Page 440 - Introduction to Paleobiology and The Fossil Record

Chapter 16

Fishes and basal tetrapods

Key points

• Vertebrates are characterized by a skeleton made from bone (apatite).

• The oldest vertebrates are small fish-like creatures from the Early Cambrian of China.
• Armored fi shes were abundant in Devonian seas and lakes.

• After the Devonian, the cartilaginous and bony fishes radiated in several phases.
• Conodonts commonly occur as tooth-like elements that are useful in biostratigraphy,
as are some other fish teeth and scales (ichthyoliths).

• Tetrapods arose during the Devonian from lobe-fi nned fish ancestors, and fi sh-eating

amphibians diversified in the Carboniferous.
• The fi rst reptiles were small insect eaters.
• Synapsids dominated ecosystems on land during the Permian and Triassic.
• These groups were heavily hit by the end-Permian mass extinction event, and diapsid
reptiles, most notably the dinosaurs, were key forms through the Mesozoic.

Most species do their own evolving, making it up as they go along, which is the way
Nature intended. And this is all very natural and organic and in tune with mysterious
cycles of the cosmos, which believes that there’s nothing like millions of years of really

frustrating trial and error to give a species moral fiber and, in some cases,
backbone.

Terry Pratchett (1991) Reaper Man