DELTURINAE, ARMBRUSTER, REIS & PEREIRA

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 : 279-280

DELTURINAE, ARMBRUSTER, REIS & PEREIRA , NEW SUBFAMILY

Genera included: Delturus Eigenmann & Eigenmann, 1889 and Hemipsilichthys Eigenmann & Eigenmann, 1889 .

Type genus: Delturus Eigenmann & Eigenmann, 1889 .

Diagnosis: Delturinae is diagnosed by two uniquely derived synapomorphies (from Armbruster, 2004), not seen in any other loricariid and not reversed in any known member of the subfamily: (1) pterotic-supracleithrum with a long, thin, dorsomesial process that originates just ventral to where the hyomandibula contacts the pterotic-supracleithrum (character 115– 1); and (2) anteromesial processes of pelvic basipterygium absent (character 170–1).

The following characters are also hypothesized as synapomorphic transitions for the Delturinae , but are shared with a number of other loricariid subgroups: (1) interhyal bone large, almost rectangular (a reversal, character 27–0, shared with Astroblepus , the Loricariinae , Chaetostoma , Cordylancistrus , Dolichancistrus , Leptoancistrus , and Pseudolithoxus ); (2) interhyal bone located well above the ventral margin of the hyomandibula (character 28–1, shared with Lithogenes and the Loricariinae ); (3) quadrate very wide, nearly as wide as long (character 64–2, shared with Otocinclus and Pseudorinelepis ); (4) quadrate with a small flap extending ventrally to symplectic foramen (character 66–1, shared with the clade Hypostomini, Pterygoplichthyini, and Ancistrini ); (5) small sesamoid ossification mesial to the preopercle and connected by a ligament to the opercle and angulo-articular (character 73–1, shared with Lithogenes and Pogonopoma ); (6) rib of sixth vertebral centrum flared distally so that its tip is much wider than its shaft (character 128–1, shared with Neoplecostomus , Otocinclus , Acanthicus , Megalancistrus , Lasiancistrus , Lithoxus , Neblinichthys , and Pseudancistrus ); (7) nuchal plate entirely covered by plates or thick skin (character 147–1, shared with Chaetostoma , Cordylancistrus , Dolichancistrus , Leptoancistrus ); (8) anterolateral processes of pelvic basipterygium straight (character 167–2, shared with Pogonopoma and a number of Ancistrini genera); (9) nuptial males with hypertrophied odontodes on cheeks (character 183–1, shared with Isbrueckerichthys , Pareiorhaphis , and some Loricariinae as Ixinandria , Rineloricaria , Sturisoma , and Sturisomatichthys ); (10) nuptial males with hypertrophied odontodes on snout, anterior to cheek plates (character 188–1, shared with Isbrueckerichthys , Pareiorhaphis , some Loricariinae as Ixinandria , Rineloricaria , Sturisoma , and Sturisomatichthys , Pseudorinelepis , and a number of Ancistrini genera); (11) postdorsal ridge formed by raised, median, azygous plates between dorsal and adipose fins (character 192–1, shared with Corymbophanes and Leptoancistrus ); (12) five transverse rows of plates on the least deep part of the caudal peduncle (character 196–3, shared with Isbrueckerichthys , some Pareiorhaphis , and Hypostominae except Corymbophanes ).

KEY TO SUBFAMILIES OF THE LORICARIIDAE

1a. Lateral and dorsal plates anterior to the dorsal fin absent..................................................... Lithogeneinae

1b. Lateral plates anterior to the dorsal fin always present (predorsal plates absent in Pareioraphis nudula) ............................................................................................................................................................................ 2

2a. Ventral surface of the pectoral girdle exposed (i.e. supporting odontodes) mesial to the coracoid strut ............................................................................................................................................... Hypoptopomatinae

2b. Ventral surface of the pectoral girdle covered in skin or plates mesial to the coracoid strut (coracoid strut may be exposed; plates may cover the pectoral girdle, but odontodes are supported by the plates and not the girdle).................................................................................................................................................................. 3

3a. Caudal peduncle dorsoventrally flattened; adipose fin absent .................................................... Loricariinae

3b. Caudal peduncle not dorsoventrally flattened; oval, round, or triangular in cross-section; adipose fin rarely absent ................................................................................................................................................................. 4

4a. Postdorsal ridge formed from several azygous preadipose plates. Teeth almost symmetrically bifid ............................................................................................................................................................ Delturinae

4b. Postdorsal ridge usually absent. Teeth asymmetrical or unicuspid .............................................................. 5

5a. Dorsal-fin spinelet V-shaped, dorsal-fin spine lock functional ................................................. Hypostominae

5b. Dorsal-fin spinelet rectangular or absent, dorsal-fin spine lock not functional ............... Neoplecostominae

Three other characteristics found by Armbruster (2004) to diagnose Delturus are also present in H. nimius but are absent in H. gobio and H. papillatus . These traits are ambiguous, and may either be synapomorphies for Delturinae reversed in the ancestor of H. gobio plus H. papillatus , or convergent for Delturus on the one hand, and for H. nimius on the other. Pending further resolution of that question, the characters are here included as tentative synapomorphies for Delturinae : (1) dorsal fin with supranumerary branched rays (eight to ten in Delturus and seven to nine in H. nimius ) (character 142–1, shared with Pterygoplichthys , and a number of Ancistrini ); (2) dorsal-fin spinelet V-shaped (a reversal, character 148–0, shared with Hypostominae ); and (3) dorsal-fin membrane extended posteriorly (character 143–1, shared with Spectracanthicus and Parancistrus ; contrary to the situation in Delturus ; however, in H. nimius the membrane never contacts the first preadipose plate).

On the basis of external morphology, a member of the Delturinae can easily be identified by the combination of two characters: (1) a high preadipose keel, formed by the azygous preadipose plates, and (2) jaw teeth almost symmetrically bifid ( Fig. 2 ). These two traits in combination are not seen in any nondelturine loricariid.

KEY TO GENERA OF DELTURINAE

1. Adults with body strong and massive, usually attaining large sizes around 200 mm SL (but D. brevis smaller); eye large (orbital diameter 18.0–24.5% HL); dorsal-fin membrane extended posteriorly and contacting first preadipose plate ................................................................................................................ Delturus

1′. Adults with body slender and elongate, usually attaining sizes smaller than 100 mm SL; eye small (orbital diameter 8.6–16.9% HL); dorsal-fin membrane not or slightly extended posteriorly but never in contact with first preadipose plate ...................................................................................... Hemipsilichthys

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.