Casuriidae is a scientific term for a bird family which today is known to have only four surviving members. These are three species of cassowary and one species of Emu. Formerly, the Emus were classified in their own family, but they are regarded as closely related enough to the cassowaries, hence they have been classified as belonging to the same family.

The Emu is characterized by legs adapted for running. As a ratity, the theories concerning its evolution are many and often controversial. It is still a mystery whether the emus or cassowaries are the more primitive in this family. Some fossils from Australia initially thought to be from the emus were recognized to represent a distinct genus, Emuarius. This genus had a skull similar to the cassowary, while the lower leg and foot were those of an Emu. The family casauriidae is common in Australia and parts of Papua New Guinea and nearby islands. However, it is believed that their distribution may have been even wider in the past, and the current distribution may not necessarily reflect the natural range of their habitat particularly because cassowaries have been extensively traded in the past few centuries. Cassowaries are large ratites, and are known to be among the largest birds of the world. Their feathers are black and unkempt, and they have brightly colored skin on their necks. They have a helmet like growth on top of their head. This ‘helmet’ grows slowly throughout the birds initial few years.

Although the function of this helmet was initially thought to be for pushing aside heavy growth as they moved in dense vegetations, its real function is not clearly understood. However, more recently, observations have revealed that the bird uses the helmet to push aside litter in the forest as it searches for food on the ground. The helmet may also be useful in indicating the age of the bird.

Cassowaries can run and jump. Their speed goes up to fifty kilometers an hour and they can jump up to one and a half meters from a standing position. Another well known feature of the cassowaries is their dagger-like claw in their inner toe. This claw can be a deadly weapon, and the birds may use it in defending themselves by jumping and kicking with both feet. Males, especially, are known to be exceedingly violent when defending their young and nests. Other distinct features of cassowaries include a very long after shaft, and flight feathers that are reduced and curved under the body. Their wings are undersized, and like the majority of ratites, cassowaries have no fluff on the tail. Just like other ratites, they have three toes and short middle phalanges.

Cassowaries’ habitat is the rainforest, as they require a huge provision and variety of fruit for their diet. These birds are generally shy and difficult to spot in the wild, although they travel regular paths in the forest. Cassowaries are usually solitary birds, though they pair up during the breeding season.