Dodo :
Last Dodo was seen in the 16th century. It was an one kind of big fatty bird which had very small wings. So, naturally they didn't fly. Their length was upto 1 metre & weighed about 10-18 Kg. They lived in Mauritius island. Massive hunting of them is the main reason for its extinction.
Tasmanian Tiger :
Last Tasmanian Tiger was hunted in 1920. They lived in Tasmania, Australia & New Guinea. Though it was looking like tiger but, actually they were not tigers. They were very similar to dogs. But, these species of dogs had strips like tigers. Their length was upto 2 metres & weighed about 30 Kg.Massive haunting is also the extinction of Tasmanian Tiger.
Sabre-toothed Tiger :
Sabre-toothed Tigers are animals of Jurassic Period. They existed 55 millions years ago. Like modern age tigers they were also carnivores. They have two blade-like canine teeth which are up to 50 cm long. But, their tail was very short like as modern goats. They preyed on sloths and mammoths. The main reason of their extinction is climate change & defeats competition with ancient humans (cro magnon?)
Mammoth :
Mammoth existed about 3.5 millions years ago in Africa, northern Eurasia and North America . Mammoth is the old version of modern elephant. But their bodies was covered with long hairs & very long curved tusks. They were over 4 metres tall and could weigh over 6 tons. Massive hunting and climate change is the reason behind of their extinction.
Great Auk :
Great Auk were last seen in the North Atlantic and Northern Spain in the year of 1835. They were also big, fatty and flightless bird like Dodo. Their average height was 75-85 cm and weighed about 5kg. Like penguins they were very good swimmer. A large natural disaster is the main reason of their extinction.
Stellers Sea Cow :
This species of Sea Cow was named after George Steller. He was a naturalist who first discovered them in 1741. But, after discovering of them within 27 years all Stellers Sea Cow was massively hunted to extinction. Their average length was 8-9 metres and weighed about 8-10 tons. They lived in Near Islands, southwest of Alaska and the Commander Islands in the Bering Sea.
some reference links for further reading:
https://onekindplanet.org/top-10/extinct/
http://www.huffingtonpost.in/entry/11-extinct-animals_n_4078988
https://owlcation.com/stem/Top-10-Most-Beautiful-Extinct-Animals