taxonID	type	description	language	source
461DA55ADA0FFFCC236FFBEDC326ECE2.taxon	description	Pleurobranchidaisrecoveredmonophyleticwithfullsupportand includes three main clades. For the first time in molecular phylogeny, Tomthompsonia antarctica (Fig. 1 A) forms a discrete, early divergent clade with maximum support across matrices and analyses. Thus, we erect Tomthompsoniidae fam. nov. to encompass a single known genus and species endemic to deep waters in Antarctica (Thiele 1912, Wägele and Hain 1991, Hain et al. 1993). Then, two main clades sister to each other are recovered, Pleurobranchaeidae and Pleurobranchidae (bs = 88, pp = 0.95). Within Pleurobranchaeidae, the type species Euselenops luniceps (Fig. 1 B) is first found as a sister to a clade composed of the type species of both Pleurobranchaea and Pleurobranchella. Among the four specimens of Euselenops available, a conflicting signal is found in the 18 S of the specimens sequenced by Wollscheid-Lengeling et al. (2001) and, unfortunately, their relationships are not always well-recovered (see Supporting Information, Figs S 1, S 2). Excluding these from our concatenated analyses rendered Pleurobranchaeidae monophyletic without maximum support (bs = 91). COI p - distances for both remaining specimens of E. luniceps from Singapore and Vietnam seem to represent cases of hidden speciation (86 % identity). Considering both type taxa Pleurobranchaea meckeli (Blainville, 1825) (Fig. 1 C) and Pleurobranchella nicobarica Thiele, 1925 (Fig. 1 D) were present in our dataset, and Pleurobranchella is placed within a clade composed of P. meckeli, P. maculata (Quoy and Gaimard, 1832), P. californica MacFarland, 1966, and P. japonica Thiele, 1925 (bs = 100, pp = 1). However, Pleurobranchella is morphologically distinct from Pleurobranchaea, including such immediately recognizable features as an ample notum and differences in the reproductive system (Martynov and Schrödl 2009). We, therefore, keep the genus Pleurobranchella distinct and valid. Finally, P. cf. novaezealandiae from the Western Pacific clusters with our P. japonica from Japan with a 99.1 % identity, thus suggesting both specimens belong to P. japonica.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCD213DFF18C264EA89.taxon	description	Although not supported in the ML and BI phylogenies, Pleurobranchidae is for the first time recovered as a clade in our analyses. All valid, representative genera within the family are for thefirsttimepresent, namely Bathyberthella, Berthella, Berthellina, Boreoberthella, Pleurehdera, and Pleurobranchus. Berthella is consistently found paraphyletic and four clades classifiable as three different genera are recovered. Bearing that in mind, most genera are found monophyletic with maximum support, although how genera are related to each other is not always well supported. Berthellina is recovered monophyletic with full support, the species B. edwardsii (Vayssière, 1897) from the Mediterranean and Eastern Atlantic (94.3 – 99 % identity) is the sister-group to the Indo-Pacific species. The latter group is composed of B. citrina (Rüppell and Leuckart, 1828) from the Red Sea (100 % identity), B. punctata (Quoy and Gaimard, 1832) from Australia, and a clade of B. delicata (Pease, 1861) species with probabl hidden speciation spanning from the Red Sea, the Maldives (Fig. 1 E), and Hawaii (90.7 – 93.6 % identity). All Bathyberthella antarctica Willan and Bertsch 1987 (Fig. 1 F) specimens from across the Weddell Sea and the Scotia Arc conformed to a monophyletic clade (bs = 100, pp = 1) with a 95 – 100 % identity. A clade containing Berthella perforata (Philippi, 1844) specimens from Italy (99.1 – 100 % identity) and the type species of Berthella, B. plumula (Montagu, 1803), with specimens from the Northeast Atlantic and the Mediterranean Sea (98.7 – 100 % identity) was fully recovered only in the ML analysis (bs = 100). This clade also included B. ocellata (Delle Chiaje, 1830) from Greece (Fig. 1 G), B. medietas Burn, 1962 from Australia, B. sideralis Lovén, 1846 from Sweden, and B. platei (Bergh, 1898) from 15 m depth Chile and 250 m depth in the Falkland Islands (99.3 – 99.5 % identity). A second ‘ Berthella’ clade (bs = 99, pp = 1) is largely composed of the B. stellata (Risso, 1826) group agreeing to the recently recognized species in Ghanimi et al. (2020 b) yet adding some more complexity. The B. stellata (Fig. 1 I) group is found in tropical and temperate waters from the Eastern Pacific, Caribbean, and Mediterranean seas, including B. andromeda Ghanimi, Schrödl, Goddard et al., 2020, B. strongi (MacFarland, 1966), B. nebula Ghanimi et al., 2020, and B. vialactea Ghanimi et al., 2020. This latter group is sister to a Pacific one composed of B. pellucida (Pease, 1860) from Hawaii, B. cf. postrema from New Caledonia, our newly sequenced B. cf. ‘ stellata ’ from Japan, and Pleurehdera haraldi Ev. Marcus and Er. Marcus, 1970 from Palmyra Atoll in the middle of the Pacific. Since Pleurehdera haraldi is the type and only species of the genus and nests within this second ‘ Berthella ’ clade, we suggest transferring all the above-mentioned species to the genus Pleurehdera. Interestingly, only in the BI analysis, a sister relationship between specimens belonging to Berthella s. s. and the Pleurehdera clade was recovered yet without full support (pp = 0.95). Sister to both B. stellata and the Pacific group we found B. martensi (Pilsbry, 1896), with specimens from Australia and the Pacific side of Panama (99.3 % identity) and a likely hidden species from the Maldives (c. 85 % identity) (Fig. 1 H). This clade deserves the erection of a new genus (see Systematic description). A fourth ‘ Berthella ’ clade (bs = 92, pp = 0.99) is composed of the North Pacific clade that includes specimens of Berthella californica (Dall, 1900) from California to Panama, two specimens of Boreoberthella augusta Martynov and Schrödl 2009 (Fig. 1 J) from Japan (100 % identity), and Berthella chacei (J. Q. Burch, 1944) from Russia, Canada, and the USA (99 – 99.7 % identity). Given the present phylogenetic scenario and the morphological characters discussed below, we hence establish Boreoberthella californica comb. nov. (Fig. 1 K) and Boreoberthella chacei comb. nov. Finally, we recovered a monophyletic clade of Pleurobranchus species (bs = 100, pp = 1) (Fig. 1 L), containing the type species P. peronii Cuvier, 1804 and mainly recovering the species groups already studied by Goodheart et al. (2015).	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCE23CEFBFBC42DE8BE.taxon	description	(Fig. 1 H) urn: lsid: zoobank. org: act: 8 D 6 B 1 A 52 - 6901 - 4 EF 6 - 853 E- 0 A 68 B 0859 EB 6.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCE23CEFBFBC42DE8BE.taxon	type_taxon	Type species: Tomoberthella martensi (Pilsbry, 1896) comb. nov.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCE23CEFBFBC42DE8BE.taxon	diagnosis	Diagnosis: Dorsum divided into distinctive, autotomizable areas. Mantle and head delimited by black margins. Jaw platelets’ central cusp broad, with smooth margins.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCE23CEFBFBC42DE8BE.taxon	etymology	Etymology: The genus name is constructed in apposition of tomos (Ancient Greek for slice or section) that denotes cut pieces, alluding to the sectorized mantle, and Berthella.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCE23CEFBFBC42DE8BE.taxon	description	Genre: Feminine.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCE23CEFBFBC42DE8BE.taxon	discussion	Remarks: Originally, ‘ Berthella ’ martensi was included in the genus Gymnotoplax (Pilsbry, 1896). However, the type species of the genus Gymnotoplax is Pleurobranchus americanus A. E. Verrill, 1885, collected off the coast of the NE United States in 457 m. The genus Gymnotoplax was originally described to include two species: G. americanus (A. E. Verrill, 1885) and G. martensi Pilsbry, 1896, but the type species was not designated. Posteriorly, Zilch (1959) designated G. americanus as the type species of Gymnotoplax genus, and Marcus (1977) also agreed. An exposed shell was considered characteristic of the genus and thus deserving the erection of Gymnotoplax. Willan (1978, 1987) revised the original material and consistently showed that G. americanus consists of a single specimen with an exposed shell because of a damaged dorsum. Thus, Willan (1978) considered, pending clarification of the identity of its type species, Gymnotoplax as genus dubium. Accordingly, the genus Gymnotoplax cannot be used as a valid name for ‘ Berthella ’ martensi. Moreover, ‘ B. ’ martensi was described based on a juvenile specimen off Mauritius, and Pilsbry (1896) mentioned that this specimen has a frontal incision. This character may be referring to the partite mantle typical of this ‘ martensi group’, and thus specimens with a typical partite mantle from the Indo-Pacific were attributed subsequently to this species. Yet the exposed shell of G. americanus is an artefact that cannot be matched to the partite mantle of ‘ B. ’ martensi. Therefore, according to the morphological diagnosis, we erect the new genus Tomoberthella gen. nov. for martensi species described by Pilsbry (1896). Molecular data further reinforces the morphological uniqueness of Tomoberthella martensi comb. nov., which appears as a distinct clade sister to the species of Pleurehdera, and most probably represents a species complex.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCD23DCFD35C263E8A3.taxon	description	(Fig. 1 A) urn: lsid: zoobank. org: act: F 71 DA 1 C 1 - 2926 - 4 ED 0 - 9 C 52 - 88514 B 67 D 4 E 4.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCD23DCFD35C263E8A3.taxon	type_taxon	Type species: Tomthompsonia antarctica (Thiele, 1912).	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCD23DCFD35C263E8A3.taxon	diagnosis	Diagnosis: Internal helicoid shell. Gland producing sulphuric acid, opening into oral tube and pedal gland absent. Long penial sheath covering penial lobe.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
461DA55ADA08FFCD23FDFDB7C5FAE9D5.taxon	description	urn: lsid: zoobank. org: act: 9750 A 7 F 4 - 9 CED- 4 D 91 - AD 7 F-BAFE 8387115 C.	en	Moles, Juan, Brenzinger, Bastian, Berning, Maria I., Martynov, Alexander, TatianaKorshunova, Schrödl, Michael (2024): Systematic rearrangements in an all-genus phylogeny of side-gilled slugs (Heterobranchia: Pleurobranchida). Zoological Journal of the Linnean Society 202 (2): 1-11, DOI: 10.1093/zoolinnean/zlad162, URL: https://doi.org/10.1093/zoolinnean/zlad162
