Dinosaur Look

2000/10/31 Roa Zubia, Guillermo - Elhuyar Zientzia

• Eboluzioa
• Zoologia

Reading the fossil record is not easy. However, when the results are presented to all audiences they are very clear. But not everything is known and sometimes more forceful hypotheses or theories arise that rule out long-accepted ideas. The realm of dinosaurs is no exception.

The great herbivores that lived 70 million years ago have always appeared eating tall, long-necked leaves and trees. But Australian paleontologist Roger Seymour of Adelaide University has reason to reject this image. In his opinion, the dinosaurs carried the long hills horizontally. The arguments of this claim have been recently published in the prestigious journal Procedings of the Royal Society of London.

Heart beads

Seymour's arguments are based on the study of hearts. For 24 years he has studied reptiles, mammals and birds to clarify the influence of the morphology of their hearts and blood pressure on the wall thickness. The size of the heart of any animal is limited by two factors. The first is the height difference between the head and the heart and, the second, if the animal is of warm or cold blood.

Giraffe is hot blood, long neck, and high blood pressure. He needs a heart of thirteen kilos to get blood to his head. Birds also need large hearts because they are animals of warm blood and high pressure. Reptiles, on the contrary, have a slow metabolism, are of cold blood and flow at low pressure.

The barosaur, for example, says that to pump blood above the vertical neck, it should be a left ventricle of 2,000 kilos. This is impossible for at least three reasons. On the one hand, this heart would occupy a huge space; on the other hand, the heart itself would need more energy than all the other organs of the body; finally, the walls of the heart would be very thick and mechanically would not be anything effective, because they would deform because they would spend much more energy than pumping blood.

In view of all this, there are only two explanations for blood pressure to be fair: placing the necks horizontally or having animals of cold blood. In the latter case, another small heart could help raise blood in the neck. However, I would need a large walled heart. Therefore, this option is not very effective when pumping.

"It's the debate over the last 30 years when dinosaurs were hot or cold, but we'll probably never know the speed of their metabolism," explains Seymour. "However, it does not seem fair to bring these animals with their heads raised."