What does it mean for a type of plant to “vegatatively dominate” as opposed to “taxonomically dominate”?

I'm reading Plants and the K-T Boundary, by Douglas Nichols and Kirk Johnson. On page forty-seven the authors write the following: "By the Campanian many floras were vegetatively co-dominated by angiosperms, conifers, and ferns, but taxonomically dominated by angiosperms."

My first intuition was that this means angiosperms, conifers, and ferns were equally dominating the available resources in many ecosystems, but that at the same time the angiosperms had become more evolutionary diverse. But I'm very new to reading about paleobotany, and biology in general, so I thought I'd better check that. Thanks for your time.

What is the difference between vegetative and taxonomic domination in the above example?