Up until a few days ago it was a commonly held belief that modern birds evolved from theropod dinosaurs such as the tyrannosaurus or allosaurus. Now new evidence has been found in favour of the theory that birds evolved separately on a parallel path to dinosaurs.
The discovery may be new, but the evidence has been there all along. Simply put, it is virtually impossible for birds to have evolved from dinosaurs. Researchers at the Oregon State Univserity (OSU) in the US pinpointed the largest significant difference in their skeletal structures – their thigh bones – as proof of this fact. Up until now the relatively fixed position of the bird’s thigh bone and the role that it plays in keeping this creature alive has gone largely unnoticed. While virtually every other land animal has a moveable thigh bone, the bird’s thigh bone, or femur, is largely fixed, making them ‘knee runners’. What is most remarkable about this feature is that it is fundamental to the continued functioning of the animal; it is the fixed position of the femur and other bird bones that keeps their air-sac lung from collapsing when the bird inhales oxygen.
Research has revealed that warm-blooded birds need about 20 times more oxygen than do reptiles which are cold-blooded. As such, they have a unique lung structure which allows for a much higher rate of gaseous exchange and activity. It is this soft and delicate structure which is carefully protected by the fixed skeletal structures that surround the lungs.
According to Devon Quick, an OSU instructor of zoology, their unusual thigh complex and the way it supports the lungs is “fundamental to bird physiology.” Quick noted that “It’s really strange that no one realized this before. The position of the thigh bone and muscles in birds is critical to their lung function, which in turn is what gives them enough lung capacity for flight.” This only adds to other evidence that birds likely did not evolve from dinosaurs – such as the feathers, wings, bones and unique locomotion and lung system that is peculiar to birds – and supports the relatively new theory that they evolved separately on a parallel path to these extinct creatures.
Feathers are the most unique aspect of a bird’s anatomy. The feathers of a bird are made up of keratin, which is the same substance that hair, hooves and beaks are made of. The shaft, or center spine, of the feather is stiff and the tip is flexible for flight. The barbs of the feather hook together to form an air tight seal to resist the wind and also to provide insulation. The bird’s wing consists of primary feathers forming the point of the wing, and secondary and tertiary feathers further up. Contour feathers give the bird its overall shape. Down feathers provide insulation.
Now let us consider the internal anatomy of a bird. The skeleton of a bird weighs less than its feathers and thus flight is possible. The bones are so light due to their internal honeycomb structure. The inner anatomy of the bird wing, like our arm, is made up of a humerus and two lower limb bones. The digits are highly modified for flight. The breast bone of the bird has a deep keel for the attachment of flight muscles. This keel is absent in flightless birds.
Further to the internal anatomy of a bird is a look at those organs which assist in flight. There are two types of flight muscles, namely, white and red muscle. White muscle is used for bursts of activity, such as taking off quickly. Active flying birds, such as those which migrate (e.g. geese), have red flight muscles supplied with lots of blood vessels. Heat from flight must be regulated, this is done by means of the respiratory system. Birds have at least nine air sacs connecting chambers in their bodies. This supplies the muscles with extra oxygen to use. Birds have a four chambered heart like our own, only it beats at a much faster pace.
Now let us look at the parts of a bird’s anatomy used for finding and consuming food. The bill of a bird is merely an extension of the jaws and is covered in keratin. It has many nerve endings so as to feel and taste its food. Bills vary in shape and size according to the feeding habits of bird species. The bird’s gullet has a small sac called a crop in which undigested food is stored for later use, such as when feeding nestlings.
The feet of a bird function in harmony with it’s bill. In bird anatomy, the feet vary according to function. For example, birds of prey have sharp talons for killing prey; wood peckers have two toes pointing forward and two pointing back to climb effectively; and ducks have webbed feet for paddling. Interestingly, birds will not fall off a branch when sleeping due to a special locking mechanism in their legs.
All the above just briefly demonstrates what fascinating creatures birds are and how perfectly adapted the bird’s anatomy is for survival.
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