Giant+Short-Faced+Kangaroo+(Ancient)

**Present Animal (Wallaby) Future Animal (Wallion)**

The //**Procoptodon goliah**//, also known as the **Giant Short-Faced Kangaroo**, was the biggest example of the macropod family that ever existed. It stood between 2 and 3 meters tall and weighed around 230 kilograms. The Giant Short-Faced Kangaroo lived on the Australian continent between 1,600,000 and 40,000 years ago, during the Pleistocene epoch, although there is some evidence that the species may have survived to as recently as 18,000 years ago. Unlike any kangaroo or wallaby living today, the Giant Short-Faced Kangaroo had forward-pointing eyes and a flat face. It only had one toe on each foot, with a single hoof-like claw at the end of each one. Their front paws were equally strange – each paw had two extra-long fingers with long claws.

The Procoptodon goliah is not only one of the largest marsupials to have ever lived on the Australian continent, it is also one of the strangest.

The following report describes both the habitat of the Giant Short-Faced Kangaroo, and five different structural, behavioral and physiological adaptations that this animal has evolved in order to thrive in its environment.

= Scientific Classification =

**Habitat**
 * ** Level ** || ** Classification ** ||
 * Kingdom || Animalia ||
 * Phylum || Chordata ||
 * Class || Mammalia ||
 * Infraclass || Marsupialia ||
 * Order || Diprotodontia ||
 * Family || Macropodidae ||
 * Genus || Sthenurinae ||
 * Species || Procoptodon ||

During the Pleistocene epoch 2,588,000 to 12,000 years ago, the world went through a long period of repeated glaciations. The Australian continent was very close to its current position, but due to relatively large polar icecaps, sea levels were much lower, creating land bridges between continents. As a result of the waxing and waning cycles of the polar icecaps, the climate in Australia continued to interchange between icehouse phases (dry, cold conditions) and greenhouse phases (wetter, warmer conditions). The Giant Short-Faced Kangaroo was able to survive in a wide range of climates, from the semi-arid areas of South Australia, to the temperate sclerophyll forests of western New South Wales, and the cave deposits on the Nullarbor Plain.
 * Climate**

Like the Red-necked Wallaby after it, the Giant Short-Faced Kangaroo lived on the Australian continent. It mainly inhabited open woodlands in central Northern Australia. When the species first appeared 1,600,000 years ago, the Earth was transitioning into an icehouse phase and tropical rainforests in northern Australia were beginning to recede. The Giant Short-Faced Kangaroo thrived in the temperate environment of the woodlands. Its fossils have been found in South Australia, Darling Downs in Queensland, Lake Menindee in New South Wales, among many other sites. This suggested that its geographical range spanned most, if not all of Australia.
 * Geographical range**

Like all wallabies and kangaroos after it, the Giant Short-Faced Kangaroo was a herbivore. Their diet was probably very similar to that of wallabies today, consisting primarily of grasses and leaves. The Giant Short-Faced Kangaroo would have been able to access a wider variety of plants than present day wallabies though, as their height and long arms would have enabled them to reach the leaves of tall trees.
 * Diet**

During the Pleistocene epoch, the continent of Australia was home to a wide variety of Australian Megafauna. These animals were gigantic in size, often with equal to or greater than 30% greater body mass than their closest living relatives. These included the //Diprotodon optatum,// the largest marsupial that ever lived. Weighing up to two tonnes and approximately three metres long, it resembled a giant wombat. The //Zaglossus hacketti// inhabited Western Australia. It was a sheep sized echidna, the largest monotreme so far uncovered by humans. The //Zygomaturus// was a giant horned marsupial similar to the present day hippopotamus in both size and build. The //Dromornis stirtoni// was a flightless bird that stood approximately three metres tall and weighed about 500 kilograms. It is one of the largest birds so far discovered. Predators of these herbivorous giants included the deadly Marsupial Lion, the largest carnivorous mammal known to have ever existed in Australia. It hunted large animals such as the Diprotodon and giant browsing kangaroos like the Giant Short-Faced Kangaroo. The Marsupial Lion shared part of its range with the //Megalania//, a six metre long goanna. It was the largest terrestrial lizard known to have existed.
 * Predators/Other animals**

= Adaptations and Environmental Pressures =

Like the wallabies and kangaroos that came after it, one structural adaptation of the Giant Short-Faced Kangaroo was its muscular tail. The tail of the kangaroo serves as a steadying “rudder” when leaping, and can function as a third leg when the kangaroo is stationary and resting. The tail may also give extra traction to the kangaroo as it moves around, providing an extra point of contact between the kangaroo and the forest floor.
 * Adaptation 1 (Structural):**

As a result of this adaptation, kangaroos rarely, if ever, lose their balance and tip over. Although they are bipedal like humans, kangaroos are much steadier than Homo sapiens. They have the ability to travel at high speeds through rough, uneven terrain. This allows Giant Short-Faced Kangaroos to escape easily from their predators, which include the [|Marsupial Lion] and the [|Megalania]. This increases their chances of survival and reproducing.

The environmental pressure that gave rise to the kangaroos’ tail could potentially have been the sheer vastness of the Australian continent combined with the generally low fertility of Australian land. These two factors mean that the distance between two food sources for the Giant Short-Faced Kangaroo may be very far. Kangaroos developed their strong tails to increase their mobility and allow them to reach food faster. This increases the chance of survival. The strong tail would have also allowed wallabies to increase their chances of escaping from predators by enhancing their balance and mobility.

One of the most bizarre structural adaptations of the Giant Short-Faced Kangaroo are its legs, or more specifically, its feet. The Giant Short-Faced Kangaroo appears to only have a single toe on each foot, somewhat similar to a horse’s hoof, but sharp and claw-like in appearance. Scientifically speaking, their “single toe” is actually an extremely developed fourth toe. All the other metatarsals (bones that form the toes of a foot) were so reduced that they were essentially merged with the bone structure of the fourth toe. This gives the appearance of having one toe on each foot. Like the kangaroos and wallabies that came after it, the Giant Short-Faced Kangaroo had a system of elastic tendons within its muscular legs that allowed it to propel itself by using the spring action of its tendons as opposed to using muscular effort. This adaptation, combined with their uniquely shaped toes, allowed the Giant Short-Faced Kangaroo to leap huge distances. It is believed that these kangaroos would first dig their claw-like toes into the ground, then use the leverage and their elastic tendons to propel themselves into the air.
 * Adaptation 2 (Structural):**

As a result of this adaptation, Giant Short-Faced Kangaroos moved relatively quickly for their size and weight. They used their uniquely shaped feet to travel swiftly through forests and woodlands. However, their speed advantage was most apparent on the plains and open woodlands of the Australian bush, where they could use their leaping ability to travel long distances and escape from predators, thus increasing their chance of survival.

One possible environmental pressure that could have stimulated the gradual development of the uniquely shaped feet and the big, strong hind legs of Giant Short-Faced Kangaroos is the sheer vastness of the Australian continent combined with the generally low fertility of Australian land. These two factors mean that the distance between two food sources for the wallaby may be very far. Giant Short-Faced Kangaroos developed their large fourth toe and efficient method of travelling to allow them to reach food faster. This increases the chance of survival. The strong hind legs would have also allowed wallabies to increase their chances of escaping from predators such as the Marsupial Lion and the Megalania, which roam the Australian landscape.

The arms of the Giant Short-Faced Kangaroo are in many ways as unique and fascinating as its legs. Not only were the forelimbs unusually longand mobile for a marsupial, the middle two fingers of each front paw were elongated, with long, curved claws. The structure of the forelimbs allowed Giant Short-Faced Kangaroos to reach above their head, something that no wallabies or kangaroos today can achieve. The long claws on each paw were used to grab branches on trees, bringing them within eating distance.
 * Adaptation 3 (Structural/behavioural):**

As a result of this adaptation, Giant Short-Faced Kangaroos could reach leaves on tall trees by balancing on their hoof-like toes and reaching up with their claws. Their muscular tail would have been used as a prop to make this process easier. By reaching food that most other herbivores at that time could not access, Giant Short-Faced Kangaroos could survive in a wider variety of environments where other animals may starve to death. This gave Giant Short-Faced Kangaroos a competitive advantage in terms of feeding themselves.

A possible environmental pressure that may have given rise to the Giant Short-Faced Kangaroo’s versatile forelimbs is intense competition for food between the many herbivores that inhabited Australia during the Pleistocene epoch. The arid nature of the Australian continent meant that animals had to compete over a limited amount of food. The ancestors of the Short-Faced Kangaroo were forced, through natural selection, to give themselves an advantage over the other animals by developing an adaptation that allowed them to access a wider range of plants, thus increasing their chance of survival.

The Giant Short-Faced Kangaroo had a very short, deep skull and a large, well developed lower jaw, hence the name. By studying the shape of its skull, scientists believe that the head structure of the Giant Short-Faced Kangaroo provided a powerful mechanical advantage to its chewing muscles. Although it was not a carnivore, the Procoptodon had a very strong bite. It was undoubtedly able to eat even the toughest stems and leaves in the forests of Australia.
 * Adaptation 4 (Structural):**

As a result of this adaptation, Giant Short-Faced Kangaroos could consume a wider range of leaves and grasses than present day wallabies and kangaroos, which have much smaller lower jaws and weaker chewing muscles. By having the ability to eat plants that most other herbivores at that time could not consume, Giant Short-Faced Kangaroos could survive in a wider variety of environments where other animals may starve to death. This gave Giant Short-Faced Kangaroos a competitive advantage in terms of feeding themselves.

The environmental pressure that stimulated this adaptation could have been very similar to the environmental pressure that gave rise to the ability of a Short-Faced Kangaroo to reach above its head - intense competition for food between the many herbivores that inhabited Australia during the Pleistocene epoch. The arid nature of the Australian continent meant that animals had to compete over a limited amount of food. The ancestors of the Short-Faced Kangaroo were forced, through natural selection, to give themselves an advantage over the other animals by developing an adaptation that allowed them to access a wider range of plants, thus increasing their chance of survival. Another environmental pressure might simply have been that many of the plants in Australia during the Pleistocene epoch were much tougher and harder than plants today.

One structural adaptation that distinguishes the Giant Short-Faced Kangaroo from all wallabies and kangaroos today are its forward-facing eyes. Living kangaroos’ eyes are on the sides of their heads, giving them a 300 degree ﬁeld of view, excellent for spotting predators. In contrast, while the forward-facing eyes of the Giant Short-Faced Kangaroo gave it a narrower field of vision, they provided a good degree of binocular vision and a better perception of distance than kangaroos with a wide ﬁeld of view.
 * Adaptation 5 (Structural):**

As a result of the improved perception of distance that forward-facing eyes provided, Giant Short-Faced Kangaroos could move at high speed through areas of open forest and tall shrubs, where there were numerous obstacles to negotiate. The binocular vision may have also helped Giant Short-Faced Kangaroos when reaching up into tall trees to select the most nutritious leaves, increasing their chance of survival.

Scientists are unsure of the environmental pressure that gave rise to forward-facing eyes in Giant Short-Faced Kangaroos. Perhaps the giant kangaroo was simply too big for most Australian predators (with the obvious exception of the Marsupial Lion and the Megalania) to attack and therefore had no need for a wide ﬁeld of view. So instead of developing an adaptation to increase their chances of escaping from predators, they evolved an adaptation to assist them as they move through the forest in search of food.

= Selection Pressure - Why Did It Go Extinct? =

The Giant Short-Faced Kangaroo died out at around the same period of time as the majority of the Australian Megafauna around 40,000 years ago. The exact reason that caused the Procoptodon to go extinct is still being debated by scientists. Some believe that when humans first arrived on the Australian continent as far back as 60,000 years ago, their fire burning habits and over-hunting caused the death of most Australian Megafauna. This is proven by Aboriginal cave drawings in sacred sites. Others believe that climate change drove the giants to extinction more than 40,000 years ago. The answer is probably a combination of both theories.

Prehistoric extinctions can very rarely be attributed to a single cause. It is likely that humans modified the Australian landscape through their use of fire and also hunted the Giant Short-Faced Kangaroo, driving their numbers down. Climate change made Australia less hospitable to the large animals, which are often more sensitive to environmental change. Over the course of thousands of years, the Giant Short-Faced Kangaroo population shrunk and ultimately disappeared.

= Bibliography =

> = =
 * About. (2011). //Procoptodon//. Retrieved June 23, 2011, from []
 * Wikipedia. (2011). //Procoptodon//. Retrieved July 23, 2011, from []
 * Australian Museum. (2010). //Procoptodon goliah//. Retrieved July 25, 2010, from []
 * MSN. (2006). //Giant kangaroo likely killed off by humans.// Retrieved July 25, 2010, from []
 * Australian Wildlife. (2011). Kangaroo. Retrieved June 25, 2011, from []