Brazilian scientists have described two new species of miniature loricariid catfish in the genus Hisontous.
The descriptions of the two species, named Hisonotus chromodontus and Hisonotus luteofrenatus by Heraldo Britski and Julio Garavello, are published in the most recent issue of the Brazilian Journal of Biology.
Hisonotus chromodontus is distinguished from all other members of the genus in having teeth that are tipped reddish-brown, and a combination of the following characters: 20"40 premaxillary and 15"38 dentary teeth; 23-24 plates in longitudinal series; lateral line almost complete, represented by 19"22 perforated and one or two non-perforated plates; dorsal surface of pectoral spine with about five longitudinal series of odontodes; abdomen in adults entirely covered with large plates, two to four in lateral series between the tip of the cleithrum and pelvic-fin base; a large dark brown lateral stripe extending from tip of snout, through inferior orbit, to end of caudal peduncle; transverse dark bars very inconspicuous or absent.
Hisonotus luteofrenatus is distinguished from other members of the genus except H. insperatus in having a pair of rostral plates at the tip of the snout, and from H. insperatus in having more premaxillary and dentary teeth.
The following combination of characters serve to further distinguish H. luteofrenatus from congeners: 25"26 plates on longitudinal series; lateral line almost complete with 23"24 perforated plus last non-perforated plates; abdomen in adults entirely covered with large plates, five to eight plates in lateral series between tip of cleithrum and base of pelvic fin; large dark brown lateral stripe extending from tip of snout to caudal blotch; dorsum with basal dark blotch near origin of dorsal-fin region and three transverse dark brown bars located at end of dorsal-fin base, middle and end of caudal peduncle; yellow line extending from anterior part of each orbit, over inferior nostrils, both converging to tip of snout.
Both species are named after their distinguishing characters: H. chromodontus from the Greek chroma, meaning colour and odontos, meaning tooth, in reference to the reddish-brown tip of the teeth and H. luteofrenatus from the Latin luteo, meaning yellow and frenatus, meaning with a bridle, in reference to the yellow pair of lines running dorsally along the snout.
Hisonotus chromodontus and H. luteofrenatus are miniature species (reaching about 3 cm standard length) found in the upper Tapajs River drainage, both species caught in streams with shallow, clear water, low current and a sandy substrate.
For more information, see the paper: Britski, HA and JC Garavello (2007) Description of two new sympatric species of the genus Hisonotus Eigenmann and Eigenmann, 1889, from upper Rio Tapajs, Mato Grosso state, Brazil (Pisces: Ostariophysi: Loricariidae). Brazilian Journal of Biology 67, pp. 413"420.