anda Ribeiro).
Material and methods
Specimens were collected with hand nets at Tabay stream, Jardín América, Misiones, Argentina. Appropriate actions were taken to minimize pain or discomfort of fish. Specimens were euthanized by immersion in an anesthetic solution (0.1% 2-phenoxyethanol), and then fixed in a 4% formaldehyde for one week, washed in water for one day and transferred to a 70% ethanol solution for preservation. These steps are approved by the ethical use animals of Fundación Miguel Lillo (FML) that consider animal welfare laws. Field studies did not involve endangered species. Collection permit was granted by Ministerio de Ecología of Misiones (Disp 074/15). Measurements were taken point-to-point as linear distances with digital calipers to the nearest 0.1 mm. Number of vertebrae, ribs, odontodes, unsegmented dorsal- and anal-fin rays, and caudal-fin procurrent rays were taken from 11 radiographed specimens (rd) and two cleared and stained  specimens (c&s) whenever possible. Branchiostegal rays were counted in c&s specimens. The number of post-Weberian vertebrae includes the compound caudal centrum counted as a single element. Anteriormost unbranched fin rays are represented by lower case Roman numerals and branched fin rays by Arabic numerals. The musculature of the dorsolateral head was observed in one paratype (ms). Counst of the holotype are given in parentheses. Meristic and morphometric data, nomenclature in the osteology, myology and cephalic laterosensory system follows the most recent contributions in that sense [13,14,15,16]. The new taxon plus the putative close species T. crassicaudatus, T. igobi, and T. stawiarski are treated as Trichomycterus stawiarski group in the text. Species from the Trichomycterus hasemani group were not included in the comparisons considering their well-supported relationship with non-trichomycterinae taxa [2,17]. Institutional abbreviations: CI-FML (Colección ictiológica Fundación Miguel Lillo, San Miguel de Tucumán). LGEP (Laboratorio de Genética Evolutiva-Peces, Posadas). IBIGEO-I (Instituto de Bio y Geociencias del NOA- Ictiología, Salta, Argentina)
The electronic edition of this work follows with the requirements of the International Code of Zoological Nomenclature, and hence the new names contained herein are available under that Code from the electronic edition of this article. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix “http://zoobank.org/”. The LSID for this publication is: urn:lsid:zoobank.org:act:D4B81E7D-0D04-4907-852B-A36931736CBE
Trichomycterus ytororo, new species
Argentina, Misiones, Jardín América, Tabay stream, Paraná River basin.
Paratype c&s specimen, CI–FML 7241, 67.3 mm SL. Abbreviations: DPR: dorsal procurrent caudal-fin rays, PH+H1+2 = lower caudal plate comprised by co-ossification of parhypural and hypurals 1 and 2; H4+5 = plate comprised by co-ossification of hypurals 4 and 5; pu1 + u1 = preural centrum 1 and ural centrum 1, pu2 = preural centrum 2; PS: pleurostile, VPR: ventral procurrent caudal-fin rays.
CI–FML 7240 (rd), 94.2 mm SL, Argentina, Misiones, Jardín America, Tabay Waterfalls, Paraná River basin, 27°00’00”S 55°10’44”W, November 2016, G. E. Terán, M. Benitez, F. Alonso, G. Aguilera & J. M. Mirande.
All collected with holotype. CI–FML 7241, 67.3–103.8 mm SL, (8 rd, 1 c&s). LGEP 542, 4, 64.6–107.3 mm SL, (2 rd, 1 c&s, 1ms). IBIGEO-I 354, 3, 60.9–79.2 mm SL, (3 rd).
Trichomycterus ytororo is distinguishable from all congeners by the presence of 31–35 dorsal caudal procurrent rays (Fig 3; vs. 29 or less). In addition, Trichomycterus ytororo exhibits two characters shared only by three congeners (Table 1; T. crassicaudatus, T. igobi, and T. stawiarski): the procurrent caudal-fin rays thickly ossified and rigid with a slender distal tip and the dorsal procurrent caudal-fin rays ex