Study Shows Dinosaurs Diverged Long Prior to the End of the Cretaceous
There’s a popularist view that the dinosaurs were at their most diverse and at the peak of the evolution when it comes to the amount of new species evolving; at ab muscles end of the Cretaceous. The Chicxulub impact then wiped out the fantastic dinosaur dynasty leaving the planet for the mammals to exploit. The Chicxulub impact refers to the asteroid impact event that resulted in the demise of the dinosaurs sixty-five million years ago. Fossil evidence does not support this idea, studies in the Hell Creek Formation (Maastrichtian faunal stage), of the western United States indicate that the amount of species of dinosaur was declining in this part of the world towards the conclusion of the Cretaceous. Approximately ten different genera are known from the youngest Cretaceous sediments, whilst older strata from this area show proof additional different dinosaur types.
Hell Creek Formation Data
Certainly some of the finest known dinosaurs date from ab muscles end of the Mesozoic. Animals wandering the Hell Creek area by the end of the Cretaceous include Triceratops, what dinosaur has 500 teeth Ankylosaurus and of course Tyrannosaurus rex. Previously, these gigantic representatives of the dinosaur families, (Triceratops, Ankylosaurus and T. rex are just about the largest kind of dinosaur from these three families), were thought to indicate that dinosaurs just got too big and lumbering to survive and for this reason they went extinct. Scientists now know that the reason why for the conclusion Cretaceous mass extinction event, the extinction not merely of the dinosaurs but in addition the Ammonites, Plesiosaurs, Mosasaurs, Pterosaurs and an entire host of other plants and animals, were complex and probably involved numerous factors.
A Family Tree for the Dinosauria
Given the limitations of the prevailing dinosaur fossil record it’s difficult to piece together a “dinosaur family tree” but a task to map dinosaur evolution and to highlight the key evolutionary shifts in Dinosauria has just been completed. The outcomes with this study, led by a team of researchers from the University of Bristol has just been published in the British Journal Proceedings of the Royal Society B.
This study indicates that the dinosaurs as friends diversified rapidly in the Late Triassic (225 – 200 million years ago) and then underwent a second evolutionary surge in the Mid Jurassic (170 -160 million years ago). The scientists studied a sizable portion of the described dinosaur species and pieced together an evolutionary “family tree of dinosaurs” ;.The team estimate that their study covered something similar to 70 percent of all the known and described dinosaur species.
Bursts of Evolution
This new study contradicts earlier research that shows the dinosaurs diversifying throughout the Cretaceous. The established view is that although dinosaurs as friends diversified throughout their entire existence, using periods, the evolution of new forms was speeded up. One period was the first to mid Cretaceous which saw the emergence of a greater variety of Ornithischian dinosaurs – the rise of the Hadrosaurs, Ceratopsians and the Pachycephalosaurs, for example. These kinds of new dinosaur were evolving during a time when many life forms on Earth were diversifying. Dating from about 125 to 80 million years back, there appears to have been an enormous surge of increased terrestrial biodiversity. Now period is known as the Cretaceous Terrestrial Revolution, life on Earth over this period changed dramatically. The Angiosperms (flowering plants), social insects, modern lizards, Mosasaurs and many types of mammals all evolved. It have been believed that the rapidly diversifying dinosaurs were part with this move towards greater biodiversity, the paper published by the Bristol team demotes dinosaur evolution in this period to an even more peripheral role. This new study indicates that by enough time of the Cretaceous Terrestrial Revolution, all the key dinosaur types that were to survive before end of the Cretaceous were already established.
New Research Challenges Earlier Theories
This new work certainly contrasts with a lot of the accepted thinking regarding dinosaur diversity. Most palaeontologists feel that during the first to middle Jurassic there were only four main sets of dinosaurs, whilst throughout the Cretaceous this expanded to nine, namely:
Megalosaurs/Allosaurs, Tyrannosaurs, Sauropods, Hysilophodontids, Hadrosaurs, Pachycephalosaurs, Ceratopsians, Ankylosaurs and Stegosaurs.
The fossil record for the terrestrial vertebrate life of the Mesozoic is extremely incomplete so it’s difficult to trace evolutionary links between several types of animals. The work of the Bristol University team is certainly helping to open up the debate, but devoid of reviewed the particular paper we cannot really comment any further. It will be interesting to find out how the evolution of non-avian dinosaurs, the birds has been assessed in this study. Very little is famous in regards to the evolution of birds, however they do seem to own diversified and developed new species very quickly throughout the mid to late Cretaceous, a growth in speciation which was largely unchecked by the Cretaceous mass extinction event.
Late Triassic Diversification
Certainly, it’s not surprising that the dinosaurs diversified throughout the Late Triassic, the planet was just coping with the Permian mass extinction (an event that saw an estimated 57% of marine families and 70% of terrestrial vertebrate genera becoming extinct). Life on Earth slowly began to recuperate and those types of organisms left started initially to diversify to fill those environmental niches that were empty and those soon to be left empty by the “dead clades walking” like the last of the Lystrosaurs. It absolutely was after the Permian mass extinction event that numerous sets of vertebrates got a chance to diversify, including our personal mammalian ancestors.