Archosaur Cousins: Birds and ‘Gators

Bird, Meet Cousin Alligator’. So reads the headline on a fascinating Nov. 4 Harvard Gazette story on Assistant Professor Arkhat Abzhanov.

A professor of organismic and evolutionary biology, Abzanhov is exploring relationships among archosaurs.

Alligators and birds are part of the same larger group, called archosaurs, which has existed for 250 million years and which has given rise not only to birds and crocodilians, but also to dinosaurs. Though dinosaurs are now extinct, the crocodilians, such as alligators, crocodiles, and narrow-jawed gharials live on, and scientists see in them many characteristics of the primitive archosaurs.

In the late 1970s I first became aware of the great revisions in how paleontologists conceived of dinosaurs. Suddenly, awkward quadripeds became powerful bipeds.

But the recreation of my imagination about the dinosaurs was nothing compared to the realisation that the birds shared their lineage. The blue jays hopping on the almost leafless maple remind me of the first erect dinosaur models I saw.

Now scientists, such as Prof. Abzanhov, are expanding our knowledge of these complex, ancient relationships using DNA analysis.

Crocodilians retained many of the characteristics of the primitive archosaurs, such as a more complex skull with bones lost in avian evolution, a large body, and a more conserved body plan.

“If you look at the entire archosaur branch, we have one of the most derived groups, birds, still around,” Abzhanov said. “Unfortunately, we don’t have the intermediate group in dinosaurs, but we have crocodilians, one of the most basal groups.”

An altogether fascinating article, filled with insights like that….

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