Amazonspinther, Bührnheim & Carvalho & Malabarba & Weitzman, 2008

Bührnheim, Cristina M., Carvalho, Tiago P., Malabarba, Luiz R. & Weitzman, Stanley H., 2008, A new genus and species of characid fish from the Amazon basin - the recognition of a relictual lineage of characid fishes (Ostariophysi: Cheirodontinae: Cheirodontini), Neotropical Ichthyology 6 (4), pp. 663-678 : 669

Phylogeny of Amazonspinther

A single most parsimonious cladogram (tree length = 53, Consistency Index = 0.88, Retention Index = 0.92) was obtained from the analysis of 44 characters and 8 taxa ( Table 2 , excluding the fossil Megacheirodon , discussed below). Amazonspinther was found to be closely related to Spintherobolus , and both genera as sister group to Serrapinnus ( Fig. 10 ). Amazonspinther dalmata is a miniature characid according to Weitzman & Vari’s (1988) definition. Those authors stated that miniature characid fish species mature sexually at less than 20 mm SL, and are not reported to exceed 25 to 26 mm SL in the wild. Females of A. dalmata are fully mature at a very small size (15.73 mm SL), and the largest known specimen reached less than 20 mm SL. Mature males, however, were not found among the specimens examined.

The current phylogenetic hypothesis available (Malabarba, 1998) for the small sized cheirodontines is strongly based on secondary sexual characters of males, and the lack of mature males of A. dalmata does not allow the examination of thirteen characters potentially informative to access the relationships of A. dalmata with cheirodontines. Nevertheless the new species is found to share several uniquely derived characters with the species of Spintherobolus as defined by Weitzman & Malabarba (1999), supporting a hypothesis of phylogenetic relationship between A. dalmata and the Neotropical Cheirodontinae .

Coding of characters 6, 7, 8, 9, 10, 11, 12, 13, 14, 22, 23, 32 and 37 below depended on the examination of fully mature males. We performed two distinct analyses, one in which all these characters were coded as missing for A. dalmata , and the second with all these characters coded as the outgroup (“0”) for A. dalmata . Character 28, the relatively short pectoral-fin was also coded as missing in the latter analysis, because the average percentuals of SL would fit in state 1, but minimum and maximum percentiles of SL would not (Appendix 1). In both analyses, A. dalmata resulted as sister taxon to Spintherobolus ( Fig. 10 , characters coded as missing). Characters 1 through 35 were extensively described and discussed by Malabarba (1998) and Weitzman & Malabarba (1999), and are presented here in summarized format reporting the respective numeration in those papers (Appendix 1).

Figures

Fig. 10. Phylogeny of Amazonspinther dalmata and related cheirodontine taxa based on the single resulting most parcimonious tree (tree length = 53, Consistency Index = 0.88, Retention Index = 0.92). Characters 6, 7, 8, 9, 10, 11, 12, 13, 14, 22, 23, 28, 32 and 37 were coded as missing in the data matrix for A. dalmata. Characters 10, 11, 12, 22, 23, 27 are ambiguous and were optimized using ACCTRAN (above) or DELTRAN (below) optimizations.