Primeval Predators

There is of course another kind of aggression in dinosaurs and other creatures, one that has more to do with basic survival, and with it culinary needs, than with social dominance. All those big herbivores—those hadrosaurs, sauropods, and ankylosaurs of the Gobi and elsewhere—were potential food items for predators. Theropods like Tyrannosaurus and its Gobi cousin Tarbosaurus represent the extreme in this predatory lifestyle. As noted earlier, the skulls in some of these monsters are more than four feet long, with recurved six-inch teeth. The skeletons are framed for at-tack—from the front of their sinuous line of sturdy neck vertebrae through their powerful hind limbs down to the vicious claws on the three functional toes of their hind feet.

Thus armed, one would imagine these tyrannosaurids as the ultimate terror. Indeed, many have proclaimed the group to be the greatest and most "terror-ific" terrestrial predators of all time. Others, like Jack Horner and Don Lessem, reject this reputation for active aggression and violence in tyrannosaurids. Instead, they suggest that these animals were primarily scavengers, preferring the less difficult challenge of removing great chunks from inert corpses. This notion is inspired, in part, by the absurdly shortened forelimbs of tyrannosaurids. These feeble splints of bone end in two-fingered hands with sharp claws, but they don't extend far enough from the torso for the animal to scratch an itch on its lower neck. Horner and others reason that these wimpy appendages were rather extracurricular. And, without their effective use, the animal had no business attacking hulking hadrosaurs or armor-plated ankylosaurs.

The argument, to me, sounds a bit overwrought. Certainly snakes, crocodiles, and other infamous killers have attained this status without the benefits of long grasping forelimbs. Indeed the scimitar-toothed jaws of tyrannosaurids were sufficient to snatch, crush, and carry away a victim, or at least carry away a good chunk of meat from the prey. Moreover, there is some evidence to suggest violent behavior in tyrannosaurids. The famous skeleton of Tyrannosaurus rex at the American Museum (AMNH 5027) shows broken ribs and fused trunk vertebrae that resulted from injury. This is backed up by another skeleton (not at the American Museum) that has teeth of an alien tyrannosaurid embedded in its skull. The broken ribs or fractured humeri in some of these beasts might not indicate such combat at all, but instead a violent struggle with a particularly feisty prey, whether plant-eater or meat-eater. Were tyrannosaurids scavengers or predators? Maybe both, but there is no convincing reason to say they weren't terrific killers.

Many scenarios are offered for the murderous manner of assault likely to have been employed by the great carnosaurs. These are based largely on examples of mayhem in the living fauna. A popular notion is that a beast like Tyrannosaurus used a "hit-and-run" or "land shark" approach. The predator jumps the prey and inflicts a mortal wound, a gaping chasm of

Primeval Croc Runs

muscle, organs, and blood, with its slashing teeth. It then retires to wait out the bloodletting of the shocked and dying victim, zooming in at the right moment to finish off the game. Although this strategy is largely attributed to species like the great white shark, something similar is seen in a formidable land predator, the ora or Komodo dragon (Varanus komodoensis). This "dragon" is actually the world's largest lizard, reaching a length of ten feet and a weight of 300 pounds. Though the ora indulges in carrion feeding, it often kills its game, which on rare occasions even includes humans, by surprise attack. It hides in the high grass or the bush and lunges out at the prey, which might have had the poor judgment to follow a well-beaten path that serves as the ora's favorite game trail.

The teeth of the ora are designed to disembowel. When chomping on its victim, the ora clamps its broad muzzle onto the flanks and moves its jaws backward. Walter Auffenberg, a zoologist who has thoroughly studied these nasty creatures, notes that if one drew a line connecting all the tips of the upper teeth it would resemble the profile of a scalpel. The longest teeth are about midway along the tooth row. Thus, with the back-

ward movement of the jaw the taller teeth incise more profoundly into the flesh than the teeth behind them. As implements for both the first strike and the subsequent feeding these teeth rip through a mass of muscle and organs with astounding and horrific efficiency. To make matters worse for the victim, the Komodo is perhaps endowed with the foulest and most lethal breath in the animal kingdom. Its mouth is an incubation chamber for a virulent kind of bacteria to which the ora has built up an immunity. These bacteria, however, can thrive and grow in the wound of the prey, promoting a slow and painful death. The product is a pestilential carcass, but one safe for ora feeding.

It has not escaped the notice of some paleontologists, like Ralph Molnar, that the width of the muzzle and the profile of the tooth row in the ora are remarkably similar to those in forms like Tyrannosaurus and Tarbosaurus. The largest teeth are near but not at the front of the upper jaw. Retraction of this row would create the kind of gaping wound produced by the ora; of course the wound would be of much greater dimensions.

Mark Norell prospects at the foot of the Flaming Cliffs, the world's most famous dinosaur site. Jim Clark and the author in background.

(Photo by Fred Conrad.)

Champmen Andrews Mongolia 1920

Roy Chapman Andrews (center) in the Gobi, scanning the horizon. (Photo courtesy of the American Museum of Natural History.)

Camel caravan of Andrews' Central Asiatic Expedition at the base of the Flaming Cliffs. (Photo courtesy of the American Museum of Natural History.)

Camel caravan of Andrews' Central Asiatic Expedition at the base of the Flaming Cliffs. (Photo courtesy of the American Museum of Natural History.)

The dinosaur Protoceratops andrewsi first collected at Flaming Cliffs, next to a nest of eggs originally thought to belong to Protoceratops. (Photo courtesy of the American Museum of Natural History.)

Tarbosaurus, a terrifying Asian relative of Tyrannosaurus, in the Natural History Museum in Ulaan Baatar. (Photo by Michael Novacek.)

The extraordinary fighting dinosaurs

{Protoceratops and Velociraptor) found at Tugrugeen Shireh by the Polish-Mongolian team. (Photo by Zofia Kielan-Jaworowska.)

Where are those fossil sites? Malcolm McKenna (in plaid) and the author scan the map while Mark Norell (background) prepares dinner. (Photo by Fred Conrad.)

The author (left) with Mark Norell. "We are unlikely successors to the 1920s expedition members in their ironed khaki and wide-brimmed hats."

(Photo by Amy Davidson.)

Malcolm McKenna's discovery of Estesia, a fossil lizard new to science. His ring finger for scale. (Photo by Michael Novacek.)

The Cretaceous lizard Estesia emerges from the rock through skilled fossil preparation by Lorraine Meeker.

(Photo by Chester Tarka.)

The Cretaceous lizard Estesia emerges from the rock through skilled fossil preparation by Lorraine Meeker.

(Photo by Chester Tarka.)

Fossil Preparation

Part of the 1994 Mongolian Academy-American Museum Expedition assembled at Naran Bulak ("Sun Spring"). Back row (from left to right): Batsuk (driver), John Lanns (mechanic), Jim Carpenter (entomologist), Jim Clark (dinosaur and crocodile expert), Amy Davidson (preparator and collector), Lowell Dingus (geologist), Luis Chiappe (fossil bird expert), Sota (driver), the author (expedition leader). Front row (from left to right) Carl Swisher (geologist), Gunbold (field assistant), Demberelyin Dashzeveg (mammal expert, coleader), Mark Norell (dinosaur and lizard expert, coleader). (Photo by Michael Novacek.)

The author with his prized Velociraptor skeleton at Flaming Cliffs. (Photo by Amy Davidson.)

The author with his prized Velociraptor skeleton at Flaming Cliffs. (Photo by Amy Davidson.)

Ukhaa Tolgod, perhaps the richest site in the world for Cretaceous dinosaurs and other fossil vertebrates. The "Camel's Humps" are at right center. (Photo by Mark Norell.)

We virtually tripped over skulls of dinosaurs, like this

Protoceratops, at Ukhaa Tolgod. (Photo by Michael Novacek.)

Roy Chapman Andrews Eggs Nest

Mark Norell clutches a nest of dinosaur eggs found near "Eldorado."

(Photo by Michael Novacek.)

Mark Norell clutches a nest of dinosaur eggs found near "Eldorado."

(Photo by Michael Novacek.)

Perle and Mark Norell (right) remove an armored ankylosaur skull from the red sands of the Flaming

Cliffs. (Photo by Michael Novacek.)

Perle and Mark Norell (right) remove an armored ankylosaur skull from the red sands of the Flaming

Cliffs. (Photo by Michael Novacek.)

Luis Chiappe (right) and Amy Davidson prepare the nesting Oviraptor for removal from the sands of Ukhaa Tolgod. (Photo by

Mark Norell.)

Luis Chiappe (right) and Amy Davidson prepare the nesting Oviraptor for removal from the sands of Ukhaa Tolgod. (Photo by

Mark Norell.)

The first skeleton of Oviraptor found in the 1920s at the Flaming Cliffs. (Photo courtesy of the American Museum of Natural History.)

The first skeleton of Oviraptor found in the 1920s at the Flaming Cliffs. (Photo courtesy of the American Museum of Natural History.)

American Museum Natural History 1920

The egg with the skeleton of the oviraptorid embryo (below) found with a small juvenile Velociraptor-Xs\e. form (above right) from Ukhaa Tolgod. The first known embryo of a meat-eating dinosaur. (Photo by Mick Ellison.)

(Below) The nesting Oviraptor, "Big Mama," from Ukhaa Tolgod. The forelimbs with their huge claws embrace a clutch of at least twenty eggs. (Photo Dennis Finnin.)

(Below) Reconstruction of the oviraptorid embryo in its egg. (Drawing by Mick Ellison, courtesy of the American Museum of Natural History.)

(Below) Reconstruction of the oviraptorid embryo in its egg. (Drawing by Mick Ellison, courtesy of the American Museum of Natural History.)

The skull and forelimb of a "gemlike" multituberculate mammal Kryptobaatar, from Ukhaa Tolgod Note the "chipmunk-like" front incisors

(Below) The stunning skull of the tiny placental mammal Zalambdalestes, found by Jim Clark at Tugrugeen Shireh. (Photo by Mick Elli son.]

The skull and forelimb of a "gemlike" multituberculate mammal Kryptobaatar, from Ukhaa Tolgod Note the "chipmunk-like" front incisors

The "Sugar Mountain Mammal," one of five showcase skeletons of placental mammals found at the Sugar Mountain site in Ukhaa Tolgod.

(Photo by Mick Ellison.)

Whether tyrannosaurids employed a "hit-and-run" or "land shark" strategy is of course a matter of pure speculation. We have no direct evidence that these prehistoric predators preferred to wait in ambush and then patiently sit out the bloodletting. And we surely do not know whether the tyrant king measured up to the ora in a capacity for mixing the bite with a saliva spiced with virulent bacteria We can at least say that these big theropods seemed to have the right equipment for a horrendous and lethal slashing attack, one that might rival—though on a much bigger scale—the ora's.

I've encountered, first hand, oras in the wild. In February 1991,1 led a group of American Museum tourists along one of these "game trails" on Komodo Island. It was a warm and somewhat stifling walk through thick brush in land that time forgot. Komodo Island is a small piece of crust in the steamy Indonesian seas. The island is crowned with ancient, plant-carpeted volcanoes. It is as arresting and primeval as any Hollywood dream for the birthplace of King Kong. We were apparently safe though, escorted by a couple of resident guides armed with rather puny sticks en route to a viewing area some two miles inland. At the observation pit we could watch the oras fight among themselves. The beasts are routinely fed fresh game at this site, a maneuver that is supposed to congregate the lizards and at least allow a better sense of their movement in the bush.

This rather artificial, tourist-oriented procedure doesn't work perfectly. On our way back to the beach, what seemed to be the biggest of all ora—"ora rex"—confronted us on the trail. At a length of ten feet and a fighting weight of a few hundred pounds, he was a vicious, snarling monster. He did not back off. Instead he continued to hiss threateningly as our guides furiously tried to beat him off the trail. Meanwhile, an only slightly smaller ora came out on the trail, blocking our retreat and closing in on us from behind. There were some gasps, and a few purses and pairs of sunglasses flew in the air. Much to the alarm of my group, I disappeared into the bush, but I reemerged with my own stick. I helped the guides do battle with our "attacker" at the front of the column. At last we got the beast back to the edge of the trail. A few minutes later a group of excited and grateful tourists came spilling out onto the sanctuary of a white sand beach and a row of zodiac boats waiting to escort them to the afternoon cocktail party on our cruise ship. It was an amusing but not altogether harmless encounter. I couldn't imagine the horror of contending with a dragon of Ko-modo that managed to spring from the bushes in a surprise attack. A stick wouldn't do much good under the circumstances. Some tourists have been killed and consumed on Komodo Island in this manner.

Dinosaur predators come in all shapes and sizes. While there are things like forty-foot tyrannosaurids, some theropods are smaller than ten-foot oras. Velociraptor as I've noted is not awesome in proportions. But its abilities in the hunt can hardly be doubted. Unlike tyrannosaurids, the front limbs of many of these smaller theropods are well developed and armed with vicious, large claws—grappling hooks. And of course there are those killing scimitar-like claws on the hind foot that I described in Chapter 2. Perhaps these animals used such claws rather than teeth to strike the first disemboweling blow.

Perhaps as well they hunted and killed cooperatively in packs. There has been much speculation on the subject of pack hunting in meat-eating theropods. A dinosaur trackway from the Lower Cretaceous Glen Rose Formation in Texas (such trackways are rare in the Gobi strata) show marks of a small group, possibly four theropods, moving in the same direction as a larger congregation of sauropods. But the footprints are ambiguous. They could have been left by a theropod pack on the hunt. Or, as the orientation of some of the prints indicates, they may simply represent the movement of individual theropods in ways that did not track the sauropods. It makes sense that certain predators would team up to bring down bigger game. But, as one might expect, there is no decisive fossil evidence for this strategy in dinosaurs. Just the same, new studies of trackways by Martin Lockley strongly suggest that various and sundry theropods relied on cooperative hunting and killing.

Sometimes the clues left by fossils about the predatory lifestyles of dinosaurs are even more tantalizing and mysterious. Zofia Kielan-Jaworowska discovered one such fossil enigma during the 1965 season in the Gobi, when she spotted a dozen or so bones in soft sandstones at Altan Ula III. She gingerly scraped the surface of the sand to reveal an enormous eleven-inch claw resembling a sickle. When the team returned the next day they uncovered a shoulder girdle and two enormous three-digit

Velociraptors Hunting
A hunting pack of Deinonychus, a dromaeosaur relative of Velociraptor (EdHeck, reprinted with permission, AMNHj

forelimbs over eight feet long! It could be ascertained from the proportions of the bones that the beast was big, about Tarbosaurus size. But in the latter the forelimbs are stunted and spindly, with didactyl hands and claws no more than two inches in length. This creature was something entirely different—unlike any dinosaur known. The Altan Ula arms were given the name Deinocheirus ("terrible hand"), a label any hapless prey on the verge of disembowelment might agree with. Some reconstructions of Deinocheirus depict it as a great swarthy serpent with huge clawed fore-limbs, suspended from the shoulders like the drooping arms of a giant ground sloth. It has also been suggested that these creatures may actually have been anteaters, who used their great claws to dissect giant ten-foot-high termite nests. But who knows? These depictions are only slightly better than pure fantasy. To this day, all we have of one of the most extraordinary dinosaurs that ever lived are a few bits of skeleton, those amazing forelimbs and claws.

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