Phalloceros circummontanus, Souto-Santos & Mejia & Arcila & Buckup, 2025

Phalloceros circummontanus , new species urn:lsid:zoobank.org:act:B654C0E5-936B-4AED-9B65-884BD27B8045

( Figs. 1A, 2A; Tab. 1)

Phalloceros harpagos (Tietê) View in CoL . — Thomaz et al., 2019:270 View Cited Treatment , fig. 3 (hypothesis of phylogenetic relationships among congeners).

Phalloceros harpagos View in CoL (Haplotype 5). — Oliveira et al., 2024:5, fig. 2 (Haplotype 5 clade in a gene tree with results of four molecular species delimitation analyses).

Holotype. MNRJ 55366 View Materials , 25.7 mm SL, female, Brazil, Minas Gerais, Caldas, small stream on the left bank of the rio Pardo (upper rio Paraná basin: rio Grande drainage), on the road from Caldas to Fim dos Campos, 400 m east of the road to São Pedro de Caldas , 21°54’45”S 46°19’30”W, 22 Nov 2003, P. A. Buckup & R. Souza-Lima. GoogleMaps

Paratypes. All from Brazil, State of Minas Gerais: rio Grande drainage (tributary of upper rio Paraná basin). Rio das Mortes drainage: MNRJ 31883 View Materials , 113 View Materials , 12.3–36.7 mm SL, Carandai , rio Carandaí , upstream from Carandaí , Ponte Alta neighborhood, 20°57’12”S 43°46’34”W, 2 Sep 2007, P. A. Buckup, M. R. Britto, U. Jaramilo, L. Villa- GoogleMaps

Verde & J. Maldonado. MNRJ 54586 View Materials , 65 View Materials , 10.3–25.3 mm SL, Santa Cruz de Minas, tributary of the Rio das Mortes, downstream of Bom Despacho waterfall, near Min. Gabriel Passos Avenue, 21°7’15”S 44°12’16”W, 22 May 2023, I. C. A. Souto-Santos, B. C. A. Souto-Santos, D. C. A. Souto-Santos & M. V. Santos. Rio Sapucaí drainage: MNRJ 54494 View Materials , 5 View Materials , 12.9–41.2 mm SL, Itamonte, rio da Colina, upstream of Itamonte, rio Verde drainage, 22°19’24”S 44°50’20”W, 20 May 2023, I. C. A. Souto-Santos, B. C. A. Souto-Santos, D. C. A. Souto-Santos & M. V. Santos. MNRJ 54589 View Materials , 9 View Materials , 18.5–28.5 mm SL, Carmo do Rio Claro , Pedra Molhada village , 21°00’18”S 46°14’49”W, 30 Oct 2021, A. Katz & V. M. Azevedo-Santos. MNRJ 23975 View Materials , 172 View Materials , 13.0– 42.6 mm SL, São Bento do Sapucaí , córrego Monjolinho, at bridge about 1.5 km east of road SP-042, 22°42’50”S 45°42’15”W, 31 May 2002, P. A. Buckup, L. Ingenito, A. T. Aranda, C. Chamon & F. P. Silva. Rio Pardo drainage: MNRJ 26119 View Materials , 52 View Materials /4, 8.9–25.3 mm SL, MCP 55062 View Materials , 20 View Materials , 9.3 View Materials –26.0 mm SL, collected with the holotype GoogleMaps .

Non-type specimens. All from Brazil, grouped according to hydrographic drainage from north to south. Upper rio Paraná basin, Paranaíba : MNRJ 51292 View Materials , 6 View Materials , 16.4–30.9 mm

SL, Distrito Federal, Brasília, ribeirão do Torto (tributary of rio São Bartolomeu), Torto,

Vila dos Operários, 15°41’59”S 47°54’28”W, 13 Sep 2018, F. H. Soares. MNRJ 54227 View Materials GoogleMaps ,

1, 18.6 mm SL, Distrito Federal, Brasília, ribeirão da Gama (drainage of the Paranoá, São

Bartolomeu), Brasília airforce base, 15°52’6”S 47°53’28”W, 19 Dec 2022, C. H. Luz.

Tietê: LBP 14607, 2, 22.2–26.5 mm SL, São Paulo, Botucatu, rio Araquá , 22°44’50”S

48°28’30”W, 25 Nov 2011, F. Roxo, M. Mehana & G. S. C. Silva. ZUEC-PIS 6159 , 32 , 10.0– 22.1 mm SL, São Paulo , Itirapina Ecological Station, approx . 22º14’ S 47º53’W, 10 Jan 2002, G. B. MNRJ 54859 View Materials , 2 View Materials , 21.4–28.3 mm SL, São Paulo , Valinhos, small stream tributary of rio Atibaia, Dom Pedro I highway bridge GoogleMaps , 22°55’49”S 46°56’22”W, 11 Sep 2023, P. A. Buckup, E. Mejia & I. C. A. Souto-Santos. Iguatemi: MNRJ 54801 View Materials , 25 View Materials , 12.1–33.1 mm SL, Mato Grosso do Sul , Mundo Novo , córrego Santa Maria upstream from BR-163 culverts, right bank tributary of rio Iguatemi GoogleMaps , 23°54’56”S 54°17’31”W, 9 Sep 2023, P. A. Buckup, E. Mejia & I. C. A. Souto-Santos. Lower Iguaçu : MNRJ 54789 View Materials , 22 View Materials , 12.3–26.6 mm SL, Paraná , Santa Terezinha de Itaipu, Ribeirão São João and adjacent floodplains next to a culvert in secondary road paved with stones GoogleMaps , 25°32’4”S 54°25’2”W, 3 Sep 2023, P. A. Buckup, E. Mejia & I. C. A. Souto-Santos. Rio Paraíba do Sul basin, Pomba: MNRJ 54588 View Materials , 28 View Materials , 11.9–36.8 mm SL, Minas Gerais , Oliveira Fortes , rio Formoso, tributary of rio Pomba, on side road of BR-040 GoogleMaps , 21°21’6”S 43°35’24”W, 24 May 2023, I. C. A. Souto-Santos, B. C. A. Souto-Santos, D. C. A. Souto-Santos & M. V. Santos. Paraibuna : MNRJ 54209 View Materials , 6 View Materials , 16.2–25.5 mm SL, Minas Gerais , Santa Rita da Jacutinga, Vargem do Sobrado Waterfall GoogleMaps , 22°5’13”S 44°8’19”W, 30 May 2022, I. C. A. Souto-Santos, E. B. Neuhaus & A. Barcia. MNRJ 52959 View Materials , 4 View Materials , 17.3–26.3 mm SL, Minas Gerais , Santa Rita da Jacutinga, Vargem do Sobrado Waterfall GoogleMaps , 22°5’13”S 44°8’19”W, 1 Dec 2021, M. R. Britto , I. C. A. Souto-Santos & E. B. Neuhaus. MNRJ 52952 View Materials , 52 View Materials , 14.1–35.8 mm SL, Minas Gerais , Santa Rita da Jacutinga , Ribeirão Jacutinga, rio Preto drainage GoogleMaps , 22°8’5”S 44°5’5”W, 1 Dec 2021, M. R. Britto, I. C. A. Souto-Santos & E. B. Neuhaus. Pedras: MNRJ 54489 View Materials , 30 View Materials , 9.8 View Materials –28.0 mm SL, Rio de Janeiro , Itatiaia , rio das Pedras at Três Bacias , close to Koskela restaurant at 4065 Três Cachoeiras Avenue GoogleMaps , 22°25’14”S 44°32’15”W, 19 May 2023, I. C. A. Souto-Santos, B. C. A. Souto-Santos, D. C. A. Souto-Santos & M. V. Santos. Caçapava Velha : MNRJ 54504 View Materials , 7 View Materials , 14.4–30.6 mm SL, São Paulo , Caçapava, creek on corner of SP-062 and Egydia Maria Street GoogleMaps , 23°4’1”S 45°39’45”W, 1 July 2022, E. B. Neuhaus & V. C. Gomes. Barreiro de Baixo: MNRJ 41749 View Materials , 1 View Materials , 18.1 mm SL, Rio de Janeiro , Porto Real , rio Barreiro de Baixo, Resende – Bulhões road GoogleMaps , 22°27’57”S 44°22’1”W, 8 Nov 2013, P. A. Buckup & T. S. Parente. Comando : MNRJ 24441 View Materials , 44 View Materials , 8.6–31.4 mm SL, São Paulo , Jacareí , next to bridge south of Colonião neighborhood, east of Jacareí GoogleMaps , 23°17’46”S 45°53’43”W, 16 Feb 2002, P. A. Buckup, F. P. Silva & R. Souza-Lima. AMNH 22673 About AMNH , 11 About AMNH , 15.5–26.1 mm SL, São Paulo , Jacareí , rio Paraíba do Sul , 14 July 1908, J. D. Haseman. Ilha Grande Bay , Mambucaba : MNRJ 43438 View Materials , 50 View Materials , 10.3–27.8 mm SL, São Paulo , São José do Barreiro , rio Mambucaba next to Gavião bridge GoogleMaps , 22°50’13”S 44°34’28”W, 6 Jun 2015, P. A. Buckup & R. Arruda. Perequê-Açu : MNRJ 50623 View Materials , 1 View Materials , 22.3 mm SL, Rio de Janeiro , Paraty , rio Sertões , entering through Engenho D’Ouro restaurant at Penha GoogleMaps , 23°13’26”S 44°45’35”W, 25 Aug 2015, R. Souza-Lima and others. MNRJ 50628 View Materials , 16 View Materials , 13.2–34.2 mm SL, Rio de Janeiro , Paraty , middle rio Sertões , trail to rio Estiva Preta from gate of Sítio Bela Vista at beginning of dirt section of Paraty-Cunha road, approximately km 13 GoogleMaps , 23°12’32”S 44°49’50”W, 7 Jul 2016, R. Souza-Lima and others. Rio Itapanhaú basin: MNRJ 41734 View Materials , 12 View Materials , 11.9–34.6 mm SL, São Paulo , Mogi das Cruzes, headwaters of rio Grande, Natureza de Taiacupeba District GoogleMaps , 23°41’52”S 46°8’23”W, 7 Nov 2011, P. A. Buckup, D. F. Almeida, R. Souza-Lima & R. R. Rodrigues GoogleMaps .

Diagnosis. The Phalloceros circummontanus is a member of a group of species (also including P. caudimaculatus (Hensel, 1868) , P. elachistos Lucinda, 2008 , P. enneaktinos Lucinda, 2008 , P. harpagos , P. heptaktinos Lucinda, 2008 , P. leticiae Lucinda, 2008 , P. maldonadoi Souto-Santos, Lucinda & Buckup, 2023 , P. mikrommatos Lucinda, 2008 , P. ocellatus Lucinda, 2008 , and P. titthos Lucinda, 2008 ) with the tip of the female urogenital papilla oriented caudally (vs. tip curved to the right in P. alessandrae Lucinda, 2008 , P. anisophallos Lucinda, 2008 , P. buckupi Lucinda, 2008 , P. lucenorum Lucinda, 2008 , P. malabarbai Lucinda, 2008 , P. megapolos Lucinda, 2008 , P. pellos Lucinda, 2008 , P. reisi Lucinda, 2008 , P. spiloura Lucinda, 2008 , and P. uai Lucinda, 2008 ; tip curved to the left in P. leptokeras Lucinda, 2008 ). Phalloceros circummontanus is distinguished from P. caudimaculatus , P. heptaktinos , P. leticiae , P. mikrommatos , and P. ocellatus by the possession of a hook in the gonopodial appendix (vs. hook absent in the gonopodial appendix); from P. titthos , by the convexity of the dorsal profile between the tip of the snout and the origin of the dorsal fin in both males and females (vs. dorsal profile straight); from P. enneaktinos , by having a dark pigmented lateral spot located modally in the 16 th scale (vs. spot absent or difuse, located modally in the 18 th scale) ( Tab. 2), and the possession of seven or eight dorsal-fin rays, very rarely nine (vs. nine, very rarely eight or ten) ( Tab. 3); from P. harpagos and P. elachistos , by having a posterior rounded flap on the gonopodial appendix in small (15.4–21.2 mm SL) specimens (vs. flap absent in all size classes of mature males). Additionally, P. circummontanus differs from P. harpagos by having a flattened hood-like projection of skin located between the anus and the urogenital papilla of most females (vs. hood-like projection of skin always absent); and from P. maldonadoi by the symmetrical hood or hood absent (vs. asymmetrical hood always present).

Description. Morphometric data of holotype and paratypes in Tab. 1. Overall appearance shown in Fig. 1A. Body elongate, fusiform. Greatest body depth at dorsal-fin origin. In lateral view, dorsal profile convex from snout to dorsal-fin origin, posteroventrally slanted at dorsal-fin base, nearly straight at caudal peduncle. Ventral profile of head convex at lower jaw, nearly straight from anguloarticular to isthmus. In females, ventral profile increasingly convex from isthmus to anal-fin origin, slightly posterodorsally slanted at anal-fin base, straight at caudal peduncle. In males, ventral profile straight from isthmus to anal-fin origin, slightly convex at caudal peduncle. Distal margin of dorsal fin gently curved. Distal margin of caudal fin rounded. In adult males, base of anal and pelvic fins displaced to anterior portion of belly. Gonopodium base wider than tip. Distal margin of anal fin in females nearly straight. Pectoral fin rounded, symmetrical. Mouth superior. Dermal papillae present on symphyseal portion of lower lip. Maxilla vertically oriented; posterior tip of maxilla not reaching level of anterior margin of orbit. Nares dorsally positioned; anterior and posterior nasal pores separated. Orbital margin circular. Margin of eye free. Teeth unicuspid. Outer premaxillary teeth 14(1), 15(2) or 18(1). Outer dentary teeth 10(1), 12(1), 18(1) or 19(1). Maxilla and vomer toothless. Fourth ceratobranchial toothless; inner surface of fifth ceratobranchial covered with numerous unicuspid teeth. Branchiostegal rays 5(4). Scales cycloid, 28(3) or 29*(17) in longitudinal series, 7(7) or 8*(13) in transverse series. Series of scales around caudal peduncle 15(2) or 16*(18). Dorsal-fin rays 7(19), 8*(89) or 9(4). Branched pectoral-fin rays 5(1), 6(12) or 7*(3). Pelvic-fin rays 5(4). Anal-fin rays in females 10(8) or 11*(3). Anal-fin rays in males 9(2). Branched caudal-fin rays 11*(5) or 12(10). Predorsal scales 14(1), 15*(14) or 16(5). Epipleural ribs 12(4). Pleural ribs 13(2) or 14(2). Vertebrae 31(3) or 32*(2).

Genital morphology. Adult females larger than males, with anal-fin base between vertebrae 15 and 19; anal fin fan shaped; abdominal cavity surrounded by all ribs. Adult females with urogenital papilla located between anus and anal fin ( Fig. 2). Papilla usually covered anteriorly by an expanded dermal flap (i.e., a “hood”, Souto-Santos et al., 2023b); hood absent in some large specimens ( Fig. 3). Papilla pointing caudally; base of papilla aligned with anus and anal fin. Hood much thinner than papilla. Hood and papilla fused near their base on both sides.

Adult males with anal-fin base between vertebrae 9 and 13; anal fin spear-shaped; abdominal cavity between posterior ribs occupied by hypertrophied haemal spines (= gonapophyses), modified anal-fin pterygiophores and associated muscles; anal-fin rays 3 to 5 greatly elongate, modified into gonopodium. Gonopodium of adult males with conspicuous ornamentation at tip ( Fig. 4). Serrae on posterior branch of the fourth ray-R4p 9(4), 10(3). Pair of appendices coalesced at base, on tip of third ray-R3. Each appendix with distal curvature, bearing hook at point of inflection. Distal half of appendix narrower than proximal half; narrowest region located between hook insertion and tip of appendix. Each appendix usually with rounded, distal flap of skin in small males (<22 mm SL); flap absent in larger males (> 22 mm SL) ( Fig. 5). Juvenile males without appendices or with skin covering hooks. Gonopodial suspensory with three large gonapophyses projected anteriorly, from ventral surface of 14 th to 16 th vertebrae ( Fig. S1). Gonapophysis-bearing vertebrae also bearing posteriorly-directed parapophyses with ribs.

Color in ethanol after field fixation in formalin. Background color burlywood, darker on dorsal region. Eye black with greenish grey pupil. Posterior border of scales and underlying skin with numerous brown chromatophores, most concentrated at short distance from scale posterior border, conferring reticulate pattern to sides of body, mainly on dorsal region. Brown or black chromatophores scattered throughout body skin, more concentrated on dorsum, snout, opercle, and ventral surface of mandible. Conspicuous vertically elongate dark spot on flank, located posteriorly to dorsal-fin origin, on 14 th (6), 15 th (15), 16 th *(81), 17 th (60) or 18 th (7) scale of longitudinal series, covering one(3), one-and-a-half*(12) or two(5) scales on horizontal axis, one(2), one-and-a-half(2), two*(14), two-and-a-half(1) or three(1) scales on vertical axis. Light vertical bars on flank in some specimens. Dorsal-fin membrane hyaline bearing dark band of chromatophores on distal border of fin and another near fin base. Pectoral, pelvic, and caudal fins hyaline. In males, chromatophores along R3 of gonopodium forming dark line or diffuse pigmentation. First three anal-fin rays of females often with chromatophores forming patch of dark pigmentation.

Geographical distribution. Phalloceros circummontanus is widely distributed in the rio Paraná basin, encompassing the Brazillian states of Goiás, Minas Gerais, São Paulo, Paraná, and Mato Grosso do Sul. The species is also known from the upper rio Paraíba do Sul basin, and coastal basins from the rio Mambucaba in the State of Rio de Janeiro to rio Itapanhaú in the State of São Paulo ( Fig. 6).

Ecological notes. Phalloceros circummontanus occurs in small headwater streams formerly surrounded by Atlantic Rainforest. The species has been collected in still water and fast-flowing hill-side streams, in clear, black or turbid water, over mud, sand and gravel bottoms.

Etymology. The specific name circummontanus (Latin, adjective, masculine, singular) is a combination of the word circum, meaning around, with the word montanus, meaning “of mountains”. It is an allusion to the distribution of the species around the Serra da Mantiqueira and Serra do Mar mountain ranges, as well as associated highlands that dominate the Southeastern Region of Brazil.

Conservation status. Phalloceros circummontanus is widely distributed in six Brazillian states, with an estimated Extension of Occurrence (EOO) of 605,600 km ². A substantial number of specimens recorded from numerous localities and collecting expeditions over the past two decades suggests that the species is not threatened, despite the extensive human occupation of southeastern Brazil. Based on these criteria, P. circummontanus is provisionally categorized as Least Concern (LC) according to the International Union for Conservation of Nature (IUCN, 2024).

Molecular delimitation. To validate the distinction of Phalloceros circummontanus from morphologically similar species, we compared DNA sequences of the mitochondrial CO1 gene from 34 individuals of P. circummontanus with 32 samples of P. enneaktinos , 17 samples of P. harpagos , and 18 samples of P. titthos . These sequences included samples from the type-localities and additional localities from the known distribution ranges of each species ( Tab. S2). DNA-sequence comparisons confirmed that the four species are genetically distinct ( Tab. 4). The unprecedented sequencing of four topotypes of P. harpagos resulted in a single reference haplotype (Genbank accessions: PQ279178, PQ279112, PQ279104, PQ279170), not related to haplotypes of P. circummontanus ( Figs. S5, S 6). The genetic divergence between P. circummontanus and P. harpagos is more than 6%, far exceeding accepted maximum levels of intraspecific divergence in fishes (Hebert el al., 2003a,b; Pereira et al., 2013). Additionally, the Refined Single Linkage delimitation method (Ratnasingham, Hebert, 2013) performed by the BOLD Systems (http://www.boldsystems.org/) assigned the four species to distinct Barcode Index Numbers (BIN). Specimens of P. circummontanus were assigned to BIN AAB5569, P. enneaktinos were assigned to BIN AAC0280, P. harpagos were assigned to BIN AFX6626, and specimens of P. titthos were assigned to BIN AAB5570.