Life on Lan8 - of cycads Cycads The modern cycads are a...

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Life on Land The Jurassic terrestrial environments saw an increase in gymnosperm groups such as the cycads, ginkgoes, and cycadeoids. Reptilian groups also became more adept at flying, while the dinosaurs grew in size with such giants as Apatosaurus and Brachiosaurus , and ferocious predators like Allosaurus . The first birds appeared, as did the most famous fossil bird, Archaeopteryx . Plants The Jurassic was a time of increasing diversity for the cycads and a similar-looking group, the cycadeoids. The cycadeoids, sometimes known as the Bennettitales, produced leaves that superficially resembled cycad leaves. However, details of the reproductive structures indicate the two were not closely related. During the Mesozic leaves of these groups were so common that paleobotanists refer to the era as the age
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Unformatted text preview: of cycads. Cycads The modern cycads are a pale remnant of the dominant plants of the Mesozoic, with today only 160 species in 11 genera, confined to the tropics. Cycads retain some fern-like features, notably pinnate leaves and circinate vernation. However, they (usually) produce cones of nonphotosynthetic reproductive structures. These cones are unisexual, in fact the plants are dioecious, having separate male and female plants. Based on structure of the leaf cuticle, cycads are usually separated from the cycadeoids. A number of leaf genera from the Mesozoic have been assigned to the cycads: Taeniopteris and Nilssonia ....
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