The evolutionary tree of dinosaurs contains a great deal of information. The horizontal axis represents time, and the vertical axis represents dinosaurian diversity. All the major families of dinosaurs are indicated with horizontal lines that record their known distribution in time, as based upon present fossil evidence. Future finds of dinosaur skeletons may extend the time ranges backwards or forwards in time.
There are two “fixed” time lines that do not seem to be breached, however. The dinosaurs arose from a single ancestor some 230 million years ago, in the Middle to Late Triassic, and it is unlikely that older dinosaur skeletons will be found. The second “fixed” time line corresponds to the extinction of the last dinosaurs 66 million years ago. Despite strenuous efforts to find post-Mesozoic dinosaur specimens, and many reports of supposed discoveries, no such remains have withstood close scrutiny. Most usually, post-mesozoic dinosaur bones have been reworked, that is, removed from the rock by natural erosion and redeposited in a younger sediment.
The most important aspect of this phylogenetic tree is the representation of the relationships between the different families. This is based on recent cladistic anlyses, carried out by a number of North American and European vertebrae paleontologists after 1985, and the pattern shown here is quite revolutionary in the sense that it is dramatically different from anything in popular books of this sort. It is also important because it shows a much higher degree of resolution than the earlier phylogenies; that is, the pattern of relationships is shown in a much more detailed way than was possible before.
Related Websites - One Year Ago This Month I Quit My Job. How Has It Been So Far? Actually, it was September 1st of last year, but who is counting. Close enough, right? Either way, about a year ago I up and quit my job. After many discussions at home with the wife...
- My Life as a Volunteer Tax Preparer - Season Finale I finished my second tax season as a volunteer tax preparer. It was hectic with lots of last minute filers scrambling for appointments. I had several interesting experiences. The first was with a retired man...
- Economic Headlines From A Year Ago What were you doing a year ago today? I was at work, probably writing on sticky-notes some ideas for Weakonomics. Check on November in the archives if you want to know what I was writing...
- 28 things I wish I knew about money 28 years ago By Arthur Make any mistakes with your money or finances? If you are breathing air you likely have. Here are the top things I wish someone taught me about money 28 years ago: Hint: You...
- What I Drive Doesn't Try To Define Me Or To Impress Others. Only a few more days of vacation! While I finalize things around here and get back on the road in 2 days, please enjoy one of my favorite and most popular posts from a year...
- David Harper Memorial Tree Dedication On behalf of the Meaford & District Chamber of Commerce, Meaford Municipal Farmers’ Market, Meaford BIA and friends in the community, a David Harper Memorial Tree Dedication will take place on Friday, June 19th at 3pm. The ceremony will coincide with...