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Marcusia ernesti Hyman, 1953 (Fig. 6) Material examined: One specimen. Sagittal histological sections stained with AZAN of one individual. 42 slides: MNCN 4.01/2461 to MNCN 4.01/2502. Location: Playa Carbón Beach, in Las Baulas National Marine Park of Guanacaste, Costa Rica, 10 ° 20’53.4 “N 85 ° 51’44.5” W; May 87 2018. Fig. 6A. Habitat: Low intertidal, below stones on sand Description: External features (Fig. 6B,C): Oval-elongated body shape, wavy margins, anterior and posterior end rounded. Small marginal tentacles in the frontal region, separated. Length: 23 mm. Dark brown almost black dorsal colouration with white irregular spots. Whitish ventrally. Colourless region at cerebral eye level. Pharynx ruffled large located in the central area. Reproductive system: Consists of a common elongated atrium in which the male atrium opens laterally and the female distally (Fig. 6D). The male copulatory organ is formed by an elongated muscular bulb that encloses the seminal vesicle and the penis papilla. The ejaculatory duct is lined by a well-developed prostatic glandular epithelium (Fig. 6C). Without prostatic vesicle. The female apparatus includes the vagina that turns caudally and widens, covered with glandular epithelium. Distribution: Marcusia ernesti has been found only in the Pacific Ocean. This species is known from Baja California, Gulf of California, Sonora (Mexico), Clarion Island (Mexico) (Hyman, 1953) and now from Costa Rica in this study., Published as part of Soutullo, Patricia, Cuadrado, Daniel & Noreña, Carolina, 2021, First study of the Polycladida (Rhabditophora, Platyhelminthes) from the Pacific Coast of Costa Rica, pp. 363-381 in Zootaxa 4964 (2) on page 373, DOI: 10.11646/zootaxa.4964.2.7, http://zenodo.org/record/4709585

Cryptostylochus sesei n. sp. (Fig. 1) Material examined: A single specimen designated as holotype Holotype: sagittal serial sections stained in Azan. 119 slides: MNCN 4.01 /2267 a MNCN 4.01 /2385 Type locality: Playa Carbón, Las Baulas National Marine Park of Guanacaste, Costa Rica, 10 ° 20’53.4 “N 85 ° 51’44.5” W; May 17, 2018 (Fig. 1B) Habitat: Low intertidal, under stones and sand. Etymology: The name of the species “ sesei ” is after Jose Manuel Soutullo, also known as “Sesé”, father of the first author. Description: External characteristics (Fig. 1A, C): Body shape rounded. Length 35 mm. Background colour dark yellow densely speckled with orange. The pigmentation disappears towards the body edge and gets a transparent aspect. Ventral surface almost unpigmented, dirty white that turns almost coffee brown at the edges, also around the reproductive organs, in the medial region the silhouette of the pharynx is distinguished. Nuchal tentacles at the end of the first third of the body. Cerebral eyes between the tentacles on a depigmented patch. Tentacular eyes at the top of the tentacles; marginal eyes surrounding the body edge. Pharynx ruffled in the middle of the body (approx. 12 mm long, 7 mm wide in the holotype) Reproductive System (Fig. 1 D, E, F): Reproductive organs are located in the last third of the body. Male copulatory organ encloses a seminal vesicle, a prostatic vesicle and a penis papilla lodged in a well-developed heart-shaped atrium. Seminal vesicle muscular, voluminous and elongated (Fig. 1D). The wide vasa deferentia open proximally through a single vas deferens in the seminal vesicle. The prostatic vesicle is surrounded by strong muscle fibres and covered by a monoglandular lining. With a caudo-frontal orientation lies dorsally of the whole female organ (Fig. 1D). The prostatic and seminal ducts join to give rise to the ejaculatory duct surrounded by the short penis papilla (Fig. 1E). The male copulatory organ is entirely bordered by a reticulated network of muscle fibres, but does not form a compact muscle bulb (Fig. 1D,E). The female reproductive system is formed by the vagina interna and the vagina externa, without Lang’s vesicle. In the vagina externa pours the cement and shell glands. The female and male gonopore are separated, but close to each other (Fig. 1F). Remarks: The species captured in Costa Rica belongs to the genus Cryptostylochus due to the presence of frontal, marginal, cerebral and tentacular eyes; absence of pseudosclerotized structures; monoglandular prostatic vesicle and absence of Lang’s vesicle. Currently Cryptostylochus comprises 3 species; C. coseirensis (Bock, 1925), C. hullensis Faubel & Gollasch, 1996 and C. koreensis Bulnes, Faubel & Park, 2005. Cryptostylochus sesei n.sp. shares with C. coseirensis, C. koreensis and C. hullensis the presence of frontal, marginal, tentacular and cerebral eyes, as well as the presence of nuchal tentacles. However, it differs significantly from these species in the configuration of different types of eyes and in the size of the tentacles. C. sesei n.sp. present marginal eyes on the posterior and anterior regions of the body, while in C. coseirensis these occur only in the anterior region of the tentacles. In C. koreensis the marginal eyes surround the entire body edge and in C. hullensis they are found in their anterior body-end. Only C. koreensis presents frontal eyes. The tentacles of C. sesei n.sp. are not very conspicuous and difficult to see; they are just two dorsal protuberances. In C. coseirensis, C. hullensis and C. koreensis, these are clearly developed. Between the four species, significant differences can be found within the internal anatomy. C. hullensis and C. coseirensis present a spherical prostatic vesicle with inner large finger-like prolongations; C. koreensis and C. sesei n. sp. show an elongated monoglandular prostatic vesicle with short and numerous inner prolongations, marked in C. sesei n. sp., almost inconspicuous in C. koreensis. On the other hand, C. sesei n. sp. differs from the other species in the entrance to the prostatic duct, which is practically in the distal region of the ejaculatory duct. On the contrary, in the other species of the genus, it is located in the middle region of the ejaculatory duct. Finally, C. koreensis and C. hullensis have a short and small atrium and in C. sesei n. sp. and C. coseirensis the atrium is tall and elongated. The differences and similarities found between the four species allow us to confirm that the species of Costa Rica is a new species of Cryptostylochus, closely related to the species of Korea, C. koreensis., Published as part of Soutullo, Patricia, Cuadrado, Daniel & Noreña, Carolina, 2021, First study of the Polycladida (Rhabditophora, Platyhelminthes) from the Pacific Coast of Costa Rica, pp. 363-381 in Zootaxa 4964 (2) on pages 364-366, DOI: 10.11646/zootaxa.4964.2.7, http://zenodo.org/record/4709585, {"references":["Bock, S. (1925) Papers from Dr. Th. Mortensen's Pacific Expedition 1914 - 16. Parts I - III. Videnskabelige Meddelelser fra Dansk Naturhistorisk Forening i KJObenhavn, 79, 1 - 84.","Faubel, A. & Gollasch, S. (1996) Cryptostylochus hullensis sp. nov. (Polycladida, Acotylea, Platyhelminthes): a possible case of transoceanic dispersal on a ship's hull. Helgolander Meeresuntersuchungen, 50 (4), 533 - 537. https: // doi. org / 10.1007 / BF 02367165","Bulnes, V. N., Faubel, A. & Park, J. K. (2005) Two new marine species from South Korea with remarks on the family Stylochidae (Acotylea, Polycladida, Plathelminthes). Journal of Natural History, 39, 2089 - 2107. https: // doi. org / 10.1080 / 00222930500081997"]}

Prostheceraeus fitae n. sp. (Fig. 8) Material examined: Three individuals studied. One specimen collected in Playa Langosta, sagittally sectioned and designated as holotype. 44 slides: MNCN 4.01 /2576 to MNCN 4.01 /2619. Two more specimens collected in Playa Carbón sagittally sectioned and stained with Azan. Type locality: Playa Langosta 10 ° 17’32.2 “N 85 ° 51’12.7” W, Las Baulas National Park of Guanacaste, Costa Rica (Fig. 8A), May 17-24, 2018. Habitat: Intertidal zone of Playa Langosta, under stones within a rock pool 20 cm deep. Etymology: The name of the species, Prostheceraeus fitae n.sp., is dedicated to Josefa Novelle, mother of the first author, also called “Fita”. Description: External features (Fig. 8B,C): Elongated body shape with straight lateral margins and rounded posterior end. Few, short marginal waves. Background colour ivory yellowish with black elongated stains. The body margin with a pigmented band formed by a thin purple border followed by a lilac stripe that gradually darkens into a dim violet band. The marginal colouration surrounds the entire body, including pseudotentacles, pointed and with a dark violet tone. A thin orange-lilac line is drawn from behind the tentacles to the back region, in the middle dorsal region. A white patch with numerous cerebral eyes is located between the two tentacles. Ventrally whitish or colourless. Pharynx, tubular in living organisms, acquires bell shaped outline in fixed individuals. Reproductive system is located in the middle body region. Male and female gonopore separated. Reproductive System (Fig. 8D,E): The male copulatory organ comprises in a seminal and prostatic vesicle, a folded penis papilla and a naked ejaculatory duct. The spermiducal bulb opens into the oval seminal vesicle. The seminal vesicle is surrounded by a well-developed muscle layer. The oval-shaped prostatic vesicle is anterior-dorsally oriented as shown by the prostatic duct, although the vesicular region is bent towards the posterior body end, due to the contractions during the fixation. (Fig. 8E). The spermatic duct empties into the distal region of the prostatic vesicle. Distally the characteristic penis papilla of the genus housed the short, naked ejaculatory duct without stylet (Fig. 8D). Male atrium ciliate. The female reproductive system consists of a vagina interna (Fig. 8B) in which the oviduct empties and the vesicle externa lined with a thick and ciliated epithelium. Shell and cement-gland open into the vagina externa, but no. Uterine vesicles not observed surely due to the state of sexual maturity of the studied animal. The female atrium is broad, marked by a well-developed epithelium. Remarks: Due to its elongated oval shape, smooth dorsal surface with longitudinal stripes on the back, pointed tentacles, cerebral eye clusters in two elongate rows. In addition to de frontal branch of the gut and the anterior-dorsally oriented prostatic vesicle, this species is placed within the genus Prostheceraeus. Based on the colouration pattern, mainly the longitudinal stripes, Prostheceraeus fitae n.sp. can be compared to five species of the genus: Prostheceraeus fuscolineatus Dixit, Raghunathan & Chandra, 2017; Prostheceraeus vittatus (Montagu, 1815); Prostheceraeus pseudolimax Lang, 1884; Prostheceraeus giesbrechti Lang, 1884 and Prostheceraeus roseus Lang, 1884. The violet, mauve and lilac colour of P. fitae n.sp. clearly differs from the white background colour and black stripes of P. vittatus, pink with white stripes of P. roseus, the orange stripes of P. fuscolineatus, the yellow central stripe of P. giesbrechti and the two lateral black stripes and central yellow of P. fuscolineatus. The internal anatomy of the reproductive system shows clear similarities, but P. fitae n.sp. presents a much more delicate stylet than the rest of the species and a long, narrow male atrium. The genus Prostheceraeus is well represented in the North Atlantic and the Mediterranean; on the contrary, only two species are known from the Pacific Ocean and adjacent Seas. Prostheceraeus panamensis Woodworth, 1894 from Panama is a species described on fixed material and mostly damaged; therefore, the information on colouration or body shape is ambiguous. It also lacks internal description, so a comparison is not possible. The other known species is P. fuscolineatus from the Indian Ocean, which clearly differs from P. fitae n.sp. by colouration and the shape of the dorsal longitudinal stripes, as discussed above.

Paraplanocera angeli n. sp. (Fig. 3) Material examined: A specimen from the type locality and designated as holotype. Sagittal sections stained with AZAN. 62 slides: MNCN 4.01 / 2205 to MNCN 4.01 /2266 Type locality: Playa Langosta beach, in Las Baulas National Marine Park of Guanacaste, Costa Rica, 10 ° 17’32.2 “N 85 ° 51’12.7” W; 24, May, 2018 (Fig. 3A) Habitat: Low intertidal, below stones on sand. Etymology: The name of the species, Paraplanocera angeli n.sp. is dedicated to Ángel Delso, for his help and moral support throughout the project. Description: External characteristics (Fig. 3B, C): Body shape oval, very delicate and with waved margins. Length 20 mm. Colouration transparent, yellowish intestinal branches due to the intestinal content and brilliant dots produced due to the refraction of light in the ovaries. Nuchal tentacles plumb and located at the first third of the body. Tentacular eyes at the base of tentacles and two groups of cerebral eyes between the tentacular appendix. Ruffled pharynx in the middle of the body. Male and female gonopore separated. Reproductive system (Fig 3D): copulatory organs located in the last body third. The male organ comprises a prostatic vesicle with two accessory vesicles, cirrus with bristles and two adenoids, and a short homogenously ciliated atrium. The entire complex is surrounded by a well-developed muscular layer. The prostatic vesicle is covered with a spongy epithelium that forms inside long finger like prolongations. The vasa deferentia form two spermiducal bulbs that empty separately into the distal region of the prostatic vesicle. The cirrus is sinuous and covered with short but fragile bristles. It empties directly into the ciliated male atrium. In the proximal region of the atrium appear two elongated and glandular formations that resemble the teeth of other Paraplanocera, but are not sclerotized, the so-called adenoids (Faubel 1983) (Fig. 3D). The female reproductive system shows a short and ciliated atrium that opens in a well-developed vagina bulbosa covered with long, flexible cilia. Frontally appears a ciliated, conical blind sac, the bursa copulatrix, covered with a ciliated epithelium and surrounded by a well-developed musculature. Caudally emerges the Lang´s vesicle. In this region, the female duct is covered with a cuboidal epithelium and an underdeveloped muscle layer (Fig. 3D). Remarks: The species captured in Costa Rica belongs to the genus Paraplanocera Laidlaw, 1903 due to the presence of nuchal tentacles, tentacular and cerebral eyes, adenoids and the presence of the bursa copulatrix and Lang’s vesicle within the female copulatory organ. Currently this genus consists of 10 species (Faubel 1983). Paraplanocera aurora Laidlaw, 1903; P. discus (Willey, 1897); P. fritillata Hyman, 1959; P. langi (Laidlaw, 1902); P. marginata Meyer, 1922; P. misakiensis Yeri & Kaburaki, 1918; P. oceanica (Hyman, 1953); P. oligoglena (Schmarda, 1859); P. rotumanensis Laidlaw, 1903 and P. rubrifasciata Kato, 1937. All species show sclerotized adenoids, with the exception of Paraplanocera angeli n.sp and P misakiensis. Both species share naked non-sclerotized adenoids, but can be clearly distinguished by the inner epithelium of the bursa copulatrix; folded and naked in P. misakiensis, smooth and ciliated in P. angeli n.sp. Other differences between the two species are the dorsal colouration, olive green in P. misakiensis and translucent in P. angeli n.sp.; the arrangement of the cerebral eyes, only at the level of the tentacles in P. angeli n.sp. (Fig. 3B) and the shape of the female atrium, widened in P. misakiensis and narrow and elongated in P. angeli n.sp. Therefore, the differences found between the two species establish P. angeli n.sp. as a new species of the genus Paraplanocera.

Enchiridium magec, Cuadrado, Moro & Noreña, 2017 (Fig. 5) FIGURA 5. Enchiridium magec Cuadrado, Moro & Noreña, 2017 . A. Distribution map and sample points; B. Whole live animal, dorsal view; C. Ventral view of whole live animal; D-E. Histological sections of the copulatory organs stained with Azan; F. Sagittal reconstruction of the reproduction system (D, E, F anterior end to the right). Material examined: Two specimens. One fixed in Bouin and one sagittal sectioned and stained with Azan. Deposited in the National Museum of Natural Sciences. 49 slides: MNCN 4.01/2412 to MNCN 4.01/2460 Location: Both specimens were collected in Playa Carbon (Las Baulas National Park of Guanacaste, Costa Rica) 10 ° 20’53.4 “N 85 ° 51’44.5” W; 19, May, 2018 (Fig 5A) Habitat: Low intertidal, below stones on sand. Description: External features (Fig.5B, C): Body shape elongated with smooth dorsal surface. Background colour yellow with cream dots and dark brown spots in the central area, forming a continuous longitudinal midline. Ventral colouration whitish. Without pseudotentacles or tentacles. With marginal eyes in the first third of the body and two elongated clusters of cerebral eyes. Tubular pharynx located in the anterior third of the body, anteriorly oriented. Reproductive system: Male copulatory apparatus with a single male gonopore (Fig. 5C), anterior to the female. With an elongated penis papilla armed with a long tubular stylet (Fig. 5E). Two interpolated prostatic vesicles, included in a very characteristic muscular bulb, and the seminal vesicle surrounded in a second muscular bulb (Fig. 5D). The female copulatory apparatus presents a short vagina, oriented posteriorly, surrounded by cement glands (Fig. 5F). Distribution: Enchiridium magec has been found in the Atlantic Ocean, Canary Islands, (Cuadrado et al., 2017) and in Costa Rica in this study. It is the first record for the Pacific Ocean and for the American west coast, Costa Rica.

Paraplanocera oligoglena (Schmarda, 1859) (Fig. 2) Material examined: A single specimen. Sagittal sections stained with AZAN. 110 slides: MNCN 4.01/2105 to MNCN 4.01/2204 Location: Playa Carbón Beach in Las Baulas National Marine Park of Guanacaste, Costa Rica, 10 ° 20’53.4 “N 85 ° 51’44.5” W; May 17, 2018. (Fig. 2A) Habitat: Low intertidal, below stones on sand. Description: External characteristics (Fig. 2B,C): Body shape oval or round. Length 40 mm. Dorsal pigmentation marbled coffee brown on white background, sometimes translucent yellowish by transmitted light. Ventral region of ivory colours with darker spots (Fig 2C). Body edges waved with irregular dark tones and ends in a clear, almost white border, visible from the ventral and dorsal part. Nuchal tentacles at the end of the first body third. Tentacular eyes at the base of each tentacle. Two groups of cerebral eyes between tentacles. A cloud of black dots surround the pharynx and reproductive system. The ruffled pharynx is wide and with lateral projections (approx. 12 mm long, 5 mm wide). Reproductive system (Fig 2D): male copulatory apparatus is located on the back of the specimen. Comprises a cirrus, a prostatic vesicle with accessory prostatic vesicles, two spermiducal bulbs, and lacks a seminal vesicle. The cirrus is covered with thorns from the genital pore to almost the insertion of the prostatic vesicle. Two pseudosclerotized teeth (or adenoids) are located the middle region of the cirrus (Fig. 2D). The spermiducal bulbs enter into the prostatic vesicle distally. The cirrus narrows into a short male atrium. The female is close to the male gonopore. The atrium leads to a wide vagina externa, also called vagina bulbosa, anteriorly orientated and surrounded by a very developed and “spongy” glandular tissue. The vagina interna bifurcates forming two organs: an elongated, large Lang’s vesicle whose duct is lined by a highly developed cubic epithelium and the bursa copulatrix, anterior oriented, elongated and highly developed running parallel to the male copulatory bulb (Fig. 2D). Distribution: Paraplanocera oligoglena is considered a species with a distribution located practically throughout the Pacific Ocean. It has been found in the Gulf of California and Baja California (Hyman 1953), Sri Lanka (Schmarda 1859), Hawaii (Hyman 1954, 1960), India; Maldives Islands; Fiji Islands; Papua New Guinea; New Caledonia; Red Sea; Japan; Taiwan (Kato 1944), Australia (Prudhoe 1978) and now in Costa Rica. The last record is the first for Central America and the southernmost of the Pacific coast of America. It should be noted that with the exception of the record of the Red Sea (Kato 1944), P. oligoglena has not been found outside the Pacific., Published as part of Soutullo, Patricia, Cuadrado, Daniel & Noreña, Carolina, 2021, First study of the Polycladida (Rhabditophora, Platyhelminthes) from the Pacific Coast of Costa Rica, pp. 363-381 in Zootaxa 4964 (2) on pages 366-367, DOI: 10.11646/zootaxa.4964.2.7, http://zenodo.org/record/4709585, {"references":["Schmarda, L. K. (1859) Neue wirbellose Thiere beobachtet und gesammelt auf einer Reise um die Erde 1853 bis 1857. Verlag von Wihelm Engelmann, Leipzig, 164 pp. https: // doi. org / 10.5962 / bhl. title. 85313","Hyman, L. H. (1954) Some Polyclad Flatworms from the Hawaiian Islands. Pacific Science, 8, 331 - 336.","Hyman L. H. (1960) Second report on Hawaiian polyclads. Pacific Science, 14, 308 - 330.","Kato, K. (1944) Polyclad turbellarians from the neighbourhood of the Mitsui Institute of Marine Biology. Japanese Journal of Zoology, 6, 123 - 138.","Prudhoe, S. (1978) Polyclad turbellarians from the southern coasts of Australia. Records of the South Australian Museum, 18, 361 - 384."]}

Semonia bauliensis n. sp. (Fig. 4) Material examined: A specimen from the type locality and designated as holotype. Sagittal histological sections and stained with AZAN. Deposited in the National Museum of Natural Sciences, Madrid, Spain. 26 slides: MNCN 4.01 / 2386 to MNCN 4.01 /2411. Type locality: Playa Carbón Beach, in Las Baulas National Marine Park of Guanacaste, Costa Rica, 10 ° 20’53.4 “N 85 ° 51’44.5” W; 19 May 2018 (Fig 4A) Habitat: Low intertidal, below stones on sand. Etymology: The name of the species, Semonia bauliensis n.sp., refers to the locality where this new Semonia specimen was found in Las Baulas de Guanacaste National Marine Park. Description: External characteristics (Fig. 4B, D): Body shape elongated. Length 23mm. Background colour ivory, honey brown on the area of the pharynx and copulatory organs. Ventral area beige with pharynx marked in white. In the sagittal series, as well as in the living organisms, small protuberances like tentacles can be appreciated at the anterior end. Tentacle eyes at the base of the protuberances and two cerebral eye groups. Ruffled pharynx elongated located in the middle of the body. Reproductive system: located in the posterior part of the body. Male and female system opens in a common genital atrium (Fig.4C). Dorsally, the common atrium widens in a funnel-like male atrium that covers a short rodlike penis papilla (Fig.4C). The male copulatory organ comprises a seminal vesicle and a short penis papilla, but without prostatic vesicle. The seminal vesicle is located parallel to the central body axis forming an angle of almost 90º with the penis papilla (Fig.4E). The vasa deferentia are thin and lead to the distal region of the seminal vesicle. Prostate glands that extend along the vas deferens exert the function of vesicles. The female copulatory organ consists of an elongated, S-shaped vagina, gradually widening distally (Fig.4F). Without Lang’s vesicle. Cement and shell glands pour at the end of the vagina externa, but the exact opening is diffuse. Remarks: The species collected in Costa Rica belongs to the genus Semonia due to the presence of a male copulatory apparatus with seminal vesicle and rod-like penis, common atrium and genital pore, and the lack of a Lang’s vesicle. The only species described of the genus Semonia is S. maculata Plehn, 1896 of Indonesia. The differences from S. bauliensis n.sp. are visible in the external anatomy as well as in the internal morphology of the reproductive system. Externally, the differences are located in the disposition of the cerebral eyes, around the cephalic ganglion in S. maculata and in two elongated groups on both sides of the brain in S. bauliensis n.sp.. With respect to the internal anatomical differences, the most notable feature is the size of the penis papilla and the genital atrium, clearly more developed in S. maculata. These differences are sufficiently prominent to designate Semonia bauliensis n.sp. as a new species., Published as part of Soutullo, Patricia, Cuadrado, Daniel & Noreña, Carolina, 2021, First study of the Polycladida (Rhabditophora, Platyhelminthes) from the Pacific Coast of Costa Rica, pp. 363-381 in Zootaxa 4964 (2) on pages 369-370, DOI: 10.11646/zootaxa.4964.2.7, http://zenodo.org/record/4709585, {"references":["Plehn, M. (1896) Neue Polycladen, gesammelt von Herrn Kapitan Chierchia bei der Erdumschiffung der Korvette Vettor Pisani, von Herrn Prof. Dr. Kukenthal im nordlichem Eismeer und von Herrn Prof Dr. Semon in Java. Jenaische Zeitschrift fur Naturwissenschaft, 30, 137 - 181."]}

Pseudobiceros bajae (Hyman, 1953) (Fig. 7) Material examined: Five specimens sampled. Four specimens fixed for molecular and histological studies. One sagittally sectioned and stained with Azan for the Invertebrate Collections of the Museum of Natural Science (MNCN) Madrid, Spain.. Location: Playa Carbón Beach 10 ° 20’53.4 “N 85 ° 51’44.5” W and Playa Langosta 10 ° 17’32.2 “N 85 ° 51’12.7” W, in Las Baulas National Park of Guanacaste, Costa Rica (Fig. 7A); Between May 18 and 24, 2018. 73 slides: MNCN 4.01 /2503 to MNCN 4.01 /2575. Habitat: Low intertidal, under stones on sand and in intertidal pools under stones. Description: External features (Fig. 7B, C): Elongated body shape, wavy margins, front and with rounded posterior end. Length: 38 mm. Pseudotentacles ear-shaped. Ebony black dorsal colouration uniformly dotted with small white dots. There is an unpigmented region around the pseudotentacles on which a cerebral eye cluster is located. Ventrally pigment is less. Pharynx ruffled in the first half of the body. Reproductive system (Fig. 7E, D, F): Two male copulatory organs, both formed by an elongated seminal vesicle; oval, muscular prostatic vesicle (Fig. 7E, D); without stylet, but reinforced ductus ejaculatorius and elongated, ciliated atrium (Fig. 7F). Female reproductive system formed by a vagina externa and an underdeveloped vagina that curve towards the posterior end (Fig. 7F). Distribution: Pseudobiceros baJae has been reported from the Mexican Pacific; Puerto Peñasco, Miramar and Bahia de la Paz (Hyman 1953) and now from Costa Rica in this study., Published as part of Soutullo, Patricia, Cuadrado, Daniel & Noreña, Carolina, 2021, First study of the Polycladida (Rhabditophora, Platyhelminthes) from the Pacific Coast of Costa Rica, pp. 363-381 in Zootaxa 4964 (2) on page 373, DOI: 10.11646/zootaxa.4964.2.7, http://zenodo.org/record/4709585

Pseudoceros rawlinsonae var. galaxy var. nov. Figs 1C, 3 E–I Etymology The name ‘galaxy’ comes from the pattern of the small white spots on the dorsal surface, which resemble a star galaxy. Material examined (2 specs) Holotype CAPE VERDE • S„o Vicente Island, Baía das Gatas; 16°54′09.33″ N, 24°54′25.25″ W (Fig. 1C V 2); 5 May 2017; Leopoldo Moro leg.; MNCN 4.01/2729 to 2798 (70 slides). One sagittally sectioned specimen stained with AZAN. Additional material CAPE VERDE • 1 spec.; same collection data as for holotype; RCCN. Description BODY. Shape oval. Length 2.3 cm. Smooth dorsal surface. Background color dark to velvety brown with white dots and spots that draw a longitudinal line along the body axis. One thin bright yellow external line and another internal and black line surround the entire body margin. The yellow one is interrupted at the pseudotentacles level (Fig. 3 E–F). Marginal body edges lined with transversal whitish elongated drops (Fig. 3F). Ventral coloration dark grey to black. Ventral sucker in the middle of the body (Fig. 3G). Pseudotentacles constitute two simple folds that present each of them a small cluster of tentacular eyes in their margin. Round cluster of cerebral eyes present and surrounded by a spot of white pigment. Pharynx ruffled, butterfly-shaped and located at the anterior third of the body. Oral pore, female and male gonopore close to each other and located at the anterior end (Fig. 3G). Male and female genital pores located after the pharynx in the anterior half of the body (Fig. 3 H–I). MALE REPRODUCTIVE SYSTEM. Male genital pore between the posterior lobes of the ruffled pharynx. Male copulatory organ dorso-ventrally orientated consists in a prostatic vesicle and a very muscular seminal vesicle, as well as a penis papilla armed with a stylet (Fig. 3 H–I). Vasa deferentia open separately into the seminal vesicle. Seminal vesicle rounded, frontally oriented and lined with a thick muscular wall. Prostatic vesicle rounded, muscular and smaller than the seminal vesicle. Sperm duct muscular and long, extends frontally to join the prostatic duct inside the proximal end of the conical stylet. The short ejaculatory duct appears surrounded by the stylet cone and the penis sheath. The male atrium is wide and tetra-folding (fork-like) as characteristic of the genus (Fig. 3I). FEMALE REPRODUCTIVE SYSTEM. With a short muscular vagina, backwards oriented and surrounded by cement glands. Remarks The genus Pseudoceros comprises approximately 89 species with similar copulatory organs, but bright and unique coloration patterns. However, within these patterns some taxa share evident similarities. Pseudoceros rawlinsonae var. galaxy shares with P. bicolor Verril, 1902, P. mororum and P. rawlinsonae Bolaños, Quiroga & Litvaitis, 2007 the brown background and one whitish, broad marginal band, but in P. bicolor the marginal band is wide with inner waves (Litvaitis et al. 2010: fig. 4a–i); P. rawlinsonae shows, in addition to the wide band, a thin orange line (Litvaitis et al. 2010: fig. 4j–p); in P. mororum the whitish band is interrupted and drop-shaped and additionally, two orange marginal stripes border the entire body (Cuadrado et al. 2017: fig. 6a–b); finally, the Cape Verdean species shows, together with the drop-shaped white band, two black and orange thin lines (Fig. 3 E–F). Although the four previously mentioned species can be clearly differentiated due to their coloration, this is not the case in the molecular analysis (Fig. 8). In both the Bayesian and Maximum Likelihood analyses, individuals from Cape Verde appear closely related to P. rawlinsonae, so much so that the separation of both populations (the Cape Verdean population and the Caribbean population) is only possible at the level of variety, not of species. Therefore, we determined the individuals from Cape Verde as a variety within the species P. rawlinsonae. Nonetheless, we want to emphasize that the decision to maintain this population (organisms) as a ‘variety’ of the species P. rawlinsonae is the sole and exclusive responsibility of the authors. We are aware that ‘variety’ is not a taxonomic category (according to ICZN) and that therefore it will remain a non-existent species until molecular analyses allow us to consider it as such., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 18-19, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Litvaitis M. K, Bolanos D. M. & Quiroga S. Y. 2010. When names are wrong and colours deceive: unravelling the Pseudoceros bicolor species complex (Turbellaria: Polycladida). Journal of Natural History 44: 829 - 845. https: // doi. org / 10.1080 / 00222930903537074","Cuadrado C., Moro L. & Norena C. 2017. The Polycladida (Platyhelminthes) of the Canary Islands. New genus, species and records. Zootaxa 4312: 38 - 68. https: // doi. org / 10.11646 / zootaxa. 4312.1.2"]}

Prostheceraeus crisostomum sp. nov. urn:lsid:zoobank.org:act: EC7A7E2B-99FD-447D-A189-676144875AC2 Figs 1C, 3 A–D Etymology The name of the new species, Prostheceraeus crisostomum, is dedicated to the little cat, Crisostomo, roommate during the description of this species. Material examined Holotype CAPE VERDE • Sal Island, Calheta Funda; 16°39′03.34″ N, 22°56′42,94″ W (Fig. 1C V 3); 8 Jul. 2018; Leopoldo Moro leg.; MNCN 4.01/2684 to 2698 (15 slides). One sagittally sectioned specimen stained with AZAN. Description BODY. Shape elongated. Length 0.5 cm. Smooth dorsal surface; background pigmentation ivory white, darker along the middle dorsal region of the body between the cerebral eyes and the posterior end of the body. In the posterior middle end it shows a large conspicuous black spot. Small black dots on the entire dorsal surface (Fig. 3E). Two marginal tentacles, separate. Tentacular eyes scarce and widely dispersed between the tentacles. Cerebral eyes arrow-shaped located by the central midline (Fig. 3F). Bell-shaped pharynx located in the first body half. Ventral sucker in the middle of the body. Male and female genital pores well separated and located after the pharynx (Fig. 3 G–H). MALE REPRODUCTIVE SYSTEM. Male copulatory organ oriented forward. The muscular prominent penis papilla houses a conical, elongated stylet of pseudosclerotized nature. The rounded and well developed prostatic vesicle joins transversally with the sperm duct and lies over the penis papilla (Fig. 3H). Muscular seminal vesicle oval, dorsally located and caudo-frontally oriented. The vasa deferentia join at the ventro-caudal region of the vesicle and the sperm duct open ventro-frontally. Seminal and prostatic vesicles open together into the proximal region of the developed penis papillae. The male atrium surrounded the penis papillae and opens near the posterior end of the pharynx. FEMALE REPRODUCTIVE SYSTEM. Atrium elongated and highly ciliated, continues dorsally into the long but not ciliated vagina externa. The vagina externa narrows into a non-ciliated small cavity that continues in the vagina interna. It presents a widened epithelium and ends with the entry of the oviducts (Fig. 3H). Cement and shell glands lie around the female atrium, vagina externa and distal region of the vagina interna, but opens into the small cavity (pouch) between both vaginas. Remarks Prostheceraeus crisostomum sp. nov. belongs to the genus Prostheceraeus due to the presence of cerebral, frontal and marginal eyes, true anterior tentacles, bell-shaped pharynx, the male copulatory system with prostatic vesicle, penis armed whit stylet and the presence of multiple uterine vesicles. The genus Prostheceraeus comprises 10 species, mainly characterized by coloration pattern, with colorful pigmentations and dorsal longitudinal lines of different widths, as in P. fuscolineatus Dixit, Raghunathan & Chandra, 2017, P. roseus, P. pseudolimax Lang, 1884, P. giesbrechtii, P. vittatus (Montagu, 1815) and P. zebra (Hyman, 1955) or with fine, transversal lines as in P. crozieri (Hyman, 1939). Three other species of Prostheceraeus show a color pattern free of lines or bands: P. albocinctus Lang, 1883, P. moseleyi and P. rubropunctatus Lang, 1884. These three species, together with P. crisostomum sp. nov., have a dotted pattern, but the background colors are different in the four species: caramel brown background with white or whitish spots and white marginal line in P. albocinctus, blue-gray or cream background with black dots and yellow marginal band in P. moseleyi and finally P. rubropunctatus with a pink to reddish background color, white dots and without marginal band. The base coloration of P. crisostomum is similar to P. albocinctus, but much clearer and almost ivory; the dorsal points are black like in P. moseleyi and lacks a marginal line or band similar to P. rubropunctatus. All these differences delimit P. crisostomum sp. nov. as a new species of the genus Prostheceraeus.

Distylochus fundae sp. nov. urn:lsid:zoobank.org:act: 27AE0619-D25F-48A0-8345-31D38765F732 Figs 1C, 5 E–H Etymology The name of the new species, Distylochus fundae sp. nov. refers to the type locality Calheta Funda in the Island of Sal. Material examined Holotype CAPE VERDE • Sal Island, Calheta Funda; 16°39′03.34″ N, 22°56′42.94″ W (Fig. 1C V 3); 14 Nov. 2018; Leopoldo Moro leg.; MNCN 4.01/2724 to 2725 (5 slides). One sagittally sectioned specimen stained with AZAN. Description BODY. Shape elongated. Length 0.4 cm. Smooth dorsal surface. Background pigmentation orange-garnet (Fig. 5E). Cerebral and tentacular eyes, scattered between the small tentacles (Fig. 5F). Ruffled pharynx, well developed, extending along ⅔ of the body. Male and female genital pores located in the posterior half of the body, together, but clearly separated. MALE REPRODUCTIVE SYSTEM. Male copulatory system backwards oriented, with a small penis papilla. Prostatic vesicle surrounded by muscular layers and lined with fingered granular lining, most probably polyglandular (Fig. 5 G–H). Seminal vesicle divided into two sections. A muscular and elongated proximal section, and a more rounded distal section provided with a thin wall. Both regions separated by muscle narrowing (Fig. 5H). The distal section leads to the seminal duct that opens into the prostatic duct and forms a short ejaculatory duct. The two vasa deferentia dilated to form spermatic vesicles, open into the proximal section. Male atrium small, englobing a short penis papilla (Fig. 4H). FEMALE REPRODUCTIVE SYSTEM. Apparatus simple and backwards oriented. Comprises an elongated tube without clear differentiation between external and internal vagina and ends in a small widening, without Lang’s vesicle. Remarks The new species belongs to the genus Distylochus due to the presence of few scattered marginal, tentacular and cerebral eyes. Gonopores together and are located near the posterior end. Male apparatus with a short papilla and unarmed. Seminal vesicle configured in two regions, following the “doublevesicle-system” after Faubel (1983) and female apparatus simple, without Lang’s vesicle. There are currently only three known species for the genus Distylochus: D. pusillus (Bock, 1913) recorded for Hong Kong, D. martae (Marcus, 1947) in Brazil and D. isifer (Du Bois-Reymond, 1955) also from Brazil. These species were described on fixed specimens, therefore the colors are unknown, but apparently and after the original descriptions, they have pale pigmentation that contrast sharply with the orange-vermilion colors of the new species. The most conspicuous difference of the new species is the disposition of female and male gonopore. In Distylochus fundae sp. nov. the gonopores are clearly separated, while in the Brazilian species are common and in the Chinese species are very close together. New records Following the known species that are captured in the study area. All of them have been studied through photographs and histological sections, currently in RCCN., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 24-25, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Faubel A. 1983. The Polycladida, Turbellaria; Proposal and establishment of a new system. Part I. The Acotylea. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 80: 17 - 121."]}

Stylochus neapolitanus (Delle Chiaje, 1841 –1844) Figs 1D, 7I Planaria neapolitana Delle Chiaje, 1841: vol. III: 133 (text); vol. V: 112 (description); pl. 109, figs 13– 15, 22. Stylochus neapolitanus – Lang 1884: 447–449, pl. 1, fig. 7. Material examined MOROCCO • 2 specs; Sidi Ifni; 29°22′58.00″ N, 10°10′37.88″ W (Fig. 1D M1); 2 Sep. 2016; Leopoldo Moro leg.; RCCN. Distribution Western Mediterranean Sea, Sicily (type locality) (Delle Chiaje 1841); Naples, Italy (Lang 1884); Catalonia, Spain (Novell 2003); Mar Menor, Murcia, Spain (Marquina et al. 2014); Ría de Arousa, Galicia, Spain (Noreña et al. 2015); Cape Verde (Laidlaw 1906); Rufisque, Senegal (Palombi 1939). New record Sidi Ifni, Morocco., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on page 30, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Delle Chiaje S. 1841. Descrizione e Notomia degli Animali Invertebrati della Sicilia Citeriore: Osservati Vivi negli Anni 1822 - 1830. Tom. IV. C. Batelli, Naples. https: // doi. org / 10.5962 / bhl. title. 10031","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545","Novell C. 2003. Contribucio al coneixement dels turbel. laris policladides del litoral catala. Ph Thesis, University of Barcelona, Spain. Available fromhttp: // hdl. handle. net / 10803 / 781 [accessed 18 Dec. 2020].","Marquina D., Osca D., Rodriguez J., Fernandez-Despiau E. & Norena C. 2014. State of knowledge of the Acotylea (Polycladida, Platyhelminthes) from the Mediterranean coasts of Spain: new records and new species. Zootaxa 3780: 108 - 134. https: // doi. org / 10.11646 / zootaxa. 3780.1.4","Norena C., Rodriguez J., Perez J. & Almon B. 2015. New Acotylea (Polycladida, Platyhelminthes) from the east coast of the North Atlantic Ocean with special mention of the Iberian littoral. Zootaxa 4039: 157 - 172. https: // doi. org / 10.11646 / zootaxa. 4039.1.7","Laidlaw F. F. 1906. On the marine fauna of the Cape Verde Islands, from collections made in 1904 by Mr. C. Crossland. - The polyclad Turbellaria. Proceedings of the Zoological Society of London 1906: 705 - 719. Available from https: // www. biodiversitylibrary. org / item / 97669 page / 313 / mode / 1 up [accessed 18 Dec. 2020].","Palombi A. 1939. Turbellari del Sud Africa. Policladi di East London. Archivio zoologico italiano 28: 123 - 149."]}

Pseudoceros velutinus (Blanchard, 1847) Figs 1C, 7D Proceros velutinus Blanchard, 1847: 273, pl. 8, fig. 2; pl. 9, fig. 1. Eurylepta velutina – Diesing 1850: 210; 1862: 548. — Stimpson 1857: 2. — Schmarda 1859: 26. — Diesing 1862: 548. Pseudoceros velutinus – Lang 1884: 538–539, pl. 5, fig. 4. Material examined CAPE VERDE • 1 spec.; São Vicente Island, Baía das Gatas; 16°54′09.33″ N, 24°54′25.25″ W (Fig. 1C V 2); 5 May 2017; Leopoldo Moro leg.; RCCN. Distribution Gulf of Genova, Italy (type locality) (Blanchard 1847); Suez Canal, Egypt (Palombi 1928); Rovigno, Croatia (Vàtova 1928); Canary Islands (Cuadrado et al. 2017). New record Baía das Gatas, S„o Vicente, Cape Verde. Remarks Pseudoceros velutinus is known for its velvety black pigmentation, but the coloration varies with transmitted or reflected light. Fig. 7D shows the appearance of P. velutinus with transmitted light., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 28-29, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Blanchard E. 1847. Recherches sur l'organisation des vers. Annales des Sciences naturelles. Zoologie 7: 87 - 128, 8: 119 - 149, 271 - 275. https: // doi. org / 10.5962 / bhl. title. 51506","Diesing C. M. 1850. Systema Helminthum. I. W. Braum ʾ ller, Vienna [Vindobonae]. https: // doi. org / 10.5962 / bhl. title. 46846","Diesing C. M. 1862 [1861]. Revision der Turbellarien. Abtheilung: Dendrocoelen. Sitzungsberichte der mathematischen naturwissenschaftlichen Classe der kaiserlichen Akademie der Wissenschaften zu Wien 44: 485 - 578. https: // doi. org / 10.5962 / bhl. title. 2108","Stimpson W. 1857. Prodromus descriptionis animalium evertebratorum, quae in Expeditione ad Oceanum Pacificum Septentrionalem, Johanne Rodgers Duce a Republica Federata missa, observavit et descripsit. Pars I, Turbellaria Dendrocoela. Proceedings of the Academy of Natural Sciences of Philadelphia 9: 19 - 31. https: // doi. org / 10.5962 / bhl. title. 51447","Schmarda L. K. 1859. Neue wirbellose Thiere beobachtet und gesammelt auf einer Reise um die Erde 1853 bis 1857. Bd I: Neue Turbellarien, Rotatorien und Anneliden. W. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 85313","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545","Cuadrado C., Moro L. & Norena C. 2017. The Polycladida (Platyhelminthes) of the Canary Islands. New genus, species and records. Zootaxa 4312: 38 - 68. https: // doi. org / 10.11646 / zootaxa. 4312.1.2","Marcus E. 1950. Turbellaria Brasileiros (8). Boletim da Facultade de Philosophia, Sciencias e Letras, Universidade de Sao Paulo. Zoologia 15: 5 - 190. https: // doi. org / 10.11606 / issn. 2526 - 4877. bsffclzoologia. 1950.125192","Faubel A. 1984. The Polycladida, Turbellaria; Proposal and establishment of a new system. Part II. The Cotylea. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 81: 189 - 259.","Gotte A. 1881. Zur Entwicklungsgeschichte der W ʾ rmer. Zoologischer Anzeiger 4: 189 - 191. Available from https: // www. biodiversitylibrary. org / item / 36963 page / 203 / mode / 1 up [accessed 18 Dec. 2020].","Delle Chiaje S. 1841. Descrizione e Notomia degli Animali Invertebrati della Sicilia Citeriore: Osservati Vivi negli Anni 1822 - 1830. Tom. IV. C. Batelli, Naples. https: // doi. org / 10.5962 / bhl. title. 10031","Mertens H. 1833. Untersuchungen ʾ ber den inneren Bau verschiedener in der See lebender Planarien. Memoires de l'Academie imperiale des Sciences de Saint Petersbourg. 6 eme serie, Sciences mathematiques, physiques et naturelles 2: 3 - 17. Available from https: // www. biodiversitylibrary. org / item / 247344 page / 13 / mode / 1 up [accessed 18 Dec. 2020].","Palombi A. 1928. Report on the Turbellaria. Zoological results of the Cambridge Expedition to the Suez Canal. 1924. Transactions of the Zoological Society of London 22: 579 - 630.","Vatova A. 1928. Compendis della flora e fauna del Mare Adriatico presso Rovigno con la distribuzione geografica delle species bentoniche. Memorie Reale Comitato Talassografico Italiano, Venezia, Italy 143: 154 - 174."]}

Euplana claridade sp. nov. urn:lsid:zoobank.org:act: C7E211FD-32AF-4FA4-A3EB-ACA1737DF2EE Figs 1C, 4 D–H Etymology The name of the new species, Euplana claridade, comes from “Claridade”, a journal of literary review that revolutionized Cape Verdean culture during the first half of the twentieth century. Material examined Holotype CAPE VERDE • São Vicente Island, Mindelo; 16°53′46.54″ N, 24°59′32.93″ W (Fig. 1C V1); 23 Nov. 2017; Leopoldo Moro leg.; MNCN 4.01/2709 to 2718 (10 slides). One sagittally sectioned specimen stained with AZAN. Description BODY. Shape oval. Length 1.1 cm. Smooth dorsal surface. Background pigmentation ivory white, denser along the middle dorsal region of the body and in the intestinal braches (Fig. 4D). Two clusters of 16 cerebral eyes each (Fig. 4E). Ruffled pharynx. Male and female genital pores located in the second half of the body close behind the posterior end of the pharynx. MALE REPRODUCTIVE SYSTEM. Male copulatory organ backwards oriented, englobed in a muscular bulb with a small penis papilla. Vas deferens opens proximally into the ejaculatory duct (Fig. 4 F–H). Without prostatic or seminal vesicle. Male atrium deep and thickened in the point of union with the penis (Fig. 4 F–H). FEMALE REPRODUCTIVE SYSTEM. Rounded female atrium (Fig. 4 F–H). Vagina backwards oriented, surrounded by muscular fibres. Without Lang´s vesicle. Remarks Euplana claridade sp. nov. belongs to the genus Euplana due to the absence of tentacles, prostatic vesicle and Lang´s vesicle, and presence of a true seminal vesicle and elongated coiling ejaculatory duct. The genus Euplana encompasses 3 species, E. carolinensis Hyman, 1940, E. gracilis Girard, 1853 and E. hymanae Marcus, 1947. The three species can be differentiated through the eyes number and disposition of them. E. gracilis and E. carolinensis present four cluster of eyes, two cerebral and two tentacular; E. hymanae and E. claridade sp. nov. only show two groups of cerebral eyes. Within the reproductive system another differences can have founded, E. gracilis and E. hymanae present a small, short male atrium and a backwards oriented vagina externa, while E. carolinensis and E. claridade sp. nov. share a long tubular male atriumand a forward directed vagina externa. Both species differ mainly in the male copulatory organ. The ejaculatory duct in E. carolinensis is wide and straight and by E. claridade sp. nov. is narrow and sinuous. Furthermore, the penis papilla is very short in E. carolinensis, while in E. claridade sp. nov. it is longer in comparison. On the other hand, the seminal vesicle is practically non-existent in E. claridade sp. nov., represented by the confluence of the two vasa deferentia, while in E. carolinensis it is a well-developed seminal vesicle, surrounded by circular muscles and in which the vas deferens empties proximally., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 20-22, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525

Stylochus pilidium (Götte, 1881) Figs 1 C–D, 6E, I, 7F–G Stylochopsis pilidium Götte, 1881: 189. Planaria neapolitana – Götte 1878: 75–76. Stylochus pilidium – Götte 1882: 1–56, pls I–II. — Lang 1884: 320–321, 325, 329, 341–343, 351–353, 357, 401, pl. 36. fig. 19, pl. 37, figs 1, 16–17, 22. Material examined CAPE VERDE • 3 specs; São Vicente Island, Mindelo; 16°53′46.54″ N, 24°59′32.93″ W (Fig. 1C V1); May 2017; Leopoldo More leg.; RCCN. MOROCCO • 3 specs; Sidi Ifni; 29°22′58.00″ N, 10°10′37.88″ W (Fig. 1D M 2); 2 Sep. 2016; Leopoldo Moro leg.; RCCN. Distribution Gulf of Naples, Mediterranean Sea (type locality) (Götte 1881; Lang 1884; Lo Bianco 1888); Gulf of Venice (Bock 1925); Black Sea (Rzhepishevskii 1979); Vietnam (Dawydoff 1952); Somalia (Laidlaw 1903); Zanzibar (Meixner 1907). New records S„o Vicente Island, Cape Verde (Fig. 6E). Sidi Ifni, Morocco (Fig. 6I)., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 29-30, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Gotte A. 1881. Zur Entwicklungsgeschichte der W ʾ rmer. Zoologischer Anzeiger 4: 189 - 191. Available from https: // www. biodiversitylibrary. org / item / 36963 page / 203 / mode / 1 up [accessed 18 Dec. 2020].","Gotte A. 1878. Zur Entwicklungsgeschichte der Seeplanarien. Zoologischer Anzeiger 1: 75 - 76. Available from https: // www. biodiversitylibrary. org / item / 95256 page / 89 / mode / 1 up [accessed 18 Dec. 2020].","Gotte A. 1882. Entwicklungsgeschichte von Stylochopsis pilidium n. sp. Untersuchungen zur Entwicklungsgeschichte der W ʾ rmer 1. Abhandlungen zur Bildungs- und Entwicklungs-geschichte des Menschen und der Thiere 8: 4 - 58.","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545","Lo Bianco S. 1888. Notizie biologiche riguardanti specialmente il period di maturita sessuale degli animali del Golfo di Napoli. Mittheilungen aus der Zoologischen Station zu Neapel 8: 385 - 440. Available from https: // www. biodiversitylibrary. org / item / 37441 page / 395 / mode / 1 up [accessed 18 Dec. 2020].","Bock S. 1925. Papers from Dr. Th. Mortensen's Pacific Expedition 1914 - 16. XXVII. Planarians, Pt. IV. New stylochids. Videnskabelige meddelelser fra den Naturhistoriske forening i Kjobenhavn 79: 97 - 184. https: // doi. org / 10.5962 / bhl. title. 82330","Rzhepishevskii J. K. 1979. Acorn barnacles eating away by Stylochus pilidium. Biologiya Morya 48: 23 - 28.","Dawydoff C. N. 1952. Contribution a l'etude des invertebres de la faune marina benthique de l'Indochine. Bulletin scientifique de la France et de la Belgique 39: 1 - 108.","Laidlaw F. F. 1903. On the marine fauna of Zanzibar and British East Africa, from collections made by Cyril Crossland in the years of 1901 and 1902. - Turbellaria Polycladida. Part I. The Acotylea. Proceedings of the Zoological Society of London 1903 (2): 99 - 13. Available from https: // www. biodiversitylibrary. org / item / 98617 page / 145 / mode / 1 up [accessed 18 Dec. 2020].","Meixner A. 1907. Polycladen von der Somalik ʾ ste, nebst einer Revision der Stylochinen. Zeitschrift fur wissenschaftliche Zoologie 88: 385 - 498. Available from https: // www. biodiversitylibrary. org / item / 138612 page / 405 / mode / 1 up [accessed 18 Dec. 2020]."]}

Gnesioceros sargassicola (Mertens, 1833) Figs 1B, 7L Planaria sargassicola Mertens, 1833: 13–14, pl. I, figs 4–6. Stylochus Mertensi Diesing, 1850: 216. Stylochus sargassicola – Ehrenberg 1836: 67. — Claparède 1861: 143. Planocera sargassicola – Örsted 1844: 48. Gnesioceros sargassicola – Diesing 1862: 571. Gnesioceros Mertensi – Diesing 1862: 572. Stylochus Mertensi – Moseley 1877: 23. Material examined CANARY ISLANDS – Gran Canaria Island • 1 spec.; Pasito Blanco; 27°44′50.46″ N, 15°37′31.85″ W (Fig. 1B C1); 4 Jan. 2017; Leopoldo Moro leg.; RCCN. – Tenerife Island • 1 spec.; 28°24′35.71″ N, 16°18′25.31″ W (Fig. 1B C 2); 7 Jun. 2011; Leopoldo Moro leg. RCCN. Distribution Bermuda Islands (Hyman 1939); Sargasso Sea, Caribbean Sea, Atlantic Ocean (Faubel 1983); Gulf of Mexico (Hyman 1954); Atlantic Ocean (Moseley 1877); Boa Vista Island, Cape Verde (Laidlaw 1903); Santa Marta, Colombia (Quiroga 2008); Netherlands, Puerto Rico, Florida, USA, Sargasso Sea, Atlantic Ocean (Marcus & Marcus 1968). New records Pasito Blanco, Gran Canaria, and Tenerife, Canary Islands. Remarks Gnesioceros sargassicola was limited to the Antilles and the Caribbean Sea until the record of Laidlaw (1903) for the Cape Verde Islands. The new record of G. sargassicola for the Canary Islands shows a progressive ‘colonisation’ of the Atlantic east coast. Molecular analysis The main purpose of the 28S analysis was to confirm the determinations made from the morphological study and verify the relationships among similar species. The recovered topology by both trees, Bayesian Inference (BI) as well as Maximum Likelihood (ML) strongly supports the monophyly of the suborders Acotylea and Cotylea (Fig. 8; Acotylea: BPP (Bayesian posterior probabilities) = 1 and BS (Bootstrap values of ML analysis) = 73, Cotylea: BPP = 0.98, BS = 100). Within Acotylea, the monophyly of Leptoplanoidea (BPP = 1, BS = 97) and Stylochoidea (BPP = 1, BS = 73) is well supported. Callioplana marginata Stimpson, 1857 considered within the superfamily Stylochoidea appears isolated with the highest support (BS = 100). As a sister group of Leptoplanoidea, there is a clade of species: Ilyella gigas (Schmarda 1859), Discocelis tigrina (Blanchard, 1847), Adenoplana evelinae Marcus, 1950, Amemiyaia pacifica Kato, 1944 and Phaenocelis medvedica Marcus, 1952 showing low support and not clearly grouped (Fig. 8). The main group of Leptoplanoidea encloses the family Leptoplanidae, with the genera Leptoplana Ehrenberg, 1831 and Armatoplana Faubel, 1983, and the family Notoplanidae Marcus & Marcus, 1966 with the genera Notoplana Laidlaw, 1903 and Notocomplana Faubel, 1983. Pseudostylochus Yeri & Kaburaki, 1918 and Koinostylochus Faubel, 1983 appear together and belong to the family Pseudostylochidae Faubel, 1983. Within Stylochoidea, four main clades are recovered: family Stylochidae with the genera Stylochus, Imogine Girard, 1853 and Paraplanocera Laidlaw, 1903 (see the Discussion); family Latocestidae Laidlaw, 1903 with Leptostylochus Bock, 1925 and Latocestus; family Hoploplanidae StummerTraunfels, 1933 with Hoploplana Laidlaw, 1902 and finally family Planoceridae with Paraplanocera Laidlaw, 1903 and Planocera. Callioplana marginata can be considered a sister group of Stylochoidea. Within the suborder Cotylea, the families Cestoplanidae Lang, 1884, Pericelidae Laidlaw, 1902 and Anonymidae represented by the genera Cestoplana Lang, 1884 (BPP = 1, BS 100), Pericelis (BPP = 1, BS 100) and Anonymus (BPP = 1, BS 100), respectively are presented as isolated groups. While Boninia Bock, 1923, Chromyella Correa, 1958 and Theama Marcus, 1949 form a well-supported group (BPP = 1, BS = 100), although currently belonging to separate families and not specifically related to each other. After Anonymidae, we find a well-supported branch (BPP = 0.9, BS = 95) that encompasses the families Prosthiostomidae Lang, 1884, Euryleptidae and Pseudocerotidae. This branch is, in turn, divided into two main branches (both supported by maximum values: BPP = 1, BS = 100) where Prosthiostomidae is separated from Euryleptidae and Pseudocerotidae, families with a clear relation., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 32-33, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Mertens H. 1833. Untersuchungen ʾ ber den inneren Bau verschiedener in der See lebender Planarien. Memoires de l'Academie imperiale des Sciences de Saint Petersbourg. 6 eme serie, Sciences mathematiques, physiques et naturelles 2: 3 - 17. Available from https: // www. biodiversitylibrary. org / item / 247344 page / 13 / mode / 1 up [accessed 18 Dec. 2020].","Diesing C. M. 1850. Systema Helminthum. I. W. Braum ʾ ller, Vienna [Vindobonae]. https: // doi. org / 10.5962 / bhl. title. 46846","Ehrenberg C. G. 1836. Uber die Akalephen des rothen Meeres und der Organismus der Medusen der Ostsee. Abhandlungen der Koniglichen Akademie der Wissenschaften zu Berlin 1835: 181 - 260. Available from https: // www. biodiversitylibrary. org / item / 94127 page / 269 / mode / 1 up [accessed 18 Dec. 2020].","Claparede E. 1861. Etudes anatomiques sur les annelides, turbellaries, opalines et gregarines observes dans les Hebrides. Memoires de la Societe des physique et d'histoire naturelle de Geneve 16 (4): 56 - 80, 124 - 148, 151 - 152. https: // doi. org / 10.5962 / bhl. title. 14795","Diesing C. M. 1862 [1861]. Revision der Turbellarien. Abtheilung: Dendrocoelen. Sitzungsberichte der mathematischen naturwissenschaftlichen Classe der kaiserlichen Akademie der Wissenschaften zu Wien 44: 485 - 578. https: // doi. org / 10.5962 / bhl. title. 2108","Moseley H. N. 1877. On Stylochus Pelagicus, a new species of pelagic planarian, with notes on other pelagic species, on the larval forms of Thysanozoon, and of a gymnosomatous pteropod. Microscopical Journal 17: 23 - 32.","Hyman L. H. 1939. Some polyclads of the New England coast, especially of the Woods Hole region. The Biological Bulletin (Woods Hole) 76: 127 - 152. https: // doi. org / 10.2307 / 1537854","Faubel A. 1983. The Polycladida, Turbellaria; Proposal and establishment of a new system. Part I. The Acotylea. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 80: 17 - 121.","Hyman L. H. 1954. Free-living flatworms (Turbellaria) of the Gulf of Mexico. Fishery bulletin. United States Fish and Wildlife Service 55: 301 - 302. Available from https: // www. biodiversitylibrary. org / item / 22622 page / 321 / mode / 1 up [accessed 18 Dec. 2020].","Laidlaw F. F. 1903. On the marine fauna of Zanzibar and British East Africa, from collections made by Cyril Crossland in the years of 1901 and 1902. - Turbellaria Polycladida. Part I. The Acotylea. Proceedings of the Zoological Society of London 1903 (2): 99 - 13. Available from https: // www. biodiversitylibrary. org / item / 98617 page / 145 / mode / 1 up [accessed 18 Dec. 2020].","Quiroga S. Y. 2008. Systematics and Taxonomy of Polyclad Flatworms with a special emphasis on the morphology of the nervous system. Ph Thesis, University of New Hampshire, USA. Avalilable from http: // search. proquest. com / docview / 304525403 [accessed 18 Dec. 2020].","Marcus E. & Marcus Er. 1968. Polycladida from Curacao and faunistically related regions. Studies on the Fauna of Curacao and other Caribbean Islands 26: 1 - 133. Available from https: // repository. naturalis. nl / pub / 506072 [accessed 18 Dec. 2020].","Stimpson W. 1857. Prodromus descriptionis animalium evertebratorum, quae in Expeditione ad Oceanum Pacificum Septentrionalem, Johanne Rodgers Duce a Republica Federata missa, observavit et descripsit. Pars I, Turbellaria Dendrocoela. Proceedings of the Academy of Natural Sciences of Philadelphia 9: 19 - 31. https: // doi. org / 10.5962 / bhl. title. 51447","Schmarda L. K. 1859. Neue wirbellose Thiere beobachtet und gesammelt auf einer Reise um die Erde 1853 bis 1857. Bd I: Neue Turbellarien, Rotatorien und Anneliden. W. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 85313","Blanchard E. 1847. Recherches sur l'organisation des vers. Annales des Sciences naturelles. Zoologie 7: 87 - 128, 8: 119 - 149, 271 - 275. https: // doi. org / 10.5962 / bhl. title. 51506","Marcus E. 1950. Turbellaria Brasileiros (8). Boletim da Facultade de Philosophia, Sciencias e Letras, Universidade de Sao Paulo. Zoologia 15: 5 - 190. https: // doi. org / 10.11606 / issn. 2526 - 4877. bsffclzoologia. 1950.125192","Marcus E. 1952. Turbellaria Brasileiros (10). Boletim da Facultade de Philosophia, Sciencias e Letras, Universidade de Sao Paulo. Zoologia 17: 5 - 186. https: // doi. org / 10.11606 / issn. 2526 - 4877. bsffclzoologia. 1952.125189","Bock S. 1925. Papers from Dr. Th. Mortensen's Pacific Expedition 1914 - 16. XXVII. Planarians, Pt. IV. New stylochids. Videnskabelige meddelelser fra den Naturhistoriske forening i Kjobenhavn 79: 97 - 184. https: // doi. org / 10.5962 / bhl. title. 82330","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545"]}

Parviplana sodade sp. nov. urn:lsid:zoobank.org:act: 10171C70-7431-41EF-B39D-AC3982D24143 Figs 1C, 4 A–C Etymology The name of the new species, Parviplana sodade, comes from ‘sodade’ the Cape Verdean expression for saudade and regional song with rhythms of ‘coladeira’. Material examined Holotype CAPE VERDE • São Vicente Island, Mindelo; 16°53′46.54″ N, 24°59′32.93″ W (Fig. 1C V1); 24 Nov. 2017; Leopoldo Moro leg.; MNCN 4.01/2699 to 2708 (10 slides). One sagittally sectioned specimen stained with AZAN. Description BODY. Shape oval elongated. Length 0.8 cm. Smooth dorsal surface. Background pigmentation light white, transparent where the intestinal braches can be appreciated (Fig. 4 A–B). Four clusters of cerebral eyes, two anterior with few eyes and more elongated than the posterior two. In sum around 50 cerebral eyes (Fig. 4B). Ruffled pharynx. Male and female genital pores located in the posterior half of the body. MALE REPRODUCTIVE SYSTEM. Directed backwards and with a dorso-ventrally oriented penis papilla. With elongated prostatic vesicle, tall granular lining included in the muscular penis bulb (Fig. 4C). The vasa deferentia enter the seminal vesicle separately. Seminal vesicle rounded, below the penis bulb and connected with a sort seminal duct to the prostatic vesicle (Fig. 4C). The male atrium is small and thin, with an internal fold that surrounds the distal part of the penis bulb like a penis sheath (Fig. 4C). FEMALE REPRODUCTIVE SYSTEM. With a vagina bulbosa (Fig. 4C) and backwards oriented. Cement and shell glands open in a pouch located within the vaginal complex. Lang’s vesicle present. Remarks Parviplana sodade sp. nov belongs to the genus Parviplana due to the absence of tentacles, presence of seminal vesicle, and prostatic vesicle with a tall granular lining with prostatic functions. Female apparatus with vagina bulbosa and Lang´s vesicle. Parviplana comprises 3 species, P. hymani Faubel, 1983, P. jeronimoi Pérez-García, Noreña & Cervera, 2018 and P. lynca (Du Bois-Reymond Marcus, 1958). Parviplana lynca can be easy and clearly distinguished from the other two species by the presence of nuchal tentacles, exclusive of this species. Parviplana hymani can be distinguished from P. sodade sp. nov., by the vas deferens which opens together into the seminal vesicle, and the prostate vesicle not included into de penis bulb. Parviplana sodade sp. nov. possesses more similarities with P. jeronimoi. Both species share the penis sheath and more than 25 cerebral eyes, but clear differences separate them. Parviplana jeronimoi has a fleshy appearance and amber pigmentation. The size is also noticeable different, P. jeronimoi can reach lengths of 20 mm, while P. sodade in full mature state does not reach 8 mm. Parviplana jeronimoi also presents vasa deferentia joined in a single vas deferens, a small female atrium and a corrugated surface between the two genital pores, characteristics not present in P. sodade., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 19-20, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Faubel A. 1983. The Polycladida, Turbellaria; Proposal and establishment of a new system. Part I. The Acotylea. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 80: 17 - 121."]}

Anonymus ruber Cuadrado, Moro & Noreña, 2017 Figs 1C, 7A Material examined CAPE VERDE • 3 specs; São Vicente Island, Baía das Gatas; 16°54′09.33″ N, 24°54′25.25″ W (Fig. 1C V 2); May 2017; Leopoldo Moro leg.; RCCN. Distribution Tenerife Island, Canary Islands (type locality) (Cuadrado et al. 2017). New record Baía das Gatas, S„o Vicente Island, Cape Verde. Remarks Anonymous ruber is characterized by reddish brown tones, but some individuals from Cape Verde are paler and presented cream tonalities. From an anatomical (internal or external) and molecular point of view, the species found in Cape Verde does not differ from the species in the Canary Islands (Fig. 8)., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on page 27, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Cuadrado C., Moro L. & Norena C. 2017. The Polycladida (Platyhelminthes) of the Canary Islands. New genus, species and records. Zootaxa 4312: 38 - 68. https: // doi. org / 10.11646 / zootaxa. 4312.1.2"]}

Marcusia alba sp. nov. urn:lsid:zoobank.org:act: DE4AF1C8-D784-4AB7-B536-A1E88524115B Figs 1C, 2 Etymology The name of the new species, Marcusia alba, comes from the Latin ‘ albus ’ (white), and refers to the ivory white coloration this species shows. Material examined (3 specs) Holotype CAPE VERDE • São Vicente Island, Mindelo; 16°53′46.54″ N, 24°59′32.93″ W (Fig. 1C V1); 6 May 2017; Leopoldo Moro leg.; MNCN 4.01/2620 to 2683 (64 slides). One sagittally sectioned specimen stained with AZAN. Additional material CAPE VERDE • 2 specs; São Vicente Island, Baía das Gatas; 16°54′09.33″ N, 24°54′25.25″ W (Fig. 1C V 2); 6 May 2017; Leopoldo Moro leg.; RCCN. Description BODY. Shape oval. Length 2.6 cm. Smooth dorsal surface. Background pigmentation ivory white, darker along the middle dorsal region of the body. Amber dots and thin brushstroke-like lines garnish the dorsal surface. A thin, dark stripe, sometimes interrupted, extends along the central dorsal line (Fig. 2A). Two delicate marginal folds, separate and pointed, could be interpreted as pseudotentacles. Tentacular eyes scarce and widely dispersed over the tentacles. Cerebral eyes anterior drop-shaped and crossed by the central midline. Marginal eyes only at the anterior part (Fig. 2B). Ruffled pharynx, in the middle of the body with a central oral pore. Ventral sucker at the posterior part of the body. Male and female genital pore lead in a common genital atrium (Fig. 2 D–E) that opens in the posterior body region after the pharynx (Fig. 2C). MALE REPRODUCTIVE SYSTEM. Male copulatory organ backwards oriented, with a muscular penis papilla, very muscular seminal vesicle (Fig. 2C, E) and without a prostatic vesicle, instead a simple glandular epithelium leads into the penis papilla (Fig. 2 D–E). Seminal vesicle rounded, frontal oriented and with thick muscular walls, opening into the ejaculatory duct. Short ejaculatory duct opens into the penis papillae. The male atrium is small and thin, connected to the common atrium. FEMALE REPRODUCTIVE SYSTEM (Fig. 2C, E). The vagina runs from the common genital atrium and continues dorsally into a narrowed duct that widens into a chamber, the cement pouch. The vagina continues dorsally, then curves posteriorly and ventrally and ends with the entry of the oviducts. Remarks Marcusia alba sp. nov. belongs to the genus Marcusia due to the presence of cerebral, frontal and marginal eyes, male copulatory organ enclosed in a muscular bulb, the absence of prostatic vesicle and the common male and female atrium genital, as well as the common gonopore. The genus Marcusia contained only one species, Marcusia ernesti Hyman, 1953, known from the coast of the Gulf of California (Hyman 1953). Marcusia ernesti and M. alba sp. nov. can be easily distinguished by their coloration patterns. Marcusia ernesti is black or grey with darker splotches and dotted with white spots, only visible in preserved individuals after Hyman (1953), M. alba sp. nov. is ivory white with brownish dots and stripes. The penis papilla is spherical in M. alba and elongated in M. ernesti, with the male atrium being tube-like and longer in the Californian species. Another difference lies in the eyes’ presence and distribution. Marcusia ernesti presents marginal, frontal and cerebral eyes as well as two characteristic eye clusters with diagnostic value (Hyman 1953). Marcusia alba sp. nov., on the other hand, has cerebral, marginal and tentacular eyes, but not frontal eyes or eye clusters. The differences listed are enough to consider M. ernesti and M. alba sp. nov. as two different species of the same genus. Furthermore, the molecular analyses show the genus Marcusia (represented in this case by Marcusia alba sp. nov.) as a genus closely related to Pericelis Laidlaw, 1902 within the family Anonymidae Lang, 1884, but as a clearly independent genus., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 14-16, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Hyman LH. 1953. The polyclad flatworms of the Pacific coast of North America. Bulletin of the American Museum of Natural History 100: 269 - 391. Available from http: // hdl. handle. net / 2246 / 1028 [accessed 28 Jan. 2021].","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545"]}

Stylochus salis sp. nov. urn:lsid:zoobank.org:act: 8A640FC8-D74C-4617-9766-F0FB9806BD4B Figs 1C, 5 A–D Etymology The name of the new species, Stylochus salis refers to the type locality, Sal, a Cape Verdean Island. Material examined (2 specs) Holotype CAPE VERDE • Sal Island, Calheta Funda; 16°39′03.34″ N, 22°56′42.94″ W (Fig. 1C V 3); 12 Nov. 2018; Leopoldo Moro leg.; MNCN 4.01/2719 to 2723 (5 slides). One sagittal sectioned specimen stained with AZAN. Additional material CAPE VERDE • 1 spec.; Sao Vicente Island, Mindelo (Fig. 1C V1); 16°53′46.54″ N, 24°59′32.93″ W; 6 May 2017; Leopoldo Moro leg.; RCCN. Description BODY. Shape elongated. Length 0.4 cm. Smooth dorsal surface. Background pigmentation cream white with an orange internal outline, sometimes interrupted, along the body margin and bordered by a white/ creamy outer band (Fig. 5A). Few cerebral and marginal eyes, scattered between the tentacles and anterior end (Fig. 5C). Two small nuchal tentacles with abundant basal eyes (Fig. 5B). Ruffled pharynx in the middle of the body and the oral pore in the end of the pharynx pouch and close to the gonopores. Male and female gonopores located close together in the posterior end of the body. MALE REPRODUCTIVE SYSTEM. Male copulatory organ backwards oriented and provided with an inconspicuous unarmed penis papilla. Prostatic vesicle muscular with granular lining (polyglandulartype after Bulnes et al. 2005) (Fig. 5D). Seminal vesicle elongated, empties at the distal end of the prostatic vesicle. The short penis papilla and ejaculatory duct emerge in a small male atrium (Fig. 5D). FEMALE REPRODUCTIVE SYSTEM. Shows the characteristic configuration of the genus. A tubiform canal with s-shaped ending in a small widening. Remarks Stylochus salis sp. nov. belongs to the genus Stylochus due to the presence of gonopores separate and arranged in the second body half. With large and much ruffled pharynx. Tentacular, cerebral, marginal, and often frontal eye-spots present. Male copulatory apparatus with seminal vesicle and papillate penis. Lang’s vesicle lacking (after Faubel 1983). Stylochus salis sp. nov. clearly differs from other known species of Stylochus Ehrenberg, 1831 by its peculiar cream pigmentation bordered with the internal orange outline and the white/creamy outer band. The color of the eastern Atlantic known species (S. alexandrinus, S. castaneus Palombi, 1939, S. neapolitanus, S. plessissii Lang, 1884, and S. suesensis Ehrenberg, 1831) varies between brown, light brown, reddish or beige and spotted as in S. neapolitanus. None of them present a continuous (or discontinuous) marginal line. The most conspicuous anatomical feature is the location of the oral pore, very close to the gonopore, clearly different from the central position of the oral pore in this genus. The peculiar location of the oral and genital pores distinguishes S. salis sp. nov. from the remaining species. Such a close location of the pores could only be found in the genus Latocestus Plehn, 1896 (Latocestidae, Stylochoidea)., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 22-23, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Bulnes V., Faubel A. & Park J. - K. 2005. Two new marine species from South Korea with remarks on the family Stylochidae (Acotylea, Polycladida, Plathelminthes). Journal of Natural History 39 (23): 2089 - 2107. https: // doi. org / 10.1080 / 00222930500081997","Faubel A. 1983. The Polycladida, Turbellaria; Proposal and establishment of a new system. Part I. The Acotylea. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 80: 17 - 121.","Palombi A. 1939. Turbellari del Sud Africa. Policladi di East London. Archivio zoologico italiano 28: 123 - 149.","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545","Plehn M. 1896. Neue Polycladen, gesammelt von Herrn Kapitan Chierchia bei der Erdumschiffung der Korvett Vettor Pisani, von Herrn Prof. Dr. K ʾ kenthal im nordlichem Eismeer und von Herrn Prof Dr. Semon in Java. Jenaische Zeitschrift fur Naturwissenschaft 30: 137 - 181. Available from https: // www. biodiversitylibrary. org / item / 43546 page / 147 / mode / 1 up [accessed 18 Dec. 2020]."]}

Prostheceraeus moseleyi Lang, 1884 Figs 1A, 7C Material examined AZORES • 1 spec.; São Miguel Island; 37°44′59.23″ N, 25°37′12.12″ W (Fig. 1A 1); 22 Jul. 2001; Leopoldo Moro leg.; RCCN. Distribution Tyrrhenian Sea (Lang 1884); Ria de Arosa, Spain (Noreña et al. 2015). This species has also been cited by DORIS (Données d’Observations pour la Reconnaissance et l’Identification de la faune et la flore Subaquatiques) for the English Channel and the North Sea, from the south of the United Kingdom to the Bay of Biscay (Spain) (http://doris.ffessm.fr/Especes/Prostheceraeus-moseleyi-Planaire-tachetee-716). New record S„o Miguel Island, Azores. Remarks The specimen collected in the Azores presents similar coloration to the specimen photographed by Wirtz & Debelius (2003) and determined as Euryleptidae sp., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on page 27, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545","Norena C., Rodriguez J., Perez J. & Almon B. 2015. New Acotylea (Polycladida, Platyhelminthes) from the east coast of the North Atlantic Ocean with special mention of the Iberian littoral. Zootaxa 4039: 157 - 172. https: // doi. org / 10.11646 / zootaxa. 4039.1.7","Wirtz P. & Debelius H. 2003. Mediterranean and Atlantic Invertebrate Guide. ConchBooks, Hackenheim."]}

Planocera pellucida (Mertens, 1833) Figs 1B, 7J Planaria pellucida Mertens, 1833: 8–13, pl. 1 Stylochus pellucidus – Ehrenberg 1836: 67. — Diesing 1850: 216. — Claparède 1861: 143. — Moseley 1877: 23. Planocera pellucida – Örsted 1844: 48. Gnesioceros pellucidus – Diesing 1862: 571. Material examined MADEIRA • 1 spec.; 32°41′18.52″ N, 16°58′57.36″ W (Fig. 1B); 2000; Leopoldo Moro leg.; RCCN. Distribution Atlantic Ocean, between Newfoundland and Ireland (type locality) (Mertens 1833); Pacific Ocean (Graff 1892; Woodworth 1894; Plehn 1896); Canary Islands (De Vera et al. 2009; Cuadrado et al. 2017); Vietnam (Dawydoff 1952); the North Sea (Prudhoe 1982); Japan (Kato 1938); the Mediterranean Sea (Lang 1879, 1884; Riedl 1959; Marquina et al. 2014); pelagic fauna of the Atlantic Ocean (Graff 1892; Plehn 1896); Cape Verde and Ascension islands (Plehn 1896; Laidlaw 1903); New record Madeira. Remarks Planocera pellucida, together with Pseudoceros wirtzi, Pseudoceros cf. maximus and Prostheceraeus giesbrechtii are the three polyclad species currently recorded for Madeira. As can be seen in Fig. 7J. The specimens of Planocera pellucida from Madeira do not differ molecularly from those captured in the Canary Islands., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on page 31, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Mertens H. 1833. Untersuchungen ʾ ber den inneren Bau verschiedener in der See lebender Planarien. Memoires de l'Academie imperiale des Sciences de Saint Petersbourg. 6 eme serie, Sciences mathematiques, physiques et naturelles 2: 3 - 17. Available from https: // www. biodiversitylibrary. org / item / 247344 page / 13 / mode / 1 up [accessed 18 Dec. 2020].","Ehrenberg C. G. 1836. Uber die Akalephen des rothen Meeres und der Organismus der Medusen der Ostsee. Abhandlungen der Koniglichen Akademie der Wissenschaften zu Berlin 1835: 181 - 260. Available from https: // www. biodiversitylibrary. org / item / 94127 page / 269 / mode / 1 up [accessed 18 Dec. 2020].","Diesing C. M. 1850. Systema Helminthum. I. W. Braum ʾ ller, Vienna [Vindobonae]. https: // doi. org / 10.5962 / bhl. title. 46846","Claparede E. 1861. Etudes anatomiques sur les annelides, turbellaries, opalines et gregarines observes dans les Hebrides. Memoires de la Societe des physique et d'histoire naturelle de Geneve 16 (4): 56 - 80, 124 - 148, 151 - 152. https: // doi. org / 10.5962 / bhl. title. 14795","Moseley H. N. 1877. On Stylochus Pelagicus, a new species of pelagic planarian, with notes on other pelagic species, on the larval forms of Thysanozoon, and of a gymnosomatous pteropod. Microscopical Journal 17: 23 - 32.","Diesing C. M. 1862 [1861]. Revision der Turbellarien. Abtheilung: Dendrocoelen. Sitzungsberichte der mathematischen naturwissenschaftlichen Classe der kaiserlichen Akademie der Wissenschaften zu Wien 44: 485 - 578. https: // doi. org / 10.5962 / bhl. title. 2108","Graff L. 1892. Pelagische Polycladen. Zeitschrift fur wissenschaftliche Zoologie 55: 189 - 219. Available from https: // www. biodiversitylibrary. org / item / 138505 page / 199 / mode / 1 up [accessed 18 Dec. 2020].","Woodworth W. M. 1894. Report on the Turbellaria (Albatross-Report 9). Bulletin of the Museum of Comparative Zoology at Harvard College 25: 49 - 52. Available from https: // www. biodiversitylibrary. org / item / 95212 page / 69 / mode / 1 up [accessed 18 Dec. 2020].","Plehn M. 1896. Neue Polycladen, gesammelt von Herrn Kapitan Chierchia bei der Erdumschiffung der Korvett Vettor Pisani, von Herrn Prof. Dr. K ʾ kenthal im nordlichem Eismeer und von Herrn Prof Dr. Semon in Java. Jenaische Zeitschrift fur Naturwissenschaft 30: 137 - 181. Available from https: // www. biodiversitylibrary. org / item / 43546 page / 147 / mode / 1 up [accessed 18 Dec. 2020].","De Vera A., Moro L., Bacallado J. J. & Hernandez F. 2009 [2008]. Contribucion al conocimiento de la biodiversidad de policlados (Platyhelminthes, Turbellaria) en las Islas Canarias. Revista de la Academia Canaria de Ciencias 20: 45 - 59. Available from https: // mdc. ulpgc. es / cdm / ref / collection / racc / id / 323 [accessed 18 Dec. 2020].","Cuadrado C., Moro L. & Norena C. 2017. The Polycladida (Platyhelminthes) of the Canary Islands. New genus, species and records. Zootaxa 4312: 38 - 68. https: // doi. org / 10.11646 / zootaxa. 4312.1.2","Dawydoff C. N. 1952. Contribution a l'etude des invertebres de la faune marina benthique de l'Indochine. Bulletin scientifique de la France et de la Belgique 39: 1 - 108.","Prudhoe S. 1982. Polyclad turbellarians from the southern coasts of Australia. Records of the South Australian Museum 18: 361 - 384. Available from https: // www. biodiversitylibrary. org / item / 127010 page / 380 / mode / 1 up [accessed 18 Dec. 2020].","Kato K. 1938. On a pelagic polyclad, Planocera pellucida (Mertens) from Japan. Zoological Magazine (Japan) 50: 230 - 232.","Lang A. 1879. Untersuchungen zur vergleichenden Anatomie und Histologie des Nervensystems der Plathelminthen. I. Das Nervensystem der marinen Dendrocoelen. Mittheilungen aus der Zoologischen Station zu Neapel 1: 459 - 488. Available from https: // www. biodiversitylibrary. org / item / 37435 page / 477 / mode / 1 up [accessed 18 Dec. 2020].","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545","Riedl R. 1959. Turbellarien aus submarinen Hohlen. 3. Seriata und Neorhabdocoela. Ergebnisse der Osterreichischen Tyrrhenia-Expedition 1952. Teil IX. Pubblicazioni della Stazione zoologica di Napoli Suppl. 30: 305 - 332.","Marquina D., Osca D., Rodriguez J., Fernandez-Despiau E. & Norena C. 2014. State of knowledge of the Acotylea (Polycladida, Platyhelminthes) from the Mediterranean coasts of Spain: new records and new species. Zootaxa 3780: 108 - 134. https: // doi. org / 10.11646 / zootaxa. 3780.1.4","Laidlaw F. F. 1903. On the marine fauna of Zanzibar and British East Africa, from collections made by Cyril Crossland in the years of 1901 and 1902. - Turbellaria Polycladida. Part I. The Acotylea. Proceedings of the Zoological Society of London 1903 (2): 99 - 13. 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Cycloporus gabriellae Marcus, 1950 Figs 1C, 7B Material examined CAPE VERDE • 1 spec.; São Vicente Island, Mindelo; 16°53′46″ N, 24°59′32.93″ W (Fig. 1C V1); May 2017; Leopoldo Moro leg.; RCCN. Distribution S„o Sebasti„o Isle, Brazil (Marcus 1950); S„o Paulo, Brazil (Marcus 1952); Antigua and Barbuda; Curaç„o, Netherlands Antilles; Isla de Aves, Venezuela (Marcus & Marcus 1968). New record Mindelo, S„o Vicente Island, Cape Verde. Remarks The specimens of Cycloporus gabriellae captured in Cape Verde summarize the original description of C. gabriellae published by Marcus (1950), but differ externally and in coloration from C. gabriellae of Cabo Frio, Brazil (Bahia et al. 2014). This is the first record in the eastern region of the Atlantic Ocean for the species., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on pages 25-27, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Marcus E. 1950. Turbellaria Brasileiros (8). Boletim da Facultade de Philosophia, Sciencias e Letras, Universidade de Sao Paulo. Zoologia 15: 5 - 190. https: // doi. org / 10.11606 / issn. 2526 - 4877. bsffclzoologia. 1950.125192","Marcus E. 1952. Turbellaria Brasileiros (10). Boletim da Facultade de Philosophia, Sciencias e Letras, Universidade de Sao Paulo. Zoologia 17: 5 - 186. https: // doi. org / 10.11606 / issn. 2526 - 4877. bsffclzoologia. 1952.125189","Marcus E. & Marcus Er. 1968. Polycladida from Curacao and faunistically related regions. Studies on the Fauna of Curacao and other Caribbean Islands 26: 1 - 133. Available from https: // repository. naturalis. nl / pub / 506072 [accessed 18 Dec. 2020].","Bahia J., Padula V., Passeri Lavrado H. & Quiroga S. 2014. Taxonomy of Cotylea (Platyhelminthes: Polycladida) from Cabo Frio, southeastern Brazil, with the description of a new species. Zootaxa 3873: 495 - 525. https: // doi. org / 10.11646 / zootaxa. 3873.5.3"]}

Stylochus sp. Figs 1A, 7H Material examined AZORES • 1 spec.; São Miguel Island, Ponta Delgada; 37°44′59.23″ N, 25°37′12.12″ W (Fig. 1A A1); 22 Jul. 2001; Leopoldo Moro leg.; RCCN. New record São Miguel Island, Azores. This is the first record for the genus Stylochus in the Azores. No molecular data., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on page 30, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525

Monobiceros langi Faubel, 1984 Figs 1 C–D, 7E Pseudoceros maximus Lang, 1884 (in part): 270–271, 543, pl. 30, fig. 17. Monobiceros langi Faubel, 1984: 215. Material examined CAPE VERDE • 1 spec.; São Vicente Island, Baía das Gatas; 16°54′09.33″ N, 24°54′25.24″ W (Fig. 1C V 2); May 2017; Leopoldo More leg.; RCCN. MOROCCO • 3 specs; Sidi Ifni; 29°22′58.00″ N, 10°10′37.88″O (Fig. 1D M 2); 2 Sep. 2016; Leopoldo Moro leg.; RCCN. Distribution Gulf of Naples, Italy (Lang 1884); Cádiz, Spain (Bahia et al. 2017); Crete, Greece (Bahia et al. 2017). New records Baía das Gatas, São Vicente Island, Cape Verde. Sidi Ifni, Morocco. These are the first records outside the Mediterranean Sea. Description Body oval and elongated sometimes pear-shaped, with wavy margins and thickened dorsal midline. Length 2.3 cm. The background color varies with transmitted or reflected light. With reflected light, the dorsal surface is chocolate brown, speckled with white patches. Under transmitted light, the pigmentation looks milky brown with dark margins and a dark dorsal midline that delimited the characteristic bulge (Fig. 7E). Dorsal surface smooth. Tentacles formed by simple folds and cone-like in shape. Cerebral eyes form a single large rounded cluster behind the tentacles; frontal eyes scattered between the tentacles. Compact ruffled pharynx located directly behind the cerebral eyes., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on page 29, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Faubel A. 1984. The Polycladida, Turbellaria; Proposal and establishment of a new system. Part II. The Cotylea. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut 81: 189 - 259.","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545","Bahia J., Padula V. & Schrodl M. 2017. Polycladida phylogeny and evolution: integrating evidence from 28 S rDNA and morphology. Organisms Diversity & Evolution 17: 653 - 678. https: // doi. org / 10.1007 / s 13127 - 017 - 0327 - 5"]}

Eurylepta cornuta var. melobesiarum (Schmidtlein, 1880) Figs 1C, 6 Material examined CAPE VERDE • 1 spec.; São Vicente Island, Baía das Gatas; 16°54′09.33″ N, 24°54′25.25″ W (Fig. 1C V 2); May 2017; Leopoldo Moro leg.; RCCN. Distribution Ireland (Thompson 1845); Norway (M̹ller 1776); northwest France (Keferstein 1868); United Kingdom (Gamble 1893). New record S„o Vicente Island, Cape Verde. Description Body shape oval. Length 0.5 cm. Smooth dorsal surface; background color red-orange, with white dots scattered over the dorsal surface (Fig. 6 A–C). Ventral sucker in the posterior half of the body (Fig. 6F). Small tentacles. Few tentacular eyes distributed frontally and at the base of the tentacles. Cerebral eyes fused in a single elongated oval cluster (Fig. 6B). Ruffled pharynx located at the anterior third of the body. Oral pore posterior to the cerebral ganglion. The reproductive system coincides with the original description, presenting the characteristic fold in front of the female genital pore mentioned by Lang (1884) for some specimens (Fig. 6 D–F)., Published as part of Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, pp. 1-43 in European Journal of Taxonomy 736 on page 25, DOI: 10.5852/ejt.2021.736.1249, http://zenodo.org/record/4561525, {"references":["Thompson W. 1845. Additions to the Fauna of Ireland, including descriptions of some apparently new species of Invertebrata. The Annals and Magazine of Natural History 15: 308 - 322. https: // doi. org / 10.1080 / 037454809495331","Keferstein W. 1868. Beitrage zur Anatomie und Entwicklungsgeschichte einiger Seeplanarien von St. Malo. Abhandlungen der Koniglichen Gesellschaft der Wissenschaften zu Gottingen, 14: 1 - 38. Available from https: // www. biodiversitylibrary. org / item / 109993 page / 26 / mode / 1 up [accessed 28 Jan. 2021].","Gamble FW. 1893. British Marine Turbellaria. Contributions to a knowledge of British marine Turbellaria. Quarterly Journal of Microscopical Science 34: 433 - 452. Available from https: // www. biodiversitylibrary. org / item / 49113 page / 443 / mode / 1 up [accessed 28 Jan. 2021].","Lang A. 1884. Die Polycladen (Seeplanarien) des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie. Fauna und Flora des Golfes von Neapel 11. Engelmann, Leipzig. https: // doi. org / 10.5962 / bhl. title. 10545"]}