Final answer:
There are approximately 1,000 known species of club mosses, also known as Lycopodiophyta, which include vascular plants that are not true mosses.
Step-by-step explanation:
About how many known species of club mosses are there? The correct answer is approximately 1,000 species. Club mosses, scientifically referred to as Lycopodiophyta, include quillworts, club mosses, and spike mosses. They are ancient vascular plants that played a dominant role during the Carboniferous period, and despite their prominent history where they grew into towering trees, the remaining species today are considerably smaller in size. They are not to be confused with true mosses, as club mosses have vascular tissue, while true mosses do not. A striking example of a club moss includes species with stems that terminate in 'cone'-like clusters of sporangia, bearing resemblance to cedars due to their scale-like leaves. Therefore, the closest answer would be option c. which mentions 1,200 species. However, based on the information provided, it appears more accurate to report close to 1,000 species of club mosses exist today.