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The size and weight of a full-grown human in dire need of a crash diet--about five and a half feet tall and 200 pounds--the Red Kangaroo of Australia is the , which isn't saying much when you consider the enormous sizes of its ancestors. (Just to cite two Cenozoic examples, the weighed 500 pounds, and the tipped the scales at two tons.) Male Red Kangaroos are much bigger than females, and can cover almost 30 feet in a single leap!
Although some domesticated dog breeds grow to bigger sizes--have you ever house-sat a 250-pound American Mastiff?--the consistently beefiest species of genus Canis is the , Canis lupus, full-grown individuals of which often reach 200 pounds. Unusually, Gray Wolves mate for life, which may have something to do with the serious repercussions if either partner is caught cheating--just imagine a 200-pound bundle of fur lunging at you with ared fangs!
As a general rule, the biggest dinosaurs of the Mesozoic Era were the aptly named titanosaurs, represented on this list by Argentinosaurus (slide #2). But there were also some , or duck-billed dinosaurs, that grew to titanosaur-like sizes, chief among them the 50-foot-long, 25-ton of North America. Despite its enormous bulk, "Big Paul" (so named after Paul G. Hagaa, Jr., the president of the board of trustees of the Los Angeles Museum of Natural History) may have been capable of running on its two hind legs when pursued by predators, which must have made for an impressive sight!