Age of Animals

Carboniferous Period, 358.9 - 298.9 MYA

• The land surface was at this point widely covered by genuine forests, whose fallen logs and other plant material eventually formed many of the coal and oil deposits.

		A small group of creatures, cotylosaurs, gradually found new ways to sever their ties to rivers and ponds. From the cotylosaurs, an evolutionary intermediate between amphibians and reptiles, emerged the first true reptiles. These creatures were distinguished by their small size, agile limbs and the amniote egg. With its large shell and protective membranes, the amniote egg gave reptile the
Figure 05a Carboniferous Period [view large image]	Figure 05b Reptiles [view large image]	freedom to lay their eggs on land. Their descendants include all other reptiles, dinosaurs, birds and mammals (Figure 05b).

Hylonomus is the oldest vertebrate recognized as a reptile. Unlike most of the amphibians, these animals were generally not tied to water for reproduction, but laid eggs that were able to survive in a terrestrial environment. Hylonomus had an unbroken expanse of bone behind each eye opening. Other reptiles had one or more gaps, the temporal openings, occupying various positions and enclosed by various bones. Though these patterns vary in details, the gaps themselves - or the lack of them - are the basis for splitting the reptiles into four major groups as shown in Figure 05c.

Figure 05c Groups of Reptiles [view large image]

• FA of winged insects - Giant ancestral dragonflies (see Figure 05a), had wingspreads of 30 inches and bodies 15 inches in length. They were swift-flying predators with spiny legs used in capturing prey.



• FA of seed plants (gymnosperms).

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