Читать книгу The Handy Dinosaur Answer Book - Patricia Barnes-Svarney - Страница 65

Two of the earliest known reptiles, the Hylonomus and Paleothyris, both descended from amphibians during the Middle Carboniferous period of the Paleozoic era. The best evidence of the change from amphibian to reptile was the early reptiles’ high skulls—evidence of additional jaw muscles—and thicker egg shells. The Hylonomus still claims the prize (so far) as the oldest-known reptile and lived about 315 million years ago. The Paleothyris evolved about 300 million years ago. The fossils of both these reptiles were found near Nova Scotia, Canada, in ancient tree stumps. Apparently, the animals fell into tree stumps in pursuit of insects or worms. There they were trapped and eventually died.

What amphibians are living today?

Names of modern amphibians are familiar to us: frogs, toads, salamanders, newts. They represent the descendants of groups that did not become extinct at the end of the Mesozoic era (when dinosaurs died out). Of the modern amphibians, the newts and salamanders are probably the most similar to the early amphibians, although the modern-day versions are much smaller.

The vertebrate class Amphibia today includes about 3,500 species in three orders: frogs and toads (order Anura), salamanders and newts (order Caudata), and caecilians (order Gymnophiona). There is, however, a much larger number of extinct species of amphibians: this ancient group of animals were the first vertebrates to begin exploiting terrestrial environments, where they became prey for other species.