I can't believe these actually existed...
Of the millions of species of animals that inhabit the Earth today, many more have gone extinct over the course of the planet’s history. Whether from losing the natural selection lottery or being wiped out by uncontrollable forces, natural or man-made, there have been plenty of fascinating animals that no longer exist, but we can still learn a great deal from them.

Source: Frederick York/Biodiversity Heritage Library/Wikimedia Commons
Thylacine a.k.a. Tasmanian Tiger

Source: Smithsonian Institution/Wikimedia Commons
Hailing from Australia, Tasmania and New Guinea, the thylacine was the largest known meat-eating marsupial of modern times. Though they looked like striped dogs, they were more closely related to kangaroos due to the carrying of their young in pouches.
Shy to humans, Tasmanian tigers were apex predators who hunted at night. Their extinction was largely due to excessive hunting by Australia’s British settlers who put bounties on them. Australia is pretty popular for having some of the most terrifying creatures you’ll ever see, so it’s not surprising when you see a unique animal like this being from there. These creatures went extinct around 1936. They were classed as mammals, and a lot of people would think they were related closer to dogs or cats than they were to kangaroos. When it comes to de-extinction, the theory that eventually science will be able to recreate extinct species, this is on the top of the to-do list.
Golden Toad

Source: Charles H. Smith/Wikimedia Commons
These tiny toads are an example of a species that scientists believe was wiped out by recent effects of climate change and global warming. Discovered in 1966 in a small forest region north of Monteverde, Costa Rica, these amphibians were no bigger than two inches in size. When they were alive, they were also known as the Monte Verde toad, Alajuela toad, and even orange toad. The animal is widely known as the poster child for the whole amphibian decline crisis. The golden toad was one of over 500 different species that could be classified in the Bufonidae family of “true toads.” The males were slightly larger and had longer limbs and noses while the females had enlarged cranial crests above their eye sockets. The males were much lower. Having such distinction between male and female was a unique feature found in these toads.
They were last seen in 1989, and have since been classified as extinct.
Quagga

Source: Frederick York/Biodiversity Heritage Library/Wikimedia Commons
The quagga were a subspecies of zebra that live in South Africa until the late 1800’s. Their lack of striping on their back half clearly distinguishes them from their fellow zebras and give them the appearance of a zebra mashed up with a horse. Some might think you could simply mate a horse and a zebra to come out with this bad boy… but it’s not that easy. They were believed to have been around 8 feet long and 4 feet tall up to their shoulders. While zebras seem to be white with black stripes, the white of the quagga seemed to be the striped part.
Quagga were about eight and half feet long and just over four feet tall. They were hunted by Dutch settlers and by 1878 were extinct in the wild. The few that were taken to zoos were unsuccessfully bred there with the last captive quagga died in Amsterdam in 1883.