Early reptiles completed the transition to land by developing the cleidoic or
amniote egg that could be laid on land. Reptiles have a waterproof skin containing ketatin,
usually in a series of horny (epidermal) scales. Once the amniote egg evolved, the reptiles
diversified greatly and evolved into about two dozen orders. The earliest reptiles include the extinct
captorhinids, with a solid skull roof. Most reptiles have evolved openings (fenestrae) in the
skull roof, but turtles (order Chelonia) have instead moved the skull margin forward.
Vascular plants first appeared in Silurian times, and insects during the Devonian.
The Carboniferous (Missippian plus Pennsylvanian) period saw the evolution of great coal swamps, seed ferns
(pteridosperms), many insects and other terrestrial invertebrates, and the amphibians that ate them.
At this time, all the world's southern continents were combined into a single supercontinent, Gondwanaland,
which began to break up during Permian times as the early reptiles evolved.
- The amniote egg
- Other reptilian traits
- Captorhinids
- Turtles
- Reptile classification
- Adaptive radiation
- Paleozoic land faunas
- Plate tectonics and Paleozoic continents
Illustrations
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