Researchers have reconstructed a genus of archosaur, which is considered the ancestor of reptiles and several species of birds
3.12.2002
When the movie "Jurassic Park" was released, scientists mocked him. They argued that 145-million-year-old DNA could not be extracted from a petrified mosquito, because DNA loses its stability after a few thousand years. However, now a team of scientists has succeeded in reconstructing the approximate structure of a gene of a creature that lived about 250 million years ago - an archosaur, which is considered the ancestor of dinosaurs such as Tyrannosaurus Rex, reptiles and several species of birds and crocodiles.
According to Dr. Belinda Chang, a postdoctoral fellow in the research team, Prof. Thomas Skamar and their colleagues from the Laboratory of Molecular Biology and Biochemistry at the Rockefeller University in New York, the gene they created was responsible for the visual pigment, rhodopsin, and therefore makes it possible to assess how the dinosaurs saw.
When light hits rhodopsin - a type of light-sensitive protein, found in the retina - the pigment changes and generates a series of events that lead to the ability to distinguish light. To find out what the protein looked like in the archosaur, the researchers used a statistical method that uses knowledge of the evolutionary relationship between the animals related to the archosaur, and information about the DNA structure that makes up the rhodopsin gene.
Chang and her colleagues studied the gene in 30 vertebrates - including crocodiles, chickens and eels - and tried to recreate the rhodopsin of the archosaur according to it. From the data obtained, the researchers created the most probable structure of the pigment. The assumption that the generated gene is indeed related to vision was accepted after it was inserted into monkey cells, where it produced the rhodopsin protein.
"Anyone can synthesize a gene," Chang said. "But was it the same gene that could have been in an archosaur, that's a completely different question. As soon as we had the protein, we wanted to show that we had a logical finding." According to her, the only step that could be taken was to check if the rhodopsin protein that was created was able to connect to a vitamin E derivative and become light sensitive. "What we wanted to know is not just whether there will be a response to light, but whether there is a series of responses that lead to vision," Chang said. The reconstituted rhodopsin was indeed able to initiate the sequence of events that occur in the eye and lead to vision.
Among other things, Chang tested which wavelength of light the rhodopsin molecule is most sensitive to. The test revealed that the molecule reacts normally to light of a certain wavelength - as some mammals would. However, the artificial molecule responded mainly to light on the red side of the visual spectrum in a manner similar to the ability of birds to see today.
"This means that birds have retained more ancestral characteristics than some vertebrates," Chang said. "The results of our tests show that this creature had the ability to see at night. It is difficult to estimate in what quality, but it is at least a level seen by other mammals. I don't study fossils, but from what I understand the archosaur was probably a nocturnal animal."
The new study is now causing controversy in the scientific world. The accepted assumption is that the mammals survived in the Cretaceous era, because they were active at night and could survive alongside predatory dinosaurs that lacked night vision. If it turns out that mammals and dinosaurs hunted side by side at night and in fact theoretically competed for habitat, scientists will be forced to come up with new theories on the matter.
In addition, if it turns out that the dinosaurs were active at night, this means that they were warm-blooded. This, contrary to the accepted assumption which claims that they were cold-blooded.
The heart test revealed: the dinosaur had warm blood
12.4.2000
by Tamara Traubman
Scientists have found a fossilized heart of a dinosaur for the first time. The discovery also reveals a sensational scientific finding about the dinosaurs. Contrary to everything known to scientists so far, say the team of researchers, the dinosaur that was discovered did not have cold blood like reptiles, but warm blood.
The dinosaur, or Thesulosaurus in its scientific name, lived about 66 million years ago. He walked on two and fed on plants. The researchers, who discovered it during excavations in South Dakota, gave it the name Willow, as a tribute to the wife of the farmer on whose land the fossil was discovered. Willow belongs to the type of dinosaur that many researchers believe birds evolved from.
The man who discovered Willow, Michael Hamer, a professional dinosaur collector and one of the research partners, noticed that the dinosaur's ribs were remarkably well preserved, and thought that some internal organs might have been preserved in its chest cavity. Instead of removing all the soil and dirt around the bones, he cleaned only the surface of the fossil and sent it for computed tomography (CT) scans. The researchers were surprised to discover that scans of the dinosaur's chest cavity showed a heart with a structure more similar to that of birds and mammals than to the heart of contemporary reptiles, and from this they concluded that it had warm blood.
Willow's heart consists of four chambers and a tube-like structure, which was probably the aorta - like the hearts of birds and mammals. Not all parts of the heart were preserved - delicate parts such as the atrium of the heart probably collapsed when the dinosaur died. The research is published today in the scientific journal Science.
"This challenges some of our most fundamental theories about the evolution of dinosaurs," paleontologist Dr. Dale Russell, from the University of North Carolina, one of the partners in the study, said in an interview with Haaretz. "It's really amazing that a dinosaur probably had such a developed heart. The consequences of this completely knocked me down."
He says that in light of the new findings, it will be interesting to re-examine the dinosaur's activity. A heart with four chambers allows oxygenated blood to be delivered to the body, which gives birds and mammals a relatively fast metabolism. In contrast, reptiles tend to be slower, and their oxygen consumption is lower.
Dr. Russell says that it's very possible that other dinosaur fossils also have preserved internal organs, but the researchers just didn't notice them. "To clean a fossil for the purposes of research and display of the skeleton, everything that is not bone is thrown away. It's interesting how much material we lost in this way."
{Appeared in the Haaretz newspaper, 21/4/2000{ - The Hidan site was until 2002 part of the IOL portal from the Haaretz group
