Hisonotus

Carvalho, Tiago P. & Reis, Roberto E., 2009, Four new species of Hisonotus (Siluriformes: Loricariidae) from the upper rio Uruguay, southeastern South America, with a review of the genus in the rio Uruguay basin, Zootaxa 2113 (1), pp. 1-40 : 35-36

Key to the species of Hisonotus of the rio Uruguay basin.

1 Body relatively stocky, cleithral width (27.6–30.5% in SL); 20–22 (usually 21) plates in lateral series; and 25–26 vertebrae ............................................................................................................. Hisonotus iota (rio Chapecó drainage)

- Body relatively elongated, cleithral width (20.5–27.7% in SL); 22–25 plates in lateral series; and 27–29 vertebrae .. ..................................................................................................................................................................................... 2

2 Median portion of caudal fin with a vertical light bar composed by round dots......................................................... 3

- Caudal-fin completely dark, without light bar on median portion, or presenting light areas of different patterns ..... 4

3 Odontode-free band on tip of snout absent, anterior margin of snout covered by odontodes; comparatively broader light longitudinal stripes on head ........................... Hisonotus leucophrys (Ariranhas and Rancho Grande drainages)

- A narrow odontode-free band present between dorsal and ventral series of odontodes along the anterior margin of the snout; comparatively narrow light longitudinal stripes on head .............................................................................. ...................... Hisonotus charrua (lower and middle rio Uruguay basin, and Río de La Plata tributaries in Uruguay)

4 Posterior portion of pectoral-fin spine serrate in specimens smaller than 35 mm SL; median series of lateral plates not truncated posteriorly, reaching the posterior end of caudal peduncle ...................................................................... .......................................................................................................... Hisonotus ringueleti (middle rio Uruguay basin)

- Posterior portion of pectoral-fin spine not serrate in specimens larger than 25 mm SL; median series of lateral plates truncated posteriorly, not reaching the posterior end of caudal peduncle..................................................................... 5

5 Odontodes on dorsal margin of rostrum enlarged, more than 3 times the size of remainder of dorsal surface of head; posterior portion of lateral line absent; a darkish color pattern in life............................................................................ ....................................... Hisonotus nigricauda (lower and middle rio Uruguay basin and laguna dos Patos system)

- Odontodes on dorsal margin of rostrum slightly enlarged compared to those of remainder of dorsal surface of head; posterior portion of lateral line usually present; a greenish color pattern in life ........................................................ 6

6 Median series of abdominal plates absent or composed by one triangular plate, located posteriorly, the lateral abdominal series contacting each other at belly midline; infraorbital canal entering infraorbital series via sphenotic ............................................................................................ Hisonotus megaloplax , n. sp. (rio Passo Fundo drainage)

- Median series of abdominal plates usually present, separating the lateral abdominal plates at midline; infraorbital canal entering infraorbital series via compound pterotic ............................................................................................. 7

7 Dorsal surface of head with rounded light marks, head with two wide light longitudinal stripe .................................. ......................................................................................................... Hisonotus montanus , n. sp. (rio Canoas drainage)

- Dorsal surface of head without light marks; head with two narrow light longitudinal stripe ........................................ ................................................................................................ Hisonotus aky (Yabotí-Guazú and Forquilha drainages)