Pimelodella, Pierre & Slobodian, 2024

Pierre, Veida & Slobodian, Veronica, 2024, A new species of Pimelodella (Siluriformes: Heptapteridae) from the Paraguai basin, Brazil, with a discussion regarding its distribution, Neotropical Ichthyology (e 230110) 22 (1), pp. 1-25 : 14-15

Key to the species of Pimelodella from the Paraguai basin

1a. Total vertebrae 46 (rarely 45); anal-fin adpressed terminus always anterior to adipose-fin terminus, reaching at least the vertical through three-fourths of adipose fin; adipose fin very long, slightly more than 2.0 to 2.5 times in SL ................................................................................................................. P. gracilis

1b. Total vertebrae 39–44; anal-fin adpressed terminus between verticals through adipose-fin terminus and slightly posterior to adipose-fin terminus; adipose fin 2.5 or more times in SL.............................................................................................. 2

2a. Openings of preoperculomandibular laterosensory canal at dentary large and conspicuous; posterior margin of pectoral-fin spine bearing 14–20 small, retrorse blades along basal two-thirds ( Fig. 3C ); head roof heavily ornamented..................................................................................................... P. mucosa

2b. Openings of preoperculomandibular laterosensory canal at dentary not large or particularly conspicuous; posterior margin of pectoral-fin spine not as above; head roof ornamentation inconspicuous................................................................... 3

3a. Supraoccipital process not reaching the anterior prenuchal plate; dorsal-fin spine small, approximately half or slightly more of second dorsal-fin ray total length; dorsal lobe of caudal fin notably longer than ventral caudal-lobe; hypural 5 variably fused to hypural 3+4...................................................................... P. megalura

3b. Supraoccipital process reaching the anterior prenuchal plate; dorsal-fin spine at least a third of second dorsal-fin total ray length (excepting the filamentuous portion, if present); caudal-fin lobes subequal or ventral lobe slightly longer than dorsal; hypural 5 completely free ...................................................................... 4

4a. Maxillary barbels always surpassing caudal-fin origin; posterior margin of pectoral-fin spine bearing 4–6 notably triangular, short and straight blades along basal two-thirds; dorsal fin distal third notably dark brown to black........................................................................................................ P. notomelas

4b. Maxillary barbels reaching between pelvic-fin origin and may extend beyond caudal-fin origin; posterior margin of the pectoral-fin spine not as above; dorsal fin not presenting a notably dark brown to black coloration ....................... 5

5a. Dorsal profile straight from snout to dorsal fin; dorsal-fin spine robust, large, bearing small, straight spinules along three-fourths of its distal posterior margin; posterior margin of pectoral-fin spine bearing 13–23 retrorse blades along basal two-thirds ( Fig. 3A ) ................................................................................. P. guato

5b. Dorsal profile convex from snout to dorsal fin; dorsal-fin spine not particularly robust, nor bearing spinules at its posterior margin; posterior margin of pectoral-fin spine bearing 9–13 retrorse blades along basal two-thirds .................. 6

6a. Maxillary barbels reaching at least anal-fin terminus when parallel to main body axis; adipose fin 2.5 to almost 3.0 times in SL .............................. P. taeniophora

6b. Maxillary barbels reaching between pelvic-fin origin and anal-fin terminus; adipose fin short, more than 3.5 times in SL............................................................. 7

7a. Epiphyseal branch of supraorbital canal on the head (S6) with contralateral canals connecting at midline, proceeding posteriorly as a single canal and opening in a single pore (S6+S6 diaulic pore); total vertebrae 41–42; dorsal region of body usually presenting a well-delimited darker stripe from supraoccipital process to first third of adipose-fin base .......................................................................... P. griffini

7b. Epiphyseal branch of supraorbital canal on the head (S6) emerging as two separated pores; total vertebrae 39–40; dorsal region of head and body slightly darkened, with a dark brown mark extending just between dorsal and adipose fins............................................................................................... P. laticeps

Figures

FIGURE 3 | Pectoral-fin spine of A. Pimelodella guato, paratype, CIUnB 1772, 91.2 mm SL, length of spine 16.7 mm; B. P. taeniophora, ZUFMS-PIS 6320, 68.9 mm SL, length of spine 11.4 mm; C. P. mucosa, holotype, CAS 63720, 97.4 mm SL, length of spine 22.8 mm; D. P. serrata, holotype, FMNH 57979, 55.7 mm SL, length of spine 18.3 mm; and E. P. howesi, holotype, ANSP 69036, 79.3 mm SL, length of spine 17.8 mm.