When did modern placental mammals diversify?

by Greg Mayer Almost exactly a year ago, I reported in two posts here at WEIT on a paper in Science by Maureen O’Leary and colleagues on the radiation of placental mammals. Placentals are one of three major groups of living mammals, the others being the marsupials (dominant in Australia, plus a fair number in […]

More on placental mammals

by Greg Mayer There have been a number of interesting comments by readers on my post on the recent paper on the radiation of placental mammals by Maureen O’Leary and colleagues. I want to respond briefly to a few of them here. Biogeography. Does this paper imply that the origin and geographic distribution of the  […]

The orders of modern placental mammals originated after the extinction of the dinosaurs

by Greg Mayer (Updates below.) A new study just published in Science by Maureen O’Leary and colleagues examines the phylogeny of 40 fossil and 46 extant mammals based on a very large data set of morphological and molecular characters (the latter only from the living taxa). The study has gotten a fair amount of attention […]

Your ear bones came from your jaws

by Greg Mayer Although the mammals and reptiles most people know are quite distinct– mammals are hairy, warm-blooded, live-bearers, that suckle their young, while reptiles are scaly, cold-blooded, egg-layers– a wider knowledge of the modern forms reveals that the differences are less absolute. There are many live-bearing reptiles, for example, and platypuses and echidnas lay […]

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