taxonID	type	description	language	source
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	etymology	Etymology: This species lacks fused “ simple ” chaetae, so in Latin form, sine means “ without ” and simplex for “ simple ” chaetae.	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	materials_examined	Type material / Material examined: Type material from Mediterranean Sea, Italy, Port of Livorno, Darsena Pisana area, Pisa, 43 º 41 ’ 57.89 ” N, 10 º 23 ’ 02.63 ” E, on muddy bottom intertidal sampled by hand, 30 cm depth, collected on April 1, 2021: Holotype: Complete specimen, 80 chaetigers, 53.5 mm long, 3.0 mm wide, GenBank accession number PV 449855 (NatMIP-APPh- 0019), Paratypes: 9 complete specimens, 53.0 to 44.0 mm long, 2.9 to 2.5 mm wide (NatMIP-APPh- 0020 [3 specimens], NatMIP-APPh- 0021 [3 specimens], NatMIP-APPh- 0022 [3 specimens]). Additional material: Spain, Platja de la Goja, Gola del Perellonet, Valencia, 39 ° 18 ’ 29.63 ” N, 0 ° 17 ’ 33.81 ” W, sampled by hand, collected on March 5, 2022: 17 specimens, 73.0 to 10.1 mm long, 4.5 to 1.0 mm wide (NatMIP-APPh- 0023), one of which was used for genetic analysis, GenBank accession number PV 449856.	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	diagnosis	Apomorphic features: Posterior supra-acicular neurochaetae without fused “ simple ” chaetae; otherwise, by replacement, heterogomph falcigers are present.	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	description	Description: Anterior and median width body regions similar (Fig. 2 A), tapering towards posterior end, and slightly flattened; 51.0 to 40.0 mm long, 4.0 to 3.2 mm wide, with 60 – 80 chaetigers. Prostomium with two tiny unarticulated antennae; two pairs of eyes on lateral-posterior region like a trapezium (Fig. 2 A). Two palps emerging from lateral-middle of prostomium; robust palpophores, minute and ovate palpostyles (at antennal level). Proboscis subdivided between maxillary and oral ring, with conical paragnaths, and two brown stout maxillae with 5 – 8 teeth on anterior end; maxillary ring: area I with four paragnaths, II with 16, III with 45, IV with 20; oral ring: area V without paragnaths, area VI with 3 – 9, areas VII and VIII with 34. Four pairs of tentacular cirri (anterior modified cirri) near lateral-posterior region of prostomium, may reach chaetiger 8 (Fig. 2 A). Peristomium longer than subsequent chaetigerous segments. Parapodia biramous, more developed on median chaetigers (Fig. 2 D, G), decreasing toward anterior chaetigers (Fig. 2 B, C, F), as well as in posterior ones (Fig. 2 E, H); notopodia (Fig. 3 A – C) with three conical structures — notopodial ligule 1 (noLi 1), pre-chaetal lobe 1 (prLi 1, carrying chaetae alongside others, supported by a black aciculum), and notopodial ligule 2 (noL 2); neuropodia carrying chaetae between pre-chaetal lobe 2 (prL 2, supported by a black aciculum) and post-chaetal lobe (poL), and a neuropodial ligule (neLi) achaetiger (Fig. 3 B). Dorsal and ventral unarticulated cirri shorter than dorsal and ventral ligules, respectively. Chaetation process (Figs 3 C; 4; 5): anterior notochaetae homogomph spinigers (Figs 3 C; 4 A, F); anterior neurochaetae, supra-acicular bundle: homogomph spinigers and heterogomph falcigers (Figs 3 C; 4 D, I), with blades serrated (Fig. 4 I); infra-acicular bundle: heterogomph spinigers (Figs 3 C; 4 C, H), and heterogomph falcigers with long and hook-type blades (Fig. 4 D, I). Median parapodia (Fig. 2 D, G): notochaetae homogomph spinigers; neuropodia with supra-acicular homogomph spinigers and heterogomph falcigers, and infra-acicular heterogomph spinigers and falcigers (Fig. 4). Posterior notopodia (Fig. 5 B, D) carrying homogomph spinigers; neuropodia: supra-acicular homogomph spinigers and heterogomph falcigers (to replace the simple chaetae, Fig. 5); infra-acicular heterogomph spinigers and heterogomph and homogomph falcigers (Figs 4; 5 B, D). Pygidium carrying two segmented anal cirri. Additional description information: 3 D models are presented for visual and graphic demonstration of the parapodia and chaetae (Videos S 1, S 3), and additional links are available on the Sketchfab website (parapodia: Models 1 (https: // skfb. ly / owIEU), 3 (https: // skfb. ly / owKoE); chaetae: Models 4 (https: // skfb. ly / owKpS), 5 (https: // skfb. ly / owKpK), 6 (https: // skfb. ly / owKpX), 7 (https: // skfb. ly / owKpA).	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	materials_examined	Type locality: Mediterranean Sea, Italy: Port of Livorno, Darsena Pisana area, Pisa.	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	distribution	Distribution: Western Mediterranean Sea (Spain to Italy, this study), Baltic and Eastern North seas (Teixeira et al., 2022).	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	biology_ecology	Ecological notes: In Italy, populations were found among Ficopomatus enigmaticus (Fauvel, 1923) tubes, in the vicinity of a port zone, ranging from muddy bottom to fine sand. In Spain, sediment samples were collected with a logarithmic mean grain size (Φ) of 2,116 and 0.39 % of organic matter.	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
0395878AFFE5C54FBB8BFD61FAB65CFA.taxon	discussion	Remarks: The species Hediste sinesimplex sp. nov. mainly differs from other Hediste spp. in the posterior neuropodia (Model 2 — https: // skfb. ly / owKox), specifically by lacking fused “ simple ” chaetae in the supra-acicular neurochaetae (Figs 4 E, J; 5 A, C; Model 8 — https: // skfb. ly / owKpP), which are replaced by heterogomph falcigers (Figs 4 D, I; 5 B, D). This suggests the absence of this morphological feature, as observed in other groups of the family Nereididae, and many other polychaete taxa (Cronk 2009), or character transformation, as a synapomorphic character process, from simple to falciger chaeta. Notwithstanding, the species Hediste sinesimplex sp. nov. shares all other synapomorphic features allowing for its integration in the genus Hediste, e. g. absence of proboscis paragnaths on position V, and posterior parapodia carrying bi-articulated supra-acicular homogomph falcigers. 3 D models and videos (Models 1 – 8; Videos S 1 – S 3) are provided that compare the posterior parapodia of Hediste sinesimplex sp. nov. to those of other Hediste spp. (represented by H. diversicolor). Phylogenetic analysis and species delimitation We obtained a total of 657 COI gene base pairs (bp) for Hediste specimens. The best model of molecular evolution fitting dataset was: TIM 2 + F + I + I + R 2. No base saturation was observed for the mitochondrial gene. All sequences obtained were deposited in the GenBank (accession numbers PV 449855 and PV 449856). Our phylogenetic analysis recovered a topology in which Hediste sinesimplex sp. nov. (clade highlighted in yellow; Figure 6) was recovered as a monophyletic clade that includes specific localities, including those of the present study. The genetic distance (based on the COI marker) of Hediste sinesimplex sp. nov. ranges from 5.6 % to 15.2 % when compared to other species of the genus Hediste (Table 1). The result of the ASAP model supports the split for the eight species and one lineage (Figure S 4) and bPTP although it recovers the same scenario (nine groups), however, the a posteriori probability is lower than 0.95 (Figure S 5). This result may be attributed to genetic similarity, small sample sizes, or suboptimal genetic markers.	en	Costa, Dimítri De Araújo, Rocha, Sónia, Martins, Duarte, Venâncio, Márcia, Ureña, Marta, Almeida, João, Ferreira, Gilmax Gonçalves, Christoffersen, Martin Lindsey, Antunes, Carlos (2025): Filling in another piece of the puzzle: Using Integrative Taxonomy to establish yet another new species of Hediste (Annelida, Polychaeta, Nereididae). Zootaxa 5696 (1): 28-40, DOI: 10.11646/zootaxa.5696.1.2, URL: https://doi.org/10.11646/zootaxa.5696.1.2
