Probably the best reconstructions of extinct genera as living animals are those in the BBC/Discovery channel Walking With Dinosaurs series. This was the last of the trilogy made, but the first in terms of time sequence, extending from the formation of the moon (4,533 million years ago) to the early Triassic, with the first ancestors of the dinosaurs. Most of the DVD is taken up with the period from the early Cambrian (530 million years ago) to the early Triassic (248 million years ago) and from the evolution of eyes, predation and hard parts which could be fossilized to the earliest known ancestor of the dinosaurs.

Given this time span, it is somewhat disappointing that the DVD covers only three half-hour segments and focuses only on those forms which gave rise to land vertebrates. Surely there is enough material on the evolution of plants and fish, and the dramatic change in our atmosphere produced by photosynthesis, to have made this DVD at least as long as the other two in the series!

As usual, there are details that most people will recognize are pure guesswork (colors—the fist preserved pigments had not been found at the time this DVD was produced, and as far as I know they are still limited to feathers.) Others, such as behavior, are also highly problematic, and I would like to have seen the arguments addressed in a separate discussion, if not in the main DVD. One that particularly interested me was the gorgonopsid (a synapsid or mammal-like reptile) who was shown cantering—a gait I tend to associate with animals who flex their bodies vertically (as do mammals) rather than horizontally (as do most reptiles.) The DVD does include a “making of” program that covers the entire trilogy of life, but it could easily have been longer.

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