Paracanthopoma parva

description

Description: Morphometric data for the holotype and paratypes are provided in Table 9. Body short (HL 18.0 - 22.1 % SL) (Fig. 28). Cross-section of body slightly broader than deep at pectoral-fin insertion and increasingly compressed posterior to that point, tapering to caudal fin. Dorsal profile of body straight from head to origin of dorsal fin (Fig. 28), except in specimens preserved with curved vertebral column, often those with full guts, where it is convex. Dorsal and ventral profiles of caudal peduncle straight and converging towards midline along anterior half and straight or slightly convex and diverging along posterior half, sometimes angulate at beginning of procurrent caudal-fin rays. Caudal peduncle narrow, but expanded by procurrent rays along posterior third or half. Proportion of expansion greater in smaller individuals, with most of peduncle expanded, paddle-shaped, in very small specimens, ca. 11 - 14 mm SL (e. g., ANSP 180020). Ventral profile of body gently convex until pelvic-fin origin (Fig. 28), with some specimens with greatly distented abdomens due to gut contents. Myotomes and longitudinal skeletogenous septum clearly visible along whole body. Axillary gla

A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus

diagnosis

Diagnosis: Distinguished from all congeners except Pc. carrapata, Pc. daemon, and Pc. truculenta by the presence of nine (Pc. daemon occasionally with 10) teeth on the median premaxilla (vs. 3 to 5 or 11 and more); by the presence of a single median s 6 pore, visible on the middle of skull posterior to eyes (vs. paired s 6 pores, distant from midline of skull), and by the supraoccipital anteriorly produced into large pointed spike (vs. either anteriorly concave or straight across skull roof). Distinguished from all congeners except Pc. carrapata and Pc. truculenta by the posterior margin of the anal fin well posterior to vertical through that of the dorsal fin (vs. margins of two fins approximately at same vertical or that of anal fin only slightly posterior to that of dorsal fin); and by the deeply emarginate, bilobed caudal fin (vs. truncate with round corners or only slightly concave). Distinguished from Pc. carrapata and Pc. truculenta by lacking an extensive invasion of the skull roof by head musculature, with widest exposed part of neurocranium wider than interorbital (vs. exposed part of neurocranium reduced, approximately equivalent to interorbital); and by the larger operc

A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus

discussion

Remarks: Paracanthopoma parva is a variable species, in both details of body and head shape, and in pigmentation (Figs. 29, 32). A preliminary examination of the material available initially suggested the existence of various different species across the ample geographical range of what is here considered as Pc. parva. However, potentially distinguishing characteristics are of degree or proportion, rather than qualitative, and tend to vary continuously across populations, when enough representative material is available. The few discontinuities encountered are usually associated with lack of samples from intervening areas, generating suspicions about the significance of such apparent discontinuity. Obviously there is some degree of differentiation among some of the various disjunct populations of Pc. parva, but the level of clinal morphological variation indicates that they do not warrant recognition as separate species according to the criteria and data utilized in this work. But we do not rule out the possibility that more detailed studies, perhaps including genetic markers will find grounds for the recognition of additional species within what is here considered as Pc. parva. Sm

A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus

distribution

Geographical distribution: Paracanthopoma parva is widely distributed in the uplands of the Amazon, Essequibo and Orinoco drainages in Brazil, Colombia, Ecuador, Guyana and Peru (Fig. 31). In the Amazon, it occurs in upland sectors of most major northern and southern tributaries, but is conspicuously absent from lowland areas.

A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus