Though these animals resemble modern apes in almost every way, their closest modern relatives are baboons, like the mandrill.
This family is divided into 2 subfamilies. The Monaciinae all resemble modern apes with no external tail. The Urosimiinae more closely resembles monkeys or lemurs than apes, most have more elongated heads and long tails. The Urosimiines are also the most carnivorous of the Metazoic apes. Castosarchus is even built for killing, with long, razor-sharp claws on the hands and a 6-inch retractable claw on the first digits of each hind foot for rendering. The fangs are as much as 5 inches long, and the jaws exude an extremely powerful bite, useful for tearing the flesh off even the largest gigantelopes, and crushing tendon and bones. They hunt in large packs, much like modern lions or wolves. Larger prey is killed by simply being eaten. Smaller prey, like smaller antelope, are usually grasped with the claws and the skull or vertebrae is crushed by the ape's jaws while being disemboweled using the rear claws.
The smallest apes in the Metazoic are those in the genus Arbrariel. These tiny, delicate and graceful little apes more resemble lemurs. But they are no bigger than an average-sized house cat. The largest species in fact weighs no more than 5 pounds maximum. They are omnivorous, feeding on insects, leaves and fruits. Their lifestyle is a lot like those of modern gibbons. They swing from branch to branch and tree to tree using their arms, in a motion we refer to as "brachiation". For their small size, these animals can swing an amazing 30 feet in a single leap. The tail is also prehensile, but only used when necessary. Most of the time, it is carried curled up above the body. Also like gibbons, these diminutive apes communicate with other groups with loud vocal songs. These animals spend nearly 100% of their time in the tree canopy, almost never reaching ground levels.
The largest apes in the Metazoic are those in the genus Monacium. These apes more closely resembles modern gorillas. Like gorillas, they are almost purely vegetarian. Only very occasionally feeding on insects as a source of protein. Unlike modern gorillas, Monacium apes have colorful patterns on the head, particularly the males during the breeding season. The colors are a warning to other males that he is ready to battle for his females. These apes are not very active, so usually the bright colors on the head and face are enough to ward off other intruding males. Rarely do they engage in physical combat. After the breeding season is over, the colors fade and the males take on the usual dark black fur that is typical of these species. M. fosseyi is the largest species, standing up to 9 feet tall, and weighing almost a ton. Females of these species are about half that size.
Apes in the Metazoic have few predators, mostly because they live high up in the trees, or in some of the most remote, inaccessible areas in their range. But there are some predators that brave the elements and can capture and feed on these animals. Castosarchus, as adults, have almost no enemies. The occasional Spathodon may take a weakened adult, but usually will hesitate even to do that for fear of the ape's defenses. Arbrariel may be taken by deinognathids like Elaphictis, pythons, civets, caroroos, and predatory bats. Armasenex is famously prey for such creatures as Dryptopithecus, which often lives in close association with these apes. And Chortoperegrina, which spends nearly 100% of it's time at ground level on the savanna, is often prey for a large variety of carnivores, like mongooses, snakes, monitor lizards, crocodiles, and especially, larger deinognathids.
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