View Full Version : How Did Dinosaurs Get So Big So Fast?
A new study indicates that they may have grown as much as a 100 pounds per day!
Scientists estimated the body weights of dinosaurs by measuring the thickness of the fossilized leg bones. Age was determine by counting annual growth rings in the bones. In this photomicrograph, as published in Nature, an arrow indicates a growth ring for a dinosaur known as Shuvuuia deserti.
The biggest dinosaurs grew faster than almost any animal that ever lived. This suggests that perhaps the dinosaur had some tricks that we are not aware of. After all to sustain this rate of growth is quite unusual. Maybe they were warm-blooded. There has been speculation that this may be the case based upon an area behind the eyesocket that allowed a specialized nerve to pass though. This is a trait found today in warm-blooded animals that is not present in cold-blooded animals. Before the 60ís it was considered that they were overgrown reptiles that had typical growth rates in common with todayís reptiles. But if this was the case, based upon the size of the bones and what that suggests that the weight of the dinosaur was then they had to live at least a century or in some cases much longer to achieve the mass they are estimated to have. A more realistic guess is thought to be between 12-25 years to reach adulthood. A good guess on the ages of dinosaurs comes from counting the growth rings in the bones which is a property shared by reptiles. Much the same as estimating the age of a tree.
There is one animal that we know of that can outgrow the dinosaur if this is true. That is the Blue Whale.
This issue of the inner bones structure,more precisely the amount of blood channels(typical of warm blooded animals)was the first clue regarding the seriousness of the proposal for the warm blood in dinosaurs,a view by Robert Bakker that changed deeply our understanding of their world:
Is coherent to suppose that they had an homeotermic warming system,like those of birds,which very probable are their descendants,specifically from the extraordinarily succesful saurischian theropods,regarded not only as birds ancestors,but,as being the eldest representatives of the dinosaurs(the middle triassic south-american staurikosaurus and eoraptor),probably the progenitors of the whole genus,and almost certainly of the sauropods,the long necked-tailed hervibore giants,the other branch of the saurischia.
But,IMO,is to go a little too far to call dinosaurs birds or vice-versa,as not would be proper to call us therapsids,the mammalian-like reptiles ,although as their descendants,mammalians share a good deal of traits with them(or the thecodonts with their dinosaurs descendants in turn)
The global extinction that finalized the paleozoic at the end of the permian was very much more severe than the one that killed the dinosaurs,wiping out about 95% of all living species,and all life from then to today(including of course the dinosaurs and ourselves)are descendants of that 5% that remained;the story would have been very different from all that 95 % unexploited potential to the future...
I thought that at this point a little background information might be in order. I found an article from Discover by Peter Ward dated August 1998, which hits right in the vein. It is his account while taking rock samples from the banks of the Caledon River in Africa. It seems that this area is relatively stable in geologic terms and the rock cliffs provide a visual treat to those who study such geology. In his writing he remarks about the boundary that is visible at the site. At the upper area is all red colored rock while the lower area is greenish in color. This marks the end of the Permian Period, which is the time of one of the great extinctions of earth. At about 250 million years ago 90% of the ocean species and 70% of land species perished. While there have been quite a few times when multiple species extinctionís have occurred there are 5 that are major.
During the Permian period there are indications that it did not happen immediately. Rather it was slow. The thought is that global warming caused this. The writer also believed that during that time the ocean currents were not as is now. Instead the oceans were likened to a still pond. His speculation is that the marine life died because of an increase in carbon dioxide. That marine life is extremely sensitive to carbon dioxide and it creates acids in the blood that marine life can not tolerate. For further reading on the subject follow this link:
A newly found jawbone from Madagascar is even older than eoraptor(228 mya),about 230 mya,and belonging to a prosauropod,an ancestor of sauropods quite common during the late triassic,meaning that the common ancestor of all saurischia(and maybe all dinosaurs) has to be a dinosaur even older,or,and this is quite stirring,another hypothesis holds that the ornitischia(includes triceratops,hadrosaurus,etc),are independent descendants of a tiny thecodont form very like the species called lagosuchus(already thought of ascendant of the first dinosaur,which was thought in turn to have origined all dinosaurs)...
But if this is true,if the ornitischia branched independently and we don t include lagosuchus itself as a dinosaur...then maybe the conception of dinosaurs as a genus may be an artificial,academic construction(they would be two separate branches not directly linked)°°:confused:
The most primitive suborder, the Prosauropoda, (or Prosauropodomorpha, if one wishes to divide the suborder into two infraorders) are first known from the late Carnian. They moved into the large plant-eater ecological niche vacated by the dicynodonts and rhynchosaurs when the latter two died out during the latest Carnian/earliest Norian. Within a few short million years they had grown into very large forms like Plateosaurus, Riojosaurus and Melanorosaurus, which attained lengths of 6 to 10 metres and weights of upto 2 tonnes. These creatures in turn gave rise to the Vulcanodont sauropoda during the earliest Jurassic (Hettangian or Sinemurian).
For those who have interest:
Seems proper to clarify that the carnian and norian are subdivisions of the late triassic,and that prosauropods ancestored all of sauropoda,from which vulcanodonts are the first representatives.