Cutlasstooth

The Cutlasstooth, Caedosaurus gladiadens, is a saber-toothed predatory dinosaur (South America).

Many animals flooded into the Neotropical continent about four million years ago, when the string of volcanic islands linking with the Nearctic continent to the north, fused to form a land bridge. The animals quickly evolved and developed to fill the ecological niches they found. In most instances the animals that came south were more successful and began to replace the indigenous animals that had dominated the continent for the previous 50 million years. The reason for this may be that the indigenous animals had evolved few variations in that period of time. The continent itself had not shifted substantially and there had been little change in the environment and the climate except for the spread of the grasslands. There was no necessity then, for the animals to evolve, and they had settled into a long period of decadence. animals from the north, on the other hand, had suffered millions of years of change, with changes in climate and interchange  of animals with the Palaearctic realm, and had been evolving vigorously. When they reached the Neotropical continent they were more able to adapt to the conditions found there and, as a result, the native animals suffered. The most noticeable instance is found among the meat-eaters. The first of the northern animals to reach the continent were the mountain-leapers. Being skilled at traversing high mountain ranges, they were well able to cross the mountainous neck of land that connected the two continents and spread into many of the ecological niches. Large meat-eaters quickly developed from this stock and preyed on the swift-footed sauropods of the plains. Even larger types developed, some with their heavy heads and small arms, looking as if they had evolved from the great carnosaurs of the Cretaceous period rather than the small agile coelurosaurs. One such is the cutlasstooth which has evolved huge cutting teeth that enable it to prey on the large sauropods like the lumber. Hunting in packs, cutlasstooths can set upon a lumber and slash it until it bleeds to death.

The cutlasstooth's dental arrangement is unique among dinosaurs. The first tooth of each upper row is a long, curved slashing weapon (a). Those behind it are continually growing. Once the front tooth is broken and discarded there is another to take its place (b). The jaws of the cutlasstooth can open remarkably wide, so that the lower jaw is well away from the cutting teeth when the heavy head is thrust downwards in the slashing stroke (c). The undersides of the large teeth are serrated and work against the lower teeth as carnassial (meat-shearing) blades for ripping and chewing flesh when the animal is eating. When hunting, a pack of four or five can inflict deep bleeding wounds on the flanks of their prey (d), and then wait until it bleeds to death.