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Since the 1980s I have worked on a group of extinct actinopterygian fishes called semionotids that lived some 185-210 million years ago (McCune 1986; 1987a,b; McCune et al. 1984). These fishes hold particular evolutionary interest because, like extant cichlid fishes, semionotids diversified extensively in great tropical rift valley lakes. But unlike cichlids, the fossil record of semionotids is remarkable. It is possible to collect thousands of fully articulated fishes in lake sediments retaining annual layering, thus enabling study of extremely fine-scale temporal changes in morphology and species composition. My work on semionotids has included: species-level taxonomy and phylogenetic analysis (McCune 1986, 1987a); extremely detailed microstratigraphic studies of the patterns of species richness and variation through time (McCune 1990); and broadscale biogeographic and stratigraphic study of species distributions across temporal (stratigraphic) sequences of a geographic array of individual lakes (McCune 1996). It has been possible to infer rates of speciation in semionotids and compare them to rates for other species flocks of fishes, other fishes, and island faunas (McCune 1997; McCune and Lovejoy 1998). Ongoing interests include species level taxonomy, phylogeny, and the paleoecological context and tempo of speciation. I am happy to have students investigating the systematics and evolution of analogous radiations of closely related complexes of living fishes. |