Flowering plants (angiosperms) make up around 90% of living plant species today. Prior to the rise of angiosperms, during the Jurassic and the Early Cretaceous, the higher flora was dominated by gymnosperm groups, including cycads, conifers, ginkgophytes, gnetophytes and close relatives, as well as the extinct Bennettitales. Other groups of plants included pteridosperms or "seed ferns", a collective term to refer to disparate groups of fern-like plants that produce seeds, including groups such as Corystospermaceae and Caytoniales. The exact origins of angiosperms are uncertain, with competing hypotheses including the anthophyte hypothesis, assuming flowering plants to be closely related to gynetophytes and Bennettitales as well as the more obscure Erdtmanithecales. Benettitales, Erdtmanithecales, and gnetophytes are connected by shared morphological characters in their seed coats.