Tyrannosaurus rex was one of the largest land carnivores of all time, measuring up to 43.3 feet long, and 16.6 ft tall, with an estimated mass that goes up to 7 tons. Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small and they retained only two digits. Fossils of T. rex have been found in North American rock formations dating to the last three million years of the at the end of the Maastrichtian stage, approximately 68.5 to 65.5 million years ago; it was among the last dinosaurs to exist prior to the Cretaceous-Tertiary extinction event. More than 30 specimens of T. rex have been identified, some of which are nearly complete skeletons. Some researchers have discovered soft tissue as well. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. see more on Tyrannosaurus Rex
Quagga: half zebra, half horse (extinct since 1883)
One of Africa's most famous extinct animals, the quagga was a subspecies of the plains zebra, which was once found in great numbers in South Africa's Cape Province and the southern part of the Orange Free State. It was distinguished from other zebras by having the usual vivid marks on the front part of the body only. In the mid-section, the stripes faded and the dark, inter-stripe spaces became wider, and the hindquarters were a plain brown. The name comes from a Khoikhoi word for zebra and is onomatopoeic, being said to resemble the quagga's call.
The quagga was originally classified as an individual species, Equus quagga, in 1788. Over the next fifty years or so, many other zebras were described by naturalists and explorers. Because of the great variation in coat patterns (no two zebras are alike), taxonomists were left with a great number of described "species", and no easy way to tell which of these were true species, which were subspecies, and which were simply natural variants. Long before this confusion was sorted out, the quagga had been hunted to extinction for meat, hides, and to preserve feed for domesticated stock. The last wild quagga was probably shot in the late 1870s, and the last specimen in captivity died on August 12, 1883 at the Artis Magistra zoo in Amsterdam.Because of the great confusion between different zebra species, particularly among the general public, the quagga had become extinct before it was realized that it appeared to be a separate species. The quagga was the first extinct creature to have its DNA studied. Recent genetic research at the Smithsonian Institution has demonstrated that the quagga was in fact not a separate species at all, but diverged from the extremely variable plains zebra.
Thylacine: the Tasmanian Tiger (extinct since 1936)
The Thylacine was the largest known carnivorous marsupial of modern times. Native to Australia and New Guinea, it is thought to have become extinct in the 20th century. It is commonly known as the Tasmanian Tiger (due to its striped back), and also known as the Tasmanian Wolf, and colloquially the Tassie (or Tazzy) Tiger or simply the Tiger. It was the last extant member of its genus, Thylacinus, although a number of related species have been found in the fossil record dating back to the early Miocene.The Thylacine became extinct on the Australian mainland thousands of years before European settlement of the continent, but survived on the island of Tasmania along with a number of other endemic species such as the Tasmanian Devil. Intensive hunting encouraged by bounties is generally blamed for its extinction, but other contributory factors may have been disease, the introduction of dogs, and human encroachment into its habitat. Despite being officially classified as extinct, sightings are still reported.
Steller's Sea Cow: the defenseless beast (extinct since 1768)
Formerly found near the Asiatic coast of the Bering Sea, it was discovered in in 1741 by the naturalist Georg Steller, who was traveling with the explorer Vitus Bering. The sea cow grew up to 7.9 meters (25.9 ft) long and weighed up to three tons, much larger than the manatee or dugong. It looked somewhat like a large seal, but had two stout forelimbs and a whale-like tail. According to Steller, "The animal never comes out on shore, but always lives in the water. Its skin is black and thick, like the bark of an old oak..., its head in proportion to the body is small..., it has no teeth, but only two flat white bones—one above, the other below". It was completely tame, according to Steller. Fossils indicate that Steller's Sea Cow was formerly widespread along the North Pacific coast, reaching south to Japan and California. Given the rapidity with which its last population was eliminated, it is likely that the arrival of humans in the area was the cause of its extinction elsewhere as well. There are still sporadic reports of sea cow-like animals from the Bering area and Greenland, so it has been suggested that small populations of the animal may have survived to the present day. This remains so far unproven.