Ancistrus maximus de Oliveira, Zuanon, Zawadzki & Py-Daniel 2015

Diagnosis: Ancistrus maximus is distinguished from all congeners, except A. dolichopterus, A. fulvus and A. latifrons, by having more branched rays in the dorsal fin (8 vs. 7); Ancistrus maximus is distinguished from A. dolichopterus by its color pattern, overall body color dark brown with reddish-orange spots almost half the size of pupil in adults and with reddish-orange bands on distal portion of dorsal and caudal fins only in juveniles vs. overall body color black or dark-gray with numerous white dots and with white band on distal portion of dorsal and caudal fins throughout life; Ancistrus maximus differs from A. latifrons by the absence of hypertrophied ('spiny') odontodes in lateral plates (vs. presence of elongate and strong 'spiny' odontodes later­ally oriented in A. latifrons); Ancistrus maximus differs from A. fulvus by dorsal-spine length 27.9-34.5 % SL (vs. 25.7); pectoral-spine length 30.7-42.6 % SL (vs. 26.6) and by total lateral median plates 24-25 (vs. 22) (Ref. 103398).Description: Large-sized Ancistrus, with largest specimen examined 200.8 mm SL; head and body broad and relatively deep; body rounded anteriorly in dorsal view; becoming gradually narrow from cleithrum to caudal fin; greatest width of body at cleithrum; in lateral view, dorsal profile straight from snout tip to supraoccipital, gently convex from supraoccipital to dorsal-fin origin, and nearly straight and gradually sloping down to 1st dorsal procurrent caudal-fin ray; ventral profile straight from snout tip to pelvic-fin insertion, then ascending gently to insertion of first lower caudal-fin ray; snout rounded with broad naked margin in males reaching from upper lip to pre-nasal, frontals and preopercular; narrower in females; adult males with well developed, branched tentacles along lateral border of snout and longitudinally aligned along mesethmoid, bifurcating caudally to nares; tentacles smaller and less numerous in females and juveniles, limited to lateral border of snout; females with mesethmoid forming elevated median dorsal ridge on plated snout; males with similar but inconspicuous elevation on plated area in front of eyes; eyes large and laterally positioned on head; interorbital area slightly convex; exposed part of opercle roughly triangular with posterior portion slightly elongated; opercle covered with odontodes, larger on its posterior border; dermal plates of postopercular area small and numerous; hypertrophied cheek odontodes large, strong and few (5-11); fleshy and thick odontode sheath, covering proximal half of cheek odontodes, sometimes leaving its distal 3rd exposed; oral disk circular, lips almost completely covered with small round papillae (larger on proximal region of lower lip); lips smooth around maxillae; lower lip large but not reaching pecto­ral girdle; maxillary barbel moderate, slightly smaller than orbital diameter; sometimes branched, and with large portion free from lower lip; mandibular tooth row short; teeth thin, delicate and bifurcated, mesial cusp larger; lateral cusp half length of mesial cusp; tooth crown bright red; only 1, small median buccal papilla, positioned between premaxillae; branchial opening moderate; supraoccipital large, flat, roughly heptagonal in shape, without any process, ending posteriorly in an almost straight line; dorsolateral region of trunk completely covered by plates, except at dorsal-fin base; only 2 pairs of predorsal plates between supraoccipital and nuchal plate; 1st pair composed by large, almost fused, roughly triangular plates limiting supraoccipital posteriorly; 2nd pair comprised of short and wide plates; 5 series of lateral plates, reduced to 3 on caudal peduncle; ventral surface entirely devoid of plates from snout to anal-fin insertiori; base of 1st anal-fin pterygiophore sometimes covered by skin and preanal plate element sometimes present; a single plate (sometimes absent) between adipose fin and first procurrent caudal-fin ray; 7 to 8 oblong plates on caudal-fin base; caudally oriented short odontodes present on all body plates, except for very hypertrophied odontodes on cheek plates, and slightly larger on opercle, pectoral-fin spine, and on distal border of body plates; origin of dorsal fin at midportion of body, between pectoral and pelvic-fin insertion; dorsal fin II+8 in all specimens examined; spinelet present, dorsal-fin locking mechanism developed; dorsal fin long and very high; its distal border slightly convex; tips of last branched rays reaching adipose-fin insertion when adpressed; 5 to 6 plates separating dorsal and adipose fins; adipose fin well developed, its base containing 3 to 4 plates; preadipose plate present; adipose fin with strong spine; its distal tip reach­ing first caudal-fin procurrent ray; caudal fin i,14,i; caudal fin truncated or slightly emargin­ated, with distal border of caudal-fin rays almost straight, dorsal lobe subequal to inferior lobe or with just the lower unbranched ray slightly longer than others; pectoral fin 1,6, large, arrow­shaped, reaching or surpassing urogenital opening when ad pressed, in mature males; pectoral-fin spine straight, thin, longer than branched rays and covered by large odontodes in mature males; pectoral-fin with anterior branched rays much more developed than posterior ones (first branched ray 1.9-2.9 times larger than last branched ray); pelvic fin i,5; reaching mid portion of anal-fin rays when adpressed; anal fin i,4; small, not reaching vertical of adipose-fin inser­tion; pelvic and anal fins more convex in females, with branched rays slightly longer than un­branched rays (Ref. 103398). Color in life: overall body color dark brown at dorsum, sides and abdomen; numerous pale orange to reddish-orange dots of similar size over head, trunk and fins; ventral surface with dots only at anterior portion of head and around vent; pale orange to reddish-orange dots almost same size as pupil in juveniles, becoming more numerous and proportionally smaller in adults; juveniles with narrow distal white band on caudal and dorsal fins, followed by a subdistal reddish-orange band; bands absent in adults (Ref. 103398). Color in alcohol: overall body color gray-brown; small pale orange to reddish-orange dots barely visible; white to clear distal bands on caudal and dorsal fins of juveniles (Ref. 103398).

Dorsal spines (total): 2; Dorsal soft rays (total): - 8; Analsoft rays: 5

Both igarapé Macoari and igarapé Ano Bom are small, slow-current and shallow streams with clear waters, with alternating sandy and muddy substrates, abundant deposits of leaf litter on the banks and with many submerged logs and branches. The streams at the collecting localities were almost completely shaded by the forest canopy. Many fish species were found in the same stream stretch, including the log-dwell­ing catfishes Platydoras hancockii, Trachelyopterichthys taeniatus, Trachycorystes trachycorystes, Spinipterus cf. acsi, Tatia gyrina, T. strigata, as well as many small cichlids and characins. The rio Irua is a large blackish water river with sandy substrate and acidic waters. Ancistrus maximus was collected in the clear water streams draining to a tannin-stained larger stream and river, all connected to the large and turbid rio Branco. Ancistrus maximus has never been recorded in the sediment­loaded Anaua or Branco rivers, that constitute the main connection between the sampling sites (Ref. 103398).

Ancistrus maximus is a species of catfish in the family Loricariidae. It is native to South America, where it occurs in the Branco River basin in Roraima, Brazil. The species is notable among members of Ancistrus for its comparatively large size, reaching 20.1 cm (7.9 inches) SL, a characteristic which is also the source of its specific epithet.