Lessemsaurus vs Carnotaurus
71 million years ago, in the estuarine environment of late Cretaceous Argentina, a river that breaks into many channels, spreads into wetlands and sinking mudflats, and finally flows into the ocean. At the mouth of the estuary there is a pinch point, a single place where the river is shallow enough to cross and the land on either side is traversable.
On one side of this river, Carnotaurus has been following a few hundred meters behind a herd of hadrosaurs for some time (Gasparini et al. 2015), waiting for an opportunity to pick off the slowest of the group. As the herd reaches the river, it is forced to slow, as each member makes the arduous crossing.
By sheer coincidence, other species have arrived at the river at the same time as the herd. An ankylosaur has come out of the forests upriver to attempt a crossing, and Lessemsaurus has arrived from 220 million years ago in the Triassic. Hailing from an environment of rivers and lakes (Arcucci et al., 2004), Lessemsaurus recognizes the crossing point for what it is, and is willing to put himself in the proximity of strange new creatures if it means getting across the river safely.
Carnotaurus sees his chance. He must make his kill before he risks losing the hadrosaurs on the other side of the river. Carnotaurus lunges forwards and begins to pick up speed, racing towards a young hadrosaur caught at the back of the herd. The ankylosaur catches sight of the rapid motion of the Carnotaurus first. He wheels around wildly, swinging his tail. Lessemsaurus, standing nearest to the ankylosaur, veers sharply to the side to avoid the dangerous appendage. This unexpected move pushes the Lessemsaurus directly into the path of the charging Carnotaurus, which has gained ground at incredible speed. Blocked from his intended prey by a much larger and more imposing animal, Carnotaurus attempts to turn, stop, anything, but the momentum of his body is too much. The enormous muscles in his tail and legs, which gave him the incredible acceleratory power to close in upon his prey, now work against his agility (Persons & Currie, 2011).
The Carnotaurus crashes into Lessemsaursus’s side, toppling both animals in a tangle of thrashing limbs. In the confusion, the herd of hadrosaurs make their escape across the river. The ankylosaur flees back towards the distant tree line.
The Carnotaurus frees himself, finds his feet, and stumbles to a safe distance. Stunned and more than a little concussed, this hunter is in no shape to continue its pursuit of the hadrosaurs. Nevertheless, it is clear that Carnotaurus has come out of the unexpected entanglement the better of the two. Lessemsaurus is still on his side in the shallows of the river edge, heaving for breath as his blood leaks into the water below. In the collision Carnotaurus’s skull had connected with Lessemsaurus’s ribs, fracturing and driving them into the animal’s lungs. One of Carnotaurus’s head spikes had punctured and ripped along Lessemsaurus’s side, leaving a gaping wound. Lessemsaurus will not be regaining its feet. The Carnotaurus knows this too.
Robbed of its intended meal, Carnotaurus is not one to waste a new opportunity for fresh meat. He hunkers down to wait for Lessemsaurus to die. It’s only a matter of time.