A geochronological scale measured in Millions of Years Ago or M Y A. Mesozoic era: Triassic period, 250 to 201 MYA, first dinosaurs, first mammals, conifers, ocean-living reptiles. Jurassic period, 201 to 145 MYA, dinosaurs, first birds, ocean-living reptiles. Cretaceous period, 145 to 65 MYA, dinosaurs, first flowering plants. Which describes the geological time of the first land plants.
Conifers appeared after the first flowering plants.
Conifers first appeared around 182 million years ago.
The first flowering plants appeared around 240 million years ago.
The first flowering plants were introduced toward the end of the Mesozoic era.

D. The first flowering plants were introduced toward the end of the Mesozoic era.

Explanation:

Following the Paleozoic Era, the Mesozoic Era or Age of Conifers began approximately 250 million years ago. This major geological era brought about the ancestors of many of the plant and animal groups still in existence today.

The Mesozoic era is marked by 3 divisions:

Animals and plants slowly recovered  after the mass extinction in the Permian-Triassic extinction that led to the eradication of most aquatic marine species. They evolved to exploit varying niches in their environment, leading to a boom in terrestrial animals. Over time the planet's increasingly warm climate, abundant in atmospheric oxygen and carbon dioxide, contributed to the growth of diverse megaflora, that rapidly dominated the planet's terrestrial biosphere.

By the end of the Mesozoic Era, in the Cretaceous period, flowering plants (angiosperms) largely replaced the dominant seed ferns of the Triassic, and the conifers, cycads and gymnosperms of the Jurassic.

Varied dispersal  mechanisms in angiosperms co-evolved with the evolution of certain types of fauna. Plants used animal life, including herbivorous reptiles and early mammal-like species to disperse large seeds.

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