From Ichthyosaurs to Orcas

I just finished reading Neptune's Ark: From Ichthyosaurs to Orcas by David Rains Wallace. In this book, Wallace follows the evolution of life as it adapts to land, and then as it returns to the sea in the form of marine mammals. Artfully combining personal observations with descriptions of fossil evidence and stories of the quirky scientists who discovered them, Wallace discusses current theories about ancestors for all extant marine mammals, including sea lions, seals, walruses, baleen whales, toothed whales and dolphins, sirenians, otters, and the polar bear. Focusing primarily on the west coast of North America, he also discusses other marine mammals that had their heyday here millions of years ago, such as the oyster eating bear-like creature Kolponomos, or Enaliarctos, the earliest known pinniped that perplexes scientists by creating an evolutionary gap before the next pinniped in the fossil record. The narrative is bookended by examining the mysterious narrative of the otherwise reliable naturalist Georg Wilhelm Steller (after whom the Steller sea lion is named), who described in detail observations of a "sea ape" in the eastern north Pacific that have never been substantiated by modern science. An engaging read, this was the first book I've ever read where as soon as I finished the last page, I wanted to flip back to page 1 and start all over again, since it contains so much thought-provoking information I couldn't absorb it all the first time.

The above picture is of course one of our current marine mammal inhabitants of the west coast, K12. Orcas are a relative newcomer on the evolutionary scene, even in terms of other cetaceans. According to Wallace, orcas may have displaced belugas and other toothed whales from the more temperate regions of the Pacific during the Pliocene.