Doubt about the connection between birds and dinosaurs

Researchers at Oregon State University have achieved a new discovery that explains how bird respiration and lung capacity allow them to fly - this finding shows very little chance that birds evolve from any species. Which theropod dinosaur is known.

These conclusions add to the evidence that may cause many paleontologists to rethink the prevailing view that modern birds are the direct descendants of ancient carnivorous dinosaurs, researchers. OSU said.

John Ruben, professor of zoology at OSU, said: 'It is amazing that after many centuries of bird research and their flight capabilities, we still do not understand the fundamental aspect of biology in birds. . This finding means that birds evolve along a parallel line alongside dinosaurs, which began before most dinosaurs existed. '

The study is published in The Journal of Morphology, and is funded by the National Science Foundation.

For decades we have learned that the femur of the bird is fixed and makes it run on the knee, unlike most terrestrial animals. However, what has just been discovered is that the fixed position of the bones and the muscular system are the factors that keep their lungs from breaking down when the bird inhales.

Warm-blooded birds need 20 times more oxygen than cold-blooded reptiles , and they have developed a special lung structure that allows high gas exchange rates and activity levels. Their strange thigh structure is the support element and prevents the lungs from being broken.

Devon Quick, an assistant professor of zoology at OSU, who carried out this study for a doctoral course, said: 'This is a fundamental problem for bird physiology. Strangely, no one has noticed this before. The position of the thigh bones and muscles in birds is important for their lung function, thus providing enough lung capacity for flight. '

However, all other animals on land, scientists said, can move the femur and that is part of their movement - including humans, elephants, dogs, lizards and, in ancient times, dinosaurs. This suggests that birds do not originate from theropod dinosaurs, such as tyrannosaurus or allosaurus. This finding adds to the growing evidence in the past two decades that challenge the most popular hypothesis about animal evolution.

Ruben said: 'In fossil records, birds were discovered earlier than dinosaurs, which are believed to be their ancestors. This is quite a serious problem, and there are other contradictions with the hypothesis that birds originated from dinosaurs. '

When the bird moves or runs, the hindquarters are created at the knee and ankle joints;movement in humans occurs in the joints of knees, ankles and hips.The bird's thigh does not move away from its nearly vertical position, helping to support fragile air pockets in the respiratory system.(Photo: Oregon State University)

But one of the reasons many scientists aim to hypothesize that dinosaur-derived birds are similar characteristics in the lungs. However, theropod dinosaurs have moving femur and therefore cannot have the lungs acting like birds. Their abdominal air bags, if any, have been broken. This removes an important evidence of the link between birds and dinosaurs.

Ruben remarked: 'A velociraptor cannot naturally sprout feathers and fly into the air'.

The latest findings, according to the researchers, are more relevant to birds evolving separately from dinosaurs, and developing distinct characteristics, including feathers, wings and lung systems and special movements.

However, there are still common features between birds and dinosaurs, and it is very likely that birds and dinosaurs have the same ancestors, such as the small reptile 'thecodonts'. This ancestral species may have evolved in separate lines into birds, crocodiles and dinosaurs. The lung structure and physiology of crocodiles, in fact, resemble dinosaurs rather than birds.

Quick said: 'We do not think dinosaurs and birds don't have the same ancestor at some point in the past. It is entirely possible, and is often discovered during evolution. But apparently the bird has evolved along its own evolutionary path and does not originate directly from theropod dinosaurs.

The OSU study of bird biology and physiology is one of the first studies to ask questions about the relationship between dinosaurs and birds since the 1990s. Other findings at OSU and academies Other earlier have also raised doubts.

Ruben said: 'Frankly speaking, there are many museum activities in this regard, many careers have attached to a certain point of view, even if new evidence raises questions. In some museum exhibitions, the theory that dinosaur-derived birds are thought to be a widely accepted practice. '

Refer:
Quick et al.Cardio-pulmonary anatomy in theropod dinosaurs: Implications from extant archosaurs.Journal of Morphology, 2009;DOI: 10.1002 / jmor.10752