"we've described over 20,000 different trilobite species"

and

"Most of them appeared to be ostracods... there are 13,000 existing ostracod species."

The sheer quantity of fossils and/or specimens to build out those lists of tens of thousands of species is mind boggling. I known there has been a shift from traditional species classification to a model based on genetics (cladistics). Has this changed the definition of what is considered a species? For example, can we assume that none of these 20,000 trilobite species could reliably procreate with one another?