© Author(s) 2020. CC Atribution 4.0 License An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, 1815 (Decapoda, Brachyura, Heterotremata), with a discussion of their relevance to fossil material Posodobitev filogenetske rekonstrukcije, klasifikacije in morfoloških znakov recentnih rakovic Portunoidea Rafinesque, 1815 (Decapoda, Brachyura, Heterotremata) z razpravo o njihovi pomembnosti za fosilni material Vassily A. SPIRIDONOV Shirshov Institute of Oceanology of Russian Academy of Sciences, Nakhimovskiy Prospekt 36, Moscow 117997, Russia; valbertych@gmail.com; vspiridonov@ocean.ru Prejeto / Received 9. 12. 2019; Sprejeto / Accepted 11. 4. 2020; Objavljeno na spletu / Published online 22. 4. 2020 Key words: phylogeny, evolutionary systematics, extant fauna, fossil record, Cretaceous, Eocene, Miocene Ključne besede: filogenija, evolucijska sistematika, recentna favna, fosilni zapis, kreda, eocen, miocen Zoobank: CA7E47BF-F0E7-4178-8F21-463FB908E6A4 Abstract The classification of extant Portunoidea has recently been significantly rearranged on the basis of morphological revision and molecular phylogenetic reconstructions. There is an urgent need to reach compatibility of fossil portunoid taxa with this new classification. Furthermore, several genera with a variety of both Recent and fossil representatives, e.g., the genus Portunus (sensu lato), have been split into other genera, but referring fossil species to these is still problematic. In order to facilitate the development of an integrated system that includes both extant and extinct portunoid taxa, a review of recent results regarding the phylogeny of portunoid crabs, an update of their extant taxa classification and a reappraisal of important morphological characters that can be used for assessment of both fossil and contemporary species are presented. A new subfamily, Parathranitiinae, is established within the Carcinidae and within the Portunidae, another new subfamily, Achelouinae, is introduced. Integration of palaeontological data and the evolutionary classification of extant Portunoidea is a challenging task that requires further development of comparative morphological, ecological and molecular genetic studies of modern species. Izvleček Razvrstitev recentnih portunoidnih rakovic je bila v zadnjem času bistveno preurejena na podlagi revizije morfologije in molekularnih filogenetskih rekonstrukcij. Potrebno je zagotoviti združljivost fosilnih portunoidnih taksonov z novo klasifikacijo. Več rodov z živečimi in fosilnimi predstavniki, na primer rod Portunus (sensu lato), je bilo razdeljenih na druge rodove, zato je uvrščanje fosilnih vrst vanje problematično. Da bi zagotovili razvoj integriranega sistema, ki vključuje obstoječe in izumrle portunoidne taksone, je potreben pregled novih spoznanj o filogeniji portunoidnih rakov, posodobitev njihove obstoječe klasifikacije in ponovna ocena pomembnih morfoloških znakov, ki jih je mogoče uporabiti za določanje fosilnih in recentnih vrst. V okviru družine Carcinidae je ustanovljena nova poddružina Parathranitiinae, znotraj Portunidae pa nova poddružina, Achelouinae. Vključevanje paleontološkega materiala in evolucijske klasifikacije recentnih portunoidnih rakovic je zahtevna naloga, ki zahteva nadaljnji razvoj primerjalno morfoloških, ekoloških in molekularno genetskih raziskav obstoječih vrst. GEOLOGIJA 63/1, 133-166, Ljubljana 2020 https://doi.org/10.5474/geologija.2020.014 134 Vassily A. SPIRIDONOV Introduction Portunoid crabs (superfamily Portunoidea) comprise over 420 extant and more than 200 ex- tinct species (De Grave et al., 2009), making it one of the most diverse and species-rich groups of Brachyura. Their characteristic features in- clude a specific construction of pereopods 5, preadapted for burrowing and constituting part of the swimming apparatus (Garstang, 1897a, b; Schäfer, 1954; Hartnoll, 1971; Steudel, 1998; Spiridonov et al., 2014). Another important fea- ture of portunoids is the peculiar morphology of the chelae, which is essential in maintaining the habit of active generalist predators and scaven- gers (Schäfer, 1954; Spiridonov et al., 2014). Por- tunoid crabs have a worldwide distribution (with the exception of subarctic waters of the North Pa- cific, Arctic and Antarctic), live in a variety of bi- otopes, although predominately on soft bottoms, from the intertidal and upper subtidal (Fig. 1) to deep waters of the continental slope and un- derwater rises (e.g., Geryonidae; see Manning & Holthuis, 1989; but also some representatives of generally shallow-water groups; see Spiridonov & Türkay, 2001). Particular groups have symbi- otic relationships with a variety of animal and plant taxa (Evans, 2018). Being abundant pred- ators, portunoid crabs play a significant role of ecosystems, hold a leading position among hu- man-mediated invaders (Brockerhoff & McLay, 2011) and include several highly important com- mercial species (Figs. 1G, H). Classification of Recent portunoids had been stable for about half a century, owing to the dominating taxonom- ic concept of Stephenson (1972). This state was largely reflected in the ‘Systema Brachyurorum’ by Ng et al. (2008), although it accommodated several revisions of particular species and gen- era and descriptions of new taxa introduced dur- ing the 1990s and early 2000s. Right after this ground-laying publication the taxonomy and classification of the Portunoidea entered a major revision. The impetus for this was given by pal- aeontologists (Karasawa et al., 2008), who sug- gested the first phylogenetic reconstruction of the Portunoidea based on morphological cladistics and attempted to construct a new classification for both extant and extinct portunoid taxa. Sub- sequent molecular phylogenetic reconstructions (Schubart & Reuschel, 2009; Spiridonov et al., 2014; Evans, 2018; Mantelatto et al., 2018) have significantly changed the very concept of what are portunoids, challenged both the traditional (Stephenson, 1972; Ng et al., 2008) and Karasawa et al. (2008) views on major groups and evolution- ary lineages, stimulated new comparative mor- phological analysis of extant groups and revised the classification of the Portunoidea (see a scheme that reflects recent changes in Evans, 2018, fig. 5). In the present paper, I shall review recent developments in phylogenetic reconstruction, taxonomy, variability and classification of mor- phological structures and characters in order to facilitate the integration of palaeontological and neontological data in a coherent system of the Portunoidea. It is not really my intention here to classify extinct taxa but rather to comment on some of them to stimulate further taxonomic revision by palaeontologists or jointly by palae- ontologists and neontologists. Therefore, palae- ontological data are here presented only as ex- amples without any ambitions to provide their comprehensive coverage. The purpose of the present contribution is to review recent studies on extant Portunoidea and facilitate their integration with palaeontological data, in order to: 1) synthesise relevant molecular phylogenetic reconstructions and fossil records of extant genera; 2) update the classification of modern portunoid crabs; 3) make a comparative description of the taxonomic value of morpholog- ical characters that can be applied to both extant and fossil material. Fig. 1. Examples of portunoid crabs showing characteristic habit and commercial importance. A: Carcinus maenas (Linnaeus, 1761), medium size (to about 80 mm carapace width, CW), common inhabitant of intertidal-low subtidal habitats, north- east Atlantic; a global invader; rocky intertidal, North Sea, German Bight, Wilhelmshaven. B. Carcinus aestuarii Nardo, 1869, medium-sized species, a common inhabitant of Mediterranean Sea, low subtidal, in semi-burrowed condition, Black Sea. C. Liocarcinus vernalis (Risso, 1816), medium-sized species, a common inhabitant of low subtidal sandy habitats in the Mediterranean Sea, swimming over sand bottom, Black Sea. D. same specimen as C, burrowed in sand. E. Thalamita crenata Rüppell, 1830, medium-sized species, a common inhabitant of intertidal habitats in Indo-Pacific; after burrowing in sedi- ments, mangrove, Dam Bay, Tre Island, Vietnam, South China Sea. F. Xiphonectes sp., small (to about 50 mm CW) species, in coral rubble; Mot Island, Vietnam, South China Sea. G. Portunus trituberculatus Miers, 1879, a large (about 300 mm CW) commercially important species in East Asia; fish market in Busan, Korea. H. Scylla paramomosain Estampador, 1949, a large, commercially important and cultured species in southeast Asia, fish market in NhaTrang, Vietnam. Photograph credits: V. Spiridonov (A, E, G, H); S. Anosov (B, C, D) and T. Antokhina (F). 135An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... Fig. 1. 136 Vassily A. SPIRIDONOV Material and methods The present study is based on my 20+ years’ work with collections of portunoid crabs at the Natural History Museum London, UK (NHMUK), the Naturhistorisches Museum Wien, Vienna, Austria (NHMW), the Senckenberg Museum, Frankfurt am Main, Germany (SMF), the Zoolog- ical Institute of the Russian Academy of Sciences, St Petersburg, Russia (ZIN-RAS), the Zoological Museum of Moscow University, Moscow, Russia (ZMMU), the Zoologisches Museum, Museum für Naturkunde, Berlin, Germany (ZMB), where spec- imens illustrated are deposited, as well as other European, American and Australian collections. Morphological terms generally follow usage in Stephenson & Hudson (1957), Apel & Spiridonov (1998), Ng et al. (2008) and Evans (2018). In the carapace description the epithets “quasi-hexago- nal”, “quasi-trapezoidal” etc. are preferred over “subhexagonal”, “subtrapezoidal” etc. The simplified scheme of the phylogenetic re- lationships of extant portunoid genera (Fig. 2) is based on results obtained by recent molecular phylogenetic reconstructions (Schubart & Reus- chel, 2009; Spiridonov et al., 2014; Evans, 2018; Mantelatto et al., 2018). The branching of the tree follows particular patterns agreed between dif- ferent reconstructions; where there is no agree- ment between particular studies, the relation- ships are shown as an unresolved polytomy. The updated classification of Recent Por- tunoidea is based on the principles of evolution- ary systematics (Simpson, 1961), which requires compatibility with phylogenetic reconstructions but implies a thorough morphological analysis for definition of the boundaries of taxa. In linking particular extant portunoid genera to their palaeontological records I generally fol- low Müller (1984) and Karasawa et al. (2008) with additions of recent fossil records, for instance, of Geryon Krøyer, 1838 (Feldmann et al., 2010), Bathynectes Stimpson, 1871 (Ossó & Stalennuy, 2011) and Liocarcinus Stimpson, 1871 (De An- geli et al., 2019). Since most pre-Pleistocene re- cords of Callinectes Stimpson, 1860 are based on incompete and poorly preserved material, the known range of Callinectes was corrected ac- cording to well-preserved specimens reported by Collins et al. (2014). As fossil crabs identified as Portunus (sensu lato) may indeed refer to several genera, I have specifically checked the original figure of one of the oldest representatives, namely Portunus kochi Bittner, 1893 (see Bittner, 1893, pl. 1, fig. 1). For further explanations, reference is made to the caption of Figure 2. A review of the phylogeny of the Portunoidea based on published molecular genetic reconstructions and palaeontological history of extant taxa The genera Geryon (living in the northeast Atlantic), Chaceon Manning & Holthuis, 1989 (inhabiting continental slopes and underwater rises worldwide), Raymanninus Ng, 2000 (occur- ring in the deep water of the Caribbean) form a distinct clade in all molecular phylogenetic re- constructions, which shows sister relationships to the deep-water Indo-Pacific Benthochascon Alcock & Anderson, 1899 or the Benthochas- con + Ovalipes clade. Species of Ovalipes occur mostly in the Southern Hemisphere but are also known from the northeast Pacific and northwest Atlantic. This clade is interpreted as the basal portunoid lineage that possesses a number of plesiomorphic character states and shows a close affinity to one of the most ancient potential por- tunoid taxa, the genus Eogeryon Ossó, 2016 from the upper Cenomanian (Ossó, 2016). The clade comprises the family Geryonidae (sensu Evans, 2018) and shows sister relationships to other studied portunoids (Fig. 2). The latter in turn are well separated into two major clades which are resolved in all re- constructions (Schubart & Reuschel, 2009; Spiridonov et al., 2014; Evans, 2018), although with varying internal topologies. Following the most comprehensive study by Evans (2018), one of this major lineages includes the Indo-Pacific taxa Parathranites Miers, 1886 and Coelocarci- nus Edmondson, 1930 as basal groups. All pub- lished phylogenetic trees define the related clades Carcinus Leach, 1814 + Portumnus Leach, 1814 and Pirimela Leach, 1816 or Pirimela + Sirpus Gordon, 1953. All these taxa are originally con- fined to the North Atlantic. Their possible sister clade includes morphologically diverse genera such as Thia Leach, 1816, Bathynectes, Macro- pipus Prestandrea, 1833, Necora Holthuis, 1987 and Liocarcinus, also living mostly in the Atlan- tic. The topology of relationships between these groups differ in the reviewed studies, so in Fig- ure 2 no resolved branching is shown. Polybius Leach, 1820 is nested within Liocarcinus in all reconstructions (see also Plagge et al., 2016) and is not shown in the present scheme (Fig. 2). All the genera mentioned were combined in the new- ly defined family Carcinidae (sensu Evans, 2018). Most fossil records of thus defined carcinids are no older than Miocene, and only records of Lio- carcinus spp. date back to the Eocene (De Angeli et al., 2019; Á. Ossó, pers. comm., January 2020). 137An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... Fig. 2. Schematic phylogenetic tree of extant portunoid genera based on molecular phylogenetic reconstructions by Schubart & Reuschel (2010), Spiridonov et al. (2014), Evans (2018) and Mantelatto et al. (2018). Black bands indicate the temporal ex- tension of particular genera from the first palaeontological record onwards. The tree does not have an unbiased temporal scale; the positions of nodes only indicate that the divergence between families occurred not later than the Cretaceous, the divergence between major genera not later than the Eocene, Oligocene or Miocene. Abbreviations of geological epochs: PAL – Paleocene; PLEI – Pleistocene; PLIO – Pliocene; OLI – Oligocene. 138 Vassily A. SPIRIDONOV Another large group which shows sister rela- tionships to the Carcinidae are the Portunidae (sensu Schubart & Reuschel, 2009; Spiridonov et al., 2014). The topology of clades within the Portunidae is not stable through reviewed recon- structions, although the clade of taxa referred to the Thalamitinae (sensu Apel & Spiridonov, 1998), plus symbiotic taxa formerly referred to the Caphyrinae Paulson, 1875 is always revealed (Fig. 2). The Atlantic-eastern Pacific genus Cro- nius Stimpson, 1860 was shown to be basal to this clade, the other species of which have a mostly Indo-Pacific distribution (Evans, 2018). All molecular phylogenetic studies indicate that the American and eastern Atlantic species earli- er considered to belong to the subgenus Achelous De Haan, 1833 of the genus Portunus Weber, 1795 (Ng et al., 2008) constitute a distinct clade, which in some reconstructions show sister relationships to the Thalamitinae (Spiridonov et al., 2014; Ev- ans, 2018; Mantelatto et al., 2018). Species of Portunus (sensu stricto) (occurring in the Indo-Pacific and Atlantic) are revealed as having close phylogenetic relationships with the Atlantic genera Arenaeus Dana, 1851 and Calli- nectes. Several Indo-Pacific genera, most of them earlier included in the Carupinae (sensu Apel & Spiridonov, 1998), such as Atoportunus Ng & Takeda, 2003, Carupa Dana, 1851, Catoptrus A. Milne-Edwards, 1870, Laleonectes Manning & Chace, 1990, Libystes A. Milne-Edwards, 1867 and Richerellus Crosnier, 2003) are also phyloge- netically related, although their tree cannot be perfectly resolved to date (Fig. 2). Other genera do not show a stable pattern of relationships in particular reconstructions (except for Monomia Gistel, 1848 and Cycloachelous Ward, 1942), and therefore the general phylogeny of the Portu- nidae may now be schematically presented as a polytomy (“bush” rather than a tree). One of the oldest known portunids, “Por- tunus” kochi (Bittner, 1883) from the Upper Eo- cene, can be referred to Achelous according to the morphology of the frontorbital and anterolateral margins and carapace ornamentation (see Bit- tner, 1893: pl. 1, fig. 1). This suggests a significant geological age of the Achelouinae. Such genera as Scylla De Haan, 1833 are known to have occurred since at least the Miocene, while Necronectes A. Milne-Edwards, 1881, which is morphologically very similar to Scylla, is at least of Oligocene age (Karasawa et al., 2008; Ossó & Gagnaison, 2019). Therefore, the divergence of major portunid line- ages most probably took place no later than Mid- dle Eocene or even in pre-Eocene times (Fig. 2) Updated classification of recent Portunoidea Family Geryonidae Colosi, 1923 Diagnosis: Spiridonov et al. (2014). Type genus: Geryon Krøyer, 1837. Subfamily Benthochasconinae Spiridonov, Neretina & Schepetov, 2014 Diagnosis: Spiridonov et al. (2014). Genus: Benthochascon Alcock & Anderson, 1899 Subfamily Geryoninae Colosi, 1923 Diagnosis: Spiridonov et al. (2014). Genera: Chaceon Manning & Holthuis, 1989; Geryon Krøyer, 1837(type genus); Raymanninus Ng, 2001 and Zariquieyon Manning & Holthuis, 1989. Subfamily Ovalipiinae Spiridonov, Neretina & Schepetov, 2014 Diagnosis: Spiridonov et al. (2014). Genera: Ovalipes Rathbun, 1898 (type genus). Remarks: Originally, this taxon was estab- lished at the family level, although possible sister relationships to the Geryonidae were assumed (Spiridonov et al., 2014). On the basis of his mo- lecular phylogenetic reconstruction, Evans (2018) argued for even closer relationships of Ovalipes with geryonids and suggested to consider this group as a subfamily of the Geryonidae. I ac- cept his concept here. Although Ovalipes spp. are characterised by a number of apomorphies in relation to other geryonids, they share with them apparently plesiomorphic conditions of non-fused pleomeres of the male pleon and long gonopods 2, and an apparently apomorphic ten- dency for reduction of one of the orbital fissures (see below). The grammatically correct form for the fami- ly/subfamily name is Ovalipiinae, not Ovalipinae as suggested by Spiridonov et al. (2014). It is cor- rected here. Genera incertae sedis: Echinolatus Davie & Crosnier, 2006 and NectocarcinusA. Milne- Edwards, 1861. Remarks: These genera share with the Geryo- nidae such plesiomorphic conditions as non-fused pleomeres of the male pleon and long gonopods 2, a tendency for reduction of one orbital fissure, 139An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... as well as an even number of frontal lobes and four anterolateral teeth, characters not common- ly found in the Carcinidae. On the other hand, species assigned to these genera have some char- acters that are unique to portunoid crabs, such as a double inner carpal spine and additional ante- rolateral teeth in Echinolatus spp. These genera have not yet been included in molecular phyloge- netic reconstuctions. I tentatively assign them to the Geryonidae, although they may deserve sep- arate status. Family Carcinidae MacLeay, 1838 Diagnosis: Evans (2018). Type genus: Carcinus Leach, 1814. Subfamily Carcininae MacLeay, 1838 Diagnosis: Spiridonov et al. (2014). Genera: Carcinus Leach, 1814 (type genus). Subfamily Coelocarcininae Števćić, 1991 Diagnosis: Evans (2018). Genera: Coelocarcinus Edmondson, 1930 (type genus). Subfamily Parathranitiinae Spiridonov subfam. nov. Zoobank: urn:lsid:zoobank.org:act:74EF- 9937-1342-4BF6-8847-5F220ED11882 Diagnosis (new): Carapace distinctly qua- si-hexagonal, regions well defined, with well-de- fined ridged and granular ornamentation. Fron- tal margin subdivided into 4 teeth. Infra-orbital margin consisting of several lobes. Posteriormost of five anterolateral teeth distinctly longer than others. Posterolateral corners of carapace angu- lar or spiniform. Cheliped with spines on anteri- or and posterior faces of merus, carpus with out- er spines, propodus with upper spines, dactyli of last pereopods lanceolate. Genera: Parathranites Miers, 1886 (type ge- nus). Remarks: Parathranites spp. (see Cros- nier, 2002) differ from all Carcinidae in having well-defined regions of the carapace, spiniform posterolateral corners of the carapace, and from most of the carcinids by upper spines on the che- la palm (propodus) and four frontal teeth/ lobes. Molecular phylogenetic reconstruction (e.g., Ev- ans, 2018; see Fig. 2 here) indicates the basal po- sition of the genus in relation to other groups of the family. To emphasise this peculiar position, I find it reasonable to define a new subfamily, Par- athranitiinae, within the Carcinidae. Subfamily Platyonichinae Dana, 1851 (= Portumninae Ortmann, 1899; see Davie et., 2015 for a discussion of the synonymy). Diagnosis: Spiridonov et al. (2014; as Por- tumninae). Genera: Portumnus Leach, 1815 (type genus) and Xaiva MacLeay, 1838. Subfamily Pirimelinae Alcock, 1899 Diagnosis: Spiridonov et al. (2014; as family Pirimelidae). Genera: Pirimela Leach, 1816 (type genus) and Sirpus Gordon, 1953. Subfamily Polybiinae Ortmann, 1893 Diagnosis: Spiridonov et al. (2014: 422, as fam- ily Polybiidae). Genera: Bathynectes Stimpson, 1871; Coe- nophthalmus A. Milne-Edwards, 1873; Liocar- cinus Stimpson, 1871; Macropipus Prestandrea, 1833; Necora Holthuis, 1987 and Polybius Leach, 1820 (type genus). Subfamily Nautilocorystinae Ortmann, 1893 Diagnosis: Spiridonov et al. (2014). Genera: Nautilocorystes H. Milne Edwards, 1837 (type genus). Subfamily Thiinae Dana, 1852 Diagnosis: Spiridonov et al. (2014; as Thiidae) Genera: Thia Leach, 1816 (type genus). Remarks: Nautilocorystes was referred to the Thiidae by Ng et al. (2008) on the basis of im- portant morphological similarities. In spite of an appearance that is highly unusual for por- tunoid crabs, Nautilocorystes has several char- acters, such as a cheliped morphology typical of portunids (Spiridonov et al., 2014). Thia has re- peatedly been shown to nest within the polybi- ine clade (Schubart & Reuschel, 2009; Spiridonov et al., 2014; Evans, 2018), although its significant morphological peculiarity calls for a separate status. Therefore, a subfamily rank for the Thi- inae was accepted by Evans (2018) and it is here too. The relationships of Nautilocorystes to the Carcinidae in the current concept remain un- 140 Vassily A. SPIRIDONOV clear, as no molecular phylogenetic study of this taxon has been conducted to date. Here, I tenta- tively place Nautilocorystinae as a separate sub- family of the carcinids. Family Portunidae Rafinesque, 1815 Diagnosis: Spiridonov et al. (2014). Type species: Portunus Weber, 1795. Subfamily Achelouinae subfam. nov. Zoobank: urn:lsid:zoobank.org:act:B094745A-E- EB2-408A-B91F-E30DE868449A Diagnosis (new): Carapace more than 1.5 times wider than long, quasi-hexagonal; regions well expressed; with distinct granular ridges and groups of granules both in anterior and posterior parts. Nine sharp anterolateral teeth: teeth 1 to 8 subequal, last tooth distinctly longer than others. Front narrower than posterior border, consisting of 4 or 6 lobes; outer lateral lobes may be fused with inner supraorbital lobes. Chelipeds with several teeth on anterior margin and a single posterior tooth; carpus with a single outer spine; inner spine well expressed and may be very long, reaching to chela fingers; propodus strongly costate, with a single spine; heterochely moder- ate; larger chela with flattened molariform tooth. Dactyli of pereopods 2–4 strong, knife-shaped. Merus of pereopod 5 much broader than meri of pereopods 2–4, posterior spine may be pres- ent although obsolete; propodus without spinules on posterior margin, dactylus paddle-like. Male pleon triangular, unclear sutures may be present at fused pleomere 3–5. Gonopod 1 of generalised shape, curved, thinning apically, with micro- spopic spinules. Female genital opening large, occupying about one third of sternite. Remarks: Numerous Atlantic and eastern Pa- cific species referred to Achelous, Lupella Rath- bun, 1897 or Portunus (except for Portunus sayi (Gibbes, 1850) form a distinct monophyletic clade which does not show clear relationships to other groups (Spiridonov et al., 2014; Mantelatto et al., 2018) and are characterised by distinct morpho- logical characters. It justifies placing them in a separate subfamily, Achelouinae. Genera: Achelous De Haan, 1833 (type genus) and Lupella Rathbun, 1897. Subfamily Carupinae Paulson, 1875 Diagnosis (extended from Apel & Spirido- nov, 1998): Carapace much wider than long, up to about twice, transversely oval, elliptical or indistinctly quasi-hexagonal, relatively convex; regions poorly expressed; usually with only epi- branchial ridge or smooth; sometimes with dif- fuse granules. Supraorbital fissures may be re- duced, infraorbital margin variously modified. Front much narrower than posterior border, four-, or two-lobed, or nearly entire; anterolat- eral border convex, toothed or entire. Postero- lateral reentrant poorly developed, or not at all. Secondary sulci of sternum may be absent. Basal antennal segment narrow, long, lying obliquely, not lobulate, antennal peduncle entering orbital hiatus. Chelipeds of various construction, spines on cheliped segments usually reduced in num- ber or absent. Some representatives are second- arily homoiochelic and homoiodontic, with long and thin chelae. Pereopods 2–4 usually long and thin, non-costate. Merus of pereopod 5 long and thin, not broader or not much broader than meri of pereopods 2–4, without posterior spinule; dac- tylus styliform, lanceolate, or knife-shaped. Male pleon triangular. Gonopod 1 usually with rela- tively robust subterminal spines. Female genital openings large, without cuticular emargination and caps. Genera: Atoportunus Ng & Takeda, 2003; Carupa Dana, 1851 (type genus); Catoptrus A. Milne-Edwards, 1870; Kume Naruse & Ng, 2012; Laleonectes Manning & Chace, 1990; Liby- stes A. Milne-Edwards, 1867; Pele Ng, 2011 and Richerellus Crosnier, 2003. Remarks: The name of the author of the sub- family is often spelled “Paul’son” following the English translation of the original monograph in the Russian language (Paulson, 1875). I prefer, however, “Paulson” because Otto Paulson used this spelling in his German-language publica- tions (i.e. Paulson, 1862). Subfamily Lupocyclinae Paulson, 1875 Diagnosis (new): Cephalothorax quasi-hex- agonal or quasi-circular in outline, dorsally convex. Carapace with granular ridges and/or patches. Front narrower than posterior border, consisting of 4 lobes or teeth, markedly produced beyond inner supraorbital lobes. Orbit circular. Anterolateral margin with 5–9 teeth. Postero- lateral margin with rounded corners. Expansion of basal antennal segment not produced into or- bit being directed nearly anteriorly; flagellum standing in orbital hiatus. Chelipeds long, ho- moiochelic or slightly heterochelic; merus with 4–7 spines on anterior margin and 2 spines on 141An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... posterior margin; carpus with a single spine on outer face; manus with two subdistal spines on dorsal face. Chelae very long and thin, dis- tinctly thinner than cheliped meri. Heterodonty not expressed or poorly expressed. Distal parts of chelae fingers curved in sagittal plane. Pere- opods 2–4 long, thin, dactyli narrow, ensiform, Merus of P 5 broader and shorter than meri of pereopods 2–4, with a small posterodistal spine; dactlylus lanceolate or paddle-like. Male pleon triangular. Gonopod 1 of generalised shape, rel- atively straight or curved, with sharpened distal part, without large subterminal spines. Female genital openings large, occupying half or more of length of mesial part of sternite, without cuticu- lar emargination and caps. Genera: Lupocycloporus Alcock, 1899 and Lupocyclus Adams & White, 1848 (type genus). Subfamily Necronectinae Glaessner, 1928 Diagnosis (modified after Karasawa et al., 2008): Carapace of intermediate outline between quasi-hexagonal and oval, dorsally convex, smooth with recognisable gastric and epibranchi- al finely granular ridges. Front narrower than posterior border, usually consisting of 4 lobes or teeth, not produced beyond inner supraorbital lobes. Orbit semi-oval. Anterolateral margin with 9 (or 8 in some fossil taxa) teeth. Posterolat- eral margin with rounded corners. Basal anten- nal segment with latero-distal spine; flagellum standing in orbital hiatus. Cheliped merus with 3 spines on anterior margin and 2 distal spinules on posterior margin; carpus with 1-3 spinules (of- ten reduced) on outer face; manus nearly smooth, with 1 or 2 subdistal spinules on dorsal face. Het- erochely and heterodonty well expressed; chela inflated; molariform teeth present on both che- lae. Distal parts of chelae fingers not curved in sagittal plane. Dactyli of pereopods 2–4 relative- ly broad and strong, ensiform. Merus of pereo- pod 5 much shorter than meri of pereopods 2–4, without a posterior spine; propodus without pos- terior spinules; dactylus paddle-like. Male pleon triangular. Gonopod 1 sinuous or slightly curved, without large subterminal spines. Female geni- tal openings without cuticular emargination and caps. Genera: Scylla De Haan, 1833 and Sanquerus Manning, 1989. Type genus: Necronectes A. Milne-Edwards, 1881 (extinct). Subfamily Podophthalminae Stimpson, 1860 Diagnosis: Apel & Spiridonov (1998: 169). Genera: Euphylax Stimpson, 1860 and Po- dophthalmus Lamarck, 1801 (type genus). Subfamily Portuninae Rafinesque, 1815 Diagnosis (new): Cephalothorax quasi-hex- agonal in outline, dorsally flattened. Carapace granular, usually with granular ridges and/ or patches. Frontal margin of carapace divided into even number of lobes or teeth (usually 4), usually not distinctly produced beyond inner supraorbital lobes. Orbit elliptoidal. Anterolateral margin di- vided into 9 teeth, usually without indication of reduction of particular teeth. Posterolateral reentrant well developed; posterolateral margin usually with rounded corners. Expansion of basal antennal segment produced into orbit but not fill- ing orbital hiatus completely, flagellum standing in orbital hiatus. Cheliped merus with 3–4 spines on anterior margin and 1–2 spines on posterior margin; on dorsal face along posterior margin there may be a suture and a granular line termi- nated at one of posterior spines. Carpus with a single spine or without spines but carina on out- er face. Manus with one or two subdistal spines on dorsal face. Heterochely usually expressed. Heterodonty usually expressed by a molariform tooth developed to various degrees at base of larger chela dactylus; in some cases symmetrical chelae present. Distal parts of chelae fingers not curved in sagittal plane. Dactyli of pereopods 2–4 robust, ensiform or narrowly lanceolate. Merus of P 5 much shorter and broader than meri of pere- opods 2–4, without a posterior spine, propodus without spinules on posterior margin, dactylus paddle-like. G 1 of simple shape or modified (very thin), without large subterminal spines. Female genital openings relatively compact, occupying less than half of length of mesial part of sternite, often with emarginations and caps. Genera: Arenaeus Dana, 1851; Callinectes Stimpson, 1860 and Portunus Weber, 1795 (type genus). Genera tentatively included here: Cavopor- tunus Nguyen & Ng, 2010; Cycloachelous Ward, 1942 and Monomia Gistel, 1848. Remarks: Portuninae had been the largest subfamily of Portunidae when the lumping con- cept of Stephenson (1972) became dominant. With the subsequent revalidation and redefinition of the Lupocyclinae, Thalamitinae and Necronecti- nae, this subfamily has been considered in an in- 142 Vassily A. SPIRIDONOV creasingly restricted sense (e.g., Apel & Spirido- nov, 1998; Karasawa et al., 2008; Ng et al., 2008). To date, even this restricted concept is no longer supported by molecular phylogenetic reconstruc- tions and comparative morphology (Schubart & Reuschel, 2009; Spiridonov et al., 2014; Ev- ans, 2018; Mantelatto et al., 2018). In particular, the genus Portunus (sensu lato) of Stephenson’s (1972) classification is now considered to consist of several not closely related and morphological- ly different genera. The American-eastern At- lantic genus Achelous is here taken to represent a separate subfamily. Xiphonectes A. Milne-Ed- wards, 1873, which has been considered as a sub- genus of Portunus (Ng et al., 2008), appears to be polyphyletic as well and is, for the time being, listed as a genus incertae sedis within the Portu- nidae. I tentatively include here in the Portuni- nae three additional genera previously combined in Portunus. This makes possible to formulate a consistent morphological diagnosis, until more detailed ongoing molecular genetics and com- parative morphological studies provide sufficient data for a more appropriate classification of Cav- oportunus, Cycloachelous and Monomia. Subfamily Thalamitinae Paulson, 1875 Diagnosis: Evans (2018: 40). Genera: Caphyra Guérin, 1832; Charybdis De Haan, 1833; Cronius Stimpson, 1860; Gonio- infradens Leene, 1938; Goniosupradens Leene, 1938; Lissocarcinus Adams & White, 1848; Tha- lamita Latreille, 1829 (type genus); Thalami- toides A. Milne-Edwards, 1869; Thalamonyx A. Milne-Edwards, 1873; Thranita Evans, 2018; Tri- erarchus Evans, 2018 and Zygita Evans, 2018. Remarks: Thalamitinae was recognised as a morphologically distinct subfamily of Portunidae by Paulson (1875), but the taxon was subsequent- ly largely ignored until revalidation and redef- inition by Apel & Spiridonov (1998). Spiridonov et al. (2014) provided molecular phylogenetic support for the monophyly of the most speciose thalamitine genera, Charybdis and Thalamita. Recently, Evans (2018) has presented evidence of the basal position of Cronius (formerly assigned to the Portuninae) in the thalamitine phylogenet- ic tree and has demonstrated the phylogenentic relationships of Thalamitinae (sensu stricto) and Caphyra and Lissocarcinus (formerly considered to belong to the subfamily Caphyrinae Paulson, 1875, by Ng et al., 2008). The latter two genera, along with some groups formerly referred to Tha- lamita (Trierarchus, Zygita), form a symbiotic clade within the Thalamitinae in the new concept (Evans, 2018). Genus incertae sedis: Carupella Lenz & Strunk, 1914 Remarks: Two syntypes of Carupella natalen- sis Lenz & Schtrunk, 1914 that I have examined (ZMB 19917) are juvenile, just settled crabs, most likely belonging to the Portuninae (although as- signment to the Lupocyclinae in its present con- cept cannot be completely ruled out). They may in fact belong to yet another known species for which precise identification is currently difficult due to a lack of knowledge on age-related varia- tion in portunids. Thus, the genus Carupella may be synonymous with another, established genus. The holotype of Carupella banlaensis Tien, 1969 (ZIN-RAS 1/58265) is certainly a juvenile speci- men of Portunus sp. The type of the third species of the genus, Carupella epibranchialis Zarenkov, 1970, has not been traced in the ZMMU collections where it would presumably have been deposited. It is thus appropriate to consider Carupella as a genus incertae sedis within the Portunidae until new comparative research will clarify its status. Genus incertae sedis: Xiphonectes A. Milne-Edwards, 1873 Remarks: See above under the subfamily Por- tuninae. Family Brusiniidae Števćić, 1991 Genus: Brusinia Števćić, 1991. Remarks: Brusinia spp. are very peculiar mor- phologically (Spiridonov et al., 2014) and are not nested within the Portunoidea in updated phy- logenetic trees based on the 16S RNA gene (Ev- ans, 2018). The family is tentatively considered as a portunoid group until more comprehensive data become available. Morphological characters of Portunoidea applicable to fossil material Carapace morphology Most portunoid crabs have a quasi-hexagonal carapace shape, with the maximum width usual- ly exceeding the maximum length (Fig. 3). This general carapace outline portunoids share with a number of other heterotremate crabs such as the superfamilies Cancroidea, Goneplacoidea and Pilumnoidea (Guinot, 1979; Ng et al., 2008; Davie et al., 2015). 143An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... Fig. 3. Examples of portunoid crabs with a typical quasi-hexagonal (A–E) and a derived quasi-trapezoidal carapace (F). A. Geryon trispinosus Krøyer, 1838, North Sea, ZMMU Ma 2921; B. Benthochascon hemmingi Alcock & Anderson, 1899, South China Sea, ZIN-RAS 88509; C. Xaiva biguttata (Risso, 1816), North Sea, SMF 3969; D. Achelous spinimanus Latreille, 1819, Jamaica, SMF 31987; E. Thalamita spinimana Dana, 1852, Indo-Pacific, SMF 3881; F. Podophthalmus vigil Fabricius, 1798, Vietnam, collections of the Department of Hydrobiology of Moscow University. Abbreviations: f – frontal margin; o – orbit; al – anterolateral margin; pl – posterolateral margin; mer – merus; cp – carpus; pp – propodus; d – dactylus; ch – chela. Scale bar equals 5 mm. 144 Vassily A. SPIRIDONOV In some portunoid taxa the cephalothorax is comparatively lengthened, so that the length becomes equal to or greater than the maximum width. The carapace morphology in such taxa shows a transition to a pear-shaped (Portumnus, Brusinia) or a nail-shaped (Thia, Nautilocoryst- es) outline (Fig. 4). The carapaces of Brusinia and Nautilocorystes are also distinctly longer than broad, which is an exception in the Por- tunoidea. The former genus may not even belong to the portunoid crabs phylogenetically (Evans, 2018), while the phylogenetic relationships of the latter are not yet reconstructed using molecular markers. However, all these taxa with a carapace shape that is unusual for portunoids have typi- cal characters of burrower ecomorphs (Schäfer, 1954), while some of them (e.g., Portumnus and Thia; Figs. 4B, E) are definitely known to spend most of time burrowed in sandy sediments (Spiri- donov et al., 2014). In various subfamilies and genera of Recent portunoids one can also see transitions from qua- si-hexagonal to other carapace shapes. Species of Ovalipes are flattened and approach an ovoid shape owing to arching of lateral carapace mar- gins (Fig. 4A). Several actively swimming Po- dophthalminae, e.g., Euphylax dovii Stimpson, 1860, are also flat and ovoid. Arching of lateral carapace margin is more expressed in the Lup- ocyclinae which have a quasi-circular carapace and the Carupinae with broad quasi-oval cara- paces (Fig. 5H). In the latter subfamily (genera Atoportunus, Carupa and Catoptrus) this type of carapace morphology is associated with living in reef cracks and caves (Spiridonov et al., 2014). In the non-reef-dwelling and likely non-swimming genus Libystes (Carupinae), e.g., L. edwardsi Al- cock, 1900, the carapace is quasi-hexagonal with a convex anterolateral margin bearing notable teeth, while these teeth are strongly reduced and the general outline approaches the oval one in Libystes aff. nitidus (Apel & Spiridonov, 1998: figs 5a, 6a), reaching a perfect oval condition in Libystes nitidus A. Milne-Edwards, 1867 (Fig. 5H). Another group with ovoid or quasi-circular carapaces includes symbiotic Caphyra and Trier- archus rotundifrons (A. Milne-Edwards, 1869), associated with green algae (Crosnier, 1975; Ev- ans, 2018). A very unusual quasi-circular cara- pace shape with protruding frontal and posterior regions is known for the Coelocarcininae which inhabit coarse coral sand and rubble (Ng, 2002). A trapezoidal carapace is characteristic of several portunids with extended frontorbital margin, which approaches the maximum breadth between posterior anterolateral teeth or becomes the widest part of the carapace. This is seen in Podophthalmus vigil (Fabricius, 1798) and some Thalamitinae. In the first case the extension is achieved owing to enlargement of the orbits, be- ing associated with long eyestalks, and is com- monly recorded among various and not closely related brachyuran taxa (e.g., Ocypodidae, Mac- rophthalmidae, some Goneplacidae). The second case is associated with the extension of the ba- sal antennal segment and the frontal margin and seems to be practically unique among crabs. The posterior part of carapace may be mark- edly longer than the anterior one (Geryonidae and most Carcinidae), or be nearly equal to it (a quasi-symmetrical shape in relation to the max- imum width axis carapace), and even shorter, which is characteristic of active swimmers in the Portunidae (see Schäfer, 1954: fig. 41). It is worth noting that the Parathranitiinae, a taxon appar- ently separate from most other extant carcinids, also has such quasi-symmetrical carapaces (see Crosnier, 2002). It is furthermore characteristic of Echinolatus (see Davie & Crosnier, 2006), a ge- nus incertae sedis, which I here tentatively place in the Geryonidae. Fossil portunoids, or taxa resembling por- tunoids, are mostly characterised by quasi-hex- agonal or ovoid carapaces which are mostly asymmetrical in relation to the maximum width axis (e.g., Karasawa et al., 2008; Ossó, 2016). In some cases, for instance in the Lithophylacidae Van Straelen, 1936 from the Cenomanian (lower Upper Cretaceous) quasi-trapezoidal carapac- es have been reported (Guinot & Breton, 2006). In the Cretaceous family Carcineretidae Beur- len, 1930 an intermediate condition between the quasi-quadrate and quasi-trapezoidal outline of the carapace is characteristic of the type genus Carcineretes Withers, 1922 (Withers, 1922, pl. 16; Vega et al., 2001, fig. 1; Schweitzer et al., 2007). Another Cretaceous taxon with a near-quadrate carapace is Binkhorstia ubaghsii (Van Binck- horst, 1857) currently included in the family Lon- gusorbiidae Karasawa, Schweitzer & Feldmann, 2008 (see Schweitzer et al., 2007, figs. 2 A-C). The Late Cretaceous Ophthalmoplax Rathbun, 1935, earlier considered within the Carcineretidae and currently within the Macropipidae (sensu Kara- sawa, Schweitzer & Feldmann, 2008) also has a subquadrate carapace (Schweitzer et al., 2007; Vega et al., 2013). In general, the carapace outline and symmetry/asymmetry patterns are charac- ters of considerable taxonomic value at the genus or family level. 145An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... Fig. 4. Examples of portunoid crabs with modified carapace. А. Ovalipes punctatus De Haan, 1833, Japan, SMF, no catalogue number; B. Portumnus latipes Leach, 1814, Black Sea, ZIN-RAS 25087: C. Brusinia brucei Števćić, 1991, southern Australia, Museum of Victoria MV J 61074; D. Nautilocorystes ocellatus H. Milne Edwards, 1837, NHMW, from the collection of the frig- ate “Novara” Expedition, # 83; E. Thia scutellata Fabricius, 1793, North Sea, SMF 38490. Scale bar equals 5 mm. Carapace regions The carapace of Decapoda is subdivided into regions which correspond to location of particu- lar internal organs of the cephalothorax (Glaes- sner, 1960). These regions may be separated by furrows expressed with various degrees of dis- tinctness, or practically smoothed (Figs. 1, 3, 4, 5E, H). Amongst the Portunoidea, relatively dis- tinct carapace regions are usually found in many groups with quasi-hexagonal carapace outlines (Figs. 3B, D, 5E). The species with another cara- pace outline, particularly ovoid or rounded, usu- ally have smooth carapace regions (Fig. 4). The smooth carapace regions are typical of burrowing (Portumnus spp.; Fig. 4 B) or actively swimming species (e.g., Charybdis smithii MacLeay, 1838); in the latter case, this is in contrast to related species (see Türkay & Spiridonov, 2006, pl. 1). Most fossil portunoids appear to have few dif- ferences from Recent representatives of the su- perfamily in the expression of carapace regions. Representatives of Cretaceous families referred to the Portunoidea are illustrated as having more 146 Vassily A. SPIRIDONOV strongly separated carapace regions compared to those in extant families: Carcineretidae (see Vega et al., 2001, fig. 1), Lithophylacidae Van Straelen, 1936 (see Guinot & Breton, 2006), Longusorbii- dae (see Schweitzer et al., 2007, figs 2A-C). Most records of Ophthalmoplax brasiliana (Maury, 1930) also show quite distinct carapace regions, more expressively separated than in the majority of extant portunoid taxa (Vega et al., 2013, fig. 5). The distinctness of carapace regions may be con- sidered as a character of varying taxonomic val- ue although it tends characterise taxa at the ge- nus level or higher. Carapace ridges and cuticular structures The dorsal carapace surface in portunoid crabs may be practically smooth as in Brusinia, Benthochascon, Portumnus, Nautilocorystes and Thia, evenly covered with granules (as in some Ovalipes and Chaceon) or carry complex sculp- ture, such as granular ridges, groups of gran- ules, terraces and tubercles. Smooth carapaces are characteristic, first of all, of those species which spend a significant length of time bur- rowed in sandy sediments (see Garstang, 1897a, b; Schäfer, 1954), and also of those spending much time swimming in the water column, such as Polybius henslowi Leach, 1820 or Charybdis smithii (see Türkay & Spiridonov, 2006). The absence of sculpture on the carapace decreases friction and is most likely a derived condition. Most portunoid crabs possess epibranchial gran- ular ridges that continue from last anterolateral tooth to the middle longitudinal axis of the body. In geryonids and carcinids these ridges consist of relatively sparse granules and are often inter- rupted and indistinct (Figs. 3A, B), similarly to many other heterotrenate crabs which have only epibranchial ridges. This is most probably a ple- siomorphic condition for the Portunoidea. Among the Carcinidae, some species of Liocarcinus (e.g., Liocarcinus corrugatus; see Plagge et al., 2016) and Necora (see Holthuis, 1987) have additional granular ridges and even terraces. Parathranites (Fig. 5E) is characterised by a heavily sculptured carapace (see Crosnier, 2002), while in the Portu- nidae, particularly in the Thalamitinae and such genera as Monomia and Xiphonectes that sculp- ture is most diverse and spectacular (see e.g., Fig. 1F). The location of granular ridges and patches create specific patterns useful for distinguishing species and their groups in speciose genera such as Achelous, Charybdis, Cycloachelous, Mono- mia, Thalamita and related taxa, and Xiphonect- es. Fossil taxa also show a variety of dorsal cara- pace structures. Several Cretaceous genera have strong transverse ridges, even described as keels: across most of carapace regions as in Ophthal- moplax (see Vega et al., 2013, figs. 4-1) and Icri- ocarcinidae Števčić, 2005 (Phillips et al., 2014), or across the protogastric region as in Carciner- etes (Schweitzer et al., 2007). Icriocarcinidae and Longusorbiidae are characterised by a row of massive tubercles along the posterolateral mar- gin, particularly well developed in Binkhors- tia Noetling, 1881 (see Schweitzer & Feldmann, 2011, fig. 8.1). Significant differences in carapace ornamentation of fossil taxa, judging from the variation observed in extant portunoids, support their distinctness and a relatively high taxonom- ic rank (i.e. family). Frontorbital margin The front per se is usually subdivided into sev- eral lobes or teeth, the number of which is either even (2–6), or odd (1–3). The functionality of the frontal lobes and space between them may be re- lated to the sensory functions of antennules, their protection and cleaning, although this is large- ly unstudied. In the Geryonidae, the subfamily Geryoninae is characterised by a pair of separated median teeth and the lateral teeth are completely fused with inner orbital lobes (Fig. 3A). This fu- sion can be inferred from the presence of inner orbital lobes in with distinct two parts in some species of Chaceon and Zariquieyon (Manning & Holthuis, 1989, figs. 12, 14, 18). In the Benthochas- coninae the median lobes are fused and the later- al frontal lobes can be recognised as distinct from the much smaller outer lateral lobes (Fig. 3B). In most species of Ovalipes, the frontal margin has two teeth (Fig. 6A). In O. molleri (Ward, 1933) these teeth are fused at the base so that they can be considered as a single, bifid tooth. Low projec- tions of the frontal margin, possible rudiments or vestiges of lateral frontal lobes, are located lat- erally (Fig. 6B). In O. iridescens Miers, 1886, the species most closely similar to O. molleri, only a single median tooth is present and lateral concav- ities can be recognised in the largest specimens (Fig. 6C). In O. ocellatus (Herbst, 1799) nothing besides a sharp median frontal tooth can be seen (Fig. 6D). Nectocarcinus (Fig. 5B) and Echinola- tus (see Davie & Crosnier, 2006) have a 4-lobed front that provides additional support to their placement in the Geryonidae. With few exceptions, Brusiniidae and Carci- nidae mostly have a 3-lobed front. The 4-lobed frontal region of Bathynectes (Fig. 5D) and Par- 147An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... athranites (Fig. 5E) largely resembles the condi- tion in the Benthochasconinae. Nautilocorystes, a taxon with a burrowing habit, is characterised by a narrow bilobed front with lateral frontal lobes fused with the inner supraorbital ones (Fig. 4D). However, the relationships of the above-men- tioned three genera to the Carcinidae remain to be clarified. A unique, for Recent carcinids, case of a broad bilobed front is represented by Coe- nophthalmus whose position within the Carcini- dae also remains unclear. There are several cases of transformation of a 3-lobed to an entire front, even within a single genus, e.g., in Liocarcinis navigator (Herbst, 1794). with indication of fu- sion of the original three lobes. Other examples of a practically entire front include Coelocarci- nus (see Ng, 2002) and Thia (Fig. 4E). The Portunidae show a variety of frontal shapes, although most have an even number of teeth/lobes. In some genera the number of lobes varies: 4 to 6 in Achelous, and 2 to 6 in Thalami- ta (sensu lato). In these, not closely related, taxa, some species with transitional states are also re- ported, for instance Thalamita bevisi (Stebbing, 1921) (= T. dakini Montgomery, 1931; see Apel & Spiridonov, 1998, fig. 53a, c, d). An entire fron- tal margin in some species of Libystes has been apparently evolutionarily derived from an indis- tinctly bilobed front, characteristic of other spe- cies of the genus, less deviating from the general portunoid appearance, like in Libystes edwardsi (see Apel & Spiridonov, 1998, fig. 5a). There are relatively few portunid taxa with 3-lobed fronts; most of these belong to the genus Xiphonectes, which is most probably heterogenous (Spiri- donov et al., 2014). In several Xiphonectes with a 4-lobed front the lateral lobes are broad and produced forwards, while the median ones are small and often partly fused. This may be a con- dition from which a 3-lobed front, characteristic of some species of the genus, such as X. tenuipes (De Haan, 1833), could evolve. Another example refers to some symbiotic species of Lissocarcinus in which the frontal margin is transitional be- tween triangular entire and indistinctly 3-lobed ones, while other species of the genus have an in- distinctly bilobed front (see Evans, 2018, fig. 3C, D). In the Podophthalminae the T-shaped frontal region is strongly reduced due to the enormous development of the orbits. Thus, the frontal mar- gin shows a possibility for transformation, where both fusion and separation of the lobes seem possible in phylogeny, although the core groups of the main portunoid taxa are characterised by relatively constant patterns of frontal lobes. Most fossil portunoid taxa were reported to have an even number of frontal teeth or lobes, or a flattened frontal margin with protuber- ances, usually even in number (Müller, 1984; Schweitzer & Feldmann, 2000; Karasawa et al., 2008). A 3-lobed front was particularly report- ed for species assigned to Liocarcinus and for such taxa as “Xaiva” bachmayeri Müller, 1984, Mioxaiva psammophila Müller, 1984 and “Lis- socarcinus” szoeraenyiae (Müller, 1974) from the Miocene (Müller, 1984). An example of a possible portunoid, although not referable to any Recent family, is a species with an odd number of fron- tal teeth, Psammocarcinus hericarti Desmarest, 1822 from the Eocene, in which the prolonged front “has three spiniform teeth: the middle one is the largest; the lateral ones merge with the inner orbital angle” (A. Milne-Edwards, 1860, 279; translation by Karasawa et al., 2008). A unique frontal margin in the form of a deflected rostrum is characteristic of the Carcineretidae (Schweitzer et al., 2007). Ophthalmoplax spp. also possess a peculiar front: relatively narrow, deflected and bifid (Vega et al., 2013; Internet 1). Another frontal region that is unusual for por- tunoids is interpreted for Longusorbis Richards, 1975 (Upper Cretaceous–Eocene) as located “be- tween interior-most orbital notches, axially pro- duced into long, blunt-tipped rostrum, rostrum axially sulcate, strongly down-turned distally so that distal part is nearly perpendicular to dorsal carapace” (Karasawa et al., 2008, 95). The mor- phology of the frontal margin, its subdivision into teeth or lobes and inferred patterns of their transformation thus provide a set of characters highly applicable at the generic and suprageneric levels of taxonomic hierarchy. Orbit The orbit is a complex morphological structure, consisting of several lobes, separated by notches or fissures. The margins of the lobes may be rounded or polygonal. The number of lobes is a relatively stable character, although there are some excep- tions. The supraorbital margin of one of the ba- sal portunoid genera, Chaceon, consists of inner, median and outer supraorbital lobes separated by narrow fissures (Fig. 5A). The infraorbital part in- cludes a tooth-like inner lobe, following which the inner orbital margin continues, smoothly forming an outer lobe (= 1st anterolateral tooth) (Fig. 5C). Such construction is similar to the one observed in most other portunoids although they usually have one more fissure or notch laterally of the outer lobe; moreover, in some taxa an outer infraorbital lobe, 148 Vassily A. SPIRIDONOV Fig. 5. Examples of frontorbital margins and carapaces. A. Chaceon macphersoni Manning & Holthuis, 1988, southwestern Indian Ocean, ZMMU Ma 4044, dorsal view; B. Nectocarcinus bennetti Takeda & Miyake, 1969, Maquarie Islands, ZMMU Ma 2301; C. Chaceon macphersoni Manning & Holthuis, 1988, ZMMU Ma 4044, ventral view; D. Bathynectes longispina Stimpson, 1871, Amper Seamount, Atlantic Ocean, ZMMU Ma 2392; E. Parathranites orientalis Miers, 1886, ZMB, without catalogue number; F. Thalamita savignyi A. Milne-Edwards, 1861, Gulf of Aden, ZMB 15592; G. Carupa tenuipes Dana, 1851, Japan, SMF, without catalogue number; H. Libystes nitidus A. Milne-Edwards, 1867, Maldive Islands, NHM 1991-156-1. Scale bars equal 10 mm (A, B, C, G), 5 mm (D, E, F) and 2 mm (H). separated from the 1st anterolateral tooth, is also present. In some portunoids belonging to taxa that otherwise have numerous plesiomorphies (Spiri- donov et al., 2014), one (in Nectocarcinus; Fig. 5B here; in Zariquieyon Manning & Holthuis, 1989, figs. 18, 19) or both supraorbital fissures (in Gery- on; Fig. 3A) are strongly reduced. In the Ovalipes iridescens group only a single fissure is present: this is morphogenetically correlated with a trans- formation of the front with paired median teeth to a single tooth condition (Fig. 6). Finally, Brusinia (Fig. 4C), Catoptrus and Libystes (Fig. 5H) lack 149An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... supra- and infraorbital fissures, while in Por- tumnus only a single strongly reduced supraor- bital fissure is present (Fig. 4D). These groups are morphologically different and apparently belong to different phylogenetic lineages (except for the relatively closely related Catoptrus and Libystes). Forms with reduced fissures or an entire supraor- bital margin in many cases belong to deep-water (Geryonidae) or burrowing (Ovalipes) species or are inhabitants of reef cavities and underwater caves (Catoptrus). They are characterised by a re- duction of orbits, which may be achieved by fusion of orbital lobes. An opposite case also leading to the disappearance of the orbital fissure is a long but open and shallow orbit of the Podophthalmi- nae where their long eyestalks are held. Thus, it is very likely that portunoid crabs originally had a 3-lobed supraorbital margin but in particular lineages transformation of morphogenetic pattern took place, thus leading to formation of a bilobed or an entire margin. Derived conditions from the 3-lobed supraor- bital margin involve modifications of lobes. The outer and inner lobes have various relative sizes and shapes, and may be modified to teeth, such as in Pirimela which has a long and sharp median supraorbital tooth (Fig. 3C). An unusually look- ing infraorbital margin in Bathynectes is subdi- vided into three denticulated teeth (Fig. 5E), al- though this condition may be a derivation of the typical 3-lobed one. Where the details of orbit morphology can be recognised, fossil taxa often show a condition that is characteristic for extant portunoids. two or one supraorbital fissures. In one of the earliest, Cre- taceous portunoids, Eogeryon elegius Ossó, 2016, the supraorbital margin closely resembles that of Benthochascon (Fig. 3B), while the infraor- bital margin appears to be 3-lobed (Ossó, 2016, figs 5A, B). Orbits of some Cretaceous portunoid families (Carcineretidae, Longusorbiidae) are markedly broad at the expense of a narrow front and are similar in that respect to the orbits of the Podophthalminae. Carcineretes is diagnosed as having a sinuous orbit, “with two or three in- tra-orbital spines and notches (Schweitzer et al., 2007, 19). The original reconstruction of Carci- neretes woolacotti Withers, 1922 shows four lobes of different width and shape and three notches (Withers, 1922; pl. 16). Protuberances and spines without fissures are characteristic of the orbits of Longusorbis (Schweitzer et al., 2007). The other Cretaceous genus with a narrow front, wide or- bits and long eyestalks, Ophthalmoplax, also has three supraorbital lobes and two intra-orbital spines (Schweitzer et al., 2007; Vega et al., 2013, figs. 3, 13). The median orbital tooth similar to the one in Recent Pirimelidae is seen in the Mi- ocene Pirimela lorentheyi Müller, 1984 (Müller, 1984, pl. 60, fig. 3). Some extinct portunoid taxa are also reported to have an entire supraorbital margin, e.g., Psammocarcinus A. Milne-Ed- wards, 1860 (see Desmarest, 1822, pl. V, fig. 5; A. Milne-Edwards, 1860). The most unusual orbit with a completely denticulated supraorbital mar- gin is found in Pheophthlamus mochaensis Feld- mann, Schweitzer & Encinas, 2010 (assigned to the Podophthalminae) from the Neogene of South America (Feldmann et al., 2010, fig. 11), although most of the taxa included in this subfamily have a relatively simple supraorbital margin. Thus, the orbits of portunoids provide an important set of characters that may be used at various levels of taxonomic hierarchy. Anterolateral carapace margin The anterolateral margin of the carapace is subdivided into several teeth, the first corre- sponding to the outer orbital lobe. The functional significance of the anterolateral teeth was first interpreted by Garstang (1897a), who considered them as part of the apparatus preventing enter- ing sediment particles to the branchial cavity in burrowing crabs. Brusiniidae, Geryonidae and Carcinidae do not have more than five teeth. In geryonids their number varies from three (Gery- on, Raymanninus) to five (Ovalipiinae). In Cha- ceon, which typically has five anterolateral teeth, some teeth become obsolete with age. Bentho- chascon, Nectocarcinus and Echinolatus, which are tentatively referred to this family (but are considered by me as genera incertae sedis) are characterised by four large teeth. Some species of the last-named genus possess a unique char- acter of additional denticles on the anterior mar- gin of the anterolateral teeth or bifid teeth (Davie & Crosnier, 2006, fig. 3). Most of the Carcinidae have five anterolateral teeth. Important examples of reduction of anterolateral teeth in the Carci- nidae are Coenophthalmus with three teeth and Thia with a nearly entire anterolateral margin, although one can see four notches on this mar- gin which mark the position of five reduced teeth. A very dense belt of setae bordering the lateral margin in this burrowing species probably plays the role of branchial cavity protection in the ab- sence of anterolateral teeth (Fig. 4E). The number of anterolateral teeth in the Por- tunidae varies from two to nine and is largely a taxonomic character used at the generic level. 150 Vassily A. SPIRIDONOV number of lateral teeth is subject to change in particular groups of portunoids, the major taxa have a distinct pattern of variation of this char- acter. Posterolateral and posterior carapace margin A supra-dorsal position of the 5th pair of pereopods is morphologically correlated with the development of the posterolateral reentrant which extends motion possibilities for the last pair of legs, used for burrowing and swimming. Although this reentrant is feebly developed in the non-swimming Geryonidae (Figs. 3A–B), or carcinids like Carcinus (not swimming, and not commonly burrowing) and Portumnus, Thia, Nautilocorystes and Brusinia, presumably using all legs for burrowing (Figs. 4B–D). The posterior carapace margin is bordered by a cuticular “wall” touching the 1st pleonal tergite. This margin is usually straight or gen- tly convex (e.g., Figs. 3, 4). Much rarely, for in- stance in Benthochascon, this margin is concave (Fig. 3B). The majority of portunoids have round- ed transitions between the posterolateral and posterior carapace margins. In some groups these Spiridonov et al. (2014) argued that the nine teeth corresponded to a plesiomorphic condition for this family and the number of teeth showed var- ious patterns of reduction in particular genera. Evans (2018) provided additional evidence for this in the Thalamitinae (which generally have a reduced number of teeth, from six to three) and suggested a nomenclature of teeth based on their general pattern and presumed homologies. Some oval forms, such as Libystes, have anterolateral teeth that are strongly reduced to nearly com- pletely absent (see Apel & Spiridonov, 1998, figs. 5, 6a). Podophthalmines also show a reduction of teeth (up to two), which is apparently connected to their habits and a characteristic shortening of the anterolateral margin. Noteworthy, the sin- gle extinct portunoid taxon that is characterised by nine anterolateral teeth, but not referred to the Portunidae is Archaeoportunus Artal, Ossó & Domínguez, 2010, for which a separate fami- ly was introduced (Artal et al., 2010). Otherwise, fossil taxa do not show such morphological pe- culiarities of the anterolateral margin that re- markably exceed variation observed in extant portunoids (see e.g., Internet 2). Although the Fig. 6. Frontorbital margin of carapaces in Ovalipes spp. А. O. trimaculatus (De Haan, 1833), Patagonia, ZMMU, without catalogue number. B. O. molleri (Ward, 1933) (drawn on basis of photograph in Davie & Short, 1989, fig. 14B). C. O. iridescens Miers, 1886, southwestern Indian Ocean, ZMMU Ма 2300. D. O. ocellatus, northwest Atlantic, coast of Georgia, USA, SMF 7325. Abbreviations: isl: inner supraorbital lobe; mft: median frontal teeth (tooth); msl: medial supraorbital lobe; of: orbital fissure; osl: outer supraorbital lobe. 151An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... corners are angled (e.g., subgenera Goniohellenus and Gonioneptunus of the genus Charybdis; see Türkay & Spiridonov, 2006) or even spined, as in Xiphonectes (see Spiridonov, 2016) in the Portu- nidae. The only Recent carcinoid genus having angled, or spiny posterolateral corners is Par- athranites (Fig. 5E; see also Crosnier, 2002). Most fossil portunoids studied that have variously ex- pressed posterolateral reentrants are character- ised by rounded posterolateral corners (Karasa- wa et al., 2008; see also examples via Internet 3). There are few exceptions, e.g., Psammocarcinus which shows an angled posterolateral corner (see Desmarest, 1822, pl. 5, fig. 3). A unique morphol- ogy of the posterolateral margin with a series of teeth is seen in Styracocarcinus meridionalis (Secretan, 1961), a Campanian crab considered within the Portunoidea but not assigned to any family (see Ossó, 2016, fig. 6A, B). The characters associated with the posterior part of the carapace are thus important for the diagnosis of genus-lev- el taxa within portunoid families. Pterygostomial and subhepatic regions Surfaces of the carapace regions located ven- tral to the anterolateral margin determine both an absolute and a relative height of the carapace, which is a taxonomically important character at higher levels. In most groups these surfaces are smooth, granular or markedly setose. Particu- lar taxa such as not closely related Ovalipes and Laleonectes are characterised by the presence of granular lines and other cuticular armature constituting parts of the stridulating apparatus which counterparts constitute processes of cheli- peds. The construction of this apparatus is a set of characters at the species level, for instance in Ovalipes (see Stephenson & Rees, 1968). In the deep-water species of this genus a reduction of the stridulatory apparatus occurs, which is cor- related with the development of an optical com- munication system on the basis of iridescent sur- faces reflecting polarised light under conditions of practical darkness (Parker et al., 1998). Sternal part of cephalothorax Sternites and episternites are sclerites of the sternal part of the cephalothorax. The latter join the former in their posterolateral part by dis- tinct or partly interrupted sutures. The hollow space between the lateral margin of the sternite and the respective episternite houses the condyle of the pereopod coxa, and the entire structure forms a sterno-coxal articulation. The major part of episternites 4 to 6 is usually sickle shaped; it is extended posteriorly, touching the lateral mar- gin of the next sternite over more than half of its extension. The shape of episternites 7 and 8 usually strongly deviates from the sickle-shaped one and may characterise taxa at family and sub- family levels (Fig. 7). In most portunoid crabs the width of episternites is several times less than the width of sternites but in Thia sternites are less than twice wider than episternites (Fig. 7B). Sternites and episternites of thoracomeres 1–4 is consolidated as a thoracic sternum, the parts of which may be separated by furrows of various distinctness. This has taxomomic significance for diagnosing particular families, subfamilies and genera. The longitudinal median groove is char- acteristic of most Portunoidea, although may be present in other taxa as well. Sutures between sternites 4–8 may be inter- rupted in various ways that usually characterise particular genera and subfamilies. The Portu- nidae have secondary sulci between sternites 6 and 7, which are considered as their unique syn- apomorphy, although Libystes lacks this charac- ter (Karasawa et al., 2008). Sternal characteris- tics are relatively well preserved and have been widely used in the taxonomy of fossil portunoids (Schweitzer et al., 2007; Karasawa et al., 2008). Antennules and antennae Antennules of most portunoids are relatively short, transversely folded and generally similar even in such distant groups as geryonids and por- tunids. In completely folded conditions, the an- tennules are concealed under the frontal margin and not seen dorsally. Only in podophthalmines, with their very narrow front, folded antennules cannot be completely hidden in dorsal view. Antennae differ first of all by a so-called ba- sal antennal segment which is interpreted as a fusion of the original segments 2 and 3 of the antennae (Ng et al., 2008). In a number of por- tunoid crabs this segment tends to form a dis- tolateral process entering the orbital hiatus. Size and form of this process are important taxo- nomic characters. The tendency for enlargement reaches a maximum in the Thalamitinae: the process contacts the orbital margins and isolates the antennal flagellum from the orbital hiatus. The enlarged basal antennal segment itself often bears armature, e.g., granules, ridges and spines, the pattern of which is an important taxonom- ic character at the species level in thalamitines (Stephenson & Hudson, 1957; Apel & Spiridonov, 152 Vassily A. SPIRIDONOV Fig. 7. 153An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... 1998). A highly unusual antennular morphology for portunoids is seen in Nautilocorystes, which has long setose antennae (Fig. 4D), similar to the ones of Corystes Bosc, 1802 that are in turn as- sociated with the burrowing habit of this crab (Schäfer, 1954: fig. 28). The details of antennae and antennules are rarely enough preserved to be considered for fossil taxa. Maxillipeds Although mouthparts including mandibles, maxillae and maxillipeds 1 and 2 are usual- ly not preserved, maxilliped 1 should be men- tioned here as having particular significance in portunoid taxonomy. The upper part of its endo- pod has a quasi-triangular or quasi-trapezoidal shape. Antero-mesially the so-called “portunid lobe” is attached; this usually is dentiform, stick- shaped or finger-shaped. This lobe is present in all Portunidae but also in some carcinids, for ex- ample in Bathynectes, Liocarcinus and Macro- pipus, although absent in the Carcininae, Gery- oninae and Ovalipinae along with Nectocarcinus (Spiridonov et al., 2014). In Benthochascon, the lobe is morphologically different from the one observed in other portunoids (Spiridonov et al., 2014). Currently, it is difficult to judge if the ob- served pattern is a result of parallel origin of lobes or reduction of this structure takes place independently in particular families. Functional properties of the maxilliped 1 lobe have not been studied. Maxillipeds 3 are of similar construction in all Portunoidea. The shape of the meropodite, which covers the mouth cavity anteriorly is about as long as wide, quasi-quadrilateral, with a convex setose mesial margin and is not much different in geryonids and carcinids, except for some burrowing species in which it is more elongated. In the Thalamitinae and Portuninae, meropodites of maxilliped 3 are most diverse and may have a different shape, with rounded or angular anterior margins and varying setal coverage and granulation. These usually are characters that are taxonomically important at lower taxonomic level (species, species groups and small genera). Chelipeds The relative length of the chelipeds is a charac- ter that marks taxa at the family level. While rel- atively short, not exceeding in length pereopods 2 and 3, chelipeds are most probably a plesiomorphy, characteristic of Carcinidae and most Geryonidae (Figs. 3A–C), except for some species of Ovalipes, for instance the Ovalipes iridescens group. Chelipeds of the Portunidae are the longest pair of pereopods, on acount of their long meri and chelae (Figs. 3D–F). Meri of chelipeds may be smooth or possess spines. Geryonines possess a solitary spine on the posterior surface of merus. Nearly all Portunidae and few non-portunid portunoids (Bathynectes, Parathranites and species of the Ovalipes irides- cens group) have spines on the anterior face of the merus (Figs. 3D–F). Long and spiny chelipeds are advantageous for defence (in particular, in typical defensive reaction), prey capture, courtship and mating behaviour (Schäfer, 1954; Spiridonov et al., 2014). Carpi of chelipeds may have various shapes, although the respective taxonomic characters are associated mostly with carpal spines. All por- tunoid crabs, along with several other heterotreme taxa, have an inner spine on the after carpus its length is varying between taxa but is particular- ly significant in some species of Achelous. On the other hand, this is obsolete, in Callinectes spp. The taxa referred to the Geryonidae with reservation, such as Echinolatus (see Davie & Crosnier, 2006) and some Nectocarcinus, e.g., Nectocarcinus ben- neti Takeda & Miyake, 1969 are characterised by double carpal spines, similar to the ones seen in the Mathildellidae (Goneplacoidea). Spines on the outer face of carpus are char- acteristic, first of all, of the Portunidae, but are also present in Parathranites (see Crosnier, 2002). They may undergo reduction; in particular, one of the differences between related species of Xi- phonectes, X. tenuipes (De Haan, 1835) and X. pseudotenuipes (Spiridonov, 1999) is the reduced spines in the latter (Spiridonov, 1990, figs 2E, 3B). An important character in Thalamita and related genera is an additional spinule on the upper face of the cheliped carpus. It appears to have a paral- lel origin in several groups of species and genera (Spiridonov & Neumann, 2008; Evans, 2018). Fig. 7. Sternal regions. A. Benthochascon hemingi Alcock & Anderson, 1899, South China Sea, ZIN-RAS 88509; B. Thia scute- llata Fabricius, 1793, North Sea, SMF 38490. C. Ovalipes iridescens Miers, 1886, southwestern Indian Ocean, ZMMU Ma 2300. D. Carcinus aestuarii Nardo, 1848, Black Sea, Ма 5181. E. Bathynectes longispina Stimpson, 1871, Atlantic, Amper Seamount, ZMMU Ма 2392; F. Achelous spinimanus (Latreille, 1819), Gulf of Mexico, ZMMU Ma 4848. Abbreviations: G I – gonopod 1; G O – genital opening; TS – thoracic sternum; st – sternite; est – episternite; V – VIII – number of sternites. Scale bar equals 5 mm. 154 Vassily A. SPIRIDONOV Fig. 8. Chelae. A. Nauticorystes ocellatus, NHMW, from the collection of the frigate “Novara” Expedition, # 83. B. Patrathranites orientalis Miers, 1886, ZMB, without catalogue number. Scale bar equals 5 mm. Chela morphology and patterns of heterochely Chela morphology is essential for morphologi- cal characterisation of the Portunoidea (Schäfer, 1954; Manning & Holthuis, 1981; Spiridonov et al., 2014), the presence of a large proximal mo- lariform tooth on the dactylus of one of the che- lae (heterodonty) along with serial bi- and tri- lobed conical teeth on the dactylus and the polex of both chelae. Serial teeth separated into lobes increase the cutting edge and work as scissors. 155An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... The presence of a massive molariform tooth al- lows the portunoid chelae to maintain signif- icant crushing capacity and perform various crushing techniques when feeding on molluscs. Various modifications from this basic plan and symmetrisation of chelae construction have been described by Spiridonov et al. (2014, figs. 2, 3) and interpreted in terms of belonging to particular ecomorphs: burrowers, walkers and swimmers. Reference is made to that paper for a detailed description. Typical portunoid heterodont che- lae are found in Nautilocorystes (Fig. 8), which otherwise has a very peculiar “non-portunoid” general appearance which possibly is associated with a burrowing habit (Fig. 4D). Surprisingly, this chela is very similar to the that of the Polybi- inae with a very different habit (see Spiridonov et al., 2014, fig. 2). Chelae are usually well preserved in fossil taxa which can often be recognised as portunoids by the characteristic morphological features of their palms (Müller, 1984; Schweitzer & Feldmann, 2000, 2011; Schweitzer et al., 2007; Karasawa et al., 2008; Phillips et al., 2013). Pereopods 2–4 (ambulatory legs) In portunoid crabs, pereopods 2–4 are usual- ly similar but differ in size from front to rear, P2 or P3 being the longest. The orientation of the sterno-coxal articulation allow for the parallel position of pereopods which become in that case somewhat inclined in relation to the transverse axis of the body. Meri, carpi and propodi are compressed so that the morphologically dorsal face is exposed anteriorly. In most geryonids an anterodistal process or lobe is present in meri; in Ovalipes only low lobes can be traced there. Oth- er processes and spines are rare on pereopods 2-4 and, usually, are characters used at intermediate hierarchical levels (e.g., goups of species and gen- era), such a series of spines on the anterior face of the merus is seen in Coenophthalmus (Steudel, 1998, figs. 37c-d). In most portunoids, dactyli (fingers) of pere- opods 2–4 are relatively similar, piercer shaped, or narrow knife-shaped, costate, often setose on the flexor margin. Active natatory species, such as Callinectes spp., Portunus pelagicus (Linnae- us, 1758) and related species, Polybius henslowii Leach, 1820, Euphylax dovii Stimpson, 1860 and Charybdis smithii, have leaf-shaped leg fingers, which are used in swimming. However, the mor- phology of dactyli in the the overwhelming ma- jority of cases does not differ between pereopods. Heterodactyly (differing between pereopods 2–4 shape of fingers) is characteristic of a few taxa known or presumed for their burrowing habits (Brusinia, Thia, Nautilocorystes, Ovalipes, Por- tumnus) (Fig. 4). However, the pattern of heter- odactyly in these groups differs, which makes it a taxonomic character of a relatively high level (subfamily or family). In fossil portunoid taxa, the morphology of ambulatory legs varies significantly, although this mostly refers to the more proximal seg- ments of legs, while dactyli are less frequently preserved. In particular, in the Carcineretidae, pereopod 4 has a flattened carpus and merus (Schweitzer et al., 2007). Pereopod 5 The dorsal position of the last pair of pereo- pods that is typical of portunoid crabs is achieved by a higher position of their coxae in relation to other legs (the so-called dorsal coxal shift). The fewer differences in the plane where the coxae of the 5th and other pereopods are located are known for Brusinia and Portumnus. The highest dorsal coxal shift is characteristic of such taxa as Coenophthlamus (non-swimming ecomorph), Liocarcinus, Portunus, Thalamita (all swimming or at least lifting over substrate) and Caphyra (non-swimming symbionts of cnidarians). A pe- culiar morphology of a modified pereopod 5 is an important portunoid character, used for swim- ming, burrowing and attaching to a host. The modification affects a shortening and broadening of the merus, flattening of the propodus, and ensi- form, ovate, lanceolate, or hook shape of the dac- tylus. This construction, however, is not shared by all portunoid taxa, in particular Chaceon and Geryon have the last pair of pereopods not par- ticularly different from others (Fig. 3A). This is probably also the case for such fossil family as the Icriocarcinidae (Phillips et al., 2013) of Cre- taceous age. The shape of segments of pereopod 5 provides a number of taxonomic characters which are used at various hierarchical levels. It is of inter- est to note that within a single (although prob- ably non-monophyletic) genus Liocarcinus both broad (for instance in L. vernalis; see Fig. 1C) and relatively narrow dactyli of the last pair of legs are known (e.g., in L. navigator). Even greater variation is known for symbiotic Lissocarcinus spp. (an apparently monophyletic group; see Ev- ans, 2018), where the dactyli are variously modi- fied, possibly depending on the relationships of a particular species with its host. Wherever preservation conditions enable an examination of the last pair of ambulatory legs in 156 Vassily A. SPIRIDONOV Fig. 9. Male pleons. A. Ovalipes iridescens Miers, 1886, southwestern Indian Ocean, ZMMU Ма 2300. B. Achelous hastatus (Linnaeus, 1767), Mediterranean, ZMMU Ma 1910; C. Parathranites orientalus Miers, 1886, Indo-Pacific, ZMB, without cata- logue number; D. Monomia petrea Alcock, 1899, western Indian Ocean, ZMMU 2294. Abbreviations: 1–6 – pleomeres; t – tel- son. Scale bar equals 1 mm. Pleon A nearly universal characteristic of the por- tunoid pleon is the presence of a transverse keel on the tergite of the 3rd pleomere (Figs. 9B–D) (absent in Brusinia, Ovalipes [Fig. 9A] and Caru- pa). Male pleons are characterised by a tendency for fusion of pleomere terga 3 to 5, which is, how- ever, not a universal characteristic of the group. Six separate pleomeres and the telson are appar- ently a plesiomorphic condition typical of most Heterotremata (Guinot, 1979; Davie et al., 2015). fossil crabs assigned to the Portunoidea, we see modified propodi and dactyli. While the Recent Geryoninae have the segments of pereopod 5 not much different from the anterior legs, Chaceon peruvianus (d’Orbigny, 1842) from the Miocene of South America clearly possessed broadened propodi and narrow-lanceolate dactyli of pere- opod 5 (Schweitzer & Feldmann, 2000, fig. 10-1). This indicates that a characteristic construction of pereopod 5 can undergo evolutionary reversal and/or evolve as a parallelism (Simpson, 1961) in various groups of portunoids. 157An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... In Geryon, Chaceon, Benthochascon, Ovalipes (Fig. 9A), Echinolatus, Nectocarcinus, and Brusinia pleomeres 3–5 are separated, al- though an ability of individual motion may be lost. In most carcinids and portunids they are fused, while some sutures or their traces may re- main (Figs. 9B–D). It is of interest to note that similar, possibly convergent or parallel fusion of the pleomeres is known for the American freshwater brachyuran family Trichodactylidae (Rodriguez, 1992). The functional significance of the pleomere fusion is unknown. It is possible that it is correlated with particular mechanisms of copulation (Karasawa et al., 2008). All portunoids with fused pleomeres also have short gonopods 2 (see below). Gery- onids that have separated pleomeres possess also long gonopods 2 (Spiridonov et al., 2014). A unique condition is observed in the males of Thia, where separated pleomeres (a unique char- acter of carcinids) are associated with short go- nopods 2. Since Thia is a quite specialised and not a basal taxon to the Carcinidae, it is unclear how this condition could originate and whether a reversal to non-fused pleonal segments is pos- sible. Males of most portunoids have a triangular or (in the Portunidae) T-shaped pleon (Figs. 9B– D), although a different condition is observed in Ovalipes with its quasi-rectangular pleon (Fig. 9 A). In most fossil portunoids male pleons are also triangular, while in Proterocarcinus it is quasirectangular (Feldmann et al., 2005, fig. 5 E), in some respect similar to that of Ovalipes. Not all fossil taxa can be characterised by ple- on morphology owing to preservation conditions. However, separated pleomeres 3–5, although probably immovable, are known for ancient gery- onines (e.g., Schweitzer & Feldmann, 2000, fig. 9), Longusorbiidae (Karasawa et al., 2008), Icrio- carcinidae (Philips et al., 2013), Lithophylacidae (Guinot & Breton, 2006) and the genus Ophthal- moplax (Schweitzer et al., 2007; Vega et al., 2013; Ossó-Morales et al., 2010). Surprisingly, separa- tion of pleomeres is also characteristic of such genus as Archaeoportunus, which in several oth- er respects is similar to the Portunidae (Artal et al., 2013, fig. 4b), although such Cretaceous taxa as Carcineretes had fused pleomeres (Schweitzer et al., 2007). The shape of the male pleon and the pattern of pleomere fusion can thus be regard- ed as important taxonomic characters for high- er-level portunoid taxa, in most cases of family/ subfamily rank. Discussion Recent morphological and molecular phy- logenetic studies have indicated that several high-level extant taxa of portunoid crabs (fami- lies and subfamilies) are much more diverse mor- phologically than had been intuitively expected, although possible morphogenetic transitions be- tween different character states may be inferred in many cases, as in the case of the frontal margin of Ovalipes (Fig. 6). Furthermore, each internally diverse taxon of portunoid crabs is characterised by a core suit of characters, which may be even called an “archetype” (I use this term only in- strumentally, without a reference to essentialism; see Lyubarskiy, 1995) and peripheral conditions. This is a result of mosaic evolution and leads to polythetic diagnoses of taxa in many eukaryotic groups (see Mayr & Bock, 2002; Takhtajan, 2009) and varying resolution of particular taxonomic characters (Zarenkov, 1974). A proper description and understanding of this “archetype” may help to classify extinct taxa using a comparative ap- proach to extant ones. Firstly, several families established earlier by palaeontologists and redefined by Karasawa et al. (2008), such as the Carcineretidae, Lithophy- lacidae, Longusorbiidae and Psammocarcinidae, appear to have a distinct suit of characters that do not fit even peripheral conditions of extant portunoid families. Similarities of these families to extant por- tunoid taxa may be the result of parallelism rath- er than of common origin. Although testing this is currently hardly possible, and the Portunoidea that contain the above-mentioned families should be considered as an evolutionary taxon in Simpson’s (1961) sense. The composition of the Portunoidea, including the extant families along with the Carcineretidae, Lithophylacidae, Lon- gusorbiidae and Psammocarcinidae, appears to be appropriate and can be only rejected if a com- pletely convergent origin of the core portunoid character suit in extant and extinct families is demonstrated. Ossó (2016) established the family Eogery- onidae based on Eogeryon elegius. This fam- ily apparently has an affinity to portunoids, in particular to the Geryonidae, although shows some important differences. However, taking the significant variability of taxa combined in the Geryonidae (e.g., Geryoninae, Benthochascon- inae and Ovalipiinae, possibly Echinolatus and Nectocarcinus), it would not be surprising to find additional support for considering Eogeryon as a taxon close to the ancestral geryonid. The sub- 158 Vassily A. SPIRIDONOV rectangular male pleon of Eogeryon is indeed similar to the one of Ovalipes, while the general carapace outline of this fossil portunoid resem- bles that of Benthochascon. Karasawa et al. (2008) performed a morpho- logical cladistic analysis of Recent and extinct genera of portunoids and some other taxa, show- ing affinity to this group. To make classification compatible with reconstructed phylogenies they redefined the family Macropipidae Stephenson & Campbell, 1960 and included in this sever- al fossils (Cretaceous to Neogene) genera (e.g., Ophthalmoplax), along with Recent taxa. This resulted in a quite broad diagnosis of the taxon. The extant Macropipidae (sensu Karasawa et al., 2008) turned out to be incompatible with molecu- lar phylogenetic reconstructions (Schubart & Re- uschel, 2009; Spiridonov et al., 2014; Evans, 2018). This indicated the necessity of splitting them be- tween various groups of the newly defined Carci- nidae (Bathynectes, Macropipus, Parathranites) and Geryonidae (Raymanninus, and possibly Echinolatus and Nectocarcinus). In this case, ex- tinct genera return to an uncertain status, which is not a desirable situation. Briefly commenting on this, I can suggest to examine the relationships of the genera that have numerous plesiomorphies, such as Proterocarcinus to the Geryonidae in the broad new concept, and others such as Portunites to the Parathranitinae. Ophthalmoplax appar- ently does not have affinities to the Geryonidae, but it is also different from the Carcinidae. The general quasi-guadrate outline of the carapace, well-developed carapace regions and transverse ridges, narrow bilobed frontal margin, orbits and the construction of chela (Vega et al., 2013) are not typical of any extant subfamily. Few taxa within the Recent Carcinidae have spines on the upper face of cheliped dactylus, e.g., Parathranites and Bathynectes. The former genus is also character- ised by an odd number of frontal lobes, similar to Ophthalmoplax. However, in other respects they do not have anything in common to assume close relationships. Ophthalmoplax apparently shows a unique combination of plesiomorphic and apo- morphic character states that makes close rela- tionships with an unknown ancestor of the Re- cent Carcinidae unlikely, so it would be better considered within a separate family. Several other well-preserved and relatively speciose genera, such as Coeloma A. Milne-Ed- wards, 1865, mostly of Eocene – Oligocene age, have been variously treated since their discov- ery (Karasawa et al., 2008; De Grave et al., 2009; Jagt et al., 2010). I would agree with Ossó (2016) on their very likely affinity to the Geryonidae, particularly considering the new concept of this family. Another particular, but important, task is to revise the good fossil record of the carcinid genus Liocarcinus (Hyžný et al., 2015) in the light of its recently documented paraphyly (Plagge et al., 2016), its significant persistence in the geo- logical time (Fig. 2) and the new concept of the Carcinidae. Within the Portunidae there generally are few- er problems in interpreting and positioning fossil taxa, although the classification of extant taxa at the subfamily level is still far from perfect. Clas- sification of extinct taxa could thus significantly benefit from the progress of taxonomic studies of contemporary faunas. A particularly important issue is the relatively numerous fossil examples of Portunus (sensu lato) which may, in fact, belong to other genera such as Portunus (sensu stricto), Achelous, Monomia and others. Distinguishing between them is not an easy task because many important characters are not available for study. For example, as stated above, the oldest species of the group, “Portunus” kochi resembles Achelous in several morphological characters. “Portunus” atecuicitlis Vega, Feldmann, Villalobos-Hiriart & Gio-Argaez, 1999, a common species from the Lower and Middle Miocene of Mexico, also likely belongs to Achelous on account of the construc- tion of the front and chelae (Vega et al., 2009). Another common Miocene species in the Tethys and Paratethys, “Portunus” monspeliensis A. Milne-Edwards, 1860, could be referred either to Achelous and Monomia on account of the single visible spine on the cheliped manus and well-de- veloped sculpture of the carapace (see Marangon & De Angeli, 2009, fig. 3; Gašparič & Ossó, 2016, pl. I, E, G), although the shape of the front and orbits and the relative size of the 1st anterolat- eral tooth support assignment of this species to Achelous. “Portunus” miocaenicus Müller, 1984 was referred to Monomia (as a subgenus) by the author himself. Examination of the published photograph (Müller, 1984, pl. 62, fig. 5) does not disapprove nor approve this because several im- portant characters, i.e. the sternum, pleon and merus of cheliped remain unavailable for study. A few other species may be relatively confident- ly referred to Portunus (sensu stricto), such as Portunus neogenicus Müller, 1979, which shows a similarity to the extant Indo-Pacific species Portunus sanguinolentus (Herbst, 1783) (Müller, 1984, pl. 62, figs. 3, 4). A complete revision of fos- sil “Portunus” spp. is a challenge but it is worth to undertake this task because these numerous 159An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, ... records may tell much more about the history of Cenozoic faunas when properly assigned to gen- era. Conclusions It is trivial to say that our understanding of evolution of any taxonomic group, including por- tunoid crabs, would strongly benefit from inte- gration of knowledge of extant and fossil taxa. However, we should carefully and clearly define a background for successful integration. Combin- ing extant and fossil groups of portunoid crabs into a coherent classification that is compatible with phylogenetic reconstructions implies an ac- ceptance of the concept of vertical taxa (Simpson, 1961). That is what palaeontologists explicitly or implicitly do when referring fossils to particular genera or families established on extant materi- al, even though they necessarily work with in- complete sets of characters. Some standard char- acters for extant taxa, such as genital structures, maxillipeds, even dactyli of pereopods 2–4 and others are rarely available for comparative study of fossil taxa. This calls for extension of com- parative morphological studies of Recent groups in order to find new characters that can help to classify fossil forms. Acknowledgements I am deeply indebted to Michael Türkay (decea- sed), Paul Clark, Oliver Coleman, Peter Dworschak and Victor Petryashov (deceased) for their help whi- le working in the collections of SMF, NHM, ZMB, NHMW and ZIN-RAS, respectively. I thank Rok Gašparič and other organisers of the 7th Mesozoic and Cenozoic Decapod Symposium at Ljubljana for the excellent opportunity to present this work. My grati- tude is also extended to Tatiana Antokhina and Sergey Anosov for permission to use their underwater photo- graphs of crabs, and to Matúš Hyžný and Álex Ossó for reviews of the manuscript and numerous valuable comments and suggestions, and John Jagt for lingui- stic correction of the text. This study was supported by the Russian Foundation for Basic Research Project 20-04-00067. References Adams, A. & White, A. 1848: Crustacea. 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