[tomato2juice]

> genetic research

How did they get the genetic code of the specific dinosaur branch? I recall a previous discussion here that we have very little genetic source code from dinosaurs because it's degraded in the fossils over time

[loudmax]

Any genetic code analysis is going to be from creatures that are alive today, or at most were alive a few thousand years ago. When you're looking at the fossil record, you're basing families of species on the age of the fossils and on morphology -- the shape of bones and teeth, etc.

Aside from birds, the closest living relatives of dinosaurs are crocodilians. Any DNA that birds and crocodiles have in common almost was certainly shared with dinosaurs. Scientists use this genetic bracketing to get a sense of what the DNA of ancient species might have looked like.

In the long run mutations occur at a fairly predictable rate, so geneticists can use statistical analysis to estimate how long ago two different species or families of species may have diverged.

Since the Hoatzin is a living species, geneticists can compare its DNA to the DNA of other living birds. Based on this, they can estimate how long ago Hoatzins diverged from other living birds, and they can then go to paleontologists to compare their estimate against the fossil record. Any DNA that Hoatzins share with crocodiles, but not with other living birds may indicate DNA that birds evolved after their divergence from other dinosaurs, so this offers a glimpse into what dinosaur DNA looked like.