Corythosaurus vs. Utahraptor
We find ourselves in the sub-tropics of late Cretaceous southern Alberta, over 76 million years ago, in a warm, humid, coastal floodplain. The flat landscape is scarred by sediment-laden rivers, prone to seasonal flooding, all slowly meandering East towards a warm inland sea. The network of rivers is surrounded by vast lush evergreen forests, whose floors are covered in low lying ferns and green spongy mosses.
The freshwater rivers are teeming with aquatic life, homes for turtles, frogs, freshwater-rays (Myledaphus), garpike (Lepisosteus), and even crocodile-like predators (Champsosaurus). At the river edge shoots of horsetails and other water plants line the shallows providing shelter from the current to some small animals, while providing food to others.
Out from the lush fern-covered conifer forest a large stalky four-legged plant-eater emerges. It is a lone, large-helmet-crested Corythosaurus slowly trudging towards the muddy bank of a winding river (Therrien et al., 2015). As he nears the edge of the shoreline he slowly bows his head for a drink, completely unaware that he is not truly alone.
A fierce feathered foreign predator is lurking in the forest shadows, her large forward-facing yellow eyes glaring at what she hopes will be its next meal. This dangerous invader, Utahraptor, is one of the oldest and largest dromaeosaurs to ever live. As she crouches in the underbrush she begins to plan her next move.
Despite having never seen an animal quite like this larger strange bulbous-crested creature, the hungry Utahraptor is undeterred. It is not like her to turn down the chance to take down quarry larger than itself, having faced iguanodontids, like Iguanacolossus (McDonald et al., 2010) in her home-state of Early Cretaceous Utah. However, this Late Cretaceous Corythosaurus is slightly bulkier, and the dromaeosaur is lacking her packmates.
As Corythosaurus is drinking with his head lowered, he is constantly surveying his surroundings. Having side-facing eyes allows Corythosaurus to see threats approaching from both his flanks and from behind. However, when his head is lowered his vision is slightly blocked from the rear. Utahraptor is hoping to take advantage of this, assuming Corythosaurus will behave like an iguanodon, to which Utahraptor is familiar. The raptor will try to sneak up approaching from the rear of the Corythosaurus in hopes to outmaneuver the thought-to-be vulnerable lambeosaurine. But this is a risky move.
Utahraptor breaks cover from the trees and lunges toward the back of her target. Simultaneously Corythosaurus, having quenched his thirst, raises his head. The element of surprise is blown! The would-be victim is now aware of the very immediate danger and quickly adjusts to a sturdier posture, shifting its weight to the left side of his body. It is too late for the predator to stop now. Utahraptor has her feathered arms and legs outstretched. In mid-air the predator’s jaws gape open, lined with nasty, serrated teeth. The dromaeosaur’s hind legs bend, anticipating contact with flesh. her four-toed feet each possess a retractable sickle-claw, evolved for piercing and pinning down unlucky prey.
Although the helmet-crested herbivore is slightly caught off guard, he is quickly able to swing his long muscular tail toward his fearsome attacker. The tail strikes a blow to the raptor, knocking her out of mid-air, sending her flying backwards to the right of the herbivore, until she lands hard onto a nearby log. At the same time of contact Utahraptor’s claws were able to slash lines of stinging cuts across the hadrosaur’s tail. But the carnivore now lies in a crumpled heap.
Utahraptor has broken 3 of its ribs and injured her lower right leg, her fibula protruding out from her skin. She struggles to regain her balance, but eventually stands on her two legs, her right leg slightly bent to relieve the pressure and pain. She attempts to step forward and does so, but with extreme difficulty. It appears the foreign invader’s risk of attacking while her opponent’s back was turned has backfired.
The Corythosaurus remains standing on all fours, anchored in the mud. But he feels quite weak. A glistening red liquid is seeping from the back of the corythosaur’s tail. Despite the two adversaries being wounded, the Utahraptor is smart enough to know when she’s beat. She slowly limps up the sandy riverbank, letting out a slight sound of pain with each step until she disappears back into the forest, leaving a trail of blood from her compound fractured leg.
After realizing he is significantly injured Corythosaurus emits a long, loud warning bugle to warn his nearby herd of the predator’s presence. Far from being safe, this victor is not out of harm’s way yet.