by A W Drake

Created on: April 11, 2009

The similarities between dinosaurs and birds has long been noted, but it is only comparatively recently that they have been fully studied, leading many to conclude that not only do birds share physical similarities with dinosaurs, but their relationship goes much deeper. It is now commonly accepted that birds evolved from dinosaurs, and to understand why the "birds are dinosaurs" hypothesis has grown it is necessary to look at how well the methodology of looking at the similarities between dinosaurs and birds, as well as the fossil evidence supports this view.

Dinosaurs and Birds: Methodology

Until the 1960's, all features were considered important when studying the evolutionary relationships between species. Then a German entomologist, Willy Hennig determined that as organisms evolve and their physical characteristics change, it is only those features that remain the same that are relevant. This system, known as Cladistics, or Phylogenetic Systematics, is now the standard methodology for measuring the characteristics a species shares with other organisms, and has been a primary tool in developing the understanding of the similarities between dinosaurs and birds.

In 1969 the work of John Ostrom described the similarities between Archaeopteryx (a Jurassic bird), and Deinonyclus, a theropod. He noted twenty two features both species shared which helped shape the current thinking on the relationship between dinosaurs and birds. Following his work, Jaque Goultier's studies, using the Cladistics method became the first well accepted work to produce compelling evidence that dinosaurs and birds do not just share similarities but are related. It has since been shown that there are ninety features that relate birds to dinosaurs, and it is now widely accepted that birds most likely evolved from a turkey sized theropod.

Dinosaurs and Birds: Their Similarities

Since dinosaurs are reptiles, the physical similarities they share with birds are reptilian. For instance, birds have scales on their feet just like reptiles. In fact the tissue that produces feathers is similar to tissue that produces scales. Also like reptiles birds lay eggs, and the soft anatomy of birds (their internal organs) is again very similar to that of reptiles.

Thanks to the work of people like Ostrom and Goultier we now know there are many skeletal similarities between dinosaurs and birds. Some of the main similarities include:

1/ Large eye sockets

2/ Elongated arms and forelimbs

3/ A flexible wrist

4/ Hollow,

• 1
• 2
• 3
• 4
• Next Page >>