Bird and dinosaur breathing in comparison. Air sacs pumped the air like bellows through the dino-lungs. Graphic: (c) Zina Deretsky, National Science Foundation
Reading The dromaeosaurs, a group of feathered dinosaurs, had breathing as efficient as modern birds. Researchers around Jonathan Codd from the University of Manchester conclude hook-shaped bones that are connected to the ribs in both birds and dromaeosaurs. The breathing system of the birds is unique among the vertebrates: they are constantly breathing oxygen-rich air through their lungs - not only during inhalation but also during exhalation. The most important instrument for this are so-called air bags, in which the air is temporarily stored. They blow breath like bladder bellows through the lung tissue. There has been some evidence for some time that some dinosaurs had such airbags and thus the effective bird breathing.

Codd and his colleagues now show that in dromaeosaurs another special feature of the bird's respiration occurred: they had so-called hook extensions on the ribs. Only recently has it become clear that these small bones serve as levers to move the ribs and sternum while breathing. The researchers found hook processes, among others, in the known from the movie Jurassic Park Velociraptor, in Deinonychosauriern and the Microraptor.

All three species belong to the group of dromaeosaurs, which, according to today's opinion, are closely related to the birds and partly carried feathers. Microraptor, the smallest known dinosaur, could probably even fly. Some researchers assume, because of these startling similarities, that the dromaeosaurs were actually birds that had already lost their ability to fly.

However, Codd and his colleagues do not go that far. They note, however, that the length of the hook processes in modern birds depends on the way of life: ratites have the shortest hook extensions, diving birds the longest. The length of flyable birds lies in between. Long hook processes are more effective as a lever, the researchers write, noting that the dromaeosaurs had as long processes as diving birds. They therefore assume that dromaeosaurs were highly active animals thanks to their efficient breathing, which should have been able to achieve remarkable speeds during the hunt. display

Jonathan Codd (University of Manchester) et al: Proceedings of the Royal Society B November 7, 2007, doi: 10.1098 / rspb.2007.1233 Ute Kehse

© science.de

Recommended Editor'S Choice