Pseudobunocephalus , a new genus of banjo catfish with the description of a new species from the Orinoco River system of Colombia and Venezuela ( Siluriformes : Aspredinidae )

Pseudobunocephalus, a new genus of small banjo catfishes (< 80 mm SL), is distinguished from all other aspredinid genera by the following unique features: mandibular teeth restricted to a patch near symphysis of lower jaw; no contact between the metapterygoid and quadrate; autopalatine posteriorly forked with two separate cartilages; absence of the fourth pharyngobranchial; absence of gill rakers on all branchial arches; and lack of bifid hemal spines on vertebrae that articulate with anal-fin pterygiophores. As defined Pseudobunocephalus contain a new species, P. lundbergi from the Orinoco River basin, along with five other species previously assigned to the genus Bunocephalus: P. amazonicus, P. bifidus, P. iheringii, P. quadriradiatus, and P. rugosus.


Introduction
Fishes of the family Aspredinidae are commonly known as banjo catfishes due to their overall body shape, a depressed head and slender caudal peduncle, which when seen in dorsal view somewhat resembles the musical instrument (Myers, 1960).In addition to their body shape, most aspredinids are readily distinguished from other Neotropical catfishes by their heavily keratinized skins with rows of large unculiferous tubercles arranged along the dorsal surface and sides of their bodies.Representative species are found throughout the major tropical rivers of South America (e.g., Magdalena, Orinoco, Amazon, São Francisco, Paraguay-Paraná, and Uruguay), a few rivers west of the Andes Mountains (Atrato, San Juan, and Patia) and Atlantic drainages and coastal marine waters from the Orinoco to Amazon deltas.Aspredinids live in a va-riety of habitats ranging from shallow backwaters to deep river channels to tidal estuaries.Some aspredinids appear to be semi-fossorial, during the day often resting slightly buried in leaf litter or other soft substrates.In general, most species are cryptically pigmented, benthic, and rather sluggish unless disturbed.

Material and Methods
Methods generally follow those used in Friel (1995).Measurements were taken to the nearest 0.1 mm with digital calipers or from scaled distances between landmark points recorded with the aid of a stereomicroscope equipped with a camera lucida.All fish lengths are given as standard length (SL).Caudal peduncle depth was taken as the minimum depth of the caudal peduncle.Caudal peduncle length was taken from the posterior end of the anal-fin base to the end of the hypurals.Pectoral spine length does not include the flexible distal extension.Length of the postcleithral process was taken from the anterior insertion point of the erect pectoral spine with the pectoral girdle to the posterior tip of the process.Postcoracoid process length was taken from the transverse posterior margin of the pectoral girdle aside the base of the process to its tip.All lepidotrichia are included in the fin-ray counts.Stiffened dorsal-and pectoral-fin lepidotrichia are indicated by upper case Roman numerals.Observations on internal features were made from radiographs and/or cleared and stained specimens.Vertebral counts include the five fused vertebrae of the Weberian complex; the compound caudal centrum is counted as one.Institutional abbreviations follow Leviton et al. (1985).
Additional included species.Further nomenclatural details including junior synonyms for recognized species can be found in Friel (2003).
Pseudobunocephalus amazonicus (Mees, 1989) Pseudobunocephalus bifidus (Eigenmann, 1942) Pseudobunocephalus iheringii (Boulenger, 1891) Pseudobunocephalus quadriradiatus (Mees, 1989) Pseudobunocephalus rugosus (Eigenmann & Kennedy, 1903) Diagnosis.A genus of relatively small banjo catfishes (less than 80 mm SL) distinguished from other aspredinids by having the following unique characters: the dentary teeth are restricted to broad tooth patch near symphysis of lower jaw (Fig. 1) (vs.more broadly distributed along the length of the dentary); the metapterygoid lacks a bony connection with the quadrate (Fig. 1); the posterior end of autopalatine is distinctly forked and bears two separate terminal cartilages (Fig. 2); the absence of the fourth pharyngobranchial; the absence of gill rakers on all branchial arches; and the lack of bifid hemal spines on vertebrae that articulate with anal-fin pterygiophores.
Other characters not unique to this genus, but still useful for distinguishing it from other aspredinid genera include: the anterior limits of upper and lower jaws are approximately equal (also in Acanthobunocephalus); the lateral line is truncated at approximately the level of the dorsal-fin origin (also in Acanthobunocephalus); the dorsal-and ventral-most prin-  cipal caudal rays much shorter in length than other principal caudal rays (also in Acanthobunocephalus); the dorsal-and anal-fin membranes are not adnate with body (also in Acanthobunocephalus); the interhyal is absent (also in Hoplomyzon); and the abdominal and precaudal centra lack bony horizontal lamina (also in Dupouyichthys, Ernstichthys, Hoplomyzon and Micromyzon).
Etymology.The generic name is a combination of the Greek word pseudes, meaning false or deceptive, plus the aspredinid genus Bunocephalus.It alludes to the fact that members of this new genus have previously been mistaken for juveniles of various species of Bunocephalus.

Diagnosis.
Pseudobunocephalus lundbergi can be distinguished from all congeners by having the following unique characters within the genus: dorsal surface of skull orna- mented with numerous bony knobs of equal size (Fig. 4); distinct anterior and posterior cranial fontanels separated by a bony epiphyseal bar formed between the frontals (Fig. 3); infraorbital canal exits from the sphenotic (Fig. 3) and extends anteriorly past eye, bearing up to four pores (not figured); premaxilla without a posterolateral limb; and fifth centra with posteriorly directed processes that articulate with skeletal elements of the dorsal fin.Description.Dorsal, lateral and ventral views in Fig. 4 illustrate body shape and positions of fins and barbels.Morphometric and meristic data for holotype (ANSP 168817) and 10 syntopic paratypes (ANSP 172504) are summarized in Table 1.Head depressed with only slight depression between orbits.Skull ornamentation well developed with paired series of bony knobs beginning behind eyes, converging on occiput and continuing on dorsal lamina of Weberian complex and middle nuchal plate.All bony knobs approximately equal in size.Anterior and posterior cranial fontanels present and separated by bony epiphyseal bar formed by frontals (Fig. 3).
Integument covered with small unculiferous tubercles, those on posterior body in longitudinal rows; mid-dorsal row well defined; 2-3 well-defined rows on each side of caudal peduncle; several poorly-defined rows ventrally (Fig. 4).Caudal peduncle slender, round in cross section, tapering to caudal fin.
Mouth terminal, anterior limits of upper and lower jaws approximately equal.Premaxilla with 5-6 rows of acicular teeth and lacks posterolateral process.Dentary with 12-15 rows of teeth restricted to patch near symphysis of lower jaw (Fig. 1).Anterior nostril tubular, located at tip of snout, projecting beyond upper lip.Posterior nostril simple without flap or barbel, opening anteromedial to eye.Eye without free orbital rim.All barbels simple, unbranched; maxillary barbel reaching pectoral spine insertion.Posterolateral mental barbel at least twice as long as anteromedial mental barbel.Gular fold absent, branchiostegal membranes united to each other and to isthmus, 5 branchiostegal rays (Fig. 1).Opercular opening reduced to small valvular slit on ventral surface just anterior to pectoral spine insertion.
Gill rakers absent on all branchial arches.Pharyngeal teeth well developed on upper tooth plate; 1 or 2 rows of teeth on lower tooth plates.First and second hypobranchials well ossified; fourth pharyngobranchials absent.Parurohyal triangular with slight dorsal keel.
Openings of sensory canals on head darkly pigmented.Infraorbital canal exits sphenotic (Fig. 3) and passes anteriorly beyond eye, bearing up to four pores (not figured).Lateral-line canal truncated just posterior of parapophyses of fifth vertebra and anterior to dorsal-fin origin.A few individual isolated pores scattered more posteriorly, but never connected to main lateral-line canal.Dorsal fin without spinelet; consists of relatively flexible spine and four soft rays.Dorsal-fin membrane not adnate with body.Anterior nuchal plate and supraneural absent.Middle nuchal plate ornamented with a single bony knob.Adipose fin absent.Anal fin with 5-7 soft rays (6 in holotype), anal-fin membrane not adnate with body.Pectoral fin with robust spine and 5 soft rays.Shaft of pectoral spine curved with serrations along both pre-axial and post-axial margins.Intact pectoral spine with flexible tip.Axial pore present.Postcoracoid process of pectoral girdle extends slightly past postcleithral process in lateral view.Pelvic fin with 6 soft rays, second and third rays longest, not reaching anal-fin origin, no pelvic splint.Caudal fin with 10 principal  .Vertebrae 6-9 bearing ribs; dorsal-fin pterygiophores associated with Weberian complex (vertebrae 1-5) and vertebrae 6-11.Dorsal lamina of Weberian complex ornamented with series of three bony knobs.Parapophyses of fourth vertebra form broad lamina over swim bladder.Parapophysis of fifth vertebra long, curved anteriorly and extended laterally to body surface.Parapophyses of fourth and fifth vertebrae separated by deep notch (Fig. 3).No horizontal bony lamina developed on precaudal, caudal or ural centra.Hemal spines simple, not bifid, on vertebrae articulating with anal-fin pterygiophores.
Color in alcohol.Pigmentation variable with two distinct color morphs, one dark (Fig. 4) and one light.Dark morph with head light brown and irregularly mottled with darker pigment; overall body light brown with three poorly defined dark saddles, first beneath dorsal fin, and two more on posterior body.Individual unculiferous tubercles may be unpigmented or darkly pigmented giving speckled appearance to body.Ventral sur-face light brown with dark pigment concentrated in unculiferous tubercles.All fins and barbels mottled with dark pigment.Light morphs have similar pigmentation pattern to dark morphs but lack series of dark saddles on dorsal surface.
Size and sexual dimorphism.Specimens range from 19.5-30.0mm SL.The largest specimens examined are females with ripening ova (0.5 mm in diameter).No observed dimorphism of body ornamentation, fins or pigmentation.
Distribution.Pseudobunocephalus lundbergi is currently known from just a few localities in the lower río Caura (type locality), upper río Apure, and río Meta (Fig. 5), but is likely more widely distributed within the río Orinoco basin of Colombia and Venezuela.

Discussion
In overall appearance, Pseudobunocephalus most closely resembles Acanthobunocephalus, a monotypic aspredinid genus endemic to the upper Orinoco and Casiquiare systems.Acanthobunocephalus, however, can readily be distinguished from Pseudobunocephalus, since it is the only aspredinid that possesses a lockable dorsal spine.This feature is readily apparent even in the smallest specimens less than 12 mm SL.
Based on the author's unpublished phylogenetic analysis of the Aspredinidae (Friel, 1994), Pseudobunocephalus is the sister group to all other Aspredinidae.In addition to the derived characters that support monophyly of this genus, Pseudobunocephalus also retains several primitive character states for aspredinids including: ossified second hypobranchials; lack of bony horizontal lamina on any precaudal or caudal vertebrae; no bifid hemal spines articulating with anal-fin pterygiophores; and little or no contact between the parapophyses of vertebrae 4 and 5.
Furthermore, P. lundbergi appears to be the sister taxon to all other species in this genus and lacks several derived features seen it its congeners.All other Pseudobunocephalus species (P.amazonicus, P. bifidus, P. iheringii, P. quadriradiatus, and P. rugosus) share several derived features: the infraorbital canal exits from frontal and does not to pass anterior to the eye; the presence of a single large cranial fontanel between the paired frontals and sphenotic extending from mesethmoid anteriorly to supraoccipital posteriorly (i.e., absence of an epiphyseal bar formed by the frontals); premaxilla with a distinct posterolateral limb; and the lack of any contact or articulation between first dorsal-fin pterygiophore and the Weberian complex.

Fig. 3 .
Fig. 3. Dorsal view of the neurocranium and Weberian complex of Pseudobunocephalus lundbergi, ANSP 172505.Arrow indicates the exit of the infraorbital canal from the sphenotic.Scale bar equals 1 mm.

Etymology.
The specific name is patronymic in honor of Dr. John G. Lundberg of The Academy of Natural Sciences of Philadelphia.Lundberg served as the author's Ph.D. advisor, and has made numerous contributions to the field of Neotropical ichthyology and the systematics of siluriform and gymnotiform fishes.

Fig. 5 .
Fig. 5. Distribution map for Pseudobunocephalus lundbergi with the type locality indicated by a star symbol.

Table 1 .
Summary of morphometric measurements and meristic counts for Pseudobunocephalus lundbergi (N=11; Holotype, ANSP 168817, and 10 syntopic Paratypes, ANSP 172504).Standard length expressed in mm.All other measurements expressed in percent of SL.Meristic data for holotype is identified by a * superscript.rays plus one upper and one lower procurrent ray.Caudal-fin margin rounded with outermost principal rays unbranched and shorter than branched principal rays.