![]() ![]() ![]() The fossil record of dinosaurs is presently about 25% complete. The number of dinosaurs that have ever lived is estimated at 900-1200 genera. A model of increasing diversity and a bottleneck model compensate for the biasis in the preserved fossil record. Global dinosaur diversity during the Campanian and Maastrichtian is estimated at 100 genera per stage, using a logistic model to estimate future discoveries. Dinosaurs evolved as rapidly as Cenozoic mammals. ![]() Estimates of the average duration of a dinosaur genus range from 5 million to 10.5 million years, with the most likely value about 7.7 million years. ![]() Nearly half of all dinosaur genera are of latest Cretaceous age (Campanian or Maastrichtian). Countries with the greatest known diversity of dinosaurs are (in descending order) the United States, Mongolia, China, Canada, England, and Argentina the greatest future increases may be expected from Argentina and China. Dinosaurs are known from every continent. Nearly half of all genera are based on a single specimen, and complete skulls and skeletons are known for only 20% of all dinosaurs. A critical evaluation shows that of 540 genera and 800 species of dinosaurs proposed since 1824, 285 genera and 336 species are probably valid. Dinosaurs figure prominently in discussions of mass extinctions and evolutionary metrics, but their usefulness is hampered by archaic taxonomy, imprecise biostratigraphy, and imperfect preservation that bias our understanding of dinosaur diversity. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |