Cheirodontini

Weitzman, Stanley H. & Malabarba, Luiz R., 1999, Systematics of Spintherobolus (Teleostei: Characidae: Cheirodontinae) from eastern Brazil, Ichthyol. Explor. Freshwaters 10 (1), pp. 1-43 : 8-9

Tribe Cheirodontini , Clade B

Clade B Cheirodontines have the following four synapomorphies.

(5) Twelve to twenty-eight ventral procurrent caudal-fin rays in both males and females. Outgroup Cheirodontines and other outgroup characids have 5-11 ventral procurrent caudal-fin rays, except Salminus Agassiz in Spix & Agassiz, with 16 ventral procurrent caudal-fin rays according to Roberts (1969: 428-429). Salminus has no other synapomorphies listed here for the cheirodontine clades discussed.

(6) The ventral procurrent caudal-fin rays of males are elongate and the ray halves (see Weitz ­ man, 1962: 40, discussion of the anal-fin ray halves) of each side are fused along their entire length. In most other characids and clade A Cheirodontines the ray halvesform a V shaped bone in frontal view with its two halves fused only distally, although in some, for example Astyanax cf. bimaculatus Linnaeus , the anterior two or three ray halves may be fused for 50 to 80 % of their distal length.

(7) The anterior-most ventral procurrent caudal-fin rays of the females have the proximal portions of their ray halves fused to each other, but retain an opening near their distal tips, giving a needle-like shape to these rays. Females of most outgroup characids and Cheirodontines have the entire lengths of their ray halves separate.

(8) Several of the anteriormost ventral procurrent caudal-fin rays of males project through the muscles at which point they are covered only by extremely thin skin (often lost or nearly undetectable in preserved specimens). Thus they can be easily seen along the ventral margin of the caudal peduncle ( Fig. 8 ). In other characids the anterior ventral procurrent caudal-fin rays are buried in the muscles and skin and are not visible along the ventral surface of the caudal peduncle. (9) Males of Clade B Cheirodontines have elongated hemal spines of four or more posterior caudal vertebrae (preural vertebrae), those anterior to the terminal half centrum and its processes. These are associated with the ventral procur ­ rent caudal-fin ray supports ( Fig. 8 ). Outgroup Cheirodontines and characids have only the posterior one, two, or sometimes three caudal (preural) vertebrae directly articulating with the ventral procurrent caudal-fin rays.

Figures

Fig. 8. Spintherobolus ankoseion, USNM 297935, adult male, 24.5 mm SL. Osteology of ventral procurrent caudal-fin rays and associated bony structures, anterior to right.