taxonID	type	description	language	source
8C6887DA3078C47AFC39A112D26AAC07.taxon	diagnosis	Diagnosis: Catenulida with lobulate preoral cerebral ganglia. Occasionally with ciliated pits. Asexual reproduction by paratomy. Brain formed by paired lobulate ganglia. Excretophores generally present. Male genital pore dorsal, at mouth level.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3078C47AFC39A112D26AAC07.taxon	type_taxon	Type genus: Stenostomum O. Schmidt, 1848	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3078C47BFC39A235D78DACEF.taxon	diagnosis	Diagnosis: Catenulida without either statocyst or preoral ciliated furrow. Large brain formed by a pair of anterior lobes, connected to each other by means of a transverse commissure in their posterior region, and a pair of posterior lobes. Paired ciliated pits associated with the anterior cerebral lobes. Light-refracting bodies present; number, composition and arrangement variable; frequently associated with the posterior cerebral lobes. Epithelial rhabdites and excretophores present in numerous species. Asexual reproduction as the main reproductive mechanism. Gonads known only for some species; the single testis is antero-dorsal and the ovary mid-ventral.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3078C47BFC39A235D78DACEF.taxon	type_taxon	Type species: Stenostomum leucops (Dugès, 1828) O. Schmidt, 1848.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3078C47BFC39A235D78DACEF.taxon	distribution	Distribution: Cosmopolitan.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3078C47BFC39A235D78DACEF.taxon	discussion	Valid species: See below for South American species, and Table 1 for species recorded only in other world regions.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3079C47BFFBDA34DD3E3AD69.taxon	diagnosis	Diagnosis: Stenostomidae without ciliated pits. Anterior end very prolonged (proboscidean body prolongation). Nerve ganglia form 8 – 14 pairs of sensory plates at the anterior end. Two pairs of anterior longitudinal nerves and four pairs of posterior nerves. Excretophores frequently present. Presence of larval stage (Luther’s larva), with statocyst and division by paratomy. Adult with or without statocyst and without paratomy.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3079C47BFFBDA34DD3E3AD69.taxon	type_taxon	Type species: Rhynchoscolex simplex Leidy, 1851.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3079C47BFFBDA34DD3E3AD69.taxon	distribution	Distribution: Europe, North and South America, Japan.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3079C47BFFBDA34DD3E3AD69.taxon	discussion	Valid species: Rhynchoscolex diplolithicus Reisinger, 1924; R. evelinae Marcus, 1945; R. platypus Marcus, 1945; R. pusillus Marcus, 1945; R. nanus Marcus, 1945; R. remanei Rixen, 1961.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A014D799AC6A.taxon	diagnosis	Diagnosis: Stenostomidae without light-refracting bodies. Developed anterior brain lobe with ‘ metamerically’ arranged ganglia. Posterior brain lobe simple, or poorly developed. Ciliated pits present, associated with the anterior brain lobe. Pharyngeal glands generally arranged homogeneously along the whole of the pharynx. Epithelial rhabdites present. Sensory cilia or bristles present. Excretophores present. Asexual reproduction by paratomy.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A014D799AC6A.taxon	type_taxon	Type species: Anokkostenostomum anatirostrum (Marcus, 1945) comb. nov.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A014D799AC6A.taxon	distribution	Distribution: Brazil, Surinam, Kenya, England, Finland, France, Poland, Italy, USA.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A014D799AC6A.taxon	discussion	Valid species: See below for South American species and Table 1 for species recorded only in other world regions.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A494D659A805.taxon	diagnosis	Diagnosis: Stenostomidae with ciliated pits and muscular intestine. Asexual reproduction by paratomy. Chains of zooids present.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A494D659A805.taxon	type_taxon	Type species: Myostenostomum tauricum (Nassonov, 1923) Luther, 1960.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A494D659A805.taxon	distribution	Distribution: Europe, North America and South America.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A494D659A805.taxon	discussion	Valid species: Myostenostomum bulbocaudatum Luther, 1960.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A291D3FDAF51.taxon	description	(Fig. 1 A) Description: Isolated specimens up to 0.7 mm long. Chains of up to nine zooids, with different degree of development. Elongated body, with dorso-lateral ciliated pits, anterior end slightly tapering. With constriction at the level of the oral pore. Posterior end with intestine-lacking region. Homogeneous ciliated epithelium without longer sensory cilia. Sparse small rhabdites on the ventral surface. Colour in life whitish. Cerebral ganglia with deeply dentate anterior brain lobes and a pair of internal lobes associated with the posterior ones (trilobate brain after Marcus, 1945 a). Two light-refracting bodies, with more than ten spherical corpuscles (type 1), associated with the posterior lobes. Oral pore oval. Pharynx large (greater than 1 / 5 of the body length). Two types of pharyngeal glands: (1) antero-ventral rounded glands (type a) and (2) groups of elongated club-shaped glands (type b) laterally in the posterior half of the pharynx. Transition between pharynx and intestine regulated by a muscular sphincter. Intestine with excretophores. Nephridiopore opens at the posterior intestine-lacking region.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A291D3FDAF51.taxon	distribution	Distribution: São Paulo and interior of São Paulo State, Brazil (Marcus, 1945 b). Los Talas, Berisso, Buenos Aires, Argentina, September 1998, December 1998 to January 1999, April 1999 to July 1999, December 1999 to February 2000 and May 2000. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A291D3FDAF51.taxon	materials_examined	Stored material: Ten sagittally sectioned specimens in the CHMLP. No. 5303.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A291D3FDAF51.taxon	discussion	Discussion: S. amphotum was synonymized to S. leucops (de Beauchamp, 1948; Luther, 1960), owing to the difficulty in recognizing differences in the arrangement of the pharyngeal glands. The type and arrangement of the pharyngeal glands and the layout of the rhabdites, the number of brain lobes, and the sphincter between pharynx and intestine, are enough to separate both species. On the other hand, a cladistic analysis (our unpubl. data) confirms the independence of S. amphotum and S. leucops.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A66FD603AE38.taxon	diagnosis	Diagnosis: Stenostomidae without preoral ciliated furrow. With very specialized evaginable paired ciliated pits. Light-refracting bodies present. Spots of reddish pigment in the region of the ciliated pits. Welldeveloped brain ganglia in direct contact with the ciliated pits. With only a single pair of longitudinal ventro-lateral nerves. Simple pharynx, with a dorsal band of pharyngeal glands. Without cyrtocites. Asexual reproduction by paratomy. Presence of chains of zooids (generally no more than two).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A66FD603AE38.taxon	type_taxon	Type species: Xenostenostomum microstomoides Reisinger, 1976	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47CFF91A66FD603AE38.taxon	distribution	Distribution: South America, South and Equatorial Africa; Madagascar.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47EFC39A12FD5E6AF13.taxon	description	(Fig. 1 B)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47EFC39A12FD5E6AF13.taxon	description	Description: Solitary individuals 0.6 – 0.8 mm long (minimum 0.35 mm long), diameter 0.13 mm. Chains of two zooids (1 – 1.5 mm) up to seven zooids (2.5 mm). Body cylindrical, slightly flattened ventrally. With post-pharyngeal constriction. Posterior end tapering, with intestine-lacking region, ending in a very long tail. Its proximal region is adhesive, and the posterior end bends upward (Nuttycombe & Waters, 1938; Marcus, 1945 a). Ciliated pits anterior, long and deep. Epidermal cilia longer than the thickness of the epidermis. Caudal region with long semi-rigid sensory cilia. Rod-shaped rhabdites. The epidermal cells with refractory inclusions (other than rhabdites) of several (up to six) corpuscles. White colour in life. Anterior brain lobes deeply dentate. Three pairs of subepidermal light-refracting bodies. The first pair, simple and small, located before the anterior brain lobe. The second pair, simple, at the level of the ciliated pits, above the anterior lobes. The third pair at oral pore level, above the posterior lobes; this pair is frequently the largest and formed by two spheres (type 2). Oral pore rounded, opening between the posterior brain lobes. Muscular pharynx. Pharyngeal glands (type a) opening onto the last two-thirds. A transverse line of cells can be seen ventrally to the pharynx. Conspicuous pharyngeal muscular sphincter. Intestine with a smooth outline ending at the base of the tail. The anterior intestinal region frequently with fine, dark granules. Dorsal excretory pore in the intestinelacking region.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47EFC39A12FD5E6AF13.taxon	distribution	Distribution: Valencia, Spain (Gieysztor, 1931); Virginia (Nuttycombe, 1932 b; Nuttycombe & Waters, 1938); Georgia (Nuttycombe & Waters, 1938; Kolasa, 1991), USA; São Paulo and interior of São Paulo State, Brazil (Marcus, 1945 b); Poznan, Poland (Kolasa, 1973); Kenya (Young & Kolasa, 1974 b); Italy, France and Germany (Lanfranchi & Papi, 1978).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307EC47EFC39A12FD5E6AF13.taxon	discussion	Discussion: Gieysztor (1931) mentions the occasional presence of a terminal excretory vesicle in the region of the excretory pore. The former has not been observed in the South American specimens. Marcus (1945 b) stated that the pharyngeal glands open only onto the posterior pharyngeal region, while Nuttycombe & Waters (1938) mention that the pharyngeal glands open onto the whole pharyngeal length. The transverse line of cells exhibited ventrally to the pharynx is similar to that described for S. paraguayense (Martin, 1908) Luther, 1908.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47EFF91A112D3ACAF12.taxon	description	(Fig. 1 C)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47EFF91A112D3ACAF12.taxon	description	Description: Solitary individuals, 1 – 1.5 mm long. Chains of usually two zooids, 2.5 mm long. Body digitiform, ventrally flattened. Anterior end rounded, with a short mid-dorsal groove. Posterior end with intestine-lacking region, and forming a tail with two appendages (one dorsal, short and thick and one ventral thin, and longer). Front lateral semi-spherical ciliated pits. Homogeneous ciliated epithelium with refractive inclusions. Rhabdites abundant, uniformly distributed, except for two dorsal tracts lacking rhabdites on both sides of the dorsal mid-line. Anterior brain lobes deeply dentate. Three pairs of light-refracting bodies (type 2) anterior and overlapping the sensory cells of the ciliated pits. The two first pairs are formed by a single sphere and the third pair by two or three spheres (rarely four). Oral pore rounded. The pharynx is long, occupying almost half the body. It bears longitudinal creases giving it the appearance of two ‘ oblong sacs’. Welldeveloped circular, dorsal and diagonal musculature. The claw-organ is found on the dorsal wall of the pharynx, behind the oral pore. It comprises six tentacles covered with an adhesive substance and associated with unicellular glands, and is characteristic of this species. The pharyngeal glands (type a) open onto the posterior portion of the pharynx. Presence of a muscular sphincter between the pharynx and the intestine. No excretophores present. The intestine narrows caudally. The dorsal excretory pore opens anteriorly to the dorsal appendage.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47EFF91A112D3ACAF12.taxon	distribution	Distribution: Trinidad (Kennel, 1889); near Paramaribo, Brazil (Marcus, 1945 b); Surinam (Van der Land, 1970); Paraná River, Argentina (Noreña-Janssen, 1995).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47EFF91A112D3ACAF12.taxon	discussion	Discussion: There are several differences between the specimens described by Nuttycombe & Waters (1938) and the South American specimens. These authors mention the presence of chains of up to nine zooids 7 mm long, while in South America only two specimens were found with zooid chains. They also mention the absence of pharyngeal glands. However, Marcus (1945 b) mentions small pharyngeal glands associated with the posterior region of this organ. Marcus (1945 b) describes the body as dorsally flattened and ventrally convex and he states that animals swim with their ventral surface upwards, in disparity with the descriptions of Nuttycombe & Waters (1938) and Noreña-Janssen (1995). Marcus (1945 b) does not mention the heterogeneous arrangement pattern of the rhabdites described for the specimens in North America (Nuttycombe & Water, 1938).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47FFC39A112D5E3A832.taxon	description	(Fig. 1 D)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47FFC39A112D5E3A832.taxon	description	Description: Solitary individuals, 1 mm or less long. Chains with two zooids. Body robust, anterior end blunt. Ciliated pits lateral and superficial. Tapering posterior end with intestine-lacking region. Small epidermal cilia, uniformly distributed, longer at the posterior end. Rod-like rhabdites throughout the entire epidermis. Anterior brain lobes deeply dentate. A pair of lightrefracting bodies associated with the posterior brain lobes; each one formed by one, two or three spheres, included in a colourless vesicle (type 2). Oral pore oval, transversal and surrounded by glands. Wide pharynx. The glands on both sides of the pharynx (type b) open onto the anterior end, and smaller ones (type a) open onto the whole surface. Conspicuous pharyngeal sphincter. Intestinal wall with irregularly distributed excretophores. Nephridiopore ventral, subterminal and posterior to the intestine.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47FFC39A112D5E3A832.taxon	distribution	Distribution: Virginia, USA (Kepner & Carter, 1931; Kolasa, 1991); São Paulo and Paraná State, Brazil (Marcus, 1945 b).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307CC47FFC39A112D5E3A832.taxon	discussion	Discussion: Kepner & Carter (1931) described the ciliated pits as relatively small for the specimens from Virginia and Marcus (1945 b) described them as long and extensive. This author states that this difference would not suffice to separate the species, because they share the rest of the diagnostic characters.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC47FFFBDA603D67CAFFB.taxon	description	(Fig. 1 E) Description: Isolated specimens, 0.4 – 0.5 mm long. Chains of up to six zooids (3 mm long). Anterior end blunt. Body constriction behind the ciliated pits. Tapering posterior end. Large, deep dorso-lateral ciliated pits. Uniformly ciliated epithelium. Scarce semirigid sensory cilia. Rhabdites uniformly distributed. Colour in life white. Brain large and elongated. Anterior brain lobes divided into small independent masses (‘ metamerics’). A pair of light-refracting bodies formed of small spheres included in a vesicle (type 2) associated with the anterior brain lobes. U-shaped oral pore. Short muscular pharynx. Small pharyngeal glands (type a) in the anterior region, elongated glands (type b) in the posterior region. Welldeveloped pharyngeal sphincter. An intestinal caecum with granulose epithelium, dorsal to the pharynx. High intestinal epithelium. Excretophores laterally placed. Nephridiopore terminal or subterminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC47FFFBDA603D67CAFFB.taxon	distribution	Distribution: Georgia, USA (Nuttycombe & Waters, 1935; Kolasa, 1991); São Paulo, Brazil (Marcus, 1945 b).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC47FFFBDA603D67CAFFB.taxon	discussion	Discussion: At variance with the single pair of lightrefracting bodies described by Marcus (1945 b), Nuttycombe & Waters (1935, 1938) describe a second pair, associated with the posterior lobes and larger than the first pair.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC47FFFBDA259D48EAF12.taxon	description	(Fig. 2 A) Description: Isolated specimens 0.6 – 0.8 mm long. Chains of up to 16 zooids which may reach 12 mm long. Anterior end very mobile and retractile. Large, superficial lateral ciliated pits. Presence of ciliated channels or grooves, dorsal or ventral, intimately connected to the brain ganglia. Rosette-shaped gland cells in the epidermis at the anterior end. Each rosette is formed by 2 – 4 refractive, toxic vesicles (Kepner & Carter, 1931). Posterior end truncate. No rhabdites. Colour in life whitish. Anterior lobes of the brain divided into small independent masses (‘ metamerics’). One to three pairs of light-refracting bodies, formed by one or two spheres associated with the anterior brain lobes (type 2). Oral pore very dilatable and surrounded by a layer of muscle. Long muscular pharynx. Numerous clubshaped glands (type b) open onto the pharynx and the oral pore. Intestine extended up to the caudal end. Intestinal epithelium folded, with excretophores. Nephridiopore terminal or subterminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC47FFFBDA259D48EAF12.taxon	biology_ecology	Benthic species, either predatory (Marcus, 1945 b) or scavenger (Kepner & Carter, 1931); mainly feeds on Stenostomum sp., rotifers, oligochaetes, etc.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC47FFFBDA259D48EAF12.taxon	distribution	Distribution: Virginia (Kepner & Carter, 1931; Nuttycombe & Waters, 1938), North Carolina and Georgia (Nuttycombe & Waters, 1938; Kolasa, 1991), USA; São Paulo, Brazil (Marcus, 1945 b); near Onverwacht, Surinam (Van der Land, 1970); Poznan, Poland (Kolasa, 1973); North of Europe, in laboratory aquaria (Lanfranchi & Papi, 1978).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC47FFFBDA259D48EAF12.taxon	discussion	Discussion: Several features relevant for specific identification vary according to different authors. The absence of rhabdites was mentioned by Kepner & Carter (1931) and by Marcus (1945 b). Nuttycombe & Waters (1938) mention the presence of relatively numerous fragile rhabdites in the anterior region and in lesser number in the rest of the body. Kepner & Carter (1931) describe four pairs of lightrefracting bodies associated with the anterior brain lobes. Nuttycombe & Waters (1938) state that the number and position of the light-refracting bodies is variable and each one may be formed by two spheres. Marcus (1945 b) found two or three pairs in the Brazilian specimens.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC471FC25A112D6DBAEC4.taxon	description	(Fig. 2 B)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC471FC25A112D6DBAEC4.taxon	description	Description: Single specimens 1 – 2 mm long, two- to six-zooid chains up to 6 mm long. Body cylindrical, anteriorly rounded. Dorso-lateral ciliated pits longitudinally elongated. Constriction at the level of the oral pore. Posterior end with an intestine-lacking region. Heterogeneous ciliated epithelium, with scarce semirigid sensory cilia. Dorsal epidermis with rhabdites arranged perpendicularly in rosettes. The rhabdites are parallel to the surface in the ventral epidermis, where three longitudinal lines without rhabdites can be seen. Colour in life whitish. From the apical end to the brain, the epidermis bears compact rhabdites giving it a darker colour. Anterior brain lobes deeply dentate. A pair of lightrefracting bodies type 1 associated with the posterior lobes. Dilatable, semicircular oral pore. Pharynx occupying 1 / 5 – 1 / 6 of body length. Pharyngeal glands (type a) in the anterior half. Transition between pharynx and intestine with a narrow sphincter. Excretophores irregularly distributed along the intestine. Nephridiopore proximal to the terminal end.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC471FC25A112D6DBAEC4.taxon	distribution	Distribution: Chicago (Child, 1902), Illinois and New York (Graff, 1913), Pennsylvania (Kepner & Carter, 1931), and Virginia (Nuttycombe & Waters, 1938; Kolasa, 1991), USA; southern Finland (Nassonov, 1924); Kola Peninsula (Nassonov, 1925); St Petersburg (Leningrad) (Nassonov, 1926); São Paulo and Paraná State, Brazil (Marcus, 1945 b); near Onverwacht, Surinam (Van der Land, 1970); Konin Lakes, Poland (Kolasa, 1977). Los Talas, Berisso, Buenos Aires, Argentina, October 1998 to April 1999 and March 2000. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC471FC25A112D6DBAEC4.taxon	materials_examined	Stored material: Ten sagittally sectioned specimens in the CHMLP. No. 5304.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA307DC471FC25A112D6DBAEC4.taxon	discussion	Discussion: Marcus (1945 a) indicates two forms: ‘ typica’ which corresponds to Child’s (1902) description and ‘ megista’ for the specimens coming from Tieté River, São Paulo, Brazil. The difference between these forms is based on body size, brain development, arrangement of the rhabdites and colouring of the pharynx. The specimens from Berisso, Buenos Aires, correspond to the form ‘ typica’. Mature forms of this species have been recognized. Nuttycombe & Waters (1938) and Marcus (1945 b) observed specimens with an unpaired testis at the level of the pharynx and Kepner et al. (1933) found mature female gonads.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3073C471FFBDA144D4FFA9C0.taxon	description	(Fig. 2 C) Description: Adult specimens 1 – 2 mm long. Four- to five-zooid chains, 18 mm long. Body cylindrical. Anterior end blunt. Lateral and reduced ciliated pits. A slight body constriction between the pharynx and the intestine. Rounded posterior end, without intestinelacking region. Abundant semi-rigid cilia in the anterior and posterior regions. Rhabdites grouped in bundles vertically arranged in the epidermis. Colourless in life. Anterior brain lobes separated into small independent masses (‘ metamerics’). Posterior brain lobes enclosing an internal lobe (trilobate brain). A pair of light-refracting bodies, comprising a pear-shaped vesicle (0.01 mm in diameter) and a spherical element, refractory in its inner part (type 2) associated with the posterior lobe. Oral pore rounded. Pharynx very long and provided with lateral, circular, oblique and longitudinal muscular fibres, especially developed on the anterior dorsal region. Finger-shaped glands surround the oral pore. Conspicuous pharyngeal sphincter. Excretophores regularly arranged in the anterior intestinal region; irregular on the rest of the body. Nephridiopore subterminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3073C471FFBDA144D4FFA9C0.taxon	distribution	Distribution: Ukraine, Crimea (Nassonov, 1924); São Paulo, Brazil, in aquaria (Marcus, 1945 a); margins of the Suriname River, near Paramaribo, Surinam (Van der Land, 1970).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3073C471FFBDA144D4FFA9C0.taxon	discussion	Discussion: The description given is based on Marcus’s (1945 a) description for the Brazilian specimens with some differences with the Russian specimens described by Nassonov (1924): the Brazilian specimens have glands only surrounding the oral pore. This feature contrast with the Nassonov description. Nevertheless, these glands are not clear in the original drawings. The posterior brain lobes are larger in the Brazilian specimens and the light-refracting bodies more concave in the Russian specimens. These differences would not suffice to separate them because of other similarities: the proportions of the pharynx and intestine; the space taken up by the intestine; the ciliated pits; the shape of the oral pore; the musculature and the glands surrounding the oral pore (Marcus, 1945 a).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3073C472FC25A05FD5D6AE6B.taxon	description	(Fig. 2 D)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3073C472FC25A05FD5D6AE6B.taxon	description	Description: Length variable. Two-zooid chain 1 – 1.75 mm. Cylindrical body. Rounded or pointed anterior end. Posterior end of the body with intestinelacking region forming a tail. Ciliated epithelium with small rhabdites. Epidermic cilia with rigid sensitive cilia at anterior and occasionally at the posterior end. Colour in life yellowish white. Anterior brain lobes deeply dentate. A pair of type 1 light-refracting bodies associated with the posterior brain lobes. Oral pore shape variable, rounded, triangular or elongated. Simple muscular pharynx. Two types of pharyngeal glands: type a, abundant at the distal end, opening onto the posterior region of the pharynx; and type b, arranged in bunches lateral to the pharynx, opening onto the anterior end. Excretophores present. Nephridiopore subterminal, in the intestine-lacking region.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3073C472FC25A05FD5D6AE6B.taxon	distribution	Distribution: Cosmopolitan. In South America, margins of the Surinam River, near Paramaribo, Surinam (Van der Land, 1970); Paraná River, Argentina (Noreña-Janssen, 1995).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3073C472FC25A05FD5D6AE6B.taxon	discussion	Discussion: Nuttycombe & Waters (1938) consider the validity of this species questionable. This criterion has been followed by Marcus (1945 b). These authors consider that the descriptions of this species are so broad and ambiguous as to make its recognition difficult. By contrast, Borkott (1970) in an exhaustive study of Stenostomum leucops subdivides this species into three new species: S. sthenum, S. platycaudatum and S. plebejum. The results of this research did not confirm the existence of these species in South America (Noreña-Janssen, 1995). Young & Kolasa (1974 b) identified specimens from Africa as S. leucops leucops, on the basis of Luther’s (1960) description, ascribing the differences described by Borkott (1970) to those originated in the cultures or not visible in animals captured in natural environments. In the 1990 s, Reuter (Reuter, 1988, 1991, 1994; Reuter & Palmberg, 1990; Reuter & Eriksson, 1991; Reuter & Kuusisto, 1992; Reuter, Joffe & Palmberg, 1993; Reuter et al., 1995) as well as Wikgren & Thorndyke (1990), Lindroos & Reuter (1991), Palmberg & Reuter (1992) and Grahn et al. (1995) carried out ultrastructural studies of stenostomids, mainly S. leucops. S. sthenum was not mentioned in any of them.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3070C472FF91A0C9D4A9AB7D.taxon	description	(Fig. 2 E) Description: Solitary specimens 1 – 1.5 mm long. Chains of four zooids, 2.5 mm long. Chains of six zooids, 3 mm long. Anterior end blunt. Posterior end with an intestine-lacking region. Apical ciliated pits. Constriction of the body at the level of the mouth. Live specimens are vermilion red, owing to the secretions of the glandular epidermal cells. These secretions appear as irregular spots on the surface. Body surface homogeneously covered by cilia that are longer on the mid-ventral line. Semi-rigid sensory cilia, more abundant at both body ends. The rhabdites are placed in the cells among the glands. The rhabdites and the glands are absent on the mid-ventral line and around the ciliated pits. Anterior brain lobes deeply dentate. Posterior brain lobes with developed internal lobe (trilobate brain after Marcus, 1945 a). A pair of light-refracting bodies formed by numerous spheres, type 1, associated with the posterior brain lobes. Oral pore triangular. Short bag-like pharynx, a constriction dividing it into two parts: a rostral one with thick epithelium, short cilia and cyanophilic glands; and a caudal one with long cilia and no glands. Circular musculature present. Intestine with Minot’s club-shaped cells, but without excretophores. Nephridiopore subterminal, ventral.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3070C472FF91A0C9D4A9AB7D.taxon	distribution	Distribution: Periodic pools near the Pirajussara River (tributary to the Pinheiros River), São Paulo, Brazil (Marcus, 1949).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3070C474FC39A5CBD67AAB0E.taxon	description	(Fig. 3 A)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3070C474FC39A5CBD67AAB0E.taxon	description	Description: Solitary specimens up to 0.8 mm long. Chains with 2 – 3 zooids with different degrees of development. Oval body, blunt anterior end, with a constriction behind the mouth. Extended lateral ciliated pits. Posterior end with an intestine-lacking region, with two caudal finger-like extensions, a long ventral one and a short dorsal one. Homogeneous ciliated epithelium. Small rhabdites, scarce on a mid-dorsal line from the postoral constriction to the caudal extension. Colour in life light brown. Anterior brain lobes deeply dentate. Three pairs of type 2 light-refracting bodies. The first two pairs are formed by one sphere and are placed subcutaneously over the sensory cells of the ciliated pits. The third pair is formed by two spheres, also superficial and associated with the posterior brain lobes. Oral pore triangular. Pear-shaped pharynx. Pharyngeal glands (type a) arranged in the posterior half. A row of glandular cells in the ventral region of the pharynx (area of insertion for the musculature of the buccal lower lip). Fifteen to 25 cells with refringent granules form a ‘ transverse’ row in the first third of the intestine. Nephridiopore opening between the caudal appendages.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3070C474FC39A5CBD67AAB0E.taxon	distribution	Distribution: Paraguay (Martin, 1908); São Paulo and interior of São Paulo State, Brazil (Marcus, 1945 b); Onverdacht, Surinam (Van der Land, 1970); Los Talas, Berisso, Buenos Aires, Argentina, September 1998 to July 1999, December 1999 to February 2000. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3070C474FC39A5CBD67AAB0E.taxon	materials_examined	Stored material: Four sagittally sectioned specimens in the CHMLP. No. 5305.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3070C474FC39A5CBD67AAB0E.taxon	discussion	Discussion: This species was described by Martin (1908) as W. parayguensis. Because this material came from Paraguay (South America), the original spelling was corrected by Marcus (1945 b) (article 32.5 in the ICZN, 2000). S. paraguayense was placed in the genus Stenostomum by Luther (1908) and it was considered as a synonym of Stenostomum bicaudatum Kennel, 1889 by Nuttycombe & Waters (1938). This criterion was followed by Noreña-Janssen (1995). However, Marcus (1945 b) and Van der Land (1970) recognize the validity of both species. Marcus (1945 b) mentions that the dorsal caudal appendage may be reduced or absent in some specimens.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FF91A51ED793AEF4.taxon	description	(Fig. 3 B) Description: Simple individuals 0.5 – 0.9 mm long. Two-zooid chains 1.2 mm long. Anterior end blunt. Small lateral ciliated pits. Body broader at mouth level. Body constriction between pharynx and intestine. Intestine-lacking region at posterior end. Body covered with cilia. Presence of semi-rigid sensory cilia, more abundant at both body ends. Rhabdites parallel to the axial axis. Colourless in life. Anterior brain lobes deeply dentate, internal brain lobes associated with posterior lobes (Marcus, 1945 a); posterior lobes slender. One pair of light-refracting bodies with a single refractory element (type 2), associated with the posterior brain lobes. Oral pore circular. Long sacciform pharynx with internal cilia and strong pharyngeal muscles. Clubshaped glands (type b) open between mouth and pharynx. Well-developed circular musculature can be observed in the posterior pharyngeal region. With muscles extending from pharynx to body wall. First region of the intestine with high, vacuolated cells, with contractile activity independent from the rest of the intestine, and separated from the posterior intestinal region by a marked constriction (Marcus, 1945 a). The rest of the intestine is homogeneous with irregularly arranged excretophores. The protonephridium becomes sinuous at the posterior end. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FF91A51ED793AEF4.taxon	distribution	Distribution: Tieté River, São Paulo, Brazil (Marcus, 1945 a).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FF91A163D3D1AB0E.taxon	description	(Fig. 3 C) Description: Individuals with 2 – 4 zooids, 0.7 – 0.8 mm long. Body cylindrical. Anterior end tapering. Presence of lateral constrictions in the ciliated pit regions, and at the caudal edge of the posterior lobes. Small lateral ciliated pits. Rounded posterior end, without an intestine-lacking region. Ciliated epithelium frequently with sparse longer sensory cilia. Homogeneous rhabdites. Anterior brain lobes separated into small independent masses (‘ metamerics’). A pair of internal lobes associated with the posterior lobes (trilobate brain after Marcus, 1945 a). Spherical nerve commissure. A pair of light-refracting bodies formed by a single naked sphere, with no vesicle (type 3), associated with the posterior brain lobes. Small, axially elongated oral pore. Type a pharyngeal glands. No excretophores. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FF91A163D3D1AB0E.taxon	distribution	Distribution: Virginia, USA (Kepner & Carter, 1931; Kolasa, 1991); São Paulo, Brazil (Marcus, 1945 b); Finland? (Lanfranchi & Papi, 1978).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FC39A51ED3E3AC80.taxon	description	(Fig. 3 D) Description: Chains of up to eight zooids up to 5 mm long. Body cylindrical, slightly flattened ventrally. Anterior end blunt. Deep dorso-lateral ciliated pits. Body constriction at the level of the oral pore. Elongated intestine-lacking region at the posterior end (up to one-third of the body length). Caudal portion ventrally adhesive. Long, thin and dense epithelial cilia. Presence of long semi-rigid sensory cilia. Rhabdites grouped in packets placed vertically to the epidermis. Colour in life white. Anterior brain lobe deeply dentate. Internal brain lobes associated with posterior lobes (Marcus, 1945 a). A pair of type 1 light-refracting bodies formed by numerous spheres (about 50) included into a large vesicle and associated with the posterior ganglia. Oral pore semi-lunar, surrounded by longitudinal pharyngeal muscles. Pharynx almost as wide as it is long, with little circular musculature. Presence of radial muscles between the pharynx and the body wall. Regularly arranged glands (type a) along the entire pharynx. Intestinal walls smooth. Excretophores irregularly arranged, not very conspicuous. Nephridiopore ventrally placed in the intestinelacking region (subterminal).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FC39A51ED3E3AC80.taxon	distribution	Distribution: New York and Massachusetts (Graff, 1911), Virginia (Nuttycombe, 1932 a; Nuttycombe & Waters, 1938), North Carolina, South Carolina, Tennessee and Georgia (Nuttycombe & Waters, 1938), USA; São Paulo, Brazil (Marcus, 1945 b); Russia (Beklemichev, 1917, 1921; Nassonov, 1926); Finland (Nassonov, 1924); temporary pond near Zapata Stream and Route 11, Buenos Aires, Argentina, November 1999. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FC39A51ED3E3AC80.taxon	materials_examined	Stored material: Four sagittally sectioned specimens in the CHMLP. No. 5306.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C474FC39A51ED3E3AC80.taxon	discussion	Discussion: S. tenuicauda was synonymized with S. leucops (Luther, 1960). However, the differences found not only in the material studied here, but also in the specimens described by Marcus, support the validity of at least the South American populations as a species distinct from S. leucops.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C475FC39A291D6A6A9EE.taxon	description	(Fig. 3 E) Description: Individuals of 1 – 4 zooids. Two-zooid chains 0.8 – 0.9 mm long, up to 1.8 mm in the Brazilian forms. Body cylindrical, ventrally flattened, gradually tapering. Anterior end blunt. Small, rounded, antero-lateral ciliated pits. Posterior end with a long intestine-lacking tail (1 / 3 – 1 / 2 of the total body length). Long, semi-rigid cilia concentrated at both ends of the body. Vacuolar epidermal cells, with rhabdites. Colour in life whitish. Some of the studied individuals with anastomosed pigment accumulations. Anterior brain lobes smooth. A pair of lightrefracting bodies at mouth level, with few spheres in a vesicle (type 2), associated with the posterior brain lobes. Subapical oral pore, generally with circular outline. Tubular pharynx, with small glands (type a) uniformly distributed on the pharynx. Sphincter between the pharynx and intestine. Presence of excretophores. The protonephridium becomes sinuous at the caudal end. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C475FC39A291D6A6A9EE.taxon	distribution	Distribution: Georgia, USA (Nuttycombe, 1931; Kolasa, 1991); São Paulo and São Paulo State, Brazil (Marcus, 1945 b); Poland (Kolasa, 1977); Finland, Russia, Germany (Lanfranchi & Papi, 1978); Paraná River, Argentina (Noreña-Janssen, 1995); Los Talas, Berisso, Buenos Aires, Argentina, April 1999, January and February 2000.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3076C475FC39A291D6A6A9EE.taxon	discussion	Discussion: In contrast to the observations for South American specimens, Nuttycombe (1931) does not mention the presence of a sphincter between the pharynx and the intestine.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FFBDA04FD3E4ABB8.taxon	description	(Fig. 3 F)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FFBDA04FD3E4ABB8.taxon	description	Description: Individuals with 1 – 4 zooids up to 5 mm long, solitary individuals 0.4 – 1 mm long. Mobile tapering anterior end. Small, rounded ciliated pits lateral or latero-ventrally placed. Truncate caudal end without intestine-lacking region. Vacuolar epidermic cells and short rhabdites. Long semi-rigid cilia concentrated in the anterior and posterior ends of the body. Vacuolar epidermal cells. Colour in life whitish. Anterior brain lobes forming small independent masses (‘ metameric’). A pair of light-refracting bodies, with fewer than ten spheres (type 2), associated with an extension of the posterior brain lobes. Small rounded oral pore. Long tubular pharynx (1 / 4 body length) with isolated pharyngeal glands (type a) distributed along the entire pharynx. Excretophores regularly arranged in two lateral bands, or irregularly in the North American specimens. Nephridiopore subterminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FFBDA04FD3E4ABB8.taxon	distribution	Distribution: Virginia (Nuttycombe, 1931; Nuttycombe & Waters, 1938), Georgia, North Carolina (Nuttycombe & Waters, 1938; Kolasa, 1991), USA; Nova Scotia, Canada (Jones, 1932); São Paulo State and Paraná State, Brazil (Marcus, 1945 b); Los Talas, Berisso, Buenos Aires, Argentina, July 1999. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FFBDA04FD3E4ABB8.taxon	materials_examined	Stored material: One sagittally sectioned specimen in the CHMLP No. 5307.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FFBDA04FD3E4ABB8.taxon	discussion	Discussion: Marcus (1945 b) and Luther (1960) refer to the similarity between this species and Stenostomum unicolor O. Schmidt, 1848. The largest sized specimens correspond to those mentioned by Marcus (1945 b)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	description	(Fig. 4 A)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	description	Description: Adult specimens 0.2 – 0.75 mm long. Chains with two zooids (0.5 – 1 mm) or six zooids (2.5 mm). Anterior end generally rounded, spatulate or sharply arched with ‘ anatiform’ aspect. Constriction before the pharynx. Posterior end rounded. The intestine reaches the caudal body region. Epithelium with short uniform cilia and rigid sensory cilia scattered on the body surface, more numerous in the anterior region. Rhabdites regularly distributed in the adult specimens; but in immature individuals only visible in the ciliated pits. Lateral and broad ciliated pits. Colour in life whitish. Anterior brain lobes formed by small independent masses (‘ metamerics’). No light-refracting bodies. Oral pore oval, frequently surrounded by radial or longitudinal muscular bundles. Pharynx 1.5 – 2 times longer than it is wide. Presence of conspicuous transverse muscular bundles. Elongated pharyngeal glands (type b) placed on both sides of the pharynx, grouped in clusters and opening into a simple duct. Immature individuals without pharyngeal glands. Presence of excretophores. Protonephridium slightly sinuous, nephridiopore terminal. Distribution: São Paulo, Brazil (Marcus, 1945 b); Tvaerminne, Finland (Luther, 1960); Sabakoekreek, Surinam (Van der Land, 1970); Cheshire and Yorkshire, England; near Poznan, Poland, and south of Mombasa, Kenya (Kolasa & Young, 1974 a); France (Lanfranchi & Papi, 1978); Fosso Contesora, Italy (Kolasa, 1983); south-eastern New York State, USA (Kolasa et al., 1987; Kolasa, 1991). Anokkostenostomum corderoi (Marcus, 1945) comb. nov. (Fig. 4 B) Stenostomum corderoi Marcus, 1945 Description: Solitary individuals, 0.4 – 0.8 mm long. Two-zooid chains (1.2 mm) to four-zooid chains (2 mm). Body cylindrical, anterior end blunt. Body widening at the level of the oral pore; post-buccal narrowing. Posterior end rounded. The intestine reaches the caudal body region. Small, dorso-lateral ciliated pits; occasionally with creases which make them appear larger. Ciliated epithelium with long semirigid sensory cilia, concentrated especially on the anterior body. The rhabdites are arranged in longitudinal grooves. Live specimens transparent. Large brain ganglia. Anterior brain lobes separated into small independent masses (‘ metamerics’). Posterior lobes with pharyngeal internal and external nerves. No light-refracting bodies. Oral pore wide, V-shaped, extending to the middle of the pharynx. Pharynx very voluminous (1 / 3 – 1 / 2 of the body length), differentiated into oral (2 / 3 of its length) and oesophageal regions. A strong sphincter separating the oesophageal region from the intestine. Oral region of the pharynx with scattered large glands (type a) on the musculature. The pharynx is covered by a refringent membrane that broadens at the edges of the mouth. The inner pharyngeal membrane is folded in a zigzag manner in the posterior third of the pharynx (oesophageal region). Intestine with a numerous lateral excretophores, regularly arranged. Nephridiopore terminal. Distribution: São Paulo, Brazil (Marcus, 1945 b); France (de Beauchamp 1948). Anokkostenostomum evelinae (Marcus, 1945) comb. nov. (Fig. 4 C) Stenostomum evelinae Marcus, 1945 Description: Length of simple specimens, 1.2 mm. Two-zooid chains 2 mm long. Body compact, dorsoventrally flattened. Anterior end rounded. Short lateral ciliated pits placed near the apical end of the body. Posterior end gradually tapering. Ciliated epithelium with long sensory cilia, concentrated mainly in the anterior and posterior ends. Small rhabdites. Colour white, with yellow intestine in live specimens. Short, compact brain ganglia. Solid anterior lobes and reduced posterior lobes. No light-refracting bodies. Small oral pore, longer than it is wide, its posterior end widening. Presence of radial musculature. Large, wide pharynx. Well-developed circular and parietal pharyngeal musculature. Strong pharyngeal sphincter. Well-developed pharyngeal glands (type a) in the anterior region. Presence of a caecum dorsal to the pharynx. Lateral excretophores, irregularly arranged in the anterior region, and posteriorly regular. Nephridiopore terminal. Distribution: São Paulo, Brazil (Marcus, 1945 b); near Paramaibo, Surinam (Van der Land, 1970).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	description	Description: Adult specimens 0.2 – 0.75 mm long. Chains with two zooids (0.5 – 1 mm) or six zooids (2.5 mm). Anterior end generally rounded, spatulate or sharply arched with ‘ anatiform’ aspect. Constriction before the pharynx. Posterior end rounded. The intestine reaches the caudal body region. Epithelium with short uniform cilia and rigid sensory cilia scattered on the body surface, more numerous in the anterior region. Rhabdites regularly distributed in the adult specimens; but in immature individuals only visible in the ciliated pits. Lateral and broad ciliated pits. Colour in life whitish. Anterior brain lobes formed by small independent masses (‘ metamerics’). No light-refracting bodies. Oral pore oval, frequently surrounded by radial or longitudinal muscular bundles. Pharynx 1.5 – 2 times longer than it is wide. Presence of conspicuous transverse muscular bundles. Elongated pharyngeal glands (type b) placed on both sides of the pharynx, grouped in clusters and opening into a simple duct. Immature individuals without pharyngeal glands. Presence of excretophores. Protonephridium slightly sinuous, nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	distribution	Distribution: São Paulo, Brazil (Marcus, 1945 b); Tvaerminne, Finland (Luther, 1960); Sabakoekreek, Surinam (Van der Land, 1970); Cheshire and Yorkshire, England; near Poznan, Poland, and south of Mombasa, Kenya (Kolasa & Young, 1974 a); France (Lanfranchi & Papi, 1978); Fosso Contesora, Italy (Kolasa, 1983); south-eastern New York State, USA (Kolasa et al., 1987; Kolasa, 1991).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	description	(Fig. 4 B)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	description	Description: Solitary individuals, 0.4 – 0.8 mm long. Two-zooid chains (1.2 mm) to four-zooid chains (2 mm). Body cylindrical, anterior end blunt. Body widening at the level of the oral pore; post-buccal narrowing. Posterior end rounded. The intestine reaches the caudal body region. Small, dorso-lateral ciliated pits; occasionally with creases which make them appear larger. Ciliated epithelium with long semirigid sensory cilia, concentrated especially on the anterior body. The rhabdites are arranged in longitudinal grooves. Live specimens transparent. Large brain ganglia. Anterior brain lobes separated into small independent masses (‘ metamerics’). Posterior lobes with pharyngeal internal and external nerves. No light-refracting bodies. Oral pore wide, V-shaped, extending to the middle of the pharynx. Pharynx very voluminous (1 / 3 – 1 / 2 of the body length), differentiated into oral (2 / 3 of its length) and oesophageal regions. A strong sphincter separating the oesophageal region from the intestine. Oral region of the pharynx with scattered large glands (type a) on the musculature. The pharynx is covered by a refringent membrane that broadens at the edges of the mouth. The inner pharyngeal membrane is folded in a zigzag manner in the posterior third of the pharynx (oesophageal region). Intestine with a numerous lateral excretophores, regularly arranged. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	distribution	Distribution: São Paulo, Brazil (Marcus, 1945 b); France (de Beauchamp 1948).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	description	(Fig. 4 C)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	description	Description: Length of simple specimens, 1.2 mm. Two-zooid chains 2 mm long. Body compact, dorsoventrally flattened. Anterior end rounded. Short lateral ciliated pits placed near the apical end of the body. Posterior end gradually tapering. Ciliated epithelium with long sensory cilia, concentrated mainly in the anterior and posterior ends. Small rhabdites. Colour white, with yellow intestine in live specimens. Short, compact brain ganglia. Solid anterior lobes and reduced posterior lobes. No light-refracting bodies. Small oral pore, longer than it is wide, its posterior end widening. Presence of radial musculature. Large, wide pharynx. Well-developed circular and parietal pharyngeal musculature. Strong pharyngeal sphincter. Well-developed pharyngeal glands (type a) in the anterior region. Presence of a caecum dorsal to the pharynx. Lateral excretophores, irregularly arranged in the anterior region, and posteriorly regular. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3077C475FC25A665D3B9AC64.taxon	distribution	Distribution: São Paulo, Brazil (Marcus, 1945 b); near Paramaibo, Surinam (Van der Land, 1970).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FFBDA7A0D540AC36.taxon	description	(Fig. 4 D)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FFBDA7A0D540AC36.taxon	description	Description: Solitary individuals, 0.5 mm long. Twozooid chains. Fusiform body with tapering ends. The intestine reaches the caudal region of the body. Reduced lateral ciliated pits. No rhabdites. Homogeneous ciliated epithelium, without sensory cilia. Welldeveloped cilia in the ciliated pits. Specimens colourless in life. Anterior brain lobes larger than the posterior lobes. No light-refracting bodies. Oral pore axially elongated. Fibrous pharynx. Conspicuous lip sphincter. No pharyngeal glands. No excretophores. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FFBDA7A0D540AC36.taxon	distribution	Distribution: Virginia, USA (Kepner & Carter, 1931); São Paulo, Brazil (Marcus, 1945 b).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FFBDA206D4ACA8CD.taxon	description	(Fig. 5 A)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FFBDA206D4ACA8CD.taxon	description	Description: Solitary specimens: 0.26 mm long. Chains with two zooids (0.8 mm) up to 5 – 6 zooids (2 mm). Slight ventral flattening. Anterior end narrowing abruptly. Apical zone blunt. Long ciliated pits. Intestine-lacking region at the posterior end. Conspicuous ciliated epithelium. Irregularly arranged sensory cilia, more abundant in the anterior end. Epidermis with small rhabdites. Colour in life whitish. The anterior brain lobes form independent masses (‘ metameric’). No light-refracting bodies. Oral pore transverse. Pharynx short, with radial musculature and small rounded glands (type a), which open onto its entire surface. A muscular sphincter separating the pharynx from the intestine. Irregularly arranged excretophores. Conspicuous sinuous protonephridium. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FFBDA206D4ACA8CD.taxon	distribution	Distribution: Mountain Lake, Virginia, USA (Nuttycombe & Waters, 1938); Tieté River, São Paulo, Brazil (Marcus, 1945 b); Germany, Poland (Lanfranchi & Papi, 1978); Fosso Contesora, Italy (Kolasa, 1983); south of New York State, USA (Kolasa et al., 1987; Kolasa, 1991).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FC25A75AD3CCAD68.taxon	description	(Fig. 5 B)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FC25A75AD3CCAD68.taxon	description	Description: Adult individuals 0.75 – 2.5 mm long. Two- to eight-zooid chains. Anterior region elongated. Reduced lateral ciliated pits. Body cylindrical, with a constriction before the mouth and sometimes another constriction at the level of the pharyngeal sphincter. Body tapering caudally. Intestine-lacking region at the posterior end that becomes thinner, forming a typical dorsal appendage. The ciliated epidermis forms a regular cover, except at the posterior end where cilia are scarce. Longer sensory cilia in the posterior region. Epidermis with regular vacuoles and short rhabdites. Colour in life yellowish-white. The anterior brain lobes differentiate into small independent masses (‘ metameric’). No light-refracting bodies. Oral pore and pharynx resemble a trematode acetabulum, appearing as a body projection in lateral view. The pharynx is posteriorly expanded and forms a cup onto the apical end of the intestine. The mouth and first third of the pharynx can be invaginated, proboscis-like. The pharyngeal glands are uniform (type a) in the whole pharynx. A sphincter between pharynx and intestine. No excretophores. Nephridiopore at the base of the caudal appendage.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA3075C477FC25A75AD3CCAD68.taxon	distribution	Distribution: Georgia, USA (Nuttycombe & Waters, 1935, 1938; Kolasa, 1991); São Paulo and Paraná State, Brazil (Marcus, 1945 b); near Paramaribo, Surinam (Van Der Land, 1970); Konin Lakes, Poland (Kolasa, 1977); Germany (Lanfranchi & Papi, 1978); Los Talas, Berisso, Buenos Aires, Argentina, February 1999 and February 2000. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA494D5CAAEC4.taxon	description	(Fig. 5 C)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA494D5CAAEC4.taxon	description	Description: Solitary individuals 0.15 – 0.62 mm long. Two- (0.29 mm) or three- (0.54 mm) zooid chains. Anterior and posterior ends noticeably tapering. The intestine reaches the posterior end of body. Small, lateral ciliated pits. Dense ciliated epidermis, long cilia. Thin and rigid longer sensory cilia, irregularly arranged on the whole body. Uniform rhabdites. Yellowish-white colour in life. Elongated anterior brain lobes, differentiated into small independent masses (‘ metameric’); posterior ones voluminous. No light-refracting bodies. Oral pore large. Two mobile projections at the posterior region of the oral pore. Pharynx somewhat longer than the mouth. Intestine with lobulated edges, ending near the posterior end. No pharyngeal glands. No excretophores. Nephridiopore ventral and terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA494D5CAAEC4.taxon	distribution	Distribution: Virginia (Kepner & Carter, 1931; Nuttycombe & Waters, 1938) and Georgia (Nuttycombe & Waters, 1938), USA; São Paulo, interior of São Paulo State and Paraná State, Brazil (Marcus, 1945 b); near Paramaribo and near Zanderij, Surinam (Van Der Land, 1970); Poznan, Poland (Kolasa, 1973); Los Talas, Berisso, Buenos Aires, Argentina, October 1998, February to March and June to September 1999. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA494D5CAAEC4.taxon	discussion	Discussion: The length of the solitary individuals found by Kepner & Carter (1931) in the USA (0.62 mm) is slightly greater than that recorded for the South American specimens (0.15 – 0.4 mm).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	description	(Fig. 5 D)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	description	Description: Chains with two zooids 0.72 mm long. Neither solitary individuals nor longer chains were observed. Anterior end blunt. A small, apparently tactile, tubercle in the ventral cephalic end is characteristic of this species. Small, antero-dorsal ciliated pits. Constriction posterior to the ciliated pits. Intestinelacking region at the posterior end. Densely ciliated ventral epithelium (long cilia). The cilia on the dorsal epithelium are inconspicuous. Semi-rigid sensory cilia irregularly arranged along body. Slender rhabdites. Live specimens yellowish-white, darker at the pharyngeal region because of the presence of glands and musculature. Anterior brain lobes divided into small independent masses (‘ metameric’). No light-refracting bodies. Oral pore V-shaped. Short muscular pharynx associated with elongated unicellular glands (type b), which open onto the whole length of the pharynx. Pharynx with refractory corpuscles. Anterior end of the intestine overlying the posterior part of the pharynx. Intestinal wall dentate. No excretophores. Nephridiopore terminal. Distribution: Virginia and Georgia, USA (Nuttycombe & Waters, 1938; Kolasa, 1991); São Paulo and interior of São Paulo State (Marcus, 1945 b), Brazil; margins of the Suriname River near Paramaribo, Surinam (Van Der Land, 1970); Poznan, Poland (Kolasa, 1973); Germany, Finland (Lanfranchi & Papi, 1978); Los Talas, Berisso, Buenos Aires, Argentina, January and April 1999. This species has not been previously recorded in Argentina. Discussion: Unlike the material found in Argentina, Marcus (1945 b) describes chains of up to four zooids (1 mm) for Brazilian specimens. The South American specimens show refractory corpuscles in the pharynx. This feature was not mentioned by Nuttycombe & Waters (1938). Anokkostenostomum ventronephrium (Nuttycombe, 1932) comb. nov. (Fig. 5 E) Stenostomum ventronephrium Nuttycombe, 1932 Description: Single individuals, 0.5 – 0.8 mm long. Three-zooid chains, 2 mm long. Anterior end spatulate. Long lateral ciliated pits. Posterior end without an intestine-lacking region, ending bluntly, no tail. Body uniformly covered with cilia. Semi-rigid cilia, more abundant at both body ends. With epidermal rhabdites. With groups of 10 – 15 conspicuous rhabdites at the anterior body end. These rhabdites are produced at glands situated latero-dorsally to the pharynx, which have four tracts (two dorsal and two lateral) through which the rhabdites migrate. Whitish, reddish or colourless in life. Brain ganglia with well-developed transverse commissure. No light-refracting bodies. Oral pore circular, surrounded by muscles. Long, wide, muscular and densely ciliated pharynx. Granular pharyngeal glands (type b), placed mainly ventrally and opening at mouth level. Dorsal wall of the intestine overlying the pharynx. No excretophores. The protonephridium runs dorsal to the pharynx, loops towards the left and continues ventrally or ventro-laterally to the intestine. Nephridiopore subterminal. Distribution: Virginia, USA (Nuttycombe, 1932 b; Kolasa, 1991); Tieté River, São Paulo, Brazil (Marcus, 1945 a); Italy (Kolasa, 1983). Discussion: Differences between the South and North American specimens are: absence of tail and presence of rhabdite-forming glands in the South American specimens (Nuttycombe, 1932 b; Marcus, 1945 a).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	description	Description: Chains with two zooids 0.72 mm long. Neither solitary individuals nor longer chains were observed. Anterior end blunt. A small, apparently tactile, tubercle in the ventral cephalic end is characteristic of this species. Small, antero-dorsal ciliated pits. Constriction posterior to the ciliated pits. Intestinelacking region at the posterior end. Densely ciliated ventral epithelium (long cilia). The cilia on the dorsal epithelium are inconspicuous. Semi-rigid sensory cilia irregularly arranged along body. Slender rhabdites. Live specimens yellowish-white, darker at the pharyngeal region because of the presence of glands and musculature. Anterior brain lobes divided into small independent masses (‘ metameric’). No light-refracting bodies. Oral pore V-shaped. Short muscular pharynx associated with elongated unicellular glands (type b), which open onto the whole length of the pharynx. Pharynx with refractory corpuscles. Anterior end of the intestine overlying the posterior part of the pharynx. Intestinal wall dentate. No excretophores. Nephridiopore terminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	distribution	Distribution: Virginia and Georgia, USA (Nuttycombe & Waters, 1938; Kolasa, 1991); São Paulo and interior of São Paulo State (Marcus, 1945 b), Brazil; margins of the Suriname River near Paramaribo, Surinam (Van Der Land, 1970); Poznan, Poland (Kolasa, 1973); Germany, Finland (Lanfranchi & Papi, 1978); Los Talas, Berisso, Buenos Aires, Argentina, January and April 1999. This species has not been previously recorded in Argentina.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	discussion	Discussion: Unlike the material found in Argentina, Marcus (1945 b) describes chains of up to four zooids (1 mm) for Brazilian specimens. The South American specimens show refractory corpuscles in the pharynx. This feature was not mentioned by Nuttycombe & Waters (1938).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	description	(Fig. 5 E)	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	description	Description: Single individuals, 0.5 – 0.8 mm long. Three-zooid chains, 2 mm long. Anterior end spatulate. Long lateral ciliated pits. Posterior end without an intestine-lacking region, ending bluntly, no tail. Body uniformly covered with cilia. Semi-rigid cilia, more abundant at both body ends. With epidermal rhabdites. With groups of 10 – 15 conspicuous rhabdites at the anterior body end. These rhabdites are produced at glands situated latero-dorsally to the pharynx, which have four tracts (two dorsal and two lateral) through which the rhabdites migrate. Whitish, reddish or colourless in life. Brain ganglia with well-developed transverse commissure. No light-refracting bodies. Oral pore circular, surrounded by muscles. Long, wide, muscular and densely ciliated pharynx. Granular pharyngeal glands (type b), placed mainly ventrally and opening at mouth level. Dorsal wall of the intestine overlying the pharynx. No excretophores. The protonephridium runs dorsal to the pharynx, loops towards the left and continues ventrally or ventro-laterally to the intestine. Nephridiopore subterminal.	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	distribution	Distribution: Virginia, USA (Nuttycombe, 1932 b; Kolasa, 1991); Tieté River, São Paulo, Brazil (Marcus, 1945 a); Italy (Kolasa, 1983).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
8C6887DA306BC469FFBDA173D493A964.taxon	discussion	Discussion: Differences between the South and North American specimens are: absence of tail and presence of rhabdite-forming glands in the South American specimens (Nuttycombe, 1932 b; Marcus, 1945 a).	en	Noreña, Carolina, Damborenea, Cristina, Brusa, Francisco (2005): A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters. Zoological Journal of the Linnean Society 144 (1): 37-58, DOI: 10.1111/j.1096-3642.2005.00157.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2005.00157.x
