Complex sentence: Chamberlin ranks among the ten most prolific spider taxonomists in history, describing more than 1,400 species, of which, nearly 1,000 are still recognized as valid (i.e. not taxonomic synonyms of previously described species).
Split into simpler sentences: Chamberlin ranks among the ten most prolific spider taxonomists in history. Over the course of his career, he described more than 1,400 species of spiders, of which, nearly 1,000 are still recognized as valid species (i.e. not taxonomic synonyms of previously described species).