Birds of a Feather - Part 3

We have now arrived at a very interesting point where the discoveries of the past two decades have illustrated how difficult it is to define exactly where feathered theropod dinosaurs leave off and birds begin. Many of the features once thought to be unique to birds, like a wishbone, for example, have been identified in a variety of dinosaurs. Even teeth are still found in many otherwise normal-looking Late Cretaceous birds such as Ichthyornis from the chalk deposits of Alabama. At the moment, the acquisition of fully powered flight appears to be the dividing line between theropods and birds, although even that is tentative. At least one lineage of theropod dinosaurs, the alvarezsaurids, that includes the bizarre Mononychus and Shuvuuia, each sporting a single finger on each tiny but powerfully built arm, have the appearance of “vestigial” wings that belonged to a once flighted bird that has re-adapted the wing into a warped sort of arm. This implies that flight may have evolved more than once within the theropods because the alvarezsaurids are not closely related to the lineage of theropods that share the most features with birds. Essentially, you should think of birds as flighted theropods that survived the extinction event 65 million years ago (the K/T boundary extinctions). After the K/T boundary extinctions, birds had finally evolved to the point that they had a more bird-like appearance, having lost teeth, the long tail, and the hind foot sickle-claw.

But birds didn’t quit being scary with the disappearance of the rest of the dinosaurs. At least two groups of birds became top predators after the K/T extinctions in the absence of any competing large mammal carnivores. Diatryma (Gastornis) was a large, seven-foot-plus tall flightless bird that dominated North America and Europe for several million years after the K/T, eating the ancestors of horses and whatever other mammals they could catch. Later, the flightless phorusrhacids, otherwise known as the Terror Birds, ran the plains of South America between about 62 and 2 million years ago, eating llamas and pretty much whatever else they wanted. One phorusrhacid, the nine-foot-tall Titanis walleri, made it across Central America and its fossils have been found in Florida. As a personal note, this is one of my “paleo daydreams”. You can’t get from Central America to Florida without crossing through southern Alabama. Every time it rains, I get this mental image of a Titanis skeleton eroding out of the bank of some stream in south Alabama,…

We call the Cenozoic, the time period dating from the end of the dinosaur era 65 million years ago to the present, the “age of mammals”. And it’s true that the top predators in the terrestrial realm today are mostly mammals. But there are 10,000 species of living birds, and only 4600 species of mammals, so dinosaurs are still doing quite well (although a recently released report suggests that human activities may be accomplishing what the dinosaur-killing asteroid collision could not – namely driving many species to extinction). There’s even the chance that traditional-looking dinosaurs could make a comeback. Several times over the past 20 or 30 years various research groups have shown that some of the primitive characteristics of birds ancestors are still locked away in a birds DNA. Now there are people trying to use our increasing knowledge of genetics to “reverse engineer” a dinosaur, or at least a bird with some very dinosaur-like characteristics, from a bird. I’m going to refer to such a creature as a “dino-bird” in the following paragraphs.

For example, there is a mutation in chickens known as talpid, which has teeth and jaws, not a beak. There is also a stage in embryonic chicken development with a long tail containing 16 vertebrae, very dinosaur-like, very un-chicken-like. The genes that control these mutations can be identified and theoretically, if they can be “turned on” during the development of the embryo in such a manner that they do not kill the chick embryo by interfering with later developmental stages, one could get a chicken with teeth and a long tail. Then there’s the Hoatzin, an odd-looking relative of the cuckoos that nests in the seasonally flooded forests of the Amazon. Hoatzin chicks are born with 3 claws on their hands that project off the front edge of the wing that they use to climb up small trees to escape snakes. They later lose the claws, but obviously the genes for hand claws in birds are still locked away in their genetic code, it’s just that those genes have been repressed. Of course whether or not bioengineering such an animal is ethical is another story, but my prediction is that someone somewhere is going to do it. And this raises all sorts of questions of a profound nature that scientists and perhaps society at large should begin to ponder, and here I offer but a few:

What exactly will a dino-bird look like, will we call embryonic dino-birds “chicks” (somehow when I think of the fuzzy little yellow duck chick I got one Easter when I was about 5 years old, I can’t quite reconcile the two images), will we have to redo the old expression about something being “rare as hen’s teeth”, will they get along well with house cats (my prediction is no), could they be house-trained, and what would that be like (ever smelled a chicken house?), how much will the vet charge to “declaw” your dino-bird?

Finally, a couple of closing thoughts; the next time you look at that bird on your feeder that you’ve let run out of food, or cast a disparaging glance at that scruffy-looking pigeon on the sidewalk, just remember – there’s a little of T. rex in them. Show some respect. And if we ever do invent a time machine and travel back to the age of dinosaurs I have one last prediction – dinosaurs will taste like chicken.

Contributor Profile:
James Lamb is a native Birminghamster with a nearly life-long interest in fossils. He collected his first fossil when he was 5 years old. Friends and family members assure him he has not matured much since then. James is curator of paleontology at McWane Science Center, and would like to one day see the absolute treasure trove of Alabama's fossil heritage revealed to the public. When not at work he wishes he were in the field digging up fossils. At home he enjoys reading, jogging, woodworking, and carving. He has been informed that he is in the habit of telling atrocious puns, but this comes as a surprise to him. James describes himself as a "science nerd".