Taxonomy, Phylogeny, and Conservation of an Endangered Freshwater Fish Species from Southeastern Brazil: Revisiting Historical Descriptions Using Integrative Approaches
Cambeva paolence is a rare and Endangered freshwater fish with a complex taxonomic history, originally described over a century ago. Despite its recognition as a threatened species, uncertainties persist regarding its phylogenetic placement and accurate identification due to limited and outdated morphological and molecular data. This study integrates morphological analyses, including μCT imaging of the holotype, and molecular approaches to provide a comprehensive redescription of C. paolence, clarify its phylogenetic position, distribution, and reassess its Extinction Risk. The molecular and morphological results showed that C. paolence has the synapomorphies of the Trichomycterus subgenus Cryptocambeva; thus, we proposed the generic reallocation of the species. Furthermore, Trichomycterus paolence can be distinguished from all species of the Cryptocambeva subgenus by the possession of a combination of characters: I,3 pelvic-fin rays, I,5 pectoral-fin rays, 43 free vertebrae, and 17 ribs. Also, we confirmed its occurrence in the upper Rio Tietê basin and small coastal adjacent drainages, as well as in the north portion of the Ribeira de Iguape basin through new records. Even so, the species remains categorized as “Endangered” (EN) due to severe population fragmentation, continuing declines in area and quality of habitat, and extent of occurrence smaller than 5,000 km2.
PYGIDIUM paolence was described by Eigenmann (1917) based on material collected by John D. Haseman in 1908 in southeastern Brazil (erroneously quoted as 1909 in the original description; see results). The author described the species based on the holotype (FMNH 58085, formerly CM 7081, 59.4 mm SL) and ten additional small specimens (FMNH 58119, formerly CM 7117, 25.0–27.0 mm SL; Eigenmann, 1917). One year later, Eigenmann provided redescriptions of several species of the Pygidiidae (currently Trichomycteridae) and mentioned one additional paratype of Pygidium paolence from Rio Paranaíba (FMNH 58575, formerly CM 7597, 56.5 mm SL; Eigenmann, 1918), quite distant from the upper Rio Tietê. Subsequently, the taxonomic understanding of these species began to shift. In this context, Tchernavin (1944) played a main role by standardizing the nomenclature within the group. After his work, the name Trichomycterus became widely used for all those species described as Pygidium in the late 19th and early 20th centuries, and Pygidium is currently considered a genus inquirendum in the Trichomycteridae (de Pinna and Wosiacki, 2003).
In a recent study, the species was assigned to the genus Cambeva along with 24 species of Trichomycterus (Katz et al., 2018). The new genus was proposed based on a molecular phylogeny being only distinguishable from other trichomycterine genera combining derived and plesiomorphic morphological character states (Katz et al., 2018). Cambeva paolence was neither examined in detail by the authors nor included in the molecular phylogeny, and the generic reassignment was tentatively based on general external appearance and the geographical distribution shared with congeners (see Katz et al., 2018). In a more recent paper, Costa (2021) described subgenera of Trichomycterus and used a set of characters in the parapophysis of the first vertebra to distinguish Cambeva, Scleronema, and Trichomycterus, but once more C. paolence was not examined. Additional broader phylogenetic approaches of the family based on osteology (Baskin, 1973; de Pinna, 1989, 1992), dorsolateral head muscles (Datovo and Bockmann, 2010), or molecular data (Ochoa et al., 2017, 2020; Katz et al., 2018; Fernandez et al., 2021) did not include the species, making the generic placement and relationship unclear. Probable reasons for this lack of knowledge are the outdated diagnosis and description, doubtful museum records, and rarity in the wild.
Cambeva paolence has been categorized as an Endangered species by Brazilian Extinction Risk Assessment workshops (MMA, 2022; IUCN, 2024). Until 1980, the species was known only from the type series, with one subsequent sighting that year in which it was observed but not captured (ICMBio/MMA, 2018). Non-types available in scientific collections were obtained from a comprehensive faunal survey assessing the ecological impacts of the Mario Covas Beltway construction in the municipality of São Paulo, upper Rio Tietê basin (ICMBio/MMA, 2018), and sporadic expeditions to adjacent coastal drainages. The species has also been recorded from the middle Rio Tietê basin in some extinction risk assessments (see records of ICMBio/MMA, 2018, p. 296, and the distribution map on the IUCN website). However, these records were not considered to estimate the extinction risk of the species, which is categorized as Endangered (EN) in the red list of threatened species of São Paulo State (Decreto 68.853, 2018), Brazil (MMA, 2022) and IUCN (2024) due to habitat loss, population fragmentation, and habitat degradation.
Comprehensive studies aiming at delimiting, diagnosing, and truly understanding the biology of the species, which is rare and Endangered, are necessary (Deprá et al., 2022; dos Reis et al., 2022; Reis and de Pinna, 2019; Zawadzki et al., 2020). Thus, we conducted a systematic review of Cambeva paolence, through an integrative approach using traditional methods in taxonomy and new technologies, such as μCT scans and molecular analyses. A detailed osteological redescription is provided, and a new genus combination is proposed. In addition, we confirm the restricted geographical range and the current extinction risk category of the species.
MATERIALS AND METHODS
Morphological data.—
Morphometric data were taken point to point with a digital caliper (precision of 0.1 mm) on the left side of the specimens. Measurements follow Tchernavin (1944), Costa (1992), Donin et al. (2022), and Nascimento et al. (2017; see Martins et al., 2024 for details), with the addition of the length of the first and second pectoral-fin rays, which follow DoNascimiento et al. (2014).
The holotypes of Pygidium paolence (=Cambeva paolence, FMNH 58085) and P. davisi (=Cambeva davisi, FMNH 54242) were μCT-scanned on a Phoenix v|tome|x s 240 with a dual 180 tube, at the University of Chicago, Department of Organismal Biology and Anatomy, in Chicago (RRID: SCR_024763). X-ray projection images were recorded with the following parameters: timing 150 ms per image, voltage 90 kV, current 230 μA, and voxel size 20.802 μm. The 3D images were visualized, edited, and segmented using VGStudio MAX 2.2.3 64 bit (Volume Graphics GmbH, Heidelberg, Germany). The images generated by VGStudio Max 2.2.3 were edited in the digital software Photoshop version 2021 v. 22. Additional 2D radiographs and osteological data for all types of Cambeva paolence were obtained from the Field Museum of Natural History (FMNH) and one non-type (MZUSP 108930) was cleared and stained (CS) following the protocol of Taylor and Van Dyke (1985).
Nomenclature for bones and cartilage followed Bockmann et al. (2004), except for using parurohyal following Arratia and Schultze (1990), sesamoid supraorbital following Adriaens et al. (2010), and ribs following Britz and Bartsch (2003), all based on the justification given by Costa (2021). Lateral sensory canals and associated pores followed Rizzato and Bichuette (2017). Vertebral counts exclude those in the Weberian complex, and the compound caudal centrum (PU1+U1) was counted as a single element. The counts of unsegmented rays (represented by a lowercase Roman numeral) in CS or radiographed specimens are given before the number of unbranched (represented by an uppercase Roman numeral) and branched rays (represented by an Arabic numeral), following Bockmann et al. (2004). In the description, an asterisk denotes the counts of the holotype, and each meristic character is followed by the number of specimens examined in parentheses. Institutional abbreviations follow Sabaj (2020, 2022).
Specimens were selected for analysis based on material collected and identified as Cambeva paolence or Trichomycterus paolence, and deposited in museums or scientific collections, accessed on GBIF.org (last updated list of identification material of Cambeva paolence in GBIF Occurrence Download: https://doi.org/10.15468/dl.6p4nc9). The morphological data obtained were directly compared with the diagnosis of southern Brazilian genera of the Trichomycterinae provided by Costa and Bockmann (1993), Katz et al. (2018), Ferrer and Malabarba (2020), and Costa (2021), as well as with specimens (see comparative material and material examined) including the holotypes of Pygidium paolence (=Cambeva paolence) and Pygidium davisi (=Cambeva davisi, type species of Cambeva).
Molecular data.—
DNA was extracted from muscular tissue of the specimens (voucher: LBP 35685) using the Wizard Genomic DNA Purification kit (Promega), following the manufacturer’s protocol, and quantified using a NanoDrop™ Lite Spectrophotometer. The analyses included a set of partial sequences of one nuclear gene, recombination activating gene 2 (RAG2), and two mitochondrial genes, cytochrome b (CYTB) and cytochrome c oxidase subunit I (COX1). For amplification of the RAG2 gene, primers Tricho F and Tricho R (Costa et al., 2020a) were used with the following amplification conditions: initial denaturation at 95°C for 5 min, followed by 35 cycles at 94°C for 30 s, 59°C for 30 s, and 72°C for 2 min, with a final extension at 72°C for 10 min (Cramer et al., 2011). For the CYTB gene, primers Siluri F and Siluri R (Villa-Verde et al., 2012) were used with the following amplification conditions: initial denaturation at 94°C for 4 min, followed by 35 cycles at 94°C for 1 min, 62°C for 1 min, and 72°C for 1 min, with a final extension at 72°C for 5 min (Villa-Verde et al., 2012). For the COX1 gene, primers FishF1 (Ward et al., 2005) and FR1d (Ivanova et al., 2007) were used with the following amplification conditions: initial denaturation at 95°C for 5 min, followed by 35 cycles at 94°C for 30 s, 52°C for 40 s, and 72°C for 1 min, with a final extension at 72°C for 10 min (Ivanova et al., 2007). All samples were purified using polyethylene glycol 8000 (Rosenthal et al., 1993) and subsequently sequenced using an ABI 3500 Applied Biosystems automated sequencer.
Additional sequences were obtained from GenBank, following previous studies focused on the phylogeny, biogeography, and taxonomy of species of the Trichomycterinae from southeastern and southern Brazil (e.g., Ochoa et al., 2017; Costa et al., 2020b, 2023a, 2023b, 2023c; Vilardo et al., 2020, 2023; Costa, 2021; Donin et al., 2022). All sequences obtained in this study were deposited in GenBank (COX1: PV231301; CYTB: PV235612; RAG2: PV235611). GenBank accession numbers for sequences and species used for analysis can be seen in Supplementary Material 1 (see Data Accessibility). For the outgroup, we used the non-Trichomycterinae Trichogenes longipinnis (GenBank accession number: KY857961). Access to the genetic heritage of these species was granted by the National System for Management of Genetic Heritage and Associated Traditional Knowledge (SISGEN, registration A3E0D69).
Phylogenetic analysis.—
Sequences were aligned using ClustalW (Thompson et al., 1994) in the software MEGA7 (Kumar et al., 2016). The best-fitting model of molecular substitution, based on the single marker and on the concatenated sequences, was found in the web server of IQTREE using the ModelFinder algorithm (http://iqtree.cibiv.univie.ac.at/; Trifinopoulos et al., 2016; Kalyaanamoorthy et al., 2017) using the Bayesian information criterion (BIC). We generated two Bayesian trees: the first is a gene tree based solely on COX1 sequences to assess the population variation of Cambeva paolence in the Ribeira de Iguape Ecoregion and the Rio Tietê, and the second incorporates all genetic markers to hypothesize the species’ topology in the phylogenetic tree. Both were based on a relaxed clock log normal (Drummond et al., 2006; Douglas et al., 2021) and speciation model of birth–death on an arbitrary timescale, using BEAST v. 2.5 (Bouckaert et al., 2019). A random tree was used as a starting tree for MCMC searches. The COX1 gene tree was performed based on two independent runs of 10,000,000 generations each, and trees were sampled at every 1,000th generation. The phylogenetic tree was perfomed based on two indepedent runs of 50,000,000 generations each, and trees were sampled at every 5,000th generation. Chain convergence was analyzed by Tracer 1.7.2 to determine the stationary phase and an effective sample size > 200 (Rambaut et al., 2018). After the run, 10% of the chain was discarded as a burn-in procedure in Tree Annotator v. 1.8.4 to find the maximum clade credibility tree (MCC; Drummond et al., 2012). The final MCC tree was edited using Interactive Tree of Life (iTOL; Letunic and Bork, 2021) and on Adobe Illustrator digital software v. 2020. For the COX1 alignment, we calculated the genetic distances using the Kimura-2-parameter (K2P; Kimura, 1980) model in MEGA7 (Kumar et al., 2016).
To test the topology of the phylogenetic Bayesian tree, we conducted a maximum likelihood (ML) analysis on the web server of IQTREE (http://iqtree.cibiv.univie.ac.at/; Nguyen et al., 2015; Trifinopoulos et al., 2016), using the same parameters as above to find the best substitution model. The branch supports of the ML tree were tested using ultrafast bootstrap support (UFBoot; Hoang et al., 2018). Other parameters were set as default. The figure is presented as Supplementary Material 2 (see Data Accessibility).
Extinction risk assessment.—
We calculated the extent of occurrence (EOO) in the GeoCAT webserver (https://geocat.iucnredlist.org/), measured by a minimum convex polygon of all the sites of occurrence confirmed to the species. The extinction risk assessment followed the guidelines of the International Union for Conservation of Nature for the red list of threatened species (IUCN Standards and Petitions Committee, 2024).
Trichomycterus paolence, new combination Figures 1–10, Table 1
Pygidium paolence Eigenmann (1917): 698 [original description; FMNH 58085 (ex CM 7081), holotype; type locality, alto da Serra, Rio Tieté (misspelling of Rio Tietê), São Paulo, 25 July 1908, collected by J. Haseman]. Eigenmann (1918): 328 [diagnosis in key], 332–333 [description, inclusion of a not conspecific paratype, see remarks for details; plate 51, fig. 3 p. 392, drawing of holotype. Henn (1928): 80 [type catalog of the recent fishes from Carnegie Museum]. Ibarra and Stewart (1987): 73 [type catalog of the fishes from the Field Museum of Natural History].
Trichomycterus paolence.—Burgess (1989): 322 [checklist of worldwide catfishes]. Trajano and de Pinna (1996): 89 [comparative material in the description of T. itacarambiensis]. Fernández and Bichuette (2002): 278 [comparative material in the description of Ituglanis passensis]. De Pinna and Wosiacki (2003): 283 [checklist of South America freshwater fishes; geographical coordinates of type locality estimated: 23°30′S, 46°10′W]. MMA (2004): 14 [red list of threatened fishes from Brazil]. Ribeiro et al. (2006): 158 [checklist of fishes from the Atlantic Rainforest of Boracéia; fig. 2d, live specimen photo]. Buckup et al. (2007): 125 [checklist of freshwater fishes from Brazil]. Menezes et al. (2007): 296 [figure of live specimen, notes on distribution, ecology, and Extinction Risk assessment]. Langeani et al. (2007): 189 [table 1; checklist of freshwater fishes from upper Paraná basin]. Langeani et al. (2008): 253 [red list of threatened fishes from Brazil, categorized as EN]. Lima et al. (2008): 316 [comparative material in the description of T. caipora]. Oyakawa et al. (2009): 354 [table 1; red list of threatened vertebrates from São Paulo, categorized as EN]. Marceniuk and Hilsdorf (2010): 79 [figure of live specimen on the checklist of freshwater fishes from the headwaters of Rio Tietê; notes on distribution, ecology, and Extinction Risk]. Marceniuk et al. (2011): 221 [table 1; checklist of freshwater fishes from the headwaters of Rio Tietê]. Oyakawa and Menezes (2011): 28 [table 1; checklist of freshwater fishes from São Paulo State]. Barbosa and Azevedo-Santos (2012): 360 [cited for the upper Rio Paraná in the description of T. pirabitira]. Ferrer and Malabarba (2013): 244 [comparative material in the taxonomic revision of species of Trichomycterus from Laguna dos Patos]. Pereira et al. (2013): additional information 1 [GenBank sequence of COI gene]. MMA (2014): 5 [red list of threatened fishes from Brazil, categorized as EN]. ICMBio/MMA (2018): 295 [Brazil red book of threatened species of fauna, categorized as EN]. SMA (2018): 3 [red list of threatened fishes from São Paulo, categorized as EN]. MMA/ICMBio (2019): 2 [national action plan for conservation of threatened fishes from Brazil]. Donin et al. (2022): 6 [quoted that COI gene sequence not aligned with any Cambeva].
Trichomycterus paolencis.—Ferraris (2007): 421 [checklist of worldwide catfishes; dated 1918 and misspelled T. paolencis (=T. paolence)].
Cambeva paolence.—Katz et al. (2018): 563 [description of Cambeva]. Ferrer and Malabarba (2020): 73 [comparative material in the revision of Scleronema]. MMA (2022): 115 [red list of threatened fishes in Brazil, categorized as EN]. Dagosta et al. (2024): fig. 23D [distribution map in the upper Paraná basin]. IUCN (2024): [IUCN red list website]. Martins et al. (2024): 23 [comparative material in the description of Cambeva perobana]. dos Reis et al. (2025): fig. 2 [phylogenetic position in Cambeva ultrametric tree].
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Diagnosis.—
Trichomycterus paolence can be distinguished from all trichomycterines except species of Cambeva, Scleronema, and Trichomycterus (CST-clade) by an apomorphic condition (sensu Costa, 2021) in the second free vertebrae parapophysis which is posterolaterally oriented (Fig. 2; vs. laterally oriented). Trichomycterus paolence can be distinguished from species of Cambeva and Scleronema by the proximal region of first rib which has a deep concavity and is shell-like, not extending dorsally past the parapophysis (Fig. 2A; vs. proximal region of the first rib with a flat and wide concavity that extends dorsally past the parapophysis; Fig. 2B; see Discussion section for more details about this condition and differences between this character seen by Costa, 2021); by the parapophysis of the third free vertebra being posterolaterally oriented (Fig. 2A; vs. posteriorly oriented; Fig. 2B; see Costa, 2021); by the opercle odontodophore smaller than the interopercle odontodophore (Fig. 3; vs. opercle odontodophore bigger than the interopercle odontodophore, fig. 5b in Katz et al., 2018); presence of a slight constriction on the basal portion of the anterodorsal arm of the quadrate in lateral view, making its width greater than 50% of the quadrate width at its dorsal limit (Fig. 3; vs. presence of a deep constriction on the basal portion of the anterodorsal arm of the quadrate in lateral view, making its width less than 50% of the quadrate width at its dorsal limits, fig. 5 in Katz et al., 2018); and absence of a bony flap covering the posterior segment of the maxillo-dentary ligament channel in the dentary (Fig. 6C; vs. presence of a bony flap, fig. 4b in Katz et al., 2018).
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Trichomycterus paolence can be distinguished from all subgenera in Trichomycterus except Cryptocambeva and Humboldtglanis by the possession of: 1) a prominent process on the dorsal surface of the autopalatine, close to its lateral margins (Fig. 4A; vs. process absent, fig. 2a–d in Costa, 2021); 2) an oblique arrangement of odontodes on the basal portion of opercular odontodophore (Fig. 3 vs. vertical arrangement of odontodes, fig. 3a–d in Costa, 2021); 3) ventral surface of mesethmoid delimited or folded around the vomer margins (Fig. 4B; vs. not delimited and not folded around the vomer, fig. 2a–d in Costa, 2021; except for Trichomycterus Psammocambeva astromycterus, see figs. 4 and 5b in Reis et al., 2019); 4) lateral ethmoid medially separated from its symmetrical homolog (Fig. 4C; vs. lateral ethmoid medially in contact, fig. 2a–d in Costa, 2021); 5) possession of a lateral expansion of the lateral ethmoid margin close to the sesamoid supraorbital (Fig. 4A; vs. expansion absent, fig. 2a–d in Costa, 2021); and 6) a rudimentary posterior process of the pelvic bone (Fig. 4D; vs. process well developed, fig. 6a–d in Costa, 2021).
Trichomycterus paolence is considered a member of the subgenus Cryptocambeva (sensu Costa, 2021) by having some of the synapomorphic conditions mentioned by Costa (2021): 7) a rounded, narrow, and elongated extremity of the pterotic lateral process after adjacent bones (Fig. 4A; vs. pterotic lateral process truncate and not elongated, fig. 4a–b in Costa, 2021); 8) a small posttemporo-supracleithrum, resulting in a broad interspace between this bone and adjacent bones, and a short postero-medial process attached on the distal portion of the Weberian apparatus (Fig. 4A; vs. interspace narrow, and postero-medial process attaching on the proximal portion of the Weberian apparatus, fig. 4a–b in Costa, 2021).
Trichomycterus paolence can be distinguished from all species of the Trichomycterus subgenus Cryptocambeva by the possession of three branched pelvic-fin rays (vs. four branched pelvic-fin rays), 43 free vertebrae (vs. 35–42 free vertebrae), and 17 ribs (vs. 12–16 ribs).
Additionally, T. paolence can be distinguished from most species of the subgenus Cryptocambeva (T. araxa, T. argos, T. brasiliensis, T. brunoi, T. claudiae, T. fuliginosus, T. garbei, T. giarettai, T. macrotrichopterus, T. maracaya, T. mariamole, T. mirissumba, T. novalimensis, T. pirabitira, T. potschi, T. rubiginosus, T. saturatus, and T. vermiculatus), except from T. candidus, T. listruroides, T. mimonha, and T. uberabensis and by the possession of five branched pectoral-fin rays (vs. six branched pectoral-fin rays). Trichomycterus paolence can be distinguished from T. candidus, T. listruroides, and T. uberabensis by the possession of a pelvic girdle and fin (vs. pelvic girdle and fin absent).
Description.—
Summary morphometric data of type-series and non-type materials in Table 1. Body elongated, trunk roughly cylindrical close to head and gradually becoming laterally compressed toward caudal fin. Dorsal profile of trunk convex along anterior part of body to slightly concave close to insertion of dorsal fin. Ventral profile of trunk concave close to head and becomes slightly convex on half portion of trunk until insertion of ventral fin. Dorsal and ventral profiles of caudal peduncle slightly convex. Skin crest present in ventral and dorsal margins of caudal peduncle.
Head depressed, trapezoidal to slightly triangular in dorsal view, wider posteriorly and anterior portion slightly rounded. Dorsal profile of head straight, ventral profile of head slightly convex. Eye located dorsolaterally on anterior half region of head and slightly laterally at longitudinal line of nasal barbel. Eye with round to elliptical shape anteroposteriorly, covered by thin and translucent skin. Orbital rim not free. Eye visible from lateral view.
Anterior nostril slightly smaller than diameter of eye, surrounded by flap of integument posterolaterally continuous with base of nasal barbel. Posterior nostril slightly smaller than diameter of eye, surrounded anterolaterally by thin flap of integument. Gill opening not constricted, forming free fold reaching pectoral-fin insertion. Mouth subterminal and slightly curved with corners posterolaterally oriented in ventral view. Upper lip thicker laterally. Lower lip with conspicuous fleshy lobes at corners of mouth, continuous with base of rictal barbels. Lips with small rounded papillae of approximately same size.
Barbels with broad bases, tapering gradually toward tips. Nasal barbel emerging from posterolateral region of anterior nostril with tip surpassing postotic sensory pore 1 when adpressed to head. Maxillary barbel emerging from corner of mouth with tip surpassing anterior region of pectoral fin when adpressed to head and body. Rictal barbel emerging from corner of mouth, shorter than maxillary barbel, reaching mid-half posterior portion of interopercular odontodophore when adpressed to head.
Pectoral fin with distal margin rounded, I,5* (20), first unbranched ray prolonged as a small filament (see Table 1 for percents of that filament). Pelvic fin with distal margin rounded, covering anterior margin of urogenital papilla and reaching anal-fin insertion; I,3* (20) rays. Pelvic-fin insertion anterior to dorsal-fin origin. Inner margins of contralateral pelvic fins close to each other basally. Dorsal fin with distal margin slightly rounded, ii(2), II,6 (1), or II,7* (19) rays; origin at vertical through middle of pelvic fin. Anal fin elongated with distal margin rounded; anal fin slightly smaller than dorsal fin; ii (2), I,6 (4), II,6 (1), or II,5* (15) rays; origin at vertical through first third of dorsal-fin base. Caudal fin with distal margin rounded; upper caudal lobe with I,5* (20) rays, lower caudal lobe with I,6* (20) rays.
Neurocranium.—
Mesethmoid with anterior margin straight to slightly concave and cornua short, with tapering distal ends. Anterior cranial fontanel restricted to small, rounded opening between frontals and epiphyseal bar. Posterior cranial fontanel long and wide extending from posterior portion of frontals to parieto-supraoccipital. Epiphyseal bar wider than long. Antorbital anteriorly expanded and posteriorly elongated, extending over autopalatine anterior portion supraorbital sesamoid elongate, with slightly lateral process in mid portion. Sphenotic, prootic, and pterosphenoid fused, anterior portion anterolaterally directed in dorsal view (Fig. 4). Vomer arrow-shaped with long posterior process extending to parasphenoid. Parasphenoid with long and pointed posterior process extending below basioccipital. Weberian capsule with lateral openings and anterior margin fused to basioccipital. Premaxilla rectangular with 24 (2) conical teeth similar in size and distributed in four irregular rows. Dentary with 21 or 26 (2) teeth extending from coronoid process to near dentary symphysis. Maxilla boomerang-shaped, same size as premaxilla. Autopalatine with lateral margin concave; anterior margin slightly convex; medial margin slightly concave and long posterior process extending over posterior portion of metapterygoid. Metapterygoid large and laminar (Fig. 3), anterodorsal region with expanded margin, ventral region connected to quadrate through cartilage.
Suspensorium and opercular apparatus.—
Quadrate L-shaped with slight concavity in anterior portion. Hyomandibula well developed, dorsal margin with concavity, and poorly ossified in holotype (Fig. 3). Opercle longer than interopercle. Opercular odontodophores ovoid to rounded with 10 (1) or 12 (1) conical odontodes, gradually curving medially and increasing in size posteriorly, arranged in four irregular transverse rows. Interopercular patch of odontodes elongate with 26 (1) or 29* (1) conical odontodes, arranged in four transverse rows.
Hyobranchial apparatus.—
Ventral hypohyal trapezoid. Anterior ceratohyal elongate and wider at anterior and posterior tips. Posterior ceratohyal short, triangular, with rounded posterior tip. 8* (2) branchiostegal rays: four in contact with anterior ceratohyal, two with interceratohyal cartilage, and two with posterior ceratohyal. Four posteriormost branchiostegal rays wider distally (Fig. 5A). Urohyal robust, laterally expanded anterior head with anterolateral paired process; two elongate lateral process triangular with wide bases, decreasing in width distally, anteroposteriorly directed, and posterior tip pointed; posterior margin slightly pointed. Posterior process of parurohyal laminar and elongate, shorter than lateral process.
Basibranchials 2 and 3 elongated, connected by cartilage; basibranchial 2 slightly wider than basibranchial 3. Basibranchial 4 non-visible in all specimens. Hypobranchial 1 elongated, with cartilaginous tips, approximately of same size as basibranchial 2. Hypobranchials 2 and 3 with narrow anterolateral ossified processes with large area of cartilage posteriorly; hypobranchials 2 and 3 equal in size. Five elongate ceratobranchials. Ceratobranchial 3 with prominent concavity on proximal region and posterior margin. Ceratobranchial 5 with 12 (1) or 14 (1) conical, elongated, and pointed teeth, arranged in three irregular rows. Four epibranchials; anteriormost three elongated and narrow. Epibranchial 1 L-shaped, with anterior pointed process; epibranchial 2 with mesial-anterior and distal-posterior processes; epibranchial 3 with wider process on distal-posterior margin, slightly curved mesially. Epibranchial 4 rectangular. Pharyngobranchial 3 straight and elongated, shorter than hypobranchial 1. Pharyngobranchial 4 ossified and connected to curved plate with 24 (2) conical, elongated, and pointed teeth, arranged in up to three irregular rows; teeth increasing in size posteriorly (Fig. 5B).
Fins and vertebrae osteology.—
Dorsal fin with 8* (1) pterygiophores, first inserted anterior to neural spine of 25th post-Weberian vertebrae. Anal fin with 6* (1) pterygiophores, first inserted anterior to hemal spine of 28th post-Weberian vertebra. Procurrent caudal-fin rays 14 (1) or 17* (1) dorsally and 12 (1) or 14* (1) ventrally. Hypural 3 free and hypurals 4 and 5 fused to each other. Parhypural and hypurals 1 and 2 co-ossified and fused to compound caudal centrum. Post-Weberian vertebrae 43* (1), ribs 17* (1). Parapophysis of first free vertebrae unbranched, connected with first rib by cartilage. Proximal region of first rib with deep concavity shell-like, connecting to parapophysis. Parapophysis of second free vertebra branched forming dorsal and ventral process, dorsal process elongate and posterolaterally oriented, cartilage connecting each branch. Proximal region of second rib connected to ventral process. Parapophysis of third free vertebra elongate and posterolaterally oriented. General osteological features of head and anterior half of body in Figures 6 and 7, respectively.
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Laterosensory system.—
Laterosensory canals with simple (non-dendritic) branches ending in single pores. Nasal and frontal branches of supraorbital canal continuous, with three paired pores, s1, s3, and s6. Supraorbital pore s1 located posterolaterally to anterior nostril; pore s3 at same longitudinal line as pore s1, aligned to posterior nostrils at posterior margin; and pore s6 at same longitudinal line as pores s1 and s3, aligned with posterior margin of eye. Antorbital segment of infraorbital canal present with two pores i1 and i3 (9), located posterolaterally to anterior nostril and anterolaterally to posterior nostril, respectively, or absent (11) in all specimens from Rio Juquiá, and some specimens from Rio Tietê. Sphenotic canal present with two pores, i10 located behind eye, and i11 located posterolaterally to margin of eye. Otic and postotic canal with two associated pores: po1 with preoperculo-mandibular branch, located anterolaterally to opercular odontodophore; and po2 with pterotic branch, located laterally to half-length of opercular odontodophore. Trunk canal with two pores (20) located above pectoral-fin insertion and posterior to gill opening.
Color in alcohol.—
Background of body and head gray to dark-yellow, darker on dorsal surface of body and head, and becoming lighter on ventral portions. Some specimens with chromatophores on outer skin layer forming various small dark-brown spots with same size as eye diameter on lateral and dorsal surface of body and head. Specimens with three inconspicuous (old collected specimens) or conspicuous (recent collected specimens) stripes on body (Fig. 8A): 1) lateral surface of body with mid-lateral longitudinal stripe formed by small spots of same size of eye diameter, originated from opercular region to base of caudal-fin rays, sometimes interrupted, especially in caudal-peduncle region; 2) dorsolateral region of body with dorsolateral stripe extending from opercular region to posteriormost dorsal-fin ray; 3) mid-dorsal region of body with continuous stripe from occipital region of head to dorsal-fin origin or dorsal region of caudal peduncle. Some specimens with homogenous coloration of background of body, with few darker spots on lateral and dorsal surface of body (Fig. 8B). Edges of ventral and lateral region of body with few spots aligned, but never forming well-defined stripe. All fins hyaline, with some specimens with small spots on fin rays. Base of caudal-fin rays darker than rest of body, forming trapezoid blotch.
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
Molecular data.—
A total of 27 species were included in the analysis of the gene tree using COX1, with a total of 521 nucleotide sites, 165 variable sites (31.2%), of which 125 are parsimony informative. The best substitution model according to BIC was TIM+F+I+G4 for the gene tree (Fig. 9A). The genetic distance from the sequences of T. paolence from Rio Tietê and Rio Ribeira de Iguape basin has 0.6% of divergence, calculated using K2P parameter (Supplementary Material 3; see Data Accessibility).
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
For the phylogenetic tree using concatenated genes COX1, CYTB, and RAG2, a total of 34 species were utilized, with a total of 2033 nucleotide sites: COX1, 521 bp, best fit model TIM+F+I+G4; CYTB, 858 bp, best fit model TPM2U+F+I+G4; and RAG2, 654 bp, best fit model TIM2e+G4. Trichomycterus paolence is the sister taxon of T. mimonha and is grouped with members of the T. mirissumba species group (subgenus Cryptocambeva; Fig. 9B). The ML tree topology can be seen in Supplementary Material 2 (see Data Accessibility).
Distribution, habitat, and ecology.—
We confirmed the presence of Trichomycterus paolence in a few streams and rivers in the Upper Paraná and Ribeira de Iguape Ecoregions sensu Abell et al. (2008; Fig. 10). In the former, the species has records in the Rio Tietê and tributaries at the municipality of Mogi das Cruzes, Rio Jurubatuba/Grande and tributaries at Paranapiacaba district, including the type locality Alto da Serra, and a stream tributary of the Guarapiranga reservoir at the municipality of São Paulo. Although these three localities of the Upper Paraná Ecoregion are part of the upper Rio Tietê basin, they are currently isolated by the metropolitan area of São Paulo (Langeani et al., 2008). Conversely, in the Ribeira de Iguape Ecoregion, T. paolence is found in six naturally isolated coastal drainages, Rio Guaratuba and tributaries at the municipality of Salesópolis with two close localities, Rio XV, tributary of Rio Itatinga at the municipality of Bertioga, Rio Cubatão basin with records at Rio Perequê, and Rio Mogi, Rio Capivari, a tributary of Rio Itanhaém, and Rio Juquiá at the municipality of Juquitiba on the Rio Ribeira de Iguape basin.
Citation: Ichthyology & Herpetology 113, 4; 10.1643/i2025022
All these headwater streams and rivers are inserted in dense rainforest areas of the Atlantic Forest biome along the Paulistano Plateau or the Serra do Mar escarpments. Trichomycterus paolence is usually found in clear, moderate to fast-flowing waters, with rocky or clay bottoms (Menezes et al., 2007; Langeani et al., 2008; Marceniuk and Hilsdorf, 2010; ICMBio/MMA, 2018). The species is rare and in low abundance in most localities (see number of specimens per lot in Material Examined). Individuals of T. paolence were found in the ravines of a small stream tributary of the Rio Guaratuba (Langeani et al., 2008), and the holotype was collected in a small stream with an abundance of algae and reeds (Haseman and Eigenmann, 1911). Biological and ecological studies or any other speculations about the species are unknown.
Some records attributed to the species of the middle Rio Tietê basin by ICMBio/MMA (2018; e.g., LIRP 8262, LIRP 8286, LIRP 13317, LIRP 13998) were cited as doubtful in the recent Brazilian assessment (ICMBio, 2024) and recently confirmed as not conspecific with T. paolence.
Extinction risk assessment.—
Trichomycterus paolence is currently categorized as Endangered (EN) in the red lists of Brazil (MMA, 2022) and São Paulo State (Decree 68.853, 2018) based on restricted range (EOO = 1,661 km2; calculated as the area of a minimum convex polygon drawn around the hydrographic micro-basins), severe population fragmentation, few localities, and continuing decline in the quality of habitat (ICMBio, 2024). Urban expansion is the main threat cited to the species, which causes deforestation, water pollution, and river silting. Despite our finding increased records of the species, the updated EOO calculated (approximately 2,200 km2) does not surpass the EN threshold of 5,000 km2. Additionally, T. paolence faces all those threats mentioned in the current national assessment and the previous ones (MMA, 2004, 2014; ICMBio/MMA, 2018). This condition, known for two decades, is quite worse in the subpopulations of T. paolence of the upper Tietê basin and the localities visited by J. Haseman in the early 20th century. Some of them were probably lost, and the remaining ones are severely fragmented due to impacts such as the reservoirs, highways, and water pollution in the metropolitan area of São Paulo. Therefore, we maintain the EN category of T. paolence based on criterion B1ab(iii): restricted EOO (approximately 2,200 km2), severe population fragmentation and continuing decline in area, extent, and quality of habitat.
Trichomycterus paolence is listed as part of a Brazilian plan for conserving freshwater fish from the Atlantic Forest (MMA/ICMBio, 2019) and Upper Paraná basin (ICMBio/MMA, 2024). However, we still await actions and results that may reverse the conservation status of the species. Known and practical actions to preserve the species are restricted to their records or putative presence in some protected areas (i.e., Área de Preservação Ambiental Corumbataí, Botucatu e Tejubá, APA Piracicaba/Juqueri-Mirim, Parque Estadual da Serra do Mar, Parque Natural Municipal Nascentes de Paranapiacaba, Reserva Biológica do Alto da Serra de Paranapiacaba), which maintain a well-preserved representative stretch of Atlantic Forest in southeastern Brazil.
Remarks on types and descriptions provided by Eigenmann (1917 and 1918).—
Eigenmann (1917, 1918) erroneously cited “July 25, 1909” as the date of collection of the holotype of Pygidium paolence. According to the field notebook of Haseman, the species was collected when the naturalist was exploring the surroundings of São Paulo and Santos cities at the end of July 1908 (Haseman and Eigenmann, 1911; pg. 305: “25 July 1908”). Ten additional specimens (FMNH 58119, formerly CM 7117, 18.9–25.0 mm SL), supposedly young specimens of T. paolence (Eigenmann, 1917, 1918), were used in the description, but were not designated as paratypes, and were collected a few days before (20 July 1908) in the municipality of Mogi das Cruzes. These two collection sites are relatively nearby and belong to the upper Rio Tietê basin. Eigenmann (1918) added one specimen identified by him as a paratype (FMNH 58575, formerly CM 7597) collected in the “Rio Paranahyba, into Paraná, bridge twenty-one miles above Araguary” (see Haseman and Eigenmann, 1911; pg. 306) in the redescription of T. paolence, which modified some measurement variations and fin-ray counts. However, a specimen designated as a paratype in a work other than the original description has no standing as a type specimen. Therefore, we do not consider it a paratype here, but rather as additional material examined. Furthermore, the collection point of this specimen (Minas Gerais State) is approximately 600 km from the upper Rio Tietê sample points explored by Haseman. We analyzed this specimen, which is clearly distinguished from the morphological concept of T. paolence defined here. It differs in the body depth, the distance between the pelvic-fin tip and anal-fin insertion, and the position of odontophores (see Fig. 1), as well as having I,6 pectoral-fin rays and I,4 pelvic-fin rays (vs. I,5 and I,3 in T. paolence). Therefore, we concluded this specimen is not T. paolence, and we did not consider lot FMNH 58575 in the redescription.
DISCUSSION
Using the morphological data employed to delimit Trichomycterus paolence, along with the internal morphology of the type series and molecular data, we produced the first hypothesis of phylogenetic position for this species. The results were found to be inconsistent with the hypothesis of Katz et al. (2018), which proposed the allocation of T. paolence in Cambeva based only on its geographical distribution. Despite this, morphological characters from the description of Cambeva provided by Katz et al. (2018) were retained to separate this genus from T. paolence. Furthermore, the phylogeny based on both morphological and molecular data by Costa (2021) proved to be essential for separating species groups within Trichomycterus, as well as assigning synapomorphies to the Cambeva, Scleronema, and Trichomycterus groups.
The use of individuals from the type series collected long ago, combined with modern methodologies, helped to clarify the distribution and phylogenetic position of this species. By using the μCT scans and osteological data from Trichomycterus paolence and the holotype of Cambeva davisi (type species of Cambeva; see Katz et al., 2018), we were able to assess the characters mentioned by Katz et al. (2018) and Costa (2021). Based on our data, only the parapophysis of the first free vertebra differed from the description of Costa (2021). The character observed here is the proximal region of the first rib with a flat and wide concavity that can be seen dorsally of the parapophysis in C. davisi (Fig. 2B), while Costa (2021) observed the first free vertebra parapophysis with two branches: a dorsal branch in contact with the dorsal surface of the articular zone of the first rib, and a ventral branch ventrally supporting the proximal extremity of the rib (fig. 7B of Costa, 2021). These differences should be confirmed in other species of Cambeva and Scleronema to clarify and delineate the boundaries of each genus within the CST-clade and facilitate future assessments of generic assignments.
Trichomycterus paolence does not have a distinctively narrowed area adjacent to the base of the anterior processes of the pelvic bone as shown for species of the Trichomycterus subgenus Cryptocambeva (see Costa, 2021), and shows a very similar pattern as seen in the Trichomycterus subgenus Humboldtglanis (Fig. 4C vs. fig. 6E in Costa, 2021). Despite these conditions, the molecular and other morphological data (see diagnosis section) suggest that this species is part of the subgenus Cryptocambeva. The topology in the molecular phylogeny indicates that this species is part of subgenus Cryptocambeva and thus shares this plesiomorphic condition with subgenus Humboldtglanis. Although T. mimonha is recovered as the sister species of T. paolence, it does not exhibit the same character states, instead showing the derived pattern typical of other species of Cryptocambeva, as observed in the character coding presented by Costa (2021, table A2).
Trichomycterus paolence also possesses very different characters from other species of the Trichomycterinae, such as fewer pelvic-fin rays (three vs. four branched pelvic-fin rays), a condition considered only as variation in some specimens of Scleronema (see Ferrer and Malabarba, 2020) and a rudimentary condition of some specimens in the T. candidus species complex (Costa et al., 2023a). Despite this modification of the pelvic fin, this character is not seen to be strictly related to the loss of the pelvic fin and girdle in the T. candidus species complex because the species are not phylogenetically closely related (Fig. 9B). In addition, this trait has already been shown to be a result of homoplasy in other species of the Trichomycterinae (e.g., Cambeva flavopicta, C. pascuali, C. podostemophila, and C. tropeira; see Costa et al., 2020b, 2023b); however, it is a synapomorphic condition for the T. candidus species complex in Cryptocambeva (Costa et al., 2023a).
Bockmann et al. (2004) relied on information about Trichomycterus paolence from Eigenmann’s revision of the Pygidiidae (Eigenmann, 1918). Bockmann et al. (2004) cited that the species has i,6 pectoral fin-rays, and Eigenmann (1918) mentioned that the pectoral fin has 6 or 7 total rays. However, the specimens with i,6 pectoral-fin rays are not conspecific with T. paolence, and this could have led to a misinterpretation by Bockmann et al. (2004) and other authors that used this information. It is possible that this interpretation of the data led to the misidentification of specimens from the middle Rio Tietê, close to the municipality of Boraceia (e.g., LIRP 8262, LIRP 8286, LIRP 13317, and LIRP 13998), as T. paolence and inaccurately increased the species distribution.
Although these records are included in the species’ extinction risk assessment (see records ICMBio/MMA, 2018, p. 296), they seem to have not been considered in defining its actual distribution, as only 16 km2 were used in the extinction risk evaluation (ICMBio/MMA, 2018). However, the definitive exclusion of these records from the species’ distribution does not alter its conservation status (see Extinction Risk Assessment section). New records have been found for the species in the Ribeira de Iguape Ecoregion, south of the upper Rio Tietê region, in a relatively well-preserved area (Mendonça et al., 2018; Mattox et al., 2023). The new records have increased the number of localities where the species can be found, but have not been enough to change the categorization of the species as Endangered, maintaining concerns about its conservation (see Extinction Risk Assessment section). However, we hope the new data gathered on the species’ distribution will serve as support for future Brazilian conservation assessment workshops.
The occurrence of Trichomycterus paolence in the Ribeira de Iguape Ecoregion, south of the upper Rio Tietê region, and the coastal basin of São Paulo is confirmed here based on both morphological evidence (see diagnosis) and molecular data using DNA barcoding (Fig. 9A). The species exhibits a distribution pattern similar to that of other taxa, such as Ituglanis amphipotamus (Mendonça et al., 2018) and Spintherobolus papilliferus (Mattox et al., 2023), suggesting that recent headwater captures have contributed to their broader distributions, corroborating Ribeiro (2006) and Ribeiro et al. (2006).
Nevertheless, despite this distribution in more than one ecoregion, T. paolence and S. papilliferus remain under risk of extinction due to restricted range in adjacent ecoregions. Moreover, they are among the one-quarter of freshwater species globally threatened with extinction (Sayer et al., 2025). In this case, the upper Rio Tietê region is heavily impacted by pollution, and it is unequivocal that range-restricted species are particularly vulnerable to anthropogenic environmental changes. This area has been identified as one of the most threatened regions for fish within the Upper Paraná Ecoregion, primarily due to the absence of protected areas (see Dagosta et al., 2024, p. 74).
This demonstrates the importance of reevaluating species with limited morphological data and taxonomic issues and highlights how studies integrating historical specimens as type material, newly sampled specimens, and non-invasive methodologies for osteological analyses such as μCT scans can be crucial for understanding phylogenetic position, accurate identification, and provide robust data for reassessing the current extinction risk of species.
MATERIAL EXAMINED
Cambeva castroi: All specimens from Rio Iguaçu basin, Paraná State, Brazil: NUP 3127, 3, 110.0–140.0 mm SL, municipality of Reserva do Iguaçu, Jordão reservoir, Rio Jordão basin.
Cambeva cauim: All specimens from Rio Iguaçu basin, Paraná State, Brazil: Holotype: NUP 22756, 89.6 mm SL, municipality of Cruz Machado, unnamed stream. Paratypes: MPEG 39109, 4, 29.2–82.3 mm SL, municipality of Mangueirinha, Córrego Verde; NUP 2416, 19, 20.0–97.4 mm SL, municipality of Mangueirinha, Córrego Verde.
Cambeva crassicaudata: All specimens from Rio Iguaçu basin, Paraná State, Brazil: MHNCI 12297, 4, 47.0–164.3 mm SL, municipality of Candói/Pinhão, Rio Jordão, UHE Santa Clara; NUP 3123, 1, 52.3 mm SL, municipality of Foz do Jordão, Córrego Passo do Aterrado; NUP 3783, 3, 78.6–134.5 mm SL, municipality of Candói, Rio Jordão; NUP 4006, 3, 107.5–114.3 mm SL, municipality of Candói, Rio Jordão; NUP 4826, 1, 109.7 mm SL, municipality of Candói, Rio Jordão; NUP 9998, 1, 95.1 mm SL, municipality of Guarapuava, Rio Pinhãozinho; NUP 10827, 4, 50.7–102.4 mm SL, municipality of Foz do Jordão, Jordão reservoir.
Cambeva davisi: Rio Iguaçu basin, Paraná State, Brazil: FMNH 60309 (formerly CM 2862), holotype, 42.1 mm SL, Serrinha; FMNH 54242 (formerly CM 2861), paratypes, Serrinha; NUP 4008, 11, 22.1–82.1 mm SL, municipality of Santa Clara, Rio da Lage, tributary to Rio Jordão; NUP 15914, 67, 21.3–78.2 mm SL, municipality of Cruz Machado, Rio Jacutinga, tributary to Rio Santana; NUP 17364, 34, 38.7–74.3 mm SL, municipality of Pinhão, unnamed river, tributary to Rio Lajeado Feio.
Cambeva diabola: Rio Tibagi basin, Paraná State, Brazil: NUP 17403, 4, 31.9–67.2 mm SL, municipality of Teixeira Soares, arroio Lajeado, tributary to arroio Chapada; NUP 17447, 2, 109.3–114.8 mm SL, municipality of Palmeira, Rio São Benedito, tributary to Rio Caniú; NUP 17457, 2, 53.8–92.9 mm SL, municipality of Carambeí, Rio Jotuba, tributary to Rio Pitangui; NUP 17471, 2, 57.8–83.2 mm SL, municipality of Carambeí, unnamed river, tributary to Rio Maracanã; NUP 18830, 2, 46.10–59.6 mm SL, municipality of Palmeira, Rio São Benedito, tributary to Rio Caniú; NUP 18832, 1, 62.5 mm SL, municipality of Carambeí, Rio Jotuba, tributary to Rio Pitangui. Rio das Cinzas basin: NUP 14772, 3, 34.9–78.2 mm SL, municipality of Jacarezinho, ribeirão Ubá, tributary to Rio das Cinzas; NUP 20510, 10, 39.9–54.8 mm SL, municipality of Ibaiti, unnamed river, tributary to Rio das Pedras. Rio Itararé basin: NUP 20439, 9, 40.5–62.9 mm SL, municipality of Sengés, Rio Pelame, tributary to Rio Itararé. Rio Pirapó basin: NUP 4802, 2, 55.0–60.0 mm SL, municipality of Pulinópolis, Rio Atlântico, tributary to Rio Pirapó; NUP 5579, 2, 46.0–72.7 mm SL, municipality, corrégo Remo. Rio Ivaí basin: NUP 5482, 3, 19.4–35.3 mm SL, municipality of Prudentópolis, Rio Barra Grande, tributary to Rio Ivaí.
Cambeva igobi: All specimens from Rio Iguaçu basin, Paraná State, Brazil: MHNCI 12298, 1, 170.0 mm SL, municipality of Candói/Pinhão, Rio Jordão, UHE Santa Clara; NUP 611, 4, 107.6–150.2 mm SL, municipality of Foz do Jordão, Córrego Passo do Aterrado; NUP 3704, 4, 59.4–129.9 mm SL, municipality of Candói, Rio Capivara; NUP 3824, 2, 21.2–68.0 mm SL, municipality of Candói, Rio Jordão; NUP 4007, 2, paratypes, 62.0–66.3 mm SL, municipality of Candói, Rio do Sobradinho, tributary to Rio Jordão; NUP 4009, 4, 20.8–32.3 mm SL, municipality of Pinhão, Rio Capivara; NUP 4743, 3, 119.4–144.1 mm SL, municipality of Reserva do Iguaçu, Rio das Torres; NUP 4827, 1, 66.2 mm SL, municipality of Candói, Rio Sobradinho; NUP 9866, 1, 125.9 mm SL, municipality of Guarapuava, Rio Pinhãozinho; NUP 16101, 74.4 mm SL, municipality of Pinhão, unknown name stream; NUP 18280, 6, 69.0–99.6 mm SL, municipality of Guarapuava, unnamed river stream; NUP 18873, 2, 71.2–82.9 mm SL, municipality of Guarapuava, unnamed river stream.
Cambeva iheringi: All specimens from Rio Itararé basin, Paraná State, Brazil: NUP 20440, 1, 57.9 mm SL, municipality of Sengés, Rio Pelame; NUP 20463, 2, 61.6–77.8 mm SL, municipality of Jaguariaíva, unnamed river, tributary to Rio Espigão Alto; NUP 20480, 1, 74.1 mm SL, Rio das Lanças, tributary to Rio Jaguariaíva; NUP 21042, 1, 51.0 mm SL, municipality of Sengés, Rio Pelame; NUP 21059, 1, 69.2 mm SL, municipality of Jaguariaíva, unnamed river, tributary to Rio Espigão Alto.
Cambeva mboycy: All specimens from Rio Iguaçu basin, Paraná state, Brazil: NUP 612, 7, 39.3–88.0 mm SL, municipality of Foz do Jordão, Rio Jordão; NUP 632, 2, 57.9–59.9 mm SL, municipality of Foz do Jordão, Rio Jordão.
Cambeva melanoptera: All specimens from Rio Iguaçu basin, Paraná state, Brazil: NUP 24871, 2, 35.2–91.0 mm SL, municipality of Coronel Domingos Soares, Rio Iratim.
Cambeva perobana: NUP 23907, holotype, 75.9 mm SL, Rio Mouro, basin of Rio Piquiri, Paraná, Brazil.
Cambeva taroba: All specimens from Rio Iguaçu, Paraná State, Brazil: NUP 1616, 3 paratypes, municipality of Foz do Jordão, Córrego Passo do Aterrado, tributary to Rio Jordão basin; NUP 23891, 34, 16.6–41.05 mm SL, municipality of Reserva do Iguaçu, Riacho de nome desconhecido, tributary to Rio Capão Grande, Rio Jordão basin.
Ituglanis gracilior: FMNH 142659, 2, 71.6–83.4 mm SL, municipality of La Convencion, Rio Ticumpinã, sub-basin of Rio Ucoyali, tributary to Rio Amazonas.
Ituglanis parahybae: FMNH 58576 (formerly CM 7598), holotype, 28.1 mm SL, municipality of São José da Barra, Rio Parahyba (Rio Paraíba do Sul), Brazil.
Microcambeva triguttata: FMNH 58670 (formerly CM7600a), holotype, 30.0 mm SL, Jacarahy (Jacareí), Rio Paraíba do Sul, Brazil.
Trichomycterus bogotense: FMNH 56030, holotype, 65.3, Puente de Supa, beyond Chapinero, near Bogota, Colombia.
Trichomycterus cf. mimonha: FMNH 58575 (formerly CM 7597), 1, 56.5 mm SL, Brazil, Rio Paranahyba bridge, J. D. Haseman, 15 August 1908.
Trichomycterus guianensis: FMNH 52676 (formerly CM 1003), holotype, 64.4 mm SL, Aruataima Falls, Upper Potaro River, Guyana.
Trichomycterus paolence: Holotype: FMNH 58085 [formerly CM 7081], 59.4 mm SL, Brazil, São Paulo State, district of Paranapiacaba, municipality of Santo André, near to Alto da Serra, Rio Jurubatuba/Grande, basin of Rio Tietê, upper Rio Paraná system, 23°46′22″S, 46°18′54″W. Non-types: Brazil, São Paulo State, upper Rio Tietê basin, upper Rio Paraná system: FMNH 58119 (formerly CM 7117), 11, 18.9–25.0 mm SL, municipality of Mogi das Cruzes, Rio Tietê, 23°31′01″S, 46°12′37″W; LBP 7684, 1 (tissue 36308), municipality of São Paulo, stream tributary of Guarapiranga reservoir, 23°46′16″S, 46°45′56″W; LIRP 5713, 1, 45.6 mm SL, municipality of Santo André, stream tributary of Rio Grande/Jorubatuba, 23°46′07″S, 46°17′46″W; MZUSP 99698, 7, same locality as LBP 7684; MZUSP 103686, 4, 95.2–97.1 mm SL, district of Paranapiacaba, municipality of Santo André, Rio Jurubatuba/Grande, 23°46′01″S, 46°17′18″W; MZUSP 107524, 1, municipality of Mogi das Cruzes, stream tributary of Rio Botujuru, 23°29′10″S, 46°11′31″W; MZUSP 108930, 9, 30.6–77.2 mm SL, same locality as LBP 7684; MZUSP 108931, 4, same locality as LBP 7684; MZUSP 108932, 5, 30.6–77.2 mm SL, same locality as LBP 7684; MZUSP 108933, 8, same locality as LBP 7684; MZUSP 108934, 3, same locality as LBP 7684; MZUSP 108935, 1, same locality as LBP 7684. Coastal basins of São Paulo (Ribeira de Iguape Ecoregion): DZSJRP 12397, 1, 53.9 mm SL, municipality of Cubatão, Rio Perequê, tributary of Rio Cubatão, 23°50′53.99″S, 46°24′59.01″W; LBP 611, 4, 43.0–84.0 mm SL, municipality of Juquitiba, stream tributary of Rio Juquiá, 23°57′51.99″S, 46°56′21.28″W; LBP 35685, 2, 33.0–103.2 mm SL, municipality of Juquitiba, Rio Juquiá, 23°59′13.20″S, 47°0′10.80″W; MZUSP 22752, 1, district of Paranapiacaba, municipality of Santo André, Rio Moji, tributary of Rio Perequê 23°46′60″S, 46°17′60″W; MZUSP 87572, 8, municipality of Salesópolis, stream tributary of Rio Guaratuba, 23°39′56″S, 45°54′22.99″W; MZUSP 87578, 1, municipality of Salesópolis, Rio Guaratuba, 23°40′3″S, 45°53′47″W; MZUSP 106834, 3, municipality of Bertioga, Rio do XV, RPPN Parque das Neblinas 23°45′1.04″S, 46°9′31″W; MZUSP 108622, 1, municipality of São Paulo, Rio Capivari, 23°55′44.93″S, 46°43′39.49″W.
Trichomycterus pseudosilvinichthys: FMNH 112974, 1, paratype, 52.1 mm SL, Province de La Rioja, Departamento Chilecito, Valle Gauchin, Argentina.
DATA ACCESSIBILITY
Supplemental data are available at https://www.ichthyologyandherpetology.org/i2025022. All other data underlying this article are cited in the manuscript. Unless an alternative copyright or statement noting that a figure is reprinted from a previous source is noted in a figure caption, the published images and illustrations in this article are licensed by the American Society of Ichthyologists and Herpetologists for use if the use includes a citation to the original source (American Society of Ichthyologists and Herpetologists, the DOI of the Ichthyology & Herpetology article, and any individual image credits listed in the figure caption) in accordance with the Creative Commons Attribution CC BY License.
AI STATEMENT
The authors declare that no AI-assisted technologies were used in the design and generation of this article and its figures.
Pygidium paolence. (A) Holotype, FMNH 58085, 59.4 mm SL, Alto da Serra, Rio Tietê, São Paulo, Brazil; (B) FMNH 58575, 56.5 mm SL, previously considered a paratype by Eigenmann (1918; not conspecific, see remarks section). Scale bar represents 10 mm.
Ventral view of the first five free vertebrae of (A) Trichomycterus paolence, FMNH 58085, holotype, 59.4 mm SL; and (B) Cambeva davisi, FMNH 60309, holotype, 42.1 mm SL. Abbreviations: dcs, deep concavity shell-like on first rib; fwc, flat wide concavity on first rib; p1–5, parapophysis 1–5; plo, posterolaterally oriented; po, posteriorly oriented; r1–4, ribs 1–4; and v1–5, free vertebrae 1–5. Scale bar represents 10 mm.
Lateral view of left suspensorium of Trichomycterus paolence, FMNH 58085, holotype, 59.4 mm SL. Abbreviations: hy, hyomandibula; iop, interopercle; mtg, metapterygoid; op, opercle; pop, preopercle; qu, quadrate; sc, slight constriction on the basal portion of the anterodorsal arm of the quadrate. Scale bar represents 10 mm.
Osteology of Trichomycterus paolence, FMNH 58085, holotype, 59.4 mm SL; (A) dorsal view of neurocranium; (B) ventral view of neurocranium; (C) dorsolateral view of neurocranium, highlighting the lateral ethmoid region. Abbreviations A–C: af, anterior fontanel; an, antorbital; ap, autopalatine; ep, epioccipital; fr, frontal; le, lateral ethmoid; me, mesethmoid; mx, maxilla; os, orbitosphenoid; pf, posterior fontanel; pm, premaxilla; ps, posttemporo-supracleithrum; pt, pterotic; so, sesamoid supraorbital; sp+po+pn, sphenotic–prootic–pterosphenoid complex bone; su, parieto-supraoccipital; vo, vomer; and wc, Weberian capsule. (D) Ventral view of pelvic girdle. Abbreviations: bs, basipterygium; ep, external process; ip, internal process; mp, medial process. Numbers in all figures represent characters described in the diagnosis section. Scale bar represents 10 mm.
Osteological features of Trichomycterus paolence, FMNH 58085, holotype, 59.4 mm SL: (A) ventral view of hyoid arch; (B) ventral view of gill arches. Abbreviations: ac, anterior ceratohyal; bb2–3, basibranchials 2 to 3; br1–8, branchiostegal rays 1 to 8; cb1–5, ceratobranchials 1 to 5; eb1–4, epibranchials 1 to 4; hb1–3, hypobranchials 1 to 3; ic, interceratohyal cartilage; pb4, pharyngobranchial 4; pc, posterior ceratohyal; ph, parurohyal; tp, tooth plate; vh, ventral hypohyal. Scale bar represents 10 mm.
General osteology of the head of Trichomycterus paolence, holotype, FMNH 58085, 59.4 mm SL: (A) dorsal view; (B) ventral view; (C) lateral view. Neurocranium, dentary, suspensory mandibular, gill and hyoid arches visible. Scale bar represents 10 mm.
General osteology of anterior half of the body of Trichomycterus paolence, holotype, FMNH 58085, 59.4 mm SL: (A) dorsal view; (B) ventral view; (C) lateral view. Scapular and pelvic girdles visible. Scale bar represents 10 mm.
Non-type material of Trichomycterus paolence, showing color variation. (A) MZUSP 108932, 61.1 mm SL, stream tributary of Guarapiranga reservoir, Upper Paraná Ecoregion; (B) MZUSP 87572, 70.1 mm SL, stream tributary of Rio Guaratuba, Ribeira de Iguape Ecoregion. Scale bar represents 10 mm.
The MCC ultrametric tree with arbitrary timescale of some trichomycterids generated by Bayesian inference. (A) Genetic tree constructed with COX1 gene, totaling 521 bp. (B) Phylogenetic tree constructed with concatenated genes COX1, CYTB, and RAG2, totaling 2,180 bp. Trichomycterus paolence is highlighted in red. Black circles represent posterior probability ≥ 95. See Data Accessibility for tree file.
Map of South America highlighting the southeastern region of Brazil, showing the geographic distribution of Trichomycterus paolence. Black lines on map represent ecoregions sensu Abell et al. (2008).
Contributor Notes
Associate Editor: R. E. Reis.