Final answer:
The fossil evidence suggests mammalian diversification post-dinosaur extinction, challenges previous beliefs about the timing of animal life emergence, and underscores the commonality of extinction. It also supports the transition of species like whales from land to sea and highlights Earth's vast historical biodiversity.
Step-by-step explanation:
An analysis of the fossil evidence mentioned indicates that the small dog-sized mammal lived around 55 million years ago, which is after the extinction event that wiped out the dinosaurs (65 million years ago). The presence of such mammals suggests that mammalian diversification was occurring during this time. The mention of Cynognathus, a land reptile from the Early Mesozoic Era, shows an example of a species that did not survive to the modern era, implying that extinction is a common aspect of life on Earth. The discovery of possibly the earliest animal species predating the great ice age extinction event challenges the previously held belief that no animal life existed before the Ediacaran period, showing that our understanding of the history of life on Earth is continually evolving.
The mentioned evidence from rodhocetus's ankle bone, which is unique to land animals, supports the idea that modern whales evolved from terrestrial ancestors. This also emphasizes the transition of life forms from land to sea. Overall, the various fossil records presented illustrate the rich and dynamic history of life on our planet, and highlight the rarity of species surviving long periods without extinction. Approximately 99% of all species that have existed are no longer extant, demonstrating the sheer scale of the earth's biodiversity over geological time frames.