taxonID	type	description	language	source
03B087B65446C10A23EA31AD4FE8C9B5.taxon	description	Individuals examined for morphological analyses: 30 Valves linear-elliptical to elliptical with strongly attenuated apices (Figs 2 – 11). Valve length 52.15 – 67.90 µm (average 59.23 µm; standard deviation ± 3.37 µm) and breadth 15.36 – 17.75 µm (average 16.60 µm; standard deviation ± 0.74 µm). Axial area narrow, linear from center to apex, length / breadth ratio 3.19 – 4.12. Central area transapically rounded to rhombic in shape. In SEM, raphe filiform, external proximal raphe endings straight with drop-like shaped and distal raphe endings bifurcate formed by a broad triangular lacinia that extent to the base of the valve apex (Figs 12 – 14). Each proximal helictoglossae forms two loosely interconnected ribbed nodules by a thin bridge of silica (Figs 16, 18). Distal helictoglossae form prominent thickened nodules near the apices (Figs 15, 17). Striae (16 – 18 in 10 μm) parallel at the center becoming slightly convergent at the apices. One or two Voigt faults present on the secondary side of the valve and clearly recognizable by a single row of areolae separated from the striae (Figs 7 – 11, 13). Areolae evenly spaced with rounded to linear-elliptical shaped, appearing more elliptical closer to the longitudinal canal. Each row with density of 5 – 7 areolae in 2 µm. One wide longitudinal canal is present along each valve margin that terminates at the valve apex (Figs 13 – 14). Internally, areolae are covered by a hymen. Renilimbi are evident around areolae along the axial area and longitudinal canal regions, with 2 – 4 renilimbi. Renilimbi can be found randomly spread around areolae on the valve interior (Figs 16 – 17).	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65446C10A23EA31AD4FE8C9B5.taxon	materials_examined	Type: — BRAZIL. Pará: Jurucuí Lake 02 º 32 ’ 52 ” S, 54 º 58 ’ 21 ” W, 04 October 2016, Pereira, A. C. P., plankton, station 1, (Holotype HSTM – Algas slide no 16826!, here illustrated as Figure 2, row sample; paratype HAS 6896! Verde Lake 02 ° 29 ’ 34.9 ” S 54 ° 56 ’ 51.5 ” W, 29 December 2016, Pereira, A. C. P., plankton, here illustrated as Figure 5).	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65446C10A23EA31AD4FE8C9B5.taxon	etymology	Etymology: — The specific epithet is dedicated to indigenous people who live in lower Tapajós and Arapiuns Rivers region. A noun in apposition.	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65446C10A23EA31AD4FE8C9B5.taxon	discussion	Observations: — Neidium borari shares features with two known species: N. angustirostratum Lange Bertalot et al. (2003: 85) and N. statuarium Hamilton & Siver in Siver & Hamilton (2005: 364). Lange-Bertalot et al. (2003) described N. angustirostratum from Sardinia and N. statuarium Hamilton & Siver (2005) was originally described from the Cape Cod peninsula in Massachusetts, USA. They both have smaller morphometric dimensions and higher numbers of striae in 10 μm (Table 3) than N. borari. The similarity of N. borari with these species is in the valve outline, even though it is easily separated from both species which have curved proximal raphe endings. Neidium borari, on the contrary, has straight external proximal raphe fissures. Furthermore, N. angustirostratum differs by having a subparallel and moderately oblique striation pattern and central area that is rather small and obliquely elongated towards the margins. The most prominent feature in N. statuarium is seen in SEM, where surface depressions covering the longitudinal canal and central area can be seen. Comparison of N. borari to similar taxa is presented in Table 3.	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65443C10A23EA35FF480FCD79.taxon	description	Valves linear-elliptical to elliptic-lanceolate with slightly undulate margins, middle inflated, with strongly protracted capitate apices (Figs 19 – 25). Valve length 59.56 – 66.30 µm (average 64.01 µm; standard deviation ± 2.13 µm) and breadth 13.4 – 15.1 µm (average 14.00 µm; standard deviation ± 0.52 µm). Axial area narrow, linear from center to apex, length / breadth ratio 3.19 – 4.12. Central area transapically elliptical to rhombic in shape. Raphe filiform, external proximal raphe endings recurved in opposite directions and distal raphe endings appearing bifurcate formed by triangular laciniae (Figs 24 – 25). Striae (19 – 20 in 10 μm) radiate to slightly oblique at the center becoming slightly convergent slightly towards the apices. One or two Voigt faults present on the secondary side of the valve are clearly recognizable by a single row of areolae separated from the striae (Figs 21 – 23). Areolae evenly spaced, rounded to elongate linear-elliptical in shape. Each row with density of 8 – 9 areolae in 5 µm. One wide longitudinal canal is present along each valve margin.	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65443C10A23EA35FF480FCD79.taxon	materials_examined	Type: — BRAZIL. Pará: Tapari Lake 02 º 26 ’ 22 ” S, 54 º 53 ’ 37 ” W, 16 December 2018, Pereira, A. C. P., sediment, station 1, (Holotype HSTM – Algas slide no 16827!, here illustrated as Figure 23, row sample; isotype HAS 6897! here illustrated as Figure 22).	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65443C10A23EA35FF480FCD79.taxon	etymology	Etymology: — The specific epithet is dedicated to study area from which it was collected, Itapari Lake. Itapari has the origin in the Nheengatu indigenous language of the Amazonian region, that means ita = stone + pari = surrounded, in other words, surrounded by stones. Observations: — Neidium itapariensis shares features with two species: Neidium borari and Neidium vandusenense Hamilton et al. (2019: 48). Neidium vandusenense, described from Livingstone Lake in Vancouver, Canada, differs from N. itapariensis by its greater length and width, finer striae density in 10 µm, apiculate extended apices and three or more longitudinal canals. Neidium itaparienses resembles N. borari with respect to general valve outline, length, axial and central area, and longitudinal canals. However, N. borari is broader and differs by having straight, drop-like shaped proximal raphe endings as well as parallel striae at the center. We summarize the differences between the new species and the most similar taxa in Table 3.	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65443C10723EA318B4ADECF1D.taxon	description	Individuals examined for morphological analyses: 15 Valves linear to linear-lanceolate, margins parallel, slightly convex in the center with acute rounded apices (Figs 26 – 32, 33). Valve length 73.99 – 115.10 µm (average 86.45 µm; standard deviation ± 12.13 µm) and breadth 15.22 – 20.77 µm (average 18.25 µm; standard deviation ± 1.66 µm). Axial area narrow, almost linear from center to apex, length / breadth ratio 3.92 – 5.75. Central area transapically rounded to elliptical in shape. In SEM, raphe lateral, external proximal raphe endings deflected hooks, bent at approximately 90 o angles in opposite directions from one another, and distal raphe endings bifurcate formed by broad triangular laciniae that extend to the base of the valve apex (Figs 34 – 35, 36). Internally, each proximal helictoglossa forms two loosely ribbed nodules interconnected by a thin bridge of silica (Fig. 39). Distal helictoglossae form prominent thickened nodules near the apices (Figs 37 – 38). Striae (15 – 17 in 10 μm) oblique at the center becoming slightly convergent at the apices (Figs 26 – 32, 34 – 35). Externally, one or two Voigt faults present on the secondary side of the valve and clearly recognizable by a single row of areolae separated from the striae (Figs 26, 30 – 31). Areolae evenly spaced, rounded to elongate linear-elliptical in shape, appearing more elliptical closer to the longitudinal canal. Each stria with 4 – 5 areolae in 2 µm. Two or three wide longitudinal canals are present along each valve margin, and they are accompanied by irregularly-shaped pores at the apices of the valves (Figs 33 – 34, 37).	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65443C10723EA318B4ADECF1D.taxon	materials_examined	Type: — BRAZIL. Pará: Arapiuns River 02 º 20 ’ 01 ” S, 54 º 02 ’ 01 ” W, 15 December 2018, Pereira, A. C. P., plankton, station 1, (Holotype HSTM – Algas slide no 16828!, here illustrated as Figure 26, row sample; paratype HAS 6898! Verde Lake 02 ° 26 ’ 21.7 ” S 54 ° 56 ’ 23.3 ” W, 11 December 2012, Pereira, A. C. P., plankton, here illustrated as Figure 29).	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65443C10723EA318B4ADECF1D.taxon	etymology	Etymology: — Muyrakyt „ (muiraquit „ in Portuguese) means “ knot of trees ” in Tupi language. It is the name given to various types of old artefacts of Amazonian indigenous origin that belong to Tapajó culture. They are carved in stone (green jade) or wood represented by frogs and often used as amulets. A noun in apposition.	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
03B087B65443C10723EA318B4ADECF1D.taxon	discussion	Observations: — Neidium muyrakytan is morphologically similar to N. convolutum Liu & Kociolek in Liu et al. (2020: 172), N. rolandschmidtii Metzeltin & Lange-Bertalot (2007: 177), N. sacoense Reimer in Patrick & Reimer (1966: 402) and N. sterrenburgii Metzeltin & Lange-Bertalot (2007: 180) by sharing several features: valve outline, axial area, central area and longitudinal canals. Neidium muyrakytan has a valve outline very similar to those observed in N. convolutum, N. rolandschmidtii and N. sterrenburgii. Recently, N. convolutum was described by Liu et al. (2020) from one sample collected from a wet wall of the hill near a stream in Shiwan Mountains National Forest Park, China. Neidium muyrakytan differs from N. convolutum mainly by their smaller dimensions and striae density. Another difference with N. convolutum is with respect to striation pattern at the apex which is more convergent in N. convolutum than N. muyrakytan. Furthermore, N. convolutum can be distinguished by the presence of some areolae positioned at the axial area next to the raphe and by being more rounded in outline than N. muyrakytan. Neidium rolandschmidtii was described from fossil sediments in Calado Lake, Amazon state. This taxon shares several features with our new species but differs by the larger morphometric dimensions, shape of the apices, striation pattern (more convergent towards the apex), the smaller number of striae in 10 μm, and lower density of areolae. Nedium sacoense is shorter (60 – 80 µm) and wider (19 – 25 µm) and differs by having a straight raphe (not lateral). Moreover, N. sacoense is different from N. muyrakytan by having parallel and radiate striation patterns at the center and a smaller number of longitudinal canals along each valve margin. Neidium muyrakytan can be easily distinguished from N. sterrenburgii by having a noticeable difference in striation pattern, number of striae in 10 μm, shape of the apices, and morphometric dimensions (Table 3).	en	Pereira, Andreia Cavalcante, Alves, Jannah Thalis Da Silva, Vidal, Regiane Gabriele Rocha, Kociolek, John Patrick, Torgan, Lezilda Carvalho, Melo, Sérgio (2023): Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil). Phytotaxa 606 (3): 185-200, DOI: 10.11646/phytotaxa.606.3.2, URL: http://dx.doi.org/10.11646/phytotaxa.606.3.2
