taxonID	type	description	language	source
2F1987D97047877870AA8A10FE20FE8C.taxon	materials_examined	Type species: Amphicteis acutifrons Grube, 1860	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97047877870AA8A10FE20FE8C.taxon	diagnosis	Generic diagnosis (emended after Imajima et al. (2012), and Ebbe & Purschke (2020 )). Prostomium with middle lobe delimited by incision, without glandular ridges. Four, or exceptionally three, pairs of cirriform, or exceptionally pinnate, branchiae. Buccal tentacles pinnate / papillose. 14 – 15 thoracic chaetigers; segments II + III fused; notochaetae on segment II (= paleae) absent or present, then in varying size from enlarged to regular notochaetae size. 11 or 12 thoracic uncinigers. Notopodial cirri absent. Elevated or modified notopodia absent. Two intermediate segments, i. e., without notopodia but with neuropodial tori (similar to those in thoracic uncinigers). Papillae (glandular pads?) above neuropodia on intermediate and abdominal segments usually present. One pair of dorsal nephridial papillae on segment IV.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97047877870AA8A10FE20FE8C.taxon	discussion	Remarks. Segments II + III are fused, but a separation of the segments can be observed ventrally. Paleae are clearly originating from segment II, followed by an achaetous segment III, which can be recognized by the presence of a vestigial notopodium on segment III (Fig. 4 C). We included the paleae-bearing chaetiger (segment II) into the count of thoracic chaetigers (Reuscher et al. 2009). As paleae can be absent or present, the number of thoracic chaetigers varies from 14 to 15.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97040877870AA8AB1FDCDF87E.taxon	description	(Figs 2, 3) Non. A. acutifrons Hessle 1917 Non. A. acutifrons Annenkova 1929 Non. A. acutifrons Hartmann-Schröder 1971, 1996 Non. A. acutifrons Day 1973 Non. A. acutifrons Bick and Gosselck 1985 Non. A. acutifrons Holthe 1986 Non. A. acutifrons Jirkov 2001 Non. A. acutifrons Parapar et al. 2012	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D9704C877270AA891CFF33F8F5.taxon	description	(Figs 4 – 8)	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D9704C877270AA891CFF33F8F5.taxon	diagnosis	Diagnosis. Medium-sized species of up to 21 mm in length and 2.8 mm in width. Twelve thoracic, two intermediate, and ten abdominal uncinigers with very long neuropodial cirri. Branchiae arranged in two groups separated by a median gap of about 1.5 branchial base width; three pairs in anterior transverse row and last pair in posterior position, directly below middle branchia of anterior transverse row. Paleae long and thin with filiform tips, 9 – 18 each side. One pair of nephridial papillae on segment IV. Pygidium with up to 17 anal cirri, arranged in two (more or less distinct) rows.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D9704C877270AA891CFF33F8F5.taxon	materials_examined	Material examined. Type material (based on photographs): North Atlantic Ocean, Eastport, Maine (USA). Syntypes of Ampharete cirrata Webster & Benedict, 1887, USNM 457 (3 specimens). Non-type material: Baltic Sea, north from Isle of Rügen. Site 1 – 5 (Table 1), SBRO-P 95 (23 specimens), SBRO-P 5528 (5 specimens), SBRO-P 17367 (134 specimens), ZSRO-P 2669 (16 specimens), ZSRO-P 2670 (15 specimens).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D9704C877270AA891CFF33F8F5.taxon	description	Description. Complete specimens 11 – 21 mm long and 1.7 – 2.8 mm wide in thorax (Fig. 4 A). Prostomium trilobed; median lobe U-shaped and separated by deep lateral grooves (Figs 5 A, 6 B, E); prostomial glandular ridges and eyespots absent. Nuchal organs not observed. Buccal tentacles papillose (Fig. 6 A, C). Four pairs of branchiae arranged in two distinct groups with a median gap of about one and a half times the width of branchial bases (Fig. 5 A); branchiae not fused at base; branchiae thick at base and gradually tapering towards distal end, longest branchiae reaching thoracic chaetiger 5 – 9 (Figs 4 A, 6 E); anterior three pairs of branchiae arranged in a transverse row on segment II / III, fourth pair slightly posterior to anterior row, directly below middle branchia of transverse row (Fig. 5 A, branchial bases can be slightly deformed and displaced through fixation); branchiae of segment II in 2 nd outermost position of anterior row, branchiae of segment III in outermost position of anterior row, branchiae of segment IV in innermost position of anterior row, branchiae of segment V in posterior position. One pair of nephridial papillae, dorsally between the two innermost branchiae on segment IV (Figs 5 A, 6 E). Segment II with 9 – 18 long, thin and slender paleae on each side, gradually tapering into filiform tips (Figs 5 A (only drawn 8 paleae), 6 A, B, D, E); paleae clearly protruding beyond the prostomium, at least two times as long as middle lobe of prostomium (Fig. 5 A); arranged in a semicircle, with a few small thin paleae on the outer edge of the semicircle and longer thick paleae close to prostomium (Fig. 6 D). Thorax and abdomen of about similar length; thorax slightly wider than abdomen; abdomen tapering posteriorly (Fig. 4 A). Continuous ventral shields present to segment XIV (thoracic chaetiger 12), median ventral groove present from segment XV on (thoracic chaetiger 13) until posterior end (Figs 4 A, 7 D, E). Notopodia with capillary chaetae from segment IV, present in 14 chaetigers; last 12 thoracic chaetigers (starting from segment VI) with neuropodial tori bearing a single row of uncini (Figs 4 A, 7 F); notopodia simple, fingershaped, up to three times longer than wide (Fig. 7 A); first two notopodia smaller (Fig. 4 A); tip of notopodia with small terminal lobe (not always visible); notochaetae arranged in semicircle around this lobe (Figs 4 D, E, 7 B). Notochaetae as bilimbate spinulose capillaries, tapering to slender tips; arranged in rows; capillaries from anterior row generally thinner and shorter than those of posterior row (Figs 4 D, E, 7 B, C). Thoracic neuropodia oval, last three to four neuropodia with short dorsal cirrus (Figs 4 A, 5 B, 7 A), anteriorly with small dorsal papilla (at least on two thoracic uncinigers, sometimes on all) which grows into a cirrus that becomes longer towards the posterior end of the thorax (Fig. 7 A); cirrus length about the same size as the base of respective neuropodium (Fig. 7 A). Thoracic uncini with five to six teeth in two vertical rows above rostral tooth (Figs 5 D, 7 F); 46 – 52 uncini on one torus for specimens between 13 – 16 mm length (largest specimen with 55, and smallest specimen with 34 uncini). Two intermediate segments with neuropodia with very long dorsal cirrus; cirrus usually 2 times longer than base of the respective neuropodium (varies from the same length to 3 times longer); notopodia absent; uncini resemble thoracic uncini (Figs 5 D, 7 G); 39 – 44 for specimens between 13 – 16 mm length (largest specimen with 43, and smallest specimen with 27 uncini). Notopodia on abdomen absent. Ten abdominal neuropodia formed as pinnules with very long dorsal cirrus; the ratio of the length of the cirrus to the length of the base of the respective pinnule is 1 – 3.5: 1 (Figs 5 C, 6 G); pinnules of different shapes, rounded, two- or three-lobed (Fig. 5 C); last six abdominal pinnules can be elongated, and last abdominal pinnule always elongated (Fig. 5 C). Abdominal uncini with four to five teeth in two vertical rows above rostral tooth (Figs 5 E, 7 H); 47 – 56 uncini on one pinnule for specimens between 13 – 16 mm length (largest specimen with 67, and smallest specimen with 35 uncini). Well-developed papillae (glandular pads?) above tori of intermediate segments and above first one to four pinnules of abdominal segments (Fig. 5 B). Pygidium with terminal anus; 7 – 17 anal cirri of different lengths and thicknesses, arranged in two more or less distinct rows (Figs 4 B, 6 F, G). Methyl blue staining pattern. Intense staining of prostomium, bases of noto- and neuropodia and cirri. Prominent bands on ventral thorax (continuous ventral shields), less intensely stained towards the end of thorax, not stained in abdomen. Papillae (glandular pads?) above neuropodia on intermediate and abdominal segments and branchiae stained. Nephridial papillae only visible immediately after intense staining. Rest of body evenly spotted blue, sometimes lighter band laterally between noto- and neuropodia (Fig. 4 A, B, D). ShirlastainA staining pattern. Staining pattern equivalent to methyl blue staining, but one additional structure visible: small lobe between paleae-bearing chaetiger (segment II) and first thoracic notopodium (segment IV), most likely vestigial notopodium of segment III (Fig. 4 C).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D9704C877270AA891CFF33F8F5.taxon	discussion	Remarks. One thoracic segment was missing in one of 15 specimens, resulting in 14 instead of 15 thoracic chaetigers and 11 instead of 12 thoracic uncinigers. We recommend always examining both sides of specimens, as number of chaetigers and uncinigers are important characters for distinguishing taxa (Reuscher et al. 2009). One specimen was considerably smaller (7.5 mm long) and thinner (1.1 mm wide), but last six segments were missing. Branchiae were contracted in three specimens and therefore, noticeably shorter and thicker; distance between branchiae for those specimens was only one or even less than one times shorter than branchial bases. An important character of A. cirrata is the presence of a very long dorsal cirri on the neuropodia of the intermediate segments (Fig. 5 B). Ampharete cirrata has papillae-like elevations on the intermediate and the first abdominal segments. Imajima et al. (2012) called these structures ‘ glandular pads’. Parapar et al. (2012) showed for A. finmarchica that these structures can also be ciliary tufts. The specific structure in the different Ampharete species and their possible homology needs to be clarified urgently. Uncini of the abdomen are smaller than uncini of intermediate and thoracic segments. However, uncini vary in size along one neuropodium, larger uncini were found at dorsal side of the neuropodium, continuously getting smaller towards ventral side. Extracted uncini possibly originated from different zones of the neuropodia and therefore, size differences between thoracic and intermediate as well as abdominal uncini might be less pronounced. As above described, number of uncini on one neuropodium differed depending on the total body size of specimens. More specifically, the larger the specimen the more uncini were present on one neuropodium. The pygidium showed variability regarding number, length and thickness of anal cirri. It can be difficult to describe the pygidium, as it is often contracted in fixed specimen, sometimes inside the posterior end. One specimen had longer cirri dorsally and shorter and thinner cirri ventrally. A yellow-brown pigment band ventrally on thoracic chaetiger 5 was observed in almost half of the specimens collected between 2002 – 2010 (fixed in formaldehyde solution and preserved in EtOH), but no pigmentation was found in fresh material from 2019 (treated as described above). All valid 45 species of Ampharete and 10 synonyms were examined regarding the presence of the combination of the following three characters: thin long paleae, long anal cirri (rather than anal papillae) and neuropodial cirri. Of these species only two, previously synonymized with A. acutifrons, possibly exhibit this combination of characters, A. intermedia and A. cirrata. The original description of Amphicteis intermedia Marion, 1875 was brief, describing the presence of sharp and long paleae, but not mentioning any of the other characters. Since there are no other records of this species and it was not possible to examine it, we decided to disregard A. intermedia. This species needs further investigations (species inquirenda). The description of Ampharete cirrata Webster & Benedict, 1887 from the Northwest Atlantic (Maine, USA) was also short, but contained drawings of the neuropodia. Despite all our efforts, we could not obtain the syntypes of A. cirrata from the NMNH in Washington. However, neither the description nor the photographs (Fig. 8) that we obtained from the NMNH indicated significant differences between the Baltic Sea species and A. cirrata. The specimens found in the Baltic Sea are therefore assigned to A. cirrata. Ampharete cirrata is formally deleted here from the synonym list of A. acutifrons and should be considered a valid species.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D9704C877270AA891CFF33F8F5.taxon	distribution	Distribution and ecology. Ampharete cirrata was originally described from the Northwest Atlantic (Maine, USA). Molecular investigations suggest that the distribution of A. cirrata extends beyond the Northwest Atlantic into the Northeast Atlantic (see genetics). The studied material of Ampharete from the Baltic Sea, now assigned to A. cirrata, originates from an area about 30 km north of the island of Rügen (Fig. 1). Specimens were collected in silty sediments of moderate salinity (10 – 24 psu) in depths of 40 – 50 m (Table 1). Further unpublished records indicate that A. cirrata is also present in shallower localities of about 16 m. The species densities reached from 10 – 180 individuals / m 2. Oval eggs of about 100 – 150 µm in diameter were observed in segments XI-XXII in several specimens collected in October. Genetics. In total, 1116 base pairs of the mitochondrial [16 S (n = 3) + COI (n = 9)] and 3831 base pairs of the nuclear [18 S rDNA (n = 3) + 28 S rDNA (n = 1) + Histone H 3 (identical to DQ 779715, see below; n = 9)] of A. cirrata were sequenced. GenBank accession numbers of all obtained sequences are given in Table 3. There were no differences between individuals for the three nuclear genes. For COI and 16 S, two haplotypes each were detected, differing 0.2 % and 0.3 % from each other, respectively. Phylogenetic analysis for the mitochondrial COI fragment included newly generated sequences of A. cirrata and all alleged A. acutifrons sequences from GenBank and BOLD. Two sequences of Anobothrus gracilis were used to root the tree. Excluding the specimens from the Baltic Sea, we found four distinct clades within the alleged A. acutifrons species (Fig. 9). The analysis revealed an A. acutifrons species from Washington, USA to be most closely related to A. cirrata with a divergence of about 4.5 % (Table 4). Other species summarized under the name of A. acutifrons differed 13.8 – 15.3 % from A. cirrata (Table 4). After a corresponding alignment, obtained sequences of 16 S (one of two), 28 S and Histone H 3 of A. cirrata from the Baltic Sea were completely identical to the sequences of one specimen from Iceland, which was described as A. acutifrons (GenBank accession numbers: 28 S: DQ 779673, H 3 A: DQ 779715, 16 S: DQ 779601 (Rousset et al. 2007 )).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97054876C70AA8CB1FC3EF864.taxon	description	(Fig. 10)	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97054876C70AA8CB1FC3EF864.taxon	materials_examined	Material examined. Type material: Baltic Sea, Kalmar, 55 ° 50 ‘ N, 16 ° 05 ‘ E, 19.8 1954, GNM Polych. 11192 (holotype); 55 ° 50 ‘ N, 16 ° 05 ‘ E, 19.8 1954, GNM Polych. 11103 (4 paratypes).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97054876C70AA8CB1FC3EF864.taxon	diagnosis	Diagnosis. Small species of up to 8 mm in length and 0.9 mm in width (Fig. 10 A). Twelve thoracic, two intermediate, and ten abdominal uncinigers with minute neuropodial cirri (Fig. 10 E). Prostomium triangular with three lobes, with eyespots. Branchiae arranged in two groups separated by a very small median gap of less than one branchial base width; three pairs in anterior transverse row (the middle one sometimes shifted anteriorly) and last pair in posterior position, directly below middle branchia of anterior row. Paleae long, slender with filiform tips, 6 – 10 each side (Fig. 10 B). Pygidium with lateral cirri and a number of cirriform papillae (Fig. 11 C).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97054876C70AA8CB1FC3EF864.taxon	discussion	Remarks. Type material of 7 – 8 mm in length, some specimens with eggs (Fig. 10 D). The specimens found in the Baltic Sea had a maximum length of 11 mm (SBRO), but Holthe (1986) and Hartmann-Schröder (1996) reported a maximum length of 18 mm. Minute, rounded dorsal cirri have only been observed on abdominal neuropodia. Diagnostic characters on the pygidium are often difficult to verify on fixed material because the pygidium is often retracted into the abdomen. In addition, the pygidium seems to be very variable. There are one or two rings of cirri that vary in length. Methylene blue is very helpful in identifying the length of the cirri; the pair of lateral cirri being much more intensely coloured than the remaining cirri or papillae. The lateral cirri have the shape of lobes in smaller specimens (7 mm long) and are clearly distant from the ring of pygidial cirri. The papillae of the outer ring are as long as the lateral cirri or slightly shorter, the inner ring has a number of long cirri. As the pygidium of A. baltica is very variable, we have excluded this character from the identification key.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97054876C70AA8CB1FC3EF864.taxon	distribution	Distribution and ecology. Baltic Sea. This species was found on silt and sandy bottoms in 5 – 50 m depths, 7 – 29 psu. The species densities reached from 10 – 1,000 and more individuals / m 2.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97055876E70AA8CB1FC6FFCA8.taxon	description	(Fig. 11)	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97055876E70AA8CB1FC6FFCA8.taxon	materials_examined	Material examined. Type material: Arctic, Svalbard, Edge Island, Storfjord, Whalers Point; 77 ° 20 ’ N, 20 ° 30 ’ E; depth 36 – 55 m, mud, Schwedisch Arctic Exp. 1864 sta. 00, SMNH-Type 5101 (6 paralectotypes).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97055876E70AA8CB1FC6FFCA8.taxon	diagnosis	Diagnosis. Large species of up to 80 mm in length (see Malmgren 1865, but paralectotypes 27 – 50 mm) and up to 9 mm in width (paralectotypes 4.5 – 9 mm) (Fig. 11 A). Twelve thoracic, two intermediate, and ten abdominal uncinigers with rounded or pointed short neuropodial cirri (see Remarks) (Fig. 11 E). Prostomium triangular, anterior margin rounded. Buccal tentacles papillose (Fig. 11 B). Branchiae arranged in two groups separated by a median gap of one to three branchial base width; three pairs in anterior transverse row and last pair in posterior position, directly below middle branchia of anterior transverse row. Paleae long, clearly protruding beyond prostomium, evenly tapering to long filiform tips, 10 – 20 each side (Fig. 11 A, B). Pygidium with two lateral cirri and many long papillae; length of lateral cirri and papillae are almost the same (wide tubercle may be seen if the lateral cirri are broken or lost) (Fig. 11 D).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97055876E70AA8CB1FC6FFCA8.taxon	discussion	Remarks. The body shape of paralectotypes, the form of paleae and the pygidium resemble those specimens of A. grubei depicted by Malmgren, 1865 (Plate XIX, Fig. 44). But in the original description no dorsal cirri were noted or shown, even though the specimens were much larger than paralectotypes (80 mm long). The form of dorsal cirri on intermediate and abdominal neuropodia varies depending on size of specimens: the pointed cirri present in smaller specimens (27 – 33 mm long) were about the same length as the base of respective neuropodium; while the rounded and shorter cirri present in larger specimens (50 mm long) were clearly shorter than the length of the base of respective neuropodium. Depending on the size of the specimens, small dorsal cirri may be present on at least the two last thorax segments as small pointed tips of the dorsal side of the neuropodia (3 specimens, 27 – 33 mm long). These were not observed on the larger specimens (37 – 50 mm). Short rounded dorsal cirri were present in the intermediate neuropodia of the specimen of 37 mm in length (Fig. 11 E). On the largest specimens (50 mm long, 0.9 mm wide) dorsal cirri were not observed in the intermediate neuropodia (Fig. 11 C). Since the specimens of the type material of A. grubei and A. acutifrons differ significantly in many taxonomic characters, i. e., shape of paleae and presence of neuropodial cirri on abdominal segments, they are two different species. Therefore, A. grubei is a valid species and must be deleted from the synonym list of A. acutifrons.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97055876E70AA8CB1FC6FFCA8.taxon	distribution	Distribution. Only known from the type locality, Arctic, Svalbard.	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
2F1987D97057876870AA8FD1FA46FDF4.taxon	discussion	The presented key for described species constitutes an update of the key 2 proposed by Parapar et al. (2019), based on species descriptions from Holthe (1986) and Parapar et al. (2012, 2018), following the term intermediate uncinigers after Imajima et al. (2012). Accordingly, intermediate uncinigers are excluded from the abdominal segment count. Branchial gap: width as number of branchial base, following Parapar et al. (2018). We excluded A. lindstroemi Malmgren, 1867 (part.) in Hessle, 1917 sensu Parapar et al. (2012) from this key, an undescribed species (Parapar et al., 2018), even though a brief diagnosis was given in Parapar et al. (2012).	en	Krüger, Lotte, Dietrich, Anna, Bastrop, Ralf, Bick, Andreas (2022): From synonym to valid species: Redescriptions of Ampharete acutifrons (Grube, 1860) and A. cirrata Webster & Benedict, 1887, and brief descriptions of A. baltica Eliason, 1955 and A. grubei Malmgren, 1865 (Annelida: Terebellida: Ampharetidae). Zootaxa 5174 (4): 357-380, DOI: https://doi.org/10.11646/zootaxa.5174.4.3
