taxonID	type	description	language	source
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	description	urn: lsid: zoobank. org: act: 70232 D 66 - 1 D 18 - 4 AA 4 - 9 F 2 B- 32 DF 7356 A 091 (Figs. 5 – 6; Tab. 2)	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	description	Hypancistrus sp. “ pão ”. — Santos et al., 2023: 29 (article on cytogenetics).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	materials_examined	Holotype. INPA-ICT 61050, 98.1 mm SL, Vitória do Xingu, Itaubinha, pedral, Pará State, Brazil, 02 ° 53 ’ 21 ” S 51 ° 56 ’ 26 ” W, 4 Nov 2008, L. Rapp Py-Daniel, H. Anatole & J. Bessa. Paratypes. All from Brazil, Pará State: ANSP 185238, 9, 72.2 – 95.3 mm SL, rio Acarai, upstream from confluence with rio Xingu at Porto de Moz, 02 ° 04 ’ 34 ” S 52 ° 20 ’ 42 ” W, 10 Nov 1994, A. M. Zanata, J. G. Lundberg & L. Rapp Py-Daniel. ANSP 194643, 13, 46.3 – 103.4 mm SL, rio Xingu, deep channel along right bank of river ca. 38 km southeast of Vitória do Xingu, 03 ° 05 ’ 32.39 ” S 51 ° 44 ’ 14.1 ” W, 21 Sep 2013, M. H. Sabaj, L. M. Sousa, A. Gonçalves, N. K. Lujan, D. B. Fitzgerald, P. Madoka Ito, A. Oliveira, R. Robles & ornamental fishermen. ANSP 194954, 15, 33.4 – 83.1 mm SL, rio Xingu (lower Volta Grande), rocky outcrop in main channel, 03 ° 7 ’ 45 ” S 51 ° 39 ’ 55.1 ” W, 20 Sep 2013, M. H. Sabaj, L. M. Sousa, A. Gonçalves, N. K. Lujan, D. B. Fitzgerald, P. Madoka Ito, A. Oliveira, R. Robles & fishermen. ANSP 194988, 18, 41.1 – 102.8 mm SL, rio Xingu, ca. 50 m off right bank of main channel ca. 1 km downstream of Porto de Moz, 01 ° 44 ’ 42.4 ” S 52 ° 14 ’ 53.9 ” W, 24 Sep 2013, M. H. Sabaj, A. Gonçalves, N. K. Lujan, D. B. Fitzgerald, P. Madoka Ito, A. Oliveira, R. Robles & fishermen. ANSP 195292, 2, 94.0 – 116.0 mm SL, rio Xingu, along left bank, ca. 10.4 km southwest of Senador José Porfírio, 02 ° 38 ’ 54.3 ” S 52 ° 01 ’ 41.9 ” W, 7 Mar 2014, M. Arce, A. P. Gonçalves, J. A. S. Zuanon, D. B. Fitzgerald, R. Robles, D. R. G. Ribeiro, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). ANSP 195384, 9, 44.6 – 116.0 mm SL, rio Xingu, along right bank of major right braid, directly in front of Tapará village, ca. 14.5 km northeast (downstream) of Porto de Moz, 01 ° 38 ’ 36.6 ” S 52 ° 10 ’ 13.0 ” W, 5 Mar 2014, M. Arce, A. P. Gonçalves, J. A. S. Zuanon, D. B. Fitzgerald, R. Robles, D. R. G. Ribeiro, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). AUM 74486, 4, 51.6 – 83.5 mm SL, same data as ANSP 194643. INPA-ICT 31472, 63, 38.26 – 107.33 mm SL, collected with holotype. INPA-ICT 40457, 16, 38.8 - 80.6 mm SL, Anapu, 03 ° 28 ’ 20 ” S 51 ° 11 ’ 52 ” W, 20 Sep 2013, M. Hardman, A. S. Oliveira, P. M. Ito, V. Machado, D. B. Fitzgerald, A. P. Gonçalves, L. M. Sousa & M. Sabaj-Péres. INPA-ICT 40502, 17, 42.6 - 85.3 mm SL, Senador José Porfírio, 02 ° 35 ’ 27 ” S 51 ° 57 ’ 15 ” W, 21 Sep 2013, D. R. G. Ribeiro, D. B. Fitzgerald, A. P. Gonçalves, M. Arce, D. Bastos, L. Rapp Py-Daniel, Dani & M. Sabaj-Péres. INPA-ICT 40494, 8, 34.3 – 54.8 mm SL, Anapu, 03 ° 28 ’ 20 ” S 51 ° 11 ’ 52 ” W, 21 Sep 2013, R. R. Reyes, D. B. Fitzgerald, A. P. Gonçalves, M. Arce, D. Bastos, L. Rapp Py-Daniel, L. M. Sousa, Dani & M. Sabaj-Péres. INPA-ICT 40520, 10, 35.8 – 101.0 mm SL, Vitória do Xingu, 02 ° 52 ’ 48 ” S 52 ° 00 ’ 36 ” W, 22 Sep 2013, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves, M. Sabaj-Péres. INPA-ICT 40533, 6, 31.6 – 55.4 mm SL, Vitória do Xingu, 02 ° 52 ’ 48 ” S 52 ° 00 ’ 36 ” W, 22 Sep 2013, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves & M. Sabaj-Péres. INPA-ICT 40614, 1, 68.5 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 23 Sep 2013, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves, M. Sabaj-Péres. INPA-ICT 40739, 10, 34.1 – 70.5 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 25 Sep 2013, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves & M. Sabaj-Péres. INPA-ICT 40747, 18, 54.0 – 90.3 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 24 Sep 2013, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves & M. Sabaj-Péres. INPA-ICT 40843, 15, 31.8 – 66.0 mm SL, Anapu, 03 ° 28 ’ 20 ” S 51 ° 11 ’ 52 ” W, 1 Oct 2013, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves & M. Sabaj-Péres. INPA-ICT 43082, 4, 47.6 – 89.5 mm SL, Senador José Porfírio, 02 ° 35 ’ 27 ” S 51 ° 57 ’ 15 ” W, 27 Oct 2140, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves & M. Sabaj-Péres. INPA-ICT 43152, 1, 96.0 mm SL, Senador José Porfírio, 02 ° 35 ’ 27 ” S 51 ° 57 ’ 15 ” W, 3 Mar 2014, L. M. Sousa, M. Sabaj-Péres, A. S. Oliveira & P. M. Ito. INPA-ICT 43213, 7, 62.5 – 113.3 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 4 Mar 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 43249, 7, 61.6 – 77.0 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 5 Mar 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 43260, 8, 2.1 – 84.5 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 5 Mar 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 43295, 3, 46.5 - 65.0 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 6 Mar 2013, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas, M. Sabaj-Péres. INPA-ICT 43334, 2, 80.1 – 102.6 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 7 Mar 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 43546, 2, 48.8 – 50.9 mm SL, Altamira, 03 ° 12 ’ 12 ” S 52 ° 12 ’ 23 ” W, 13 Mar 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 43229 (same data as INPA-ICT 43213), 6, 70.8 – 107.0 mm SL, Porto de Moz, 01 ° 44 ’ 54 ” S 52 ° 14 ’ 18 ” W, 4 Mar 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. LIA 0021, 1, 61.4 mm SL, Belo Monte, 03 ° 07 ’ 45 ” S 51 ° 39 ’ 56 ” W, 28 Sep 2012, D. Bastos. LIA 5098, 5, 75.3 – 88.1 mm SL, rio Xingu, off right bank, ca. 1 km northwest of Porto do Moz, 01 ° 44 ’ 42 ” S 52 ° 14 ’ 54 ” W, 14 Nov 2014, M. H. Sabaj, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). LIA 5105, 7, 75 – 113.9 mm SL, rio Xingu, off right bank, ca. 1 km northwest of Porto do Moz, 01 ° 44 ’ 42 ” S 52 ° 14 ’ 54 ” W, 14 Nov 2014, M. H. Sabaj, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). LIA 5118, 2, 72.8 – 106.49 mm SL, rio Xingu, off right bank ca. 3 km north-northwest of Porto do Moz, 01 ° 43 ’ 53 ” S 52 ° 15 ’ 20 ” W, 14 Nov 2014, M. H. Sabaj, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). LIA 5122, 2, 99.9 mm SL, rio Xingu, off right bank ca. 3 km north-northwest of Porto do Moz, 01 ° 43 ’ 53 ” S 52 ° 15 ’ 20 ” W, 14 Nov 2014, M. H. Sabaj, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). LIA 5146, 19, 62.9 – 103.43 mm SL, rio Xingu, off upstream end of island, downstream of campsite 7, ca. 3.5 km northwest (downstream) of BR- 230 ferry crossing on left bank (Belo Monte II), 03 ° 06 ’ 19 ” S 51 ° 43 ’ 28 ” W, 19 Nov 2014, M. H. Sabaj, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). LIA 5153, 3, 34.2 – 67.37 mm SL, rio Xingu, off right bank at confluence of three major braids, just upstream of campsite 7, 03 ° 07 ’ 45 ” S 51 ° 39 ’ 55 ” W, 19 Nov 2014, M. H. Sabaj, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). LIA 5161, 5, 62.3 – 80.2 mm SL, rio Xingu, off right bank ca. 20 km southeast of Vitória do Xingu, 02 ° 58 ’ 51 ” S 51 ° 51 ’ 32 ” W, 20 Nov 2014, M. H. Sabaj, L. M. Sousa & fishermen D. R. Costa (Dani), D. R. Costa (Ronca), N. S. Balão (Nelson) & A. S. Oliveira (Tonho). LIA 6305, 2, 46.7 – 51.1 mm SL, rio Xingu, rock pile in channel, 03 ° 07 ’ 45 ” S 51 ° 39 ’ 55 ” W, 29 Aug 2016, L. M. Sousa. LIA 6863, 5, 62.6 – 116.54 mm SL, Senador José Porfírio, Pedral in front of Itaubinha, 02 ° 53 ’ 19 ” S 51 ° 56 ’ 20 ” W, 8 Oct 2017, L. M. Sousa.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	diagnosis	Diagnosis. Hypancistrus seideli is distinguished from all congeners by its color pattern, having head, body and fins with alternating dark and pale vermiculations (vs. tan background color with irregular brown blotches in H. yudja and small dark spots in H. phantasma; dark background color with pale spots in H. contradens, H. inspector, H. lunaorum, H. margaritatus, and H. vandragti or with pale lines and spots in H. debilittera; body with pattern of alternating light and dark broad wavy bars in H. furunculus; and white background color with black straight stripes in H. zebra). It can be further distinguished from H. debilittera by the number of bars on fins (6 to 10 in H. seideli and 3 to 4 in H. debilittera).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	description	Description. Morphometric and meristic data presented in Tab. 2. Medium-sized loricariid, largest specimen measuring 117 mm SL. Body short and deep with deepest point at supra-occipital (17 – 36 % SL), becoming gradually slender after dorsal fin base. Head deep, snout short. In lateral view, dorsal profile convex, rising as straight line from snout to nares, becoming gently curved from that point of the end of head, then gradually declining to the end of caudal peduncle. Ventral profile straight from snout tip to pelvic-fin insertion, then ascending gradually to insertion of first caudal-fin ray. Greatest width of body at cleithrum (29 – 36 % SL). Head somewhat short (32 – 42 % SL), without ridges or carinae. Head and snout completely covered by plates with odontodes. Hypertrophied odontodes on cheek plates relatively few, completely exposed and partly set in depression anterodorsally to cleithrum. Eye large, laterodorsal; orbit round and distinctly elevated; dorsal rim of orbit surpassing level of dorsal most portion of frontal bones. Parieto-supraoccipital process short, bearing a small dorsal crest and limited posteriorly by set of predorsal plates arranged as one disjunct pair, followed by one or two closely attached pairs plus one single plate immediately anterior to dorsal-fin spinelet. Oral disk circular, lips almost completely covered with small round papillae (papillae larger on proximal region of lower lip); lips smooth near maxillae. Lower lip large but not reaching pectoral girdle. Maxillary barbel moderate, larger than orbital diameter, mostly free from lower lip. Premaxillary teeth thin, delicate and bifurcated; mesial cusp larger, lateral cusp reaching mid portion of mesial cusp. Premaxillary teeth 5 – 18, two to three times smaller than dentary teeth; tooth crown bright red. Dentary with fewer teeth than premaxillary (1 – 9), similar in shape but considerably more robust. Dentary tooth rows arranged in approx. 90 ° angle. Branchial opening small. Interbranchial distance 15 – 25 % HL. Lateral line with 19 – 25 * plates, four * to five plates between dorsal and adipose fins, 8 – 11 plates (10 *) between anal and caudal fins. Body not carinate or keeled. Caudal peduncle deep and covered by five series of plates. All body plates covered by strong odontodes. Ventral surface largely naked from snout to anal-fin insertion; pectoral, thoracic and pre-anal areas with few small, scattered plates bearing odontodes, especially on larger specimens. Single plate between urogenital opening and anal-fin insertion. All fin rays supporting odontodes; odontodes more developed on first (undivided) ray. Origin of dorsal fin in anterior third of body, between pectoral and pelvic-fin insertions. Dorsal fin II + 7 *, short, composed of spinelet, spine, and seven soft, segmented, branched rays. Dorsal-fin spinelet triangular with functional locking mechanism. Dorsal-fin spine with small odontodes along its entire margin. Tip of adpressed dorsal-fin spine reaching preadipose plate; membrane between last dorsal-fin ray and body absent. Four * to five plates separating dorsal and adipose fins. Adipose fin well developed, its base containing 5 – 6 plates; preadipose plate present. Adipose fin with strong spine bearing small odontodes on its entire surface, its distal tip reaching first caudal-fin procurrent ray. Pectoral fin with spine and 6 – 7 soft, segmented, branched rays (I + 6 * – 7). Tip of adpressed pectoral fin reaching proximal half of pelvic fin. Pelvic fin with first ray thickened and unbranched and 5 – 6 branched rays (i + 5 * – 6). Pelvic-fin tip slightly surpassing posterior end of anal-fin base. Anal fin with i + 3 – 5 rays (4 *). Caudal fin lunate with i + 13 – 14 + i rays, the dorsal and ventralmost thickened, unbranched and bearing small odontodes; lower lobe slightly longer than upper lobe. Color in alcohol. Body, head and fins with alternated dark and pale wavy lines. Number and shape of pale lines vary ontogenetically and geographically. In juveniles, the light lines are relatively thick, less wavy and sometimes interrupted, leaving a sequence of light blotches on the body. In large specimens the lines are thinner, more numerous and frequently collapsed, forming a reticulate or alveolar pattern. Individuals of a same population may exhibit highly variable patterns of vermiculation (Fig. 6). The frequency of these color types may vary along the longitudinal distribution of the species. Color in life. Similar to color in alcohol but more contrasting, with pale lines varying from white to yellowish, sometimes even pinkish. Sexual dimorphism. Hypancistrus seideli presents the same secondary sex characteristics described for H. yudja, with males presenting hypertrophied odontodes on cheeks, pectoral spine and all body plates. The males also have a slimmer body but grow larger than females, with head proportionally larger. Females present a rounder body in dorsal view (more noticeable in gravid individuals). Sex dimorphism in H. seideli was extensively discussed in Reis et al. (2022).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	distribution	Geographical distribution. Hypancistrus seideli occurs throughout the lower Xingu channel from the extreme downstream portion of Volta Grande do Xingu to the river’s confluence with the rio Amazonas (Fig. 3). Populations of Hypancistrus resembling H. seideli are found in the downstream portion of other clearwater tributaries of rio Amazonas, and their taxonomic status remains under study.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	biology_ecology	Ecological notes. Hypancistrus seideli occupies the broadest range of habitats known for the genus. The known depth range varies from <1 to 40 m, and the rocks they inhabit vary from granitoid boulders to sedimentary rocks (e. g., sandstones) of all shapes and sizes (Fig. 7). They can occur in strong currents at the downstream end of Volta Grande do Xingu (Middle Xingu), as well as in slow-flowing conditions in the Lower Xingu mouth bay (i. e., ria).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	discussion	Remarks. Hypancistrus seideli is a difficult species to diagnose using traditional taxonomic criteria, including its (conspicuous) color pattern. Its phenotypic plasticity spans an astonishing array of color patterns, many of which are recognized and named as varieties in the aquarium trade. Some morphotypes are slender with elongated caudal-fin lobes (e. g., L 66) while other forms are stouter-bodied and with a somewhat truncated caudal fin (e. g., L 333). Several intermediate forms exist, each one with an individual L code number (Haagensen, 2014).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	vernacular_names	Popular name. Acari-pão (Portuguese); King Tiger Pleco, Golden King Tiger, (English); L 66, L 236, L 287, L 333, L 399, L 400 (and perhaps some other L code numbers).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	etymology	Etymology. A patronym honoring Ingo Seidel, a renowned German aquarist whose decades of dedication to the care, understanding, and breeding of Hypancistrus species in captivity have made him a global authority. Ingo’s vast contributions to the knowledge of Hypancistrus (and other loricariid genera) through numerous books and lectures have significantly advanced the aquarium hobby, particularly in the realm of pleco breeding. This species is named in recognition of his unwavering passion and invaluable contributions to the field.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB608F6CFC9AFDE1B570FB51.taxon	conservation	Conservation status. Hypancistrus seideli is widespread throughout the entire Lower Xingu channel from the extreme downstream portion of Volta Grande do Xingu to the river’s confluence with the rio Amazonas. The species occupies slow moving stretches of the river and probably will not be negatively affected by the Belo Monte dam. Their adaptability is shown by the presence of an introduced population near the town of Altamira that became established after the release of captive specimens by aquarium fish traders some years ago. Populations of this species currently face no identified imminent threats, which would align with the Least Concern (LC) categorization, as per the criteria established by the International Union for Conservation of Nature (IUCN, 2022).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	description	urn: lsid: zoobank. org: act: A 07 CFE 91 - CEDD- 4558 - BCBE- 1 B 102690 E 030 (Figs. 1 – 2; Tab. 1)	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	materials_examined	Holotype. INPA-ICT 61049, 42.1 mm SL, rio Xingu, main channel along right bank at Pimental Dam site, ca. 37 km southeast of Altamira, Pará State, Brazil, 03 ° 25 ’ 55.3 ” S 51 ° 57 ’ 23.6 ” W, 11 Nov 2014, M. H. Sabaj, L. M. Sousa, A. P. Gonçalves, D. B. Fitzgerald, V. Machado, P. M. Ito, A. Oliveira, H. Gimênes Jr., M. Hardman, J. Tiemann, K. S. Cummings, M. C. Dreher Mansur and ornamental fishermen. Paratypes. All specimens from Xingu, Brazil, Pará State: ANSP 193084, 5, not measured, rio Xingu, deep rocky ledges in main channel, ca. 60 km east-southeast of Altamira, 03 ° 24 ’ 58.5 ” S 51 ° 42 ’ 38.6 ” W, 14 Oct 2012, M. H. Sabaj & L. M. Sousa. ANSP 194887, 10, 31.8 – 49.4 mm SL, rio Xingu (lower Volta Grande), main straight channel running from south-southwest to north-northeast, 03 ° 11 ’ 3.36 ” S 51 ° 37 ’ 2.46 ” W, 28 Sep 2013, L. M. Sousa, A. Gonçalves, N. K. Lujan, D. B. Fitzgerald, P. Madoka Ito & fishermen. ANSP 197292, 1, 42.3 mm SL, collected with the holotype; ANSP 197623, 3, 29.8 – 44.1 mm SL, LIA 5070, 2, 47.4 – 48.0 mm SL, rio Xingu, central channel, 03 ° 24 ’ 58.5 ” S 51 ° 42 ’ 38.7 ” W, 9 Nov 2014, M. H. Sabaj & L. M. Sousa. ANSP 198631, 1, 41.5 mm SL, LIA 5059, 1, 44.9 mm SL, rio Xingu, major channel just upstream of cachoeira do Jericoá, ca. 55 km east-southeast of Altamira, 03 ° 22 ’ 55.4 ” S 51 ° 44 ’ 13.0 ” W, 8 Nov 2014, M. H. Sabaj & L. M. Sousa. ANSP 198636, 2, 28.0 – 32.1 mm SL, rio Xingu, major channel along right bank, ca. 60 km southeast of Altamira, 03 ° 31 ’ 06.2 ” S 51 ° 45 ’ 08.1 ” W, 9 Nov 2014, M. H. Sabaj & L. M. Sousa. AUM 74485, 2, 44.5 – 45.7 mm SL, collected with ANSP 194887. INPA-ICT 30115, 10, 30.8 – 34.0 mm SL, Belo Monte, 03 ° 06 ’ 54 ” S 51 ° 43 ’ 15 ” W, 5 Nov 2004, L. M. Sousa & E. D. Ribeiro. INPA-ICT 31404, 19, 26.7 – 42.8 mm SL, Maia Community, rocky outcrop in front of the camp, 03 ° 30 ’ 44 ” S 51 ° 44 ’ 43 ” W, 9 Nov 2008, M. Santos, L. Rapp Py-Daniel, I. M. Soares, R. P. Ota, D. B. Fitzgerald, A. P. Gonçalves, L. M. Sousa & M. Sabaj-Péres. INPA-ICT 40757, 15, 30.8 – 51.1 mm SL, rio Xingu, below Volta Grande, narrow region of the main channel, 03 ° 11 ’ 03 ” S 51 ° 37 ’ 02 ” W, 28 Sep 2013, A. R. Martins, D. R. G. Ribeiro, R. R. Reyes, D. B. Fitzgerald, J. Zuanon, M. Arce, A. P. Gonçalves & M. Sabaj-Péres. INPA-ICT 43790, 6, 27.0 – 41.5 mm SL, deep rocky ledges in main channel, ca. 60 km east-southeast of Altamira, 03 ° 24 ’ 58.5 ” S 51 ° 42 ’ 38.6 ” W, 14 Oct 2012, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 47294, 3, 29.6 – 49.0 mm SL, rio Xingu, main channel on the right bank, ca. 60 km from Altamira, 03 ° 31 ’ 06 ” S 51 ° 45 ’ 08 ” W, 9 Nov 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 47526, 1, 31.1 mm SL, Rio Xingu, ca. 4.5 km above Praia do Caju, 03 ° 24 ’ 58 ” S 51 ° 42 ’ 39 ” W, 9 Nov 2014, L. M. Sousa, D. Fitzgerald, A. S. Oliveira, P. M. Ito, N. Lujan, R. Robles, V. Vargas & M. Sabaj-Péres. INPA-ICT 52316, 6, 31.5 – 46.7 mm SL, rio Xingu, Praia do Caju, 03 ° 22 ’ 58 ” S 51 ° 44 ’ 17 ” W, 2 Sep 2012, IBAMA. LIA 1680, 9, 31.1 – 48.0 mm SL, Pedral do Jaú, 03 ° 38 ’ 12.1 ” S 51 ° 73 ’ 67.8 ” W, 10 Nov 2013, A. Gonçalves & L. M. Sousa. LIA 1685, 4, 33.5 – 50 mm SL, region of Jericoá, 03 ° 41 ’ 56.3 ” S 51 ° 71 ’ 10.5 ” W, 10 Nov 2013, A. Gonçalves & L. M. Sousa. LIA 5076, 1, 28.6 mm SL, collected with ANSP 198636. LIA 6956, 1, 28.1 mm SL, region of Jericoá, 03 ° 24 ’ 59 ” S 51 ° 42 ’ 38 ” W, 3 Oct 2017, L. M. Sousa. LIA 6938, 4, 26.7 – 39.6 mm SL, Largo do Maia, 03 ° 31 ’ 05 ” S 51 ° 45 ’ 07 ” W, 4 Oct 2017, L. M. Sousa. LIA 6944, 3, 23.0 – 42.8 mm SL, region of Jericoá, 03 ° 22 ’ 53 ” S 51 ° 44 ’ 13 ” W, 3 Oct 2017, L. M. Sousa. ROM 112318, 3, 40.1 – 44.9 mm SL, collected with ANSP 194887.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	diagnosis	Diagnosis. Hypancistrus yudja can be distinguished from all congeners by its unique color pattern consisting of body with a light tan background and relatively large brown blotches and saddles (vs. pattern composed of small, dark, isolated spots in H. phantasma; background color dark brown to black with pale spots in H. contradens, H. inspector, H. lunaorum, H. margaritatus, and H. vandragti or with pattern of pale lines and small spots in H. debilittera Armbruster, Lujan & Taphorn, 2007; coloration composed of alternating dark and pale wavy lines that are broad in H. furunculus and narrow in H. seideli; and background white with roughly straight black stripes in H. zebra).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	description	Description. Morphometric and meristic data in Tab. 1. Small-sized loricariid, with largest examined specimen measuring 50.0 mm SL. Body short and deep, deepest point at insertion of dorsal fin (19 – 27 % SL), becoming gradually slender after dorsal-fin base. In lateral view, dorsal profile gently convex from snout to dorsal-fin insertion and gently declining from this point to end of caudal peduncle; peduncle concave from end of adipose fin to last lateral plate (11 – 18 % SL). Ventral profile straight from snout tip to pelvic-fin insertion, then ascending gently to insertion of first caudal-fin ray. Greatest width of body at cleithrum (30 - 37 % SL). Head somewhat long (35 - 41 %), without ridges or carinae. Head and snout completely covered by plates supporting odontodes. Cheek odontodes completely exposed and set in depression anterodorsally to cleithrum. Eye laterodorsal with small but conspicuous iris; orbit round and slightly elevated, dorsal rim of orbit barely reaching level of dorsalmost portion of frontal bones. Interorbital almost flat between orbital ridges. Parieto-supraoccipital process showing conspicuous crest and pointed posteriorly. Parieto-supraoccipital limited posteriorly by set of predorsal plates arranged as one disjunct pair, followed by one or two closely attached pairs plus one single plate immediately anterior to dorsal-fin. Oral disk circular, lips almost completely covered with small round papillae (papillae larger on proximal region of lower lip), margin of lower lip smooth (papillae absent). Lower lip large but not reaching pectoral girdle. Maxillary barbel moderate in size, longer than orbital diameter, almost reaching tip of cheek plates, with large portion free from lower lip. Premaxillary teeth thin, delicate and bifurcated; mesial cusp larger, lateral cusp reaching mid portion of mesial cusp; teeth somewhat numerous (4 – 14), two to three times smaller than dentary teeth; tooth crown bright red. Dentary with fewer teeth than premaxillary (1 – 7), similar in shape but considerably larger than premaxillary ones. Dentary tooth rows arranged in approx. 90 ° angle. Branchial opening small. Interbranchial distance 17 – 29 % HL. Lateral line plates 20 to 24 (21 *), three to five (4 *) plates between dorsal and adipose fin, eight to 10 * plates between anal and caudal fin. Body plates not carinate or keeled. Caudal peduncle deep and covered by five series of plates. All body plates covered by strong odontodes. Ventral surface entirely naked from snout to anal-fin insertion; single plate between urogenital opening and anal-fin insertion. All fin rays supporting odontodes, more developed on first (undivided) ray. Dorsal fin II + 7 *, pectoral fin I + 5 – 6 (modally 6 *), pelvic fin i + 4 – 5 (modally 5 *), anal fin I + 3 – 4 (modally 4 *) and caudal fin i + 13 – 14 + i (modally 14 * branched rays). Dorsal fin spinelet triangular, with functional locking mechanism. Dorsal fin reaching adipose fin when adpressed. Adipose fin slanted posteroventrally, spine strong, straight to gently curved with pointed tip reaching first caudal-fin procurrent ray; base containing five plates; preadipose plate present. Tip of adpressed pectoral fin reaching one-third of pelvic-fin length; adpressed pelvic fin slightly surpassing posterior end of anal-fin base; paired fins triangular with slightly curved posterior margin. Caudal fin lunate with the upper lobe slightly smaller than lower lobe. Color in alcohol. Overall background color pale white or cream; irregular brown to dark-brown rounded or elongated blotches along head, body and fins (Figs. 1 – 2). Ventral surface uniformly light, beige, with little or no pigmentation. Brown blotches sometimes coalesce to form saddles, dumbbells or other irregular shapes. When present, dorsal saddles usually not bilaterally symmetrical. Area between and just past dorsal posterior margin of orbits often with broad dark transverse bar; longitudinal dark oblique bars often present from orbit and nares, respectively, to ventral lateral margin of snout. All fin rays with two to three dark markings that can be organized as stripes. Some specimens showing wide dark transversal bars on dorsal fin. Color in life. Similar to preserved specimens but contrast between pale background and dark brown blotches more evident (description based on observations of several specimens in aquarium, on pictures of living specimens and in freshly collected specimens). Sexual dimorphism. Hypancistrus yudja presents the secondary sex characteristics often seen in ancistrin loricariids. Mature males possess hypertrophied odontodes on the cheek, pectoral spine and most of the body plates. Odontodes on body plates become larger on the caudal peduncle. Based on observations of aquarium-kept specimens, the hypertrophied odontodes on mature males appear to be permanent. The head slightly longer and wider in males than in females. Gravid females are usually distinguishable in dorsal view due to their wider abdominal region. Males seem to grow a little larger than females.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	distribution	Geographical distribution. Hypancistrus yudja is only known from a very small stretch of the Volta Grande do Xingu, spanning nearly 75 km of the main river course (Fig. 3).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	biology_ecology	Ecological notes. Hypancistrus yudja inhabits deep portions of the rio Xingu channel. It was only found hidden in lateritic conglomerates below 15 m of depth (Fig. 4). All specimens were collected individually by hand during diving sessions aided by air compressors or scuba equipment. Observations made on specimens kept in captivity suggest that it is a fairly shy species that remains secluded in caves for most of the day. Expert aquarium hobbyists have successfully bred this species. The female lays around 15 – 20 eggs in a cave that is protected by the male. The fry grows slowly in captivity, often taking two years or more to reach maturity. Under prime conditions they will reach 4 – 5 cm TL in about a year.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	vernacular_names	Popular name. Acari-zebra-marrom, zebra-marrom, acari-marrom (in Portuguese); Ozelot-Harnischwels (in German); Ozelot pleco, false zebra pleco, Peruvian (sic) Panther pleco (in English); L 174 (L code number).	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	etymology	Etymology. Named after the Yudjá (also known as Juruna), a group of indigenous people from Volta Grande do Xingu. In the Tupi language, Yudjá means “ the river owners ”. This ethnic group has an intimate relationship with the Xingu, being pioneers in navigation on the turbulent, rocky-bottomed waters of this river. Hypancistrus yudja is restricted to the Yudjá territory and was a source of income for the indigenous ornamental fishermen who dove below 15 m to catch specimens for the aquarium trade. Both the Yudjá people and H. yudja are struggling to survive the environmental impacts of the Belo Monte Hydroelectric Complex on Volta Grande do Xingu, and their fate is connected and deeply threatened.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
03FC87DCFB698F74FC9EFE97B53DFDB1.taxon	conservation	Conservation status. Hypancistrus yudja is restricted to a 75 km stretch of the Volta Grande region of the rio Xingu, in the state of Pará, Brazil. The species’ entire area of occurrence falls within the direct impact zone of the Belo Monte Hydroelectric Complex, placing it at high risk of extinction due to severe environmental degradation. This species can be classified as Critically Endangered (CR) under IUCN criteria A 4 a, c, d, (IUCN, 2022) due to an estimated population decline exceeding 80 %, driven by severe habitat degradation from the diversion of over 70 % of the rio Xingu’s water for hydroelectric operations, disruptions to natural flood and drought cycles, and exploitation for the ornamental fish trade. Recent scuba surveys failed to locate the species in its known habitat, further suggesting a drastic population decline.	en	Sousa, Leandro Melo de, Sousa, Erilda Barbosa de, Ribeiro, Renildo de Oliveira, Sabaj, Mark H., Zuanon, Jansen, Py-Daniel, Lúcia Rapp (2025): Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotropical Ichthyology 23 (1): e 240080, DOI: 10.1590/1982-0224-2024-0080, URL: https://doi.org/10.1590/1982-0224-2024-0080
