Pseudancistrus Bleeker 1862

Armbruster, Jonathan W., 2004, Pseudancistrus sidereus, a new species from southern Venezuela (Siluriformes: Loricariidae) with a redescription of Pseudancistrus, Zootaxa 628, pp. 1-15 : 5-8

Pseudancistrus Bleeker 1862

Figs. 1–2

Type Species: Hypostomus barbatus Valenciennes 1840

Synonyms:

Lithoxancistrus Isbrücker, Nijssen , and Cala 1988 Guyanancistrus Isbrücker 2001

Includes:

P. barbatus (Valenciennes 1840)

P. brevispinis ( Heitmans, Nijssen, and Isbrücker 1983) P. coquenani (Steindachner 1915)

P. depressus (Günther 1868)

P. genisetiger Fowler 1941

P. guentheri (Regan 1904)

P. guttatus (Valenciennes 1840) , synonym of P. barbatus (see Fisch­Muller 2003) P. longispinis ( Heitmans, Nijssen, and Isbrücker 1983) P. niger (Norman 1926)

P. nigrescens Eigenmann 1912

P. orinoco ( Isbrücker, Nijssen and Cala 1988) P. papariae Fowler 1941

P. schomburgkii ( Günther 1864)

P. s i d e re u s new species

Diagnosis: Pseudancistrus is not diagnosed by any unique characteristics. Characteristics considered as synapomorphies for Pseudancistrus from Armbruster (2004) are: no suture between pterotic­supracleithrum and hyomandibula (34­0, reversal), no contact of the hyomandibula with the prootic (35­1), straight, spoon­shaped anterior process of metapterygoid (58­1), nasal bone not much wider than laterosensory canal running through it (105­ 0), sphenotic not contacting posteriormost infraorbital externally (117­1), and a short ventral ridge on the pelvic basipterygium (172­1, lost in some species).

Pseudancistrus can be separated from the Corymbophanini and the Hypostomini by having hypertrophied odontodes on the cheek; from most of the Rhinelepini by having an adipose fin and a dorsal flap of the iris and from Pogonopoma wertheimeri by having few or no plates on the abdomen (vs. abdomen fully plated); and from the Pterygoplichthini by lacking an enlarged, respiratory stomach and by lacking or nearly lacking plates on the abdomen (vs. abdomen fully plated in adults), and from Pterygoplichthys by having seven dorsal­fin rays (vs. nine or more).

Within the Ancistrini , Pseudancistrus can be separated from Ancistrus , Dekeyseria , Exastilithoxus , Hopliancistrus , Lasiancistrus , most Lithoxus , Neblinichthys , and Pseudolithoxus by having 4–5 plate rows on the caudal peduncle (vs. 3); from Baryancistrus , Spectracanthicus , and Parancistrus by not having a membranous connection of the posterior end of the dorsal fin with the adipose fin; from some Hemiancistrus , Hypancistrus , Panaque , and Peckoltia by having 10+ odontodes on the opercle (vs. usually 0, but up to 10, odontodes); from Acanthicus , Leporacanthicus , Megalancistrus , and Pseudacanthicus by lacking hypertrophied keel odontodes on the lateral plates; from Ancistrus and Chaetostoma by having plates on the edge of the snout; and from Chaetostoma , Cordylancistrus , Dolichancistrus , and Leptoancistrus by having the spinelet and the nuchal plate of the dorsal fin supporting odontodes (vs. skin covering the spinelet and nuchal plate in all but adult male Dolichancistrus ).

Pseudancistrus can be separated from the Neopleostominae, Hemipsilichthys , and most of the Hypoptopomatinae by having a V ­shaped dorsal­fin spinelet (vs. dorsal­fin spinelet rectangular or absent); from all of the Hyopotopomatinae by lacking odontodes on the ventral surface of the pectoral girdle; from the Loricariinae by having four or five rows of plates on the caudal peduncle (vs. three) and by having an adipose fin; and from Delturus and Hemipsilichthys (a new subfamily; Armbruster 2004) by having a single (rarely two) median, preadipose plates (vs. three or more).

Description: Member of subfamily Hypostominae, tribe Ancistrini as diagnosed by Armbruster (2004). Small to large loricariids. Ventral surface from anus to head largely naked in adults. Lateral plates unkeeled except ventral plate bent to form keel­like ridge on caudal peduncle, inframedian plate row bent from pectoral­spine insertion to above pelvic fin forming ridge, and dorsal plate row bent, forming ridge from insertion of dorsal­fin spine to posterior end of adipose­fin spine (ridges on either side converging at posterior end of adipose­fin spine). Cheek plates with numerous hypertrophied odontodes, longest odontode reaching almost to posterior edge of cleithral process; cheek odontodes and supporting plates evertible at an angle greater than 75° from head primitively although advanced species may not have evertible cheek plates, 15–60 evertible cheek odontodes. Frontal, infraorbitals, nasal, opercle, preopercle (in some species), pterotic­supracleithrum, and suprapreopercle supporting odontodes.

Caudal fin emarginate to forked, lower lobe longer than upper. Lower surface flat. Head moderate in length with horizontal distance between anterior of eye and tip of snout long. Head dorsoventrally flattened. Body depth increasing slowly, in broad arc from tip of snout to insertion of dorsal fin. Body depth decreases very little to dorsal procurrent caudal­fin spines; body depth increases slightly from posterior adipose­fin insertion to insertion of upper caudal­fin spine. Dorsal surface of head between eyes moderately concave. Supraoccipital crest not raised, posterior edge of supraoccipital rounded. Eye large ( Table 1 ) with well­developed dorsal flap of iris. Gill opening restricted.

Dorsal­fin spine short (table 1); dorsal fin reaching posterior edge of preadipose plate when depressed in all species except Pseudancistrus sidereus where the dorsal fin does not reach preadipose plate. Depressed pectoral­fin spine reaching beyond base of pelvic­fin rays; depressed pelvic­fin spine typically reaching anterior insertion of anal fin (sometimes slightly beyond). Dorsal fin II7, caudal fin I14 I, anal fin I4–5, pectoral fin I6, pelvic fin I5.

Lips papillose, forming oval disk about as wide as head. Maxillary barbel short, thin, and pointed. Buccal papilla short, narrow. Teeth long, thin with pointed cusps, lateral cusp about half length of medial cusp, 45–89 dentary teeth, 38–94 premaxillary teeth.

Color: Generally dark gray, lighter on abdomen. Some species with light spots or blotches on the sides. Some species with the body mottled gray or brown. Fins generally colored as sides, but some species with bands in the caudal fin, or with orange to red edging on the dorsal and/or caudal fins.

Sexual Dimorphism: Most species with hypertrophied odontodes along the snout in both males and females, but males generally with longer snout odontodes. Pseudancistrus sidereus may have hypertrophied odontodes on the lateral plates (see description below). Some specimens with hypertrophied odontodes on tip of pectoral spine, but it is unknown if these are dimorphic.

Ecology: Found in swift flow among gravel, cobble, and boulders.

Range: Found around the Guyana Shield in the Guyanas, Venezuela, and Brazil. Also found in northeastern Brazil in the Rio Jaguaribe and Rio Grande do Norte.

Figures

FIGURE 1. Pseudancistrus barbatus showing extreme development of the hypertrophied snout odontodes, AUM 38023, 126.6 mm SL. Photo by M. H. Sabaj.

FIGURE 2. Representative examples of Pseudancistrus: A. P. brevispinis NRM 32374, 49.6 mm SL, B. Pseudancistrus sp., AUM 36409, 54.4 mm SL, C. P. nigrescens AUM 35741, 133.8 mm SL, D. P. orinoco AMNH 91023, 62.5 mm SL. Photos by J. W. Armbruster.

Tables

TABLE 1. Selected morphometrics of Pseudancistrus sidereus. Landmarks represent the two landmarks the measurement is between (see Armbruster 2003). Measurements are ratios of SL (predorsal l. to pelvic­dorsal l.) or head l. (head­eye l. to premaxillary tooth cup l.).

Landmarks Measurement	N	Average SD	Range
1–20 SL (mm)	7	162.0 15.5	148.7 – 183.0
1–10 Predorsal L.	7	38.2 0.4	37.9 – 39.0
1–7 Head L. (HL)	7	30.8 0.3	30.3 – 31.3
7–10 Head­dorsal L.	7	7.5 0.5	6.9 – 8.3
8–9 Cleithral W.	7	25.6 0.3	25.1 – 26.0
1–12 Head­pectoral L.	7	25.7 0.7	24.4 – 26.6
12–13 Thorax L.	7	22.3 1.1	20.3 – 23.5
12–29 Pectoral­spine L.	7	28.6 1.6	27.4 – 32.1
13–14 Abdominal L.	7	22.7 0.8	21.4 – 23.7
13–30 Pelvic­spine L.	7	23.5 0.9	22.4 – 24.8
14–15 Postanal L.	7	36.2 1.0	34.5 – 37.1
14–31 Anal­fin spine L.	7	8.7 0.9	7.4 – 10.4
10–12 Dorsal­pectoral D.	7	23.4 0.5	22.9 – 24.1
10–11 Dorsal spine L.	7	32.6 2.4	29.2 – 35.7
10–13 Dorsal­pelvic D.	7	20.2 0.8	19.0 – 21.1
10–16 Dorsal­fin base L.	7	26.5 0.9	25.7 – 28.4
16–17 Dorsal­adipose D.	7	18.2 0.9	16.7 – 19.5
17–18 Adipose­spine L.	7	8.5 1.1	6.3 – 9.5
17–19 Dorsal adipose­caudal D.	7	13.0 1.1	11.9 – 14.9
15–19 Caudal peduncle Dp.	7	8.6 0.2	8.2 – 8.8
15–17 Ventral adipose­caudal D.	7	20.7 0.5	20.1 – 21.3
14–17 Adipose­anal D.	7	21.0 0.6	19.9 – 21.7
14–16 Dorsal­anal D.	7	12.7 0.3	12.3 – 13.2
13–16 Pelvic­dorsal D.	7	24.8 0.9	24.0 – 26.2
5–7 Head­eye L.	7	8.7 0.3	8.3 – 9.2
4–5 Orbit Dia.	7	5.2 0.3	4.7 – 5.6
1–4 Snout L.	7	20.7 0.8	19.7 – 21.7
2–3 Internares W.	7	3.3 0.3	3.0 – 4.0
5–6 Interorbital W.	7	11.4 0.8	10.7 – 12.6
7–12 Head Dp.	7	19.4 0.2	19.1 – 19.7
1–24 Mouth L.	7	16.8 0.6	15.7 – 17.9
21–22 Mouth W.	7	20.3 0.6	19.4 – 21.1
22–23 Barbel L.	7	2.2 0.2	1.8 – 2.4
25–26 Dentary tooth cup L.	7	7.1 0.4	6.5 – 7.6
27–28 Premaxillary tooth cup L.	7	6.9 0.5	6.2 – 7.6