Rivers of Time

I must confess that I had been so busy watching Brenda and the animals that I had forgotten to unsling my rifle, still strapped across my back. I squirmed out of that sling faster than ever before and started to bring the rifle to bear.

At the same time, the giant roo took a swipe with one of its forefeet at this strange little creature that had barged into it. Brenda gave a yelp of pain and swung her camera on its cord so that it banged the roo on its nose. The roo jerked away in a startled manner and cut loose with a huge bound, over some low bush. By the time I had the beast in my sights, it had taken off on a second bound and quickly disappeared.

The whole confrontation lasted only a few seconds. I could, I suppose, have shot the roo before it passed out of sight. But the brute evidently had no intention of bothering us further, and my main concern was for Brenda. I hurried up to find her nursing a single long scratch on her forearm, with little drops of blood forming along it.

I had a bottle of disinfectant in the pocket of my safari vest, and in a few seconds I was swabbing the scratch. It was not serious—the roo's claws had barely penetrated the skin—but we don't take chances with strange infections.

I was bandaging the injured arm when I saw Brenda's eyes, looking past me, widen with apprehension. I spun round as something huge came pouring down the slope after us. A large hole yawned in the side of the slope, and we had passed that gap without noticing it in our carefree descent. The new arrival had popped out of this cave and was headed toward us with evidently unfriendly intent.

This formidable creature stood at the apex of the Australian Pleistocene food chain: not a marsupial or even a mammal, but a reptile, Megalania. It was a monitor lizard, related to the Komodo dragon but ranging up to fifteen meters in length. It thus surpassed the biggest crocodiles, the salties; to find a crocodile of such size you would have to go back to the Cretaceous. Megalania had larger and stouter limbs, enabling it to get around faster on land than any croc; and crocs can trot along faster than you might think when you see one snoozing after a meal.

One argument among paleontologists has to do with the way the limbs of quadrupeds are joined to the body. In salamanders, the legs protrude sideways and have only limited mobility. In the more primitive reptiles, the shoulder and hip joints still cause the upper part of the limb, the thigh and the upper arm, to project horizontally from the body; but the forearm and lower leg are set vertically, enabling the animal to move in a livelier way.

The final step towards full quadrupedal locomotion is the modification of the hip and shoulder joints to bring the upper limb bones to vertical, as it is in mammals. A completely vertical limb, acting as a column, can obviously support the weight of the body with less muscular effort than a limb that is bent into a right angle.

Back in the Permian, some lines of reptiles made this transition. These included the dinosaurs, the crocodiles, and those that evolved into mammals. But the ancestors of the lizards did not. Well, at the K-T boundary between Cretaceous and Paleocene, all the dinosaurs went poof, along with several other orders of reptiles. But the lizards survived, despite this awkward limb arrangement of the upper joints. The dragon that charged Brenda and me was just an oversized lizard, with the primitive hip and shoulder joints. But that fact did not stop it from being a bloody effective predator, about the nearest thing to the conventional dragon that I had ever seen—

Oh, sorry, Mr. Saito. I sometimes get to lecturing on the wonders of prehistoric life and forget the story I'm telling.

Believe it or not, in setting up this jaunt into the Aussie Pleistocene, I had completely forgotten about Megalania. I had read about the animal, of course; but in planning this mini-safari I must have thought only of the larger marsupial carnivores that we might meet. During the Cenozoic, South America had a marsupial sabertooth, Thylacosmilus, just as big and bloodthirsty as the more familiar sabertooth cats from other continents.

So here came this super-lizard, scrambling down the slope with its big yellow eyes locked on ours. It was mostly slate gray, like the Komodo dragon; but with faint grayish-green stripes on its flanks instead of those red markings on that model Megalania in the Australian Museum in Sydney.

I brought the animal's head into my sights, aimed between the eyes, and pulled the trigger. The gun went—click!

I worked the bolt and tried again: another click. The Megalania approached within a dozen meters, looking a hell of a lot more dragonny than any Komodo monitor. It was quite as intimidating as any theropod dinosaur I had ever faced, although in a fight between a Megalania and a Tyrannosaurus or an Epanterias I'd bet on the dinosaur. Being a biped, the theropod could simply bend down and grab the lizard by its spine, either the neck or the back.