Rivulus

Oscar M. Lasso-Alcalá, Donald C. Taphorn B., Carlos A. Lasso & Oscar León-Mata, 2006, Rivulus sape, a new species of killifish (Cyprinodontiformes: Rivulidae) from the Paragua River system, Caroní River drainage, Guyana Shield, Venezuela., Zootaxa 1275, pp. 21-29 : 22

[[ Genus Rivulus ]]

The killifish genus Rivulus Poey , 1860 (Cyprinodontiformes: Rivulidae) is widely distributed in both Middle and South America, where it ranges from Mexico to Argentina, and on many Caribbean islands from Cuba to Trinidad. There are more than 100 recognized species in the genus, making it the most speciose genus in the family. Although additional species continue to be found and described, only Huber (1992) has cataloged their diversity, ecology, and distribution patterns, along with their taxonomy. Phylogenetic studies of rivulids, including the genus Rivulus , reveal that it is polyphyletic, based on molecular sequence data (Hrbek and Larson, 1999; Murphy et al., 1999), but monophyletic if only morphological data are considered (Costa, 1998; Hrbek et al., 2004). Based on maximum body size, adult color pattern and habitat preference Rivulus sape would belong to the Guyana Shield species group, as proposed by Hrbek and Larson (1999), but confirmation of this awaits DNA analyses. Generally speaking, species of this clade are small (i.e., usually less than 50 mm SL, although some, such as Rivulus tecminae , attain larger sizes) brightly colored fishes that typically exhibit less sexual dimorphism than most Rivulus species and usually inhabit very small, clear-water streams or temporary isolated pools that are often devoid of other fish species (Hrbek et al., 2004). Exceptions exist for each of these conditions, however.