Science / Medicine : INSIDER’S VIEW : Many scientists believed that dinosaurs never died out, but evolved into birds. One scientist stumbled upon a possible link, a small bird-like dinosaur called the Nanotyrannus

R obert T. Bakker, a University of Colorado paleontologist, recently discovered that an unusual looking dinosaur skull unearthed in Montana in 1942 had been misidentified as a Gorgosaurus. In fact, Bakker’s research showed, the skull was from a previously unknown genus--a Pygmy relative of Tyrannosaurus rex. His discovery also suggests that the skull, at the Cleveland Museum of Natural History, may be a link between the gigantic T. rex and modern birds.

Bakker, author of “Dinosaur Heresies” and adjunct curator of paleontology at the University of Colorado, Boulder, explained how he made the discovery and what it means in a recent interview with Tamara Jones, Times Denver bureau chief .

Most people think, You want a new dinosaur? What do you do? You get yourself a truck and some safari clothes, you go out to some god-awful place, right? You go to the end of the world, you keep on driving and then you discover a new dinosaur, right?

No, that’s not how you find new dinosaurs. The best way to find new dinosaurs is in the basements of museums, because museums are libraries. Museums of natural history are like libraries of ancient manuscripts. No one read all of the Dead Sea Scrolls when they were dug up.

There are never enough scholars to study objects when they’re dug up--not right away--whether you’re talking about an antique manuscript, a Greek amphora or a dinosaur skull. So what museums do is they excavate them, they take care of them, they repair them, they put them on the shelf so they can be studied. And then they wait. They might wait six months; they might wait 40 years. There’s still a lot of stuff from King Tut’s tomb that hasn’t been analyzed.

So what I did was something that happens sort of routinely. I was visiting Cleveland for a lecture series. And they had this skull in storage--in open storage, though--since 1942. It had never been studied in detail.

It was almost exactly one year ago. So I’m down in the basement looking at giant fish. And, parenthetically, there was this dinosaur skull, this teensy-weensy little guy, which had been identified in 1946 as a Gorgosaurus , which was a very, very, very common type of meat-eating dinosaur.

It was just on top of a table next to the fish. You could walk around, you could poke your finger at it, lie on the table and look up into the roof of its mouth--all of which I did.

And I said, “Mike! Mike! This isn’t right! This is not a Gorgosaurus ! Doesn’t look like a Gorgosaurus . There’s something wrong here!” He said, “Yeah, it bothers me, too.” (Michael E. Williams is the Cleveland Museum’s curator of vertebrate paleontology.)

So, it really bothered me. Then I went from there to Drumheller, Alberta, Canada, to give another lecture series. Gorgosaurus , when I was a wee kid, was one of my favorite dinosaurs. I’d make drawings of it and diagrams and stuff. But this thing that was supposed to be yet another one, wasn’t.

The Cleveland beast sort of looks like a Labrador retriever without any hair--it has this really narrow muzzle and a wide forehead. Whereas a Gorgosaurus looks more like a lizard head. The eye sockets face sideways. That’s the thing that strikes you right away--the wide forehead and eye sockets, because when you look at this dinosaur, it’s looking right back at you. It does look like a pretty obvious feature, and I’m surprised that no one had noticed it before. It’s not subtle.

The only other meat-eating dinosaur that I could think of which is vaguely similar is the great Tyrannosaurus rex.

With T. rex , the eye sockets also face forward. So it’s a really, really rare thing to find a dinosaur with stereoscopy--both eyes facing forward. The Nanosaurus’ visual precision was much, much better than the average dinosaur. It and T. rex are the very last of the meat-eating dinosaurs. T. Rex is common but there’s only one of these in the whole world--the Cleveland Pygmy tyrant--only one.

There is one little bit of a forehead in the Los Angeles museum, actually, which may be another one. Maybe. It was identified as possibly another specimen of the Gorgo. That would be the only other specimen I know of. Many museums have Gorgos.

I went to the Tyrrell Museum (of Paleontology in Drumheller, Alberta), and they have lots of skulls and casts of skulls of Gorgosaurus , Tyrannosaurus . So I pored all over them and it did become clear that the Cleveland animal had been misidentified for 40 years. It is not a Gorgosaurus. Not even close.

In its eyes and brain case . . . it’s much more advanced. But in its teeth, it was more primitive. Sharp, delicate little teeth. Gorgosaurus has much stronger, longer teeth. It’s certainly a meat-eater, but it had a more delicate bite, for attacking smaller things for its size . . . maybe baby dinosaurs of larger kinds or there were a few smaller species of dinosaurs running around, like hundred-pounders.

T. Rex could swallow a whole Hereford. The Nano could probably swallow 60 pounds, which is a lot for an animal the size of tigers--60 pounds in one gulp.

The Cleveland animal probably weighs between 600 and 1,000 pounds soaking wet, which is really quite light for a dinosaur. That’s the weight between a tiger and a polar bear now, and a Tyrannosaurus rex will run up to 14,000 pounds.

It was clear that although it was tiny, the skull was of an adult. As you probably know, baby things, whether they’re dinosaurs or people, have soft spots in their heads--the bones of the skull aren’t all fused together. Well, in this guy, the bones of the forehead are completely grown together. This was an old animal that died, definitely adult-size for its species. Probably had long, skinny legs and a long, skinny tail--maybe 15-16 feet if you stretch it from nose to tail, but about half of that’s head. And if it stood on its tippy-toes, 10 feet tall. But not very bulky. It would appear very, very light and agile.

There are lots of questions. What color was it? Did it have feathers?

So I spent a year working on different aspects of the family tree of Tyrannosaur . Canada and Chicago and New York and the National Museum, Philadelphia--I visited every museum in this continent that’s got skulls of the Tyrannosaur family.

And it was clear that this animal--the Cleveland Pygmy--is a member of the Tyrannosaur family. It’s got certain key features, like incisors, the front teeth. . . . It’s got 10 of them and they’re tiny, they sort of look like a comb in the front. . . . All members of the Tyrannosaur family have those 10 upper nibby teeth. So it was a true Tyrannosaur.

But otherwise, it was a strange, strange beast--its own sideline of that family, so probably a new genus. Nanotyrannus is a new subfamily, a new major branch. And it’s pretty clear that although it shares the T . rex design of having both eyes face right down the snout, it evolved them independently.

I was working with Mike Williams and Phil Currie (Tyrrell Museum’s assistant director of collections and research). We’re almost certain that the greater depth perception evolved in two different lines--in Nano and Tyranno. And it evolved at the same time, very late. These are the last meat-eaters.

This means there was sort of an evolutionary arms race. There was something in the environment that demanded that the predators have better visual precision because the two latest-surviving predators both evolved that. And there’s nobody alive in these last years of the Dinosaur Age which had the old-fashioned monoscopic vision. So there’s something out there. Maybe the prey got much, much more difficult to kill, fought back.

This was about 67 million years ago, the last 2 million years of the Age of Dinosaurs. The last act; the last scene of the last act. So it was top of the line in dinosaur visual surveillance systems.

And the other interesting thing was that somewhere. . . there’s the grandfather Tyrannosaur, the common ancestor, which we haven’t found yet. We’re getting close.

In a lot of ways, Nano, being small and the way its teeth are arranged, is a lot like the earliest member of this family. And it looks a lot like a little dinosaur that Phil Currie has been studying, Troodon .

The big deal is, Phil has shown that Troodon is extremely closely related to the ancestry of birds. All birds. All modern birds--parakeets, ostriches--all birds. So thinking about Nanotyrannus and working on its anatomy has led us to the conclusion that it’s very closely related to Troodon , which Phil Currie has shown is very closely related to birds, which means that there’s a little bit of Tyrannosaurus in your parakeet.

The standard story that you can read in the textbooks and kiddie books right now is, I guess, birds are the descendants of dinosaurs, but the descendant of an animal not at all closely related to T. rex . I’m pretty convinced that birds are real close to the Tyrannosaurs . And they really look that way in other regions, too, it’s not just the skull and the ankle.

If you mentally whack the head off of T. rex and enlarge the arms, you have something that looks like a wing. Boy, the body looks like a bird! And look at the hip bone, and the ankle and the knee, and the way the toes are arranged and the back and the ribs and the neck--boy, it really does look like a bird.

So here are 8,300 species of modern birds. All of them can be traced to some dinosaur. Which dinosaur? Well, the old view was it was traced back to an animal called the Dromaesaur and that Tyrannosaurs were way over here, a sideline. And we’re saying that’s not the way it is at all.

So if we’re right on this analysis, it means that T. rex didn’t really go totally extinct, that there’s a lot of its kind, a lot of its design, preserved in birds.

A lot of dinosaurs might have had feathers. You rarely get skin impressions from meat-eating dinosaurs. It could well be that feathers evolved very, very early. There may be smaller relatives yet. We just don’t know much yet about the small end of the Tyrannosaur family. It’s the first one ever found.

The bird theory comes in two stages. The first stage was about 10 years ago, when it was first suggested, by a chap at Yale, that some kind of dinosaur was the direct ancestor of birds. Actually, the idea goes back to 1860, when it was widely believed for good reasons. One of many true things about dinosaurs believed in 1860 and then forgotten about. Then the next question was: Well, which dinosaur? Our suggestion that it’s a critter close to Tyrannosaurus, I think, will raise some eyebrows. It’s a little like the search for the headwaters of the Nile in the 1850s-1860s. It’s just the challenge to get there first.

(The Nano skull) is on display in Cleveland and molds and casts will be made, so other museums can proudly exhibit them.

The upper and lower jaws are closed, and we have to chip off the remaining rock to get at the lower jaw. It’s double-jointed . . . so the animal could expand the size of its gullet when it swallowed something very large. Beautifully preserved, too.

It also has an air-cooled brain, which is kind of fun. Most of these advanced meat-eaters-- T. rex and Gorgo and Nano--had huge canals going into the bones surrounding the brains. The canals are air passages from the lungs. Birds have that today. And one function, probably, is to cool the brain when the animal’s involved in some violent exercise, because the brain is the most delicate tissue. It’s the one part of the body you’ve got to make sure doesn’t overheat.

It suggests these things were not torpid, lizard-like predators just sitting waiting for something to stumble across their nose, but that they actively hunted.

They (paleontologists) are going to go back (to Montana) because they may find the rest of the body.

Right now, they’re engaged in scratching away the remaining very hard rock so we can get at the lower jaw and lower teeth, and more at the brain case. It’ll help us refine our ideas on its relationship to birds, and how those air holes work, where they all go.

The head looks pretty solid, but you pick up a Tyrannosaurus skull and drop it on the floor and you realize it isn’t--it’s just honeycombed with air cells.

A CAT-scan shows up the sinuses quite nicely. One can usually persuade a hospital technician to CAT-scan your dinosaur. We’re going to do that as soon as it can be arranged. This was pure serendipity. Paleontology is pretty cheap science. Take a couple thousand a year and do everything you want. It doesn’t require enormous machines with flashing lights.

It has a certain intrinsic neatness. It’s a new kind of dinosaur, which we didn’t realize existed before, and that’s fun. It’s fun to see something brand new. It’s fun to see how evolution was working at the very end.

STANDING TALL The nanotyrannus weighed 600 to 1,000 pounds and stood about 10 feet tall, small in comparison to a Tyrannosaurus rex at 12,000 to 14,000 pounds. The largest remains found of a Tyrannosaurus rex stand over 18 feet high.

A FAMILY TREE If nanotyrannus were the direct ancestor of modern birds, a family tree like this may be constructed.

MODERN BIRDS

HESPERORNIS

ICTHYORNIS

ARCHAEOPTERYX

TYRANNOSAURS

TROODONTS & ORNITHOMIMIDS

NANOTYRANNUS

ALLOSAURS

DROMAEOSAURS

DINOAVES

CERATOSAURS

NEOTHEROPODA

PODOKESAURS

THEROPODA

HERRARASAURS

LAGOSUCHIDS

ORNITHOCHEIRS

PTERODACTYLIDS

PTERODAUSTRO

RHAMPHORHYNCHS

DIMORPHODONS

PTEROSAURIA