As with many taxonomic groups, our perception of its diversity has evolved over the years as a consequence of advances in taxonomic knowledge and the availability of new study techniques. This has resulted in the presence of a number of ambiguous records in the literature. In particular, in Thailand rotifers have been recorded over a time span of over a century, starting by Weber (1907), and quite a few older records refer to taxonomic concepts that are now understood differently than at the time they were published, and/or use names that are no longer considered valid.