). Tanaka and Sato (2017) revised the generic description. The only key to species is that of Pettibone (1971), but since that time nine additional species have been described.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed).
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths present. Area I conical paragnaths present, or absent; II conical paragnaths present; III conical paragnaths present; III rod-like paragnaths absent; IV paragnaths present; IV conical paragnaths present; IV rod-like paragnaths absent. Oral ring papillae absent. Oral ring paragnaths absent.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers (rarely markedly reduced on posterior chaetigers). Prechaetal notopodial lobe present, or absent; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process present, or absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.

Remarks.
Simplisetia is a genus of estuarine nereidids characterised by the presence of fused neuropodial falcigers in posterior chaetigers and absence of oral ring paragnaths. The fused falcigers are also present in another estuarine genus, Hediste, and the two genera may be related (Bakken and Wilson 2005) although they are easily separated by the presence of numerous oral ring paragnaths in Hediste.
Simplisetia currently includes ten species, seven of which occur in Australian estuaries. Significant differences occur among Simplisetia species in the form of the fused falcigers.
Dorsal notopodial ligule not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; markedly reduced on posterior chaetigers. Prechaetal notopodial lobe absent. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Prostomium anterior margin indented. Tentacular belt greater than length of chaetiger 1.
Jaws with smooth or slightly crenulate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae present; VII-VIII papillae present. Oral ring paragnaths absent.
Remarks. Tambalagamia Pillai, 1961 is similar to Ceratocephale and, especially to Gymnonereis, with double ventral cirri being shared characters. Pettibone (1970) and Hylleberg and Nateewathana (1988) considered Tambalagamia to be a junior synonym of Gymnonereis. We follow Bakken et al. (2022) and retain Tambalagamia as separate pending phylogenetic analysis with better taxon sampling of both genera. Tambalagamia currently includes three species which can be identified using the tabular comparison of Shen and Wu (1993).
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Prostomium anterior margin indented.
Jaws with smooth or slightly crenulate cutting edge. Maxillary ring of pharynx with papillae present; in tufts. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae absent; VI one papillae present; VII-VIII papillae present (in a single row). Oral ring paragnaths absent. Maxillary ring papillae absent on Areas I and II, with double rows on Areas III and IV. Dorsal notopodial ligule present; commences chaetiger 3; markedly elongate on posterior chaetigers; markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.
Ventral neuropodial ligule of anterior chaetigers present. Ventral neuropodial ligule of anterior chaetigers approx. as long as acicular neuropodial ligule. Ventral neuropodial ligule on posterior chaetigers present. Ventral neuropodial ligule on posterior chaetigers similar to length of acicular neuropodial ligule. The neuropodial acicular ligule has three or four distinct lobes; homology of these is unclear, therefore these structures are not scored in this description.

Remarks.
Tylonereis is one of several genera of Nereididae from tropical estuaries which have papillae on both maxillary and oral rings of the pharynx. The genus contains three species, all known from coastal lagoons and lakes of the tropical Indo-Pacific. Tan and Chou (1994) provide a key to species. Sources. Pettibone (1971). Diagnosis. Dorsal cirrus terminally attached throughout, so that dorsal notopodial ligule has appearance of a cirrophore for the dorsal cirrus (minimal diagnosis). Acicular notopodial ligule reduced, much shorter than neuropodial acicular ligule; maxillary ring of pharynx with papillae present (secondary diagnosis).
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Prostomium anterior margin indented. Tentacular belt greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae present. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring paragnaths absent.
Ventral neuropodial ligule of anterior chaetigers absent. Ventral neuropodial ligule on posterior chaetigers absent. The single notopodial ligule (Pettibone 1971: fig. 25b, c, e) apparently has the notoacicula and therefore cannot be the dorsal notopodial ligule. The homology of the two acicular neuropodial lobes with those of other nereidids is unclear; therefore, these structures are not scored in this description.
Epitokes. Epitokes formed by transformation of the anterior part of the body, with the posterior part cast off (Izuka 1903;Pettibone 1971).

Remarks.
Tylorrhynchus is known from two species, both of which occur in estuarine and fresh waters of the western Pacific Ocean (Japan, China) and the nearby north-east Pacific Ocean (Khlebovich 1996). Additional information on the biology and timing of swarming is provided by Hanafiah et al. (2006). The best taxonomic resources are Izuka (1903) and Pettibone (1971), at which time a single species was recognised. Tylorrhynchus is unlike other Nereididae genera in several ways including the absence of a ventral neuropodial ligule.
Remarks. Typhlonereis is known from a single species represented by six specimens from 2222 m in the far North-east Atlantic Ocean (Bakken 2003).
Description. Palpophore barrel-shaped, approximately equal width from base to palpostyle (not overly large compared with palpostyle). Palpophore surface with a single transverse groove (palpophores well developed). Tentacular belt equal to or less than length of chaetiger 1, or greater than length of chaetiger 1.
Jaws with dentate cutting edge. Maxillary ring of pharynx with papillae absent. Maxillary ring paragnaths absent. Oral ring papillae present. Oral ring papillae arrangement solitary. Area V papillae absent; VI papillae present; VII-VIII papillae present. Oral ring paragnaths absent.
Dorsal notopodial ligule present; commences chaetiger 3; not markedly elongate on posterior chaetigers; not markedly broader on posterior chaetigers; not markedly reduced on posterior chaetigers. Prechaetal notopodial lobe present; smaller than dorsal notopodial ligule on anterior chaetigers, usually reduced or absent posteriorly; restricted to a limited number of anterior chaetigers. Notopodial acicular process absent. Dorsal cirrus not sub-terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached to dorsal notopodial ligule on posterior chaetigers; not terminally attached throughout all chaetigers.