A quick look at how archaeopteryx and orynthorhynchus have characteristics that are shared and unique. These two animals all have a shared characteristic with the dinosaurs, similarly humans have many shared characteristics with dinosaurs yet have many shared characteristics with Orang-utangs (98% shared DNA). These shared characteristics have been chosen by the DNA through a process called natural selection.
Firstly, archaeopteryx is a small to medium size animal which may have been able to fly, yet has some shared characters of the dinosaurs. These shared characters are the reptilian feet and egg and a unique bone structure similar to dinosaurs. Unique characters are what makes the animal special. The behavioural characteristics of the archaeopteryx are not known as the animal has become extinct, along with the dinosaurs. Characters which have made the animal similar to birds include the feathers and beak and some scientists rumour the internal anatomy to be similar to both birds and dinosaurs, through fossils from the Burgess Shale.
Secondly, orynthorhynchus is a small to medium size animal which is still alive today, it cannot fly, yet has a nose like a bird and webbed feet, fur instead of feathers and burrows like a mole. This strange creature is from Australia and is better known as the platypus. Therefore if the archaeopteryx can lay eggs, have a beak and webbed feet does that mean that it has platypus DNA. Hang on, that means that platypus and dinosaurs share DNA if the archaeopteryx is descended from a dinosaur. But isn't a platypus a mammal, like man.
This comes to my final point about birds being descended from dinosaurs, animals, plants, fungi, virus and bacteria which all share common foodsources that are used between the different generations. It is how we use these foodsources that makes us human, and it is the DNA that digests these foodsources to give the animal it's energy. If for instance we could digest fire (sunlight) we would be a tree, if all we needed was water and air we would be a fungus, if all we could digest was cellulose then we would be an insect, if all we could digest was certain sugars, fats and proteins then we would be human, however if we couldn't make up our mind then we would either be a bacteria or a virus.
My point being, evolution is not about descendants rather about the food that we choose to eat and the way that we digest it. As Nutritionits say ......"You are what you eat"...... Therefore to make the point clearer, birds descended from a common ancestor, like the dinosaur, they did not change from one form immediately to another, rather a process of natural selection has brought about the immediate change in evolution from birds to dinosaurs and this has probably been through foodsources and whom eats whom.