Presidential Lecture - "A Layman's View of Archaeopteryx"
given by John Price on February 13th 2006

John’s talk introduced several aspects of the controversy relating to the evolution of feathered reptiles and the possible colouration of the feathers themselves.

The dinosaurian hypothesis of bird origins suggested that these creatures were winged reptiles who could probably glide. Comparisons were made with the Tetrapteryx pro-avians found in Liaoning province in north east China.

After discussing the theory that feathers developed from reptilian scales, and how this may have occurred, John showed us the close association between modern flight feathers and fossilised Archaeopteryx feathers. It is the asymmetry of these feathers that allow birds to fly.

However, there is a problem with the different sorts of keratin contained in reptilian scales and bird feathers.



Crocodile epidermal scales contain alpha keratin, while feathers only have beta keratin. John told us that X rays studies show that keratin can be "stretched" from the alpha type found in scales to the beta type found in feathers. This reaction is reversible in some cases but keratin can be permanently "set" by the rupture of the disulphide bonds in the cystine form. This may have happened through mutation, irradiation or lack of Vitamin A. Maybe when dinosaurs changed from meat eating to leaf shredding, they lacked the ability to absorb enough Vitamin A!

John also discussed the chemistry of keratinisation and colouration of feathers.

MDH

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