Acanthicus Agassiz, 1829

Chamon, Carine C., 2016, Redescription of Acanthicus hystrix Agassiz, 1829 (Siluriformes: Loricariidae), with comments on the systematics and distribution of the genus, Zootaxa 4088 (3), pp. 395-408 : 396-397

Acanthicus Agassiz, 1829

Acanthicus Agassiz in Spix & Agassiz, 1829: 2. Type species: Acanthicus hystrix Agassiz, 1829 . Type by monotypy. Authorship follows Kottelat, 1988: 78.

—Bleeker, 1862 [tribe Acanthicini].—Isbrücker & Nijssen, 1988 [description of A. adonis ; identification key].

Diagnosis. Acanthicus can be diagnosed from other genera of Loricariidae by the combination of the following characters: presence of enlarged compound pterotic, associated to the distention of the swim bladder capsule ( Fig. 2 ) (except Megalancistrus and Panaque gr. nigrolineatus ); presence of hypertrophied odontodes on opercle and cheek plates; presence of rows of keels, formed by hypertrophied odontodes, along the body. Acanthicus can be further diagnosed from Megalancistrus by the oval shape of the swim bladder capsule surpassing the sixth rib and larger compound pterotic (vs. swimbladder capsule rounded, not surpassing the sixth rib and shorter compound pterotic; Fig. 3 ). From Panaque gr. nigolineatus it can be differentiated by the presence of long, narrow, viliform and curved teeth (vs. teeth short, wide and spoon shaped). Acanthicus can be further distinguished from all other Ancistrini (except Chaetostoma and Leptoancistrus ) by the absence of an adipose fin (vs. adipose fin present in remaining taxa). From Chaetostoma it can be diagnosed by the presence of a snout completely covered by plates (vs. snout with a wide naked area); and from Leptoancistrus by the presence of the anal fin (vs. anal fin absent). Within the Acanthicus group, Acanthicus can be differentiated by the wide premaxillae and dentary (vs. narrow premaxillae and dentary); snout completely covered by small plates (vs. tip of snout with a naked area); presence of abdominal plates (vs. abdominal plates absent); pectoral-fin spine, when adpressed, reaching almost the end of the unbranched pelvic-fin ray (vs. adpressed pectoral-fin spine not surpassing middle of pelvic-fin unbranched ray); upper count of premaxillary teeth (more than 25 in each premaxillae vs. less than 25 in each premaxillae); dentary angle oblique (vs. right angle); straight bar shaped opercle (vs. curved bar shaped opercle in other genera and triangular in Spectracanthicus murinus ); lateral line surpassing the hypural plate (vs. lateral line limited up to the hypural plate; except in Leporacanthicus ); posterior process of coracoid elongate (vs. short in remaining taxa); presence of caudal-fin filaments (vs. absent, except in Pseudacanthicus ).

Figures

FIGURE 2. Dorsal and ventral view of the cranium in Acanthicus hystrix, MZUSP 34244, 174.6 mm SL.

FIGURE 3. Dorsal and ventral view of the cranium in Megalancistrus parananus, MZUSP 4434, 249.9 mm CP.