by Robin Hussey

Created on: February 08, 2009

There is enough similarity between the fossils of dinosaurs and modern birds to conclude that birds did indeed evolve from dinosaurs.

The Wishbone

The furcula, or wish bone, has been found in many theropod dinosaurs. The furcula in birds is used to strengthen the skeleton for flight. In theropod dinosaurs the wishbone did not serve the same function and was less flexible than the corresponding bone in birds. The evolutionary connection is intriguing.

So Few Juvenile Fossils

There are very few juvenile dinosaurs found in the fossil record. This may be due to a correlation between the way birds and dinosaurs grew, very fast. If dinosaurs were more closely related to reptiles they would have a slower rate of growth, many growing after sexual maturity. The lack of juvenile fossils could be due to the fact that the rate of growth was more similar to birds. If dinosaurs grew at the rate of birds they were not juveniles very long, and that may be why we find so few fossilized in comparison to the amount of adults that have been discovered.

Eyes

Most predatory dinosaurs had forward facing eyes with evidence of well developed visual acuity. Birds have the most sophisticated vision of all species. Both predatory dinosaurs and modern birds used this well developed sense of sight for hunting their prey. It would be sensible to think that modern birds have evolved from the species that had the most developed sight in prehistoric times.

Bones

Many dinosaurs had honeycomb structures thorough their skeletal system. This honey comb structure would have given them a lighter skeleton, enabling them to be more active. Similarly, the skeletal system of birds is hollow to allow them to take flight. These hollow bones could easily have been an evolutionary step from the honeycombed ancestors of prehistory.

Avian Respiratory System

Modern birds have a very efficient respiratory system that is far superior to the respiratory system in mammals. Birds have a continues supply of new oxygen because their hollow bones actually become part of their respiratory systems. The system allows birds a higher degree of activity than their mammalian and reptilian counterparts who have inferior respiration abilities. There is evidence that dinosaurs shared this superior respiratory system. It is likely that if dinosaurs began this respiratory system birds perfected it as they evolved from dinosaurs.

In classification of animals characteristics of those animals are used to determine how alike or different those animals are. Using the classification systems that have been used for hundreds of years dinosaurs are more like birds than they are like anything else that has survived their extinction. Or, are they really extinct at all?

Source:

Larson, Peter, and Kristin Donnan. Rex Appeal. Montpelier, Vermont: Invisible Cities P, 2004.

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