Delturus, EIGENMANN & EIGENMANN, 1889

Reis, Roberto E., Pereira, Edson H. L. & Armbruster, Jonathan W., 2006, Delturinae, a new loricariid catfish subfamily (Teleostei, Siluriformes), with revisions of Delturus and Hemipsilichthys, Zoological Journal of the Linnean Society 147 (2), pp. 277-299 : 286-288

DELTURUS EIGENMANN & EIGENMANN

Delturus Eigenmann & Eigenmann, 1889: 45 (type species: Delturus parahybae Eigenmann & Eigenmann, 1889 ; by original designation).

Diagnosis: No uniquely derived features were found to diagnose Delturus . The following features are derived for Delturus but are shared with a number of other loricariid groups (from Armbruster, 2004): (1) more than six infraorbital canal plates (character 91–2); (2) ridge on lateral ethmoid, from metapterygoid contact to near the anterior margin of the bone, short (character 97–1); and (3) reduction to eight to 11 vertebrae from first normal (not bifid) neural spine behind dorsal fin up to hypural plate (character 121–2).

KEY TO SPECIES OF DELTURUS 1. Premaxilla with 15–24 teeth; dorsal fin with nine to ten (usually ten) branched rays; eye comparatively smaller (orbital diameter 53.0–64.0% of interorbital space); colour pattern with distinct dots, mainly on head ......................................................................................... Delturus parahybae (Rio Paraíba do Sul basin)

1′. Premaxilla with 26–137 teeth; dorsal fin with eight to ten (usually nine) branched rays; eye comparatively larger (orbital diameter 61.4–93.0% of interorbital space); colour pattern with small bars and vermicula- tions, mainly on head......................................................................................................................................... 2

2. Posterior margin of caudal fin convex; dorsal-fin margin rounded .................................................................. ....................................................................................... Delturus brevis sp. nov. (Rio Jequitinhonha basin)

2′. Posterior margin of caudal fin concave; dorsal-fin margin straight ............................................................... 3

3. Caudal fin plain light brown, without a distinct patternof dark spots; iris usually with a large and distinct dorsal flap ........................................................................................ Delturus angulicauda (Rio Mucuri basin)

3′. Caudal fin with distinct pattern of dark spots; iris usually with a minute and indistinct dorsal flap .... .................................................................................................................. Delturus carinotus (Rio Doce basin)

In addition, Delturus can be easily recognized by the combination of a high preadipose keel, formed by the azygous preadipose plates, almost symmetrically bifid teeth ( Fig. 2 ) on premaxilla and dentary, dorsal fin with eight to ten branched rays, large eye (orbital diameter 18.0–24.5% HL), and dorsal-fin membrane extended posteriorly and contacting first preadipose plate.

Figures

Figure 2. Teeth of the Delturinae. A, right premaxilary tooth of Delturus angulicauda, USNM 318180, lateral view. Scale bar 1 mm. B–H, dorsal view of right premaxillary tooth crown. B, D. parahybae, MCZ 7726. C, D. angulicauda, USNM 318180. D, D. carinotus, MCP 28039. E, D. brevis, MZUSP 69858. F, Hemipsilichthys papillatus, MCP 21423. G, H. nimius, MCP 31990. H, H. gobio, MCP 19780. Scale bar 250 µm.