Farlowella altocorpus , Michael E. Retzer, 2006
treatment provided by
Farlowella altocorpus , sp. nov.
(Figs. 1, 2)
Holotype. INHS 99773, 170.15 mm SL, sex unknown. Bolivia: La Paz State: Río Beni Basin: Rio Coroico, Caranavi , 4 August 1995, L.M. Page, B.M. Burr, M.H. Sabaj, J. Sarmiento & A.S. Barrera.
Paratypes. INHS 36972, 2 ex., 87.82-91.69 mm SL; same data as holotype. - SIUC 23150, 3 ex., 69.59-138.89 mm SL same data as holotype.
Diagnosis: Farlowella altocorpus is a member of the F. nattereri group ZBK as defined by Retzer and Page (1996) and is distinguished from all non-members of this group except Farlowella gracilis Regan ZBK by having five rows of anterior lateral plates. The new species is distinguished from F. gracilis ZBK by having a snout-mouth length <50% of head length versus ≥ 50% in adults. Farlowella altocorpus is distinguished from other members of the F. nattereri group ZBK by possessing a unique combination of characters: snout tip to mouth length 73-87% of pectoral fin length in adults, body depth 69-79% of pelvic fin length, body depth 49-53% of distance between pelvic and pectoral fins, head length 1.94-2.28 times length of snout tip to mouth, mid-ventral plates keeled, pectoral fins reach origins of pelvic fins, not having first anal and dorsal fin spines entirely darkly pigmented, anterior median lateral plates 14-16, posterior median lateral plates 16-18, post-anal plates 22-23, and abdominal plates 22-31.
Description: Largest specimen is the holotype, 170.15 mm SL. Morphometric data given in Table 2.
Body of Farlowella altocorpus wide and deep relative to other Farlowella ZBK species. Snout short with tip slightly expands distally (Fig. 1). Head gently slopes forward from eye to base of snout; snout points upwards. Viewed dorsally, head roughly triangular with widest point at opercles and with weak preorbital ridge. Width of body posterior to dorsal fin noticeably less wide than anterior to dorsal fin. Visible portion of the cleithrum narrow and often in two parts. Pectoral fins long, reaching origin of pelvic fin. Pelvic fins extend beyond anus but do not reach origin of anal fin. Dorsal fin insertion slightly ahead of anal fin insertion. Three complete rows of abdominal plates.
Number of teeth of upper left jaw 25-38; in lower left jaw 18-33. Total median lateral plates 32; pre-dorsal plates 8.
Overall coloration of specimens in alcohol light to dark brown. Snout dark brown under and on sides and light dorsally. A dorso-lateral dark stripe runs along sides of body from head and fades in intensity posterior to dorsal fin. Posterior edges of plates within dark lateral stripe behind eye may lack pigmentation. Contrasting near-pigmentless dorsal stripe from snout to dorsal fin that fades posterior to dorsal fin. Near-pigmentless ventrally from mouth to anal fin but more pigmented posterior to anal fin. Small dark spots may occur on dorsal and ventral near-pigmentless stripes.
Small spots of brown melanophores on spines and rays of anal, dorsal, pectoral, and pelvic fins. Interradial membranes clear. Brown bands on upper and lower rays and membranes of caudal fin (Fig. 2); pigmentation of interradial membranes of caudal fin darker in smaller specimens and faint in larger specimens.
Outer portion of upper lip pigmented with small discrete spots and inner portion unpigmented. Lower inner lip unpigmented and outer side with numerous faint melanophores.
Comparisons: Farlowella altocorpus is most similar to F. hasemani ZBK but differs in having a shorter snout-mouth length relative to the pectoral length in adults (73-87% in F. altocorpus , 91-110% in F. hasemani ZBK ), and a shallower body depth relative to the pelvic fin length (69-79% in F. altocorpus , 86% in F. hasemani ZBK ), fewer posterior median lateral plates (16-18 in F. altocorpus , 19-20 in F. hasemani ZBK ), and pectoral fins reach origins of pelvic fins (vs. not reaching in F. hasemani ZBK ). (Note that in Table 14 of Retzer and Page (1996), the snout-mouth length to pectoral length ratio for F. hasemani ZBK was incorrectly given as> 1.0.)
Farlowella altocorpus differs from F. nattereri ZBK in having a shorter and broader snout. This difference is reflected in a shorter snout-mouth length relative to the pectoral length in adults (73-87% in F. altocorpus , 91-138% in F. nattereri ZBK , Fig. 3), and not having first anal and dorsal fin spines entirely darkly pigmented. Note that in Table 14 of Retzer and Page (1996), the snout-mouth length to pectoral length ratio is incorrect due to a typographic error. The correct value in the table should have been>1.0 and was correctly given in the description for the species on page 57. The addition of new data herein has lowered the value from 1.0 to 0.91.
The body depth of Farlowella altocorpus is not as deep as that of F. hasemani ZBK but is relatively deeper when compared to the other species of the F. nattereri species group ZBK . Farlowella altocorpus differs from F. isbruckeri ZBK in having a deeper body relative to pelvic fin length (69-79% in Farlowella altocorpus , 57-68% in F. isbruckeri ZBK ), deeper body relative to pectoral fin length (45-51% in F. altocorpus , 37-41% in F. isbruckeri ZBK ), and post-anal plates (22-23 in Farlowella altocorpus , 24 in F. isbruckeri ZBK ).
Farlowella altocorpus differs from F. juarensis in having a deeper body relative to pelvic fin length (69-79% in F. altocorpus , 64% in F. juaruensis ) and a deeper body relative to distance between pelvic and pectoral fin origins (49-53% in F. altocorpus , 47% in F. juaruensis ). Farlowella altocorpus differs from F. juaruensis in having a shorter head length relative to snout tip to mouth length (1.94-2.28 times the length in F. altocorpus , 2.48 in F. juaruensis ). Respectively, F. altocorpus differs from F. juaruensis in four meristic counts: anterior median lateral plates 14-16 versus 13, posterior median lateral plates 16-18 versus 14, post-anal plates 22-23 versus 24, and abdominal plates 22-31 versus 20.
Farlowella altocorpus differs from F. odontotumulus ZBK in having a deeper body relative to pelvic fin length (69-79% in F. altocorpus , 60-64% in F. odontotumulus ZBK ) and a deeper body relative to distance between pelvic and pectoral fin origins (49-53% in F. altocorpus , 39-46% in F. odontotumulus ZBK ), and in having a longer head length relative to snout tip to mouth length (1.94-2.28 times the length in F. altocorpus , 1.67 in F. juaruensis ).
Distribution: Farlowella altocorpus is currently known only from a single locality on the Río Coroico, ( Río Beni Basin), La Paz State of Bolivia.
Etymology: From Latin, alto, meaning deep, and corpus, meaning body. The species epithet, altocorpus refers to its relatively high (alto) or deep body (corpus) relative to most of the other species of Farlowella ZBK .
Comments: The upper Rio Beni is also the type locality of Farlowella acestrichthys Pearson ZBK . Retzer and Page (1996) considered F. acestrichthys ZBK to be a junior synonym of F. nattereri ZBK . Comparison of F. altocorpus to the F. acestrichthys ZBK syntypes indicates that the species are easily distinguished from each other. Farlowella altocorpus has a distinctly shorter and broader snout relative to F. acestrichthys ZBK (Figs. 1, 4). Retzer and Page (1996) also commented that F. nattereri ZBK is a complex of species. This observation is reflected in the plot of factor scores (Fig. 5). In Figure 5, the syntypes of F. acestrichthys ZBK are separate from specimens identified as F. nattereri ZBK (AUM 23719) that are also from the type locality of F. acestrichthys ZBK . As noted by Retzer and Page (1996), closer examination of populations of this wide-ranging species will be required to accurately access F. nattereri ZBK . One of the syntypes of F. acestrichthys ZBK (CAS 77322) does appear to group with F. altocorpus and F. hasemani ZBK ; however, this is likely to be an artifact of the PCA because of the very large size of the specimen, 221.8 mm SL.
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