Reconstruction of a dinosaur from the Catalan pre-Pyrenees, about 70 milion years ago. Courtesy of Òscar Sanisidro.
Posted on 07/02/2012 5:46:24 PM PDT by null and void
Reconstruction of a dinosaur from the Catalan pre-Pyrenees, about 70 milion years ago. Courtesy of Òscar Sanisidro.
A study of extant mammals refutes the hypothesis that dinosaurs were ectotherms. The work was carried out by researchers from ICP and UAB. It has been published in Nature. The study analyzed the lines of arrested growth (LAG) in the bones of around a hundred ruminants, representative of the specific and ecological diversity of that group of mammals. The results show that the presence of these lines is not an indicator of ectothermic physiology (does not generate internal heat), as had previously been thought, since all warm-blooded mammals have them. The study therefore dismantles the key argument of the hypothesis that dinosaurs could have been cold-blooded reptiles.
The work was carried out by Meike Köhler, ICREA researcher and ICP palaeontologist; Ronny Aanes, researcher from the Norwegian Polar Institute; Nekane Marín, PhD student at the UAB and Xavier Jordana, lecturer of postgraduate studies at same university.
LAGs are seen in bone sections as dark rings, similar to those seen in tree trunks. The rings are formed, both in the studied mammals and in trees, during the unfavorable seasons (winter or dry season) when the growth of the organism is arrested as a result of a lack of resources. The presence of LAGs in bones was, until now, considered to be the clearest indicator of since the seasonal arrest of growth was related to the animal's inability to maintain a more or less constant body temperature (endothermy) during the season of scarce resources.
Köhler explains, "the study we have carried out is very powerful, both in terms of the amount of material and the diversity of species with which we worked, but we did not design it to find a response to the thermophysiology of dinosaurs. We sought to better understand the physiology of extant mammals and how the environment affects them — how their growth changes as a result of external temperatures, rain and the availability of food and water”.
Understanding this was the first step to establishing discussions in paleontological research about the physiology of animals that lived several million years ago.
But the researchers realized that what they observed in the bones of different ruminants refutes the main argument for an ectothermic physiology in dinosaurs. Many hypotheses set out from the premise that large mammals — endothermic par excellence — do not have LAGs in their hard tissues since they do not need to arrest their growth responding to external temperature conditions. In fact, since LAGs have been observed in almost all species of dinosaur, many scientists considered that they were cold-blooded reptiles.
The article published in Nature offers the first systematic study, based on an extensive sample of mammals representative of a large variety of ecosystems, which shows that LAGs do not indicate an ectothermic physiology but give us information about how the physiology (metabolism) of an animal changes according to seasonal endocrinal changes, both in cold- and warm-blooded animals. These changes represent a common heritage in all vertebrates and are a kind of internal clock that regulates the animals’ needs according to the seasonal availability of resources. Despite the fact that these physiological changes have a strong genetic component, they are also functional and their intensity depends on the ecological conditions in which the animals live. The main ecological factors are more rain and limited supply of food and water, rather than external temperature. This discovery opens up a major line of research into the conservation of biodiversity on our planet today.
"It may seem surprising that until now there has not been a similar systematic study to prove or disprove whether it is only ectotherms that leave these marks in their bones during growth. In fact, there are so many things we do not know that science does not always advance in a linear way. The ideas somehow had long been wandering among the scientific community, but the work we have published organizes them and bases them on data", says Köhler.
In fact, some previous studies had already questioned this hypothesis and among the international scientific community there has been increasing consensus about the idea that LAGs were not necessarily indicators of ectothermy. Similarly, examples of mammals that seemed to have LAGs in their bones had emerged. This study conclusively closes the debate.
I was going to say, this has been the widely accepted theory for 20 years or more.
They evolved into Democrats.
Democrats aren’t cold-blooded?
Who knew?
Like birds.
http://www.youtube.com/watch?v=VfrShu_Lp2A
Like another poster said......well known for 20 years. Now if the pinheads, with unlimited government money, can figure out that oil and gas are natural to the Earth, we'll have made some progress.
I have been reading and studying about the tendency towards and advantages of bipedalism and find it fascinating.
Bipedalism evolved, then disappeared, and then reoccurred.
Seems that Dinosaurs might have lived in a latitude that had very little ‘change’ in climate.
What did this cost to figure out , and what possible use can come of it.
“Yes, and T-Rex reportedly was actually a very large chicken...”
YOU tell him that.
big gian ping
That’s because having only one pedal doesn’t work.
Yeah, I agree this reinforces the bird theory. I saw another researcher saying dinosaurs were a lot lighter than originally thought as well.
yuk yuk yuk !
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| GGG managers are SunkenCiv, StayAt HomeMother & Ernest_at_the_Beach | |
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Thanks null and void. They'd have to have been, since dino fossils have been found in Antarctica. |
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Dino’s were warm blooded, cold blooded...well maybe not real warm or cold or maybe this or that. They were feathered or not but maybe not real feathers and they didn’t fly or maybe just when they were young...or not.
I think I got it. or not..maybe.
Chickens! Giant, toothy chickens!
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