Rhyacoglanis pulcher ( Boulenger, 1887 ) Shibatta & Vari, 2017

Shibatta, Oscar Akio & Vari, Richard P., 2017, A new genus of Neotropical rheophilic catfishes, with four new species (Teleostei: Siluriformes: Pseudopimelodidae), Neotropical Ichthyology 15 (2), No. e 160132, pp. 1-30 : 14-17

Rhyacoglanis pulcher ( Boulenger, 1887) , new combination

Figs. 9-10; Tab. 4

Pimelodus (Pseudopimelodus) pulcher Boulenger, 1887:276 , pl. xxi, figs. 1, 4 (original description; Ecuador, Canelos).

Pseudopimelodus pulcher . - Eigenmann, Eigenmann, 1888:111.

Batrachoglanis pulcher . - Eigenmann, 1910:383 (eastern Ecuador).

Microglanis pulcher . - Eigenmann, 1912:155 (observations on color pattern).

Microglanis pulcher . - Gosline, 1941:85 ( Ecuador, Canelos).

Pimelodus zungaro zungaro . - Mees, 1974:202, fig. 39, pl. 5 (partim; Ecuador, Canelos; not Bolivia, upper río Beni; Peru, río Marañon; Brazil, Mato Grosso, Sangadina).

Pseudopimelodus pulcher . - Shibatta, 2003a:404 (information on synonyms, maximum length, and distribution).

Material examined. Ecuador. Canelos. BMNH 1880.12.8.105- 107, 3, syntypes, 58.5-68.5 mm SL, Upper Amazon River basin, 1880, C. Buckley .

Diagnosis. Rhyacoglanis pulcher is distinguished from R. paranensis by the dorsal and ventral confluence of the dark subdorsal and subadipose bands (vs. separation of those bands) and total number of vertebrae (34-35 vs. 31-33). Rhyacoglanis pulcher differs from R. annulatus in the uniformly dark caudal-peduncle band (vs. band centrally light), distance from the pelvic-fin origin to the anus (11.1-14.0 vs. 8.2-9.6% SL) and distance from the anus to the anal-fin origin (13.8-15.2 vs. 15.8-16.2% SL). Rhyacoglanis pulcher is distinguished from R. epiblepsis by the pointed caudal-fin lobes (vs. rounded lobes), the very obvious body bands (vs. obscure or absent bands) and limited number of dark spots on the body (vs. spots numerous and not dark). Rhyacoglanis pulcher is diagnosed from R. seminiger by the confluence of the dark subdorsal and subadipose bands limited to dorsal and ventral regions (vs. bands completely fused), stripes on caudal fin continuous with the caudal-peduncle spot (vs. distinctly separated) and total vertebrae (34-35 vs. 32-33).

Description. Body proportions are given in Tab. 4. Body depressed from snout tip to dorsal-fin origin; progressively compressed from that point to caudal-fin base. Dorsal profile of head and body posterodorsally nearly straight from snout tip to dorsal-fin origin; dorsal-fin base slightly straight; profile nearly straight from terminus of dorsal-fin base to adipose-fin origin. Ventral head and body profile slightly convex to almost straight from lower jaw margin to posterior limit of anal-fin base. Caudal peduncle profile slightly concave along dorsal and ventral margins.

Head depressed; slightly longer than wide. Anterior margin convex in dorsal view. Head with weakly developed scattered unculiferous tubercles laterally and dorsally. Mouth terminal and wide; width more than one-half of HL. Upper jaw slightly longer than, or same length as, lower jaw. Lips thick and well developed, more so proximate to rictus. Premaxillary tooth plate posterolaterally pointed. Anterior nostril immediately posterior to vertical through rictus. Eye small, superior, covered by skin, slightly posterior to anterior one-third of HL. Opercular membrane well developed; margin falling short of pectoral-fin origin. Maxillary barbel base enlarged. Tip of adpressed maxillary barbel falling short of opercular margin. Tip of adpressed inner mental barbel surpassing base of outer mental barbel but falling short of tip of that barbel. Tip of adpressed outer mental barbel reaching opercular membrane margin.

Dorsal-fin trapezoidal with distal margin rounded and first branched ray longer than dorsal-fin base. Dorsal-fin origin immediately posterior to anterior one-third of body but anterior to one-half of SL. Tip of adpressed dorsal fin reaching slightly beyond midpoint between dorsal-fin base terminus and adipose-fin origin. First dorsal-fin ray (spinelet) small, rigid and forming dorsal-fin spine-locking mechanism. Second ray in form of spine with anterior margin smooth and posterior margin bearing retrorse serrations. Dorsal-fin rays I,6(3). Adipose fin long; base longer than that of other fins; posterior margin free and rounded. Pectoral-fin margin somewhat triangular overall with posterior margin rounded. Tip of adpressed pectoral fin falling short of pelvic-fin origin. First pectoral-fin ray strong, rigid and in form of spine with serrae along anterior and posterior margins; posterior serrations retrorse and distinctly larger than anterior serrae; pectoral-fin spine notched distally ( Fig. 3d). Pectoral-fin rays I,5(1) or I,6(2). Pelvic-fin profile almost triangular; posterior margin rounded. Pelvic-fin origin immediately posterior to vertical through terminus of dorsal-fin base. Tip of adpressed pelvic fin reaching vertical through adiposefin origin. Pelvic-fin rays i,5(3). Anal-fin margin rounded; base shorter than that of adipose fin. Anal-fin rays iii,7(2) or iv,6(1). Caudal fin forked; lobes pointed; ventral lobe slightly longer than, or almost same length as, dorsal lobe. Caudal-fin principal rays i,6,8,i. Dorsal procurrent rays 17(2) or 18(1); ventral procurrent rays 15(1), 16(1), or 17(1).

Posterior cleithral process well developed, pointed, reaching vertical through anterior of dorsal-fin base. Axillary pore present. Lateral line complete. Total vertebrae 34(2), 35(1). Ribs 9(1), 10(1) or 11(1). Gill rakers 1,1,3(1) or 1,1,4(2).

Color in alcohol. Pigmentation faded in examined specimens. Ground color light brown. Head with dark spots dorsally and ventral to eye. Body with dark subdorsal, subadipose and caudal-peduncle bands. Subdorsal band somewhat triangular, ventrally narrower and extending to ventral region of body with dorsal and ventral extensions continuous with subadipose band. Subadipose band overall rectangular with dorsal and ventral anterior and posterior extensions continuous with similar extensions of subdorsal and caudal-peduncle bands. Caudalpeduncle band with anterior margins extending along border forming a distinct anteriorly directed sideways V. Dorsal fin covered by dark band other than along distal one-fifth. Adipose fin with large dark central spot. Anal fin with two dark transverse stripes. Caudal fin hyaline other than for arched dark distal band on each lobe; bands of each lobe confluent on middle caudal-fin rays; dark pigmentation continuing anteriorly to caudal peduncle band; overall dark pigmentation in form of posteriorly directed sideways Y. Pectoral fin hyaline other than for transverse dark stripe slightly posterior to middle of fin. Pelvic fin with curved dark transverse stripe near midlength ( Figs. 9-10).

Geographical distribution. Rhyacoglanis pulcher occurs in the Ecuadorian Amazon ( Fig. 4). Though Mees (1974) indicated that R. pulcher also occurs in the río Popoi in the upper río Beni in Bolivia, the río Marañón in Peru, and at Sangadina, Mato Grosso, Brazil, we were unable to examine and confirm the identification of the specimens from the two last localities and the latter in particular represents a questionably unusually great range extension. The río Beni specimens reported on by Mees (1974) are rather R. epiblepsis , described herein.

Conservation status. Few specimens of R. pulcher were obtained from collections, suggesting that the species may be naturally rare. However there is a possibility that R. pulcher has a wider distribution in the rio Amazonas basin. In the absence of the information about geographic distribution and population dynamics necessary to properly evaluate the extent of occurrence, we recommend assigning an IUCN (2016) status of Data Deficient (DD) to R. pulcher .

Remarks. After nearly 150 years of preservation, the syntypes of Pseudopimelodus pulcher are very soft with faded coloration. However, the residual pigmentation in these specimens agrees closely with the illustration presented by Boulenger (1887), suggesting that the drawing can be taken as an accurate depiction of the original pigmentation. Most features were accurately described in the original description. Boulenger commented, however, that the “band of teeth in the upper jaw is of moderate breadth, without prolonged lateral portion”; whereas we find that the tooth band is actually posteriorly pointed.

A sample from the rio Jamari (INPA 9517), a rio Madeira tributary, agrees with the pigmentation pattern and most features of Rhyacoglanis pulcher except for having 7 branched pectoral-fin rays vs. the 5-6 rays in the type series. Unfortunately, with only two specimens from the rio Jamari and three from the type locality, it is uncertain whether this difference represents intraspecific variation or is an indication of an undescribed species of Rhyacoglanis in the rio Madeira. We tentatively identify the Madeira population as R. cf. pulcher pending study of additional specimens from those regions.

Mees (1974) proposed P. variolosus to be a synonym of P. pulcher based on the features reported by Miranda- Ribeiro (1914). However, the type locality of P. variolosus is Coxim, rio Taquary, Mato Grosso State, in a different hydrographic basin than that of P. pulcher . Examination of part of the syntype series of P. variolosus (lectotype MNRJ 818 and paralectotype MNRJ 16245), and of the description of the species by Miranda-Ribeiro (1914), shows that P. variolosus has at least two of the known synapomorphies of Rhyacoglanis , although we were not able to confirm the number of vertebrae, even via radiography. Since our analysis did not allow us to unequivocally confirm the synonymy of P. variolosus with P. pulcher , we prefer to maintain it as tentatively valid until more specimens from the rio Taquary become available.