TAXONOMY OF THE DIATOM STEPHANODISCUS NIAGARAE FROM A FOSSIL DEPOSIT IN JINGYU COUNTY, JILIN PROVINCE, CHINA

Abstract

Stephanodiscus niagarae var. niagarae, S. niagarae var. magnifica, S. niagarae var. insuetus, S. rotula, S. neoastraea, S. yellowstonensis and S. superiorensis compose a group of taxa (informally designated as the ‘niagarae complex’) having stalked rimoportulae and columnate satellite pores around the central pore of each fultoportula; in addition they usually have several rimoportulae and central as well as marginal fultoportulae. The taxonomic and geographic limits of the ‘niagarae complex’ species are sources of contention in the literature. Because most characters used to separate species within the complex are highly variable and overlap greatly between species, certain identification usually requires statistical analysis. Specimens of the ‘niagarae complex’ from a palaeolacustrine deposit in Jingyu County, Jilin Province, China are shown to belong to S. niagarae with the aid of principal component analysis.