The purple frog (Nasikabatrachus sahyadrensis), also known as the 'doughnut frog', was only discovered in 2003 as it spends most of the year buried 4m underground. Compared to similar species, the purple frog, which lives in India's Western Ghats, has an unusually small head and a strange pointed snout. (© Sathyabhama Das Biju)

The human-sized Chinese Giant Salamander can grow up to 1.8m, but is classed by experts as 'critically endangered'. It has poor eyesight but can sense the slightest vibration thanks to especially sensitive nodes which run along its body. (International Cooperation Network for Giant Salamander Conservation)

The pangolin, commonly found across south-east Asia, is the only creature in the world entirely covered in scales. Its tail, which can grow to over 50cm, has 30 scales on it alone. The creature is classed as endangered as experts say people simply 'aren't aware of these animals'. (Sunda pangolin_Carnivore and Pangolin Conservation Programme)

The rare Ganges river dolphin, found in Bangladesh, India, Nepal and Pakistan, has a uniquely large beak with huge, visible teeth. Marine biologists say that at the lowest estimate, there are 1,200 remaining in the world, giving them endangered status. (Marinebio.org)

The long-beaked echidna, with its unmissable snout, is the oldest living mammal in the world. Usually found in Papua New Guinia, it is considered critically endangered as there are currently three living species of echidna and two which have become extinct. (Picture: Wikipedia)

Also known as the 'dwarf sloth', the pygmy sloth lives off the coast of Panama and is critically endangered. Their exact population is not known, but it is feared there could be as few as 300 left in the world. (Craig Turner/ZSL)

NOTE: You can view the full Gallery here.