tag:blogger.com,1999:blog-360614506818167717.post1725637961374226527..comments2024-01-27T16:00:39.065-08:00Comments on History of the Earth: October 29. Cycads and Gingkoes Richard Gibsonhttp://www.blogger.com/profile/03330538991049552829noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-360614506818167717.post-45506012064640233992014-11-10T15:49:27.061-08:002014-11-10T15:49:27.061-08:00Thanks for your help here... yes, clearly I mistoo...Thanks for your help here... yes, clearly I mistook the issue of diversity for the issue of existence... and that was wrong. I'll re-work the text above and add a mention in the next episode I record (which will be for Weds. 12 Nov). Many thanks.Richard Gibsonhttps://www.blogger.com/profile/03330538991049552829noreply@blogger.comtag:blogger.com,1999:blog-360614506818167717.post-5156831833423541722014-11-10T15:18:42.391-08:002014-11-10T15:18:42.391-08:00Richard, your discussion of recent cycad diversity...Richard, your discussion of recent cycad diversity was poorly worded. It sounds like you are saying that cycads may have gone extinct after the Mesozoic and then resurrected somehow 10 million years ago - which doesn't make sense. There must have been survivors for that whole 55 million year period. The paper in question concerns the age of the current diversity of cycads, saying only that the current radiation of species is only about 10 million years old - not that cycads completely re-evolved only 10 million years ago. There may be cycads in the 65 to 10 million years ago time frame?? Of course there were. There HAD to be, and that paper does not dispute that. The paper is only suggesting that the current diversity does not date from the Mesozoic, not that the entire group went extinct only to "reappear" somehow 55 million years later. http://www.sciencemag.org/content/334/6057/796.fullUnknownhttps://www.blogger.com/profile/16810079457426524508noreply@blogger.com