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Thinking Critically - Dinosaur-bird link grows stronger

Dinosaurs have changed a lot since I was a kid. Last week, a University of Alberta graduate student revealed a study of a remarkable feathered dinosaur specimen with some plumage and soft tissue intact. Cartoonists loved this story.

Dinosaurs have changed a lot since I was a kid.

Last week, a University of Alberta graduate student revealed a study of a remarkable feathered dinosaur specimen with some plumage and soft tissue intact.

Cartoonists loved this story. In one, an adult stick figure walks up to a child stick figure reading about dinosaurs.

“Dinosaurs have gotten all weird since I was a kid,” she says. “They used to be awesome, but now they all have dorky feathers, right?”

The kid replies: “This says they now think raptors used their wings for stability flapping to stay on top of their prey while hanging on with their hooked claws and eating it alive.”

In the last panel, the woman sits down and joins the child reading.

I love this story not only because it continues to shed new light on dinosaurs, but because it is an amazing validation of the scientific method.

When I was in University at the end of the 1980s studying geology, the link between dinosaurs and birds was still somewhat controversial.

In fact, our paleontology professor was not even teaching it. To be fair, he was kind of a fossil himself at that point, tenured and stuck in the past.

Those of us who were paying attention, however, were fascinated by the emerging evidence of potentially warm-blooded creatures that nurtured their young.

It was exciting beyond the pale to see the data grow suggesting at least the therapod line of dinosaurs did not, in fact, go extinct, but evolved into birds.

These revelations were mind-blowing at the time and with each passing year we fill more holes in our understanding.

And that is the beauty of science. The old ideas that dinosaurs were more akin to reptiles made lots of sense It made perfect sense with the

On the other side of the dinosaur scientific experience is an example of how persistent orthodoxy can be. The link between dinosaurs and birds was originally proposed in the nineteenth century with the discovery of Archaeopteryx, a “missing link” in the vernacular of the day.

It was not until relatively recently, however, that the dinosauran ancestry of birds has become the new orthodoxy.

The writings of Gerhard Heilmann of Denmark, for example, made a good case for the bird-dinosaur link based on anatomy, embryology and behaviour (eg. nest-building).

The link broke down for Heilman because primitive reptiles, presumably the ancestors of dinosaurs, and birds, hypothetically their descendents shared a clavicle (wish bone) that had not been observed in dinosaurs.

The absence of clavicles in dinosaurs convinced Heilman to ascribe the similarities between birds and dinosaurs as convergent evolution.

Evolutionary biology is messy, however, partially because the fossil record is incomplete. In fact, clavicles had been present in dinosaur specimens, but had been destroyed or misidentified.

Heilman’s conclusions were so convincing, they were difficult to overturn for decades. The beauty of science, though, is that we can overturn old ideas.

Other scientific advancements often help make a case that could not originally be definitively realized. Molecular comparison was not available to early paleontologists, but when a Tyrannosaurus rex specimen was discovered with preserved soft tissue, researchers were able to demonstrate T. rex and birds are more closely related to each other than either are to reptiles.

Being a dinosaur  enthusiast has always been exciting, but it just keeps getting better and better.

Ask any child.