The Penguin

Eras of Life, from PosterPlus (Sorry I don't know who the artist is) I always loved the "Prehistoric Life" picture books for kids, with their huge two-page spreads of each geological era. I used to lay on the floor, propped on my elbows as I read and re-read my favorites: the Cretaceous, of course, when dinosaurs really got down to the business of being gigantic war-lizards; the Pleistocene, with its ice ages and giant twisty-horned/tusked/toothed shag-carpeted megabeasts; Oligocene South America, which warranted its own page due to the weirdness of its fantastic critters: bus-sized sloths, giant killer chickens, "camels" with elephant trunks and unpronounceable names, sabertooth cats that were actually marsupials but not really. The Progression of Life was very simple, like a chapterbook - first came the rather boring Precambrian (jellyfish and sea-pens, yadda yadda...) then the CAMBRIAN EXPLOSION! followed swiftly by the Ages of Fish, Amphibians, Mammal-Like R...

With all the attention given to the Terrible Lizards throughout their history, it's often easy to forget they weren't the only beasts terrorizing the world during the Mesozoic. In fact, the majority of reptiles of that era weren't dinosaurs at all, though they fell under the Archosaur lineage: Pterosaurs ruled the skies, whilst a variety of marine reptiles and crocodilians ruled the waters. This domination of other habitats by non-dinosaurs helps answer a nagging question about our favorite toothy monsters: with the exception of the avian-line dinos, why were dinosaurs limited only to the land? It's essential to lay down ground rules at this point, otherwise everything will become confused. First, as many a second-grader can (and will) tell you, pterosaurs and ichthyosaurs, reptiles of air and water respectively, were not dinosaurs. In fact, dinosaurs are pretty much defined by a land-based lifestyle and body plan, including hollow bones and an erect posture. Only one...