DURING DRIER CLIMATES OF THE MESOZOIC ERA, PLANTS THAT REPRODUCED USING SEEDS DIVERSIFIED
Seasonally dry conditions at the beginning of the Mesozoic (245 million years ago) favored the diversification of plants that reproduced with seeds. Plants such as cycads, ginkgoes and conifers, which had seeds, relied on either wind or animals (insects, reptiles) for pollination and seed dispersal.

Cycads
Modern cycads have short, stout trunks with a bush of long, green, hardy, leaves at the top. As the leaves fall off, their bases create a honeycomb pattern. Mesozoic cycads were more slender and branched and could grow to 45 feet (15 m) tall! Cycads are “dioecious,” (“two houses”), which means plants are either male or female. Unlike modern conifers and ginkgoes, which are pollinated by the wind, many cycads are pollinated by insects.

Cycads today are confined to tropical and warm temperate regions of South America, South Africa, Australia, Mexico, Central America, and parts of eastern Asia. However, they display a wide range of ecological roles: understory in tropical forests, epiphytes, mangroves, fire-tolerant shrubs

Ginkgoes
Ginkgoes evolved 280 million years ago. Today only a single species survives: Ginkgo biloba. This tree is extinct in the wild except in a few places in China and was “rescued” from extinction by Chinese priests before it came to Europe and North America as an ornamental plant. Ginkgos have distinctive triangular leaves. Ginkgo trees are either male or female. Ginkgo seeds, produced by female plants, are yellow and fleshy and smell like rotting meat! (Which explains the popularity of male trees.)

Ginkgo
© University of California Berkeley

Conifers
Conifers date back 310 million years, and were the dominant tree of the Mesozoic Era. Today most conifers have needle-like leaves that grow in a spiral or in pairs around the branches. Trees produce both female cones (that produce seeds) and male cones (that produce pollen.) Most conifers are wind pollinated.

Araucariaceae is an ancient family that dates back to the late Triassic, ~220 million years ago. Araucarians diversified during the Jurassic, when they were present in both the northern and southern hemisphere. They have declined in diversity since the Cretaceous and today there are only two genera, Araucaria and Agathis, which are confined to the southern hemisphere (except Africa). Araucarians can grow very tall, up to 180 feet (60 m) tall. The Petrified Forest in Arizona consists of trunks thought to be Araucarians.

Monkey Puzzle tree (Araucaria araucana): Its name derives from the belief that monkeys would have difficulty climbing it's spiky trunk. Today, it lives primarily on the flanks of the Andes mountaints in Chile and Argentina.