Its closely connected components obviously resemble the inner ears of modern jawed vertebrates such as sharks. Some features of the platypus fish also appear strikingly-similar to the inner ear of our species. The fish belongs to a group called placoderms, a class of armoured fish swimming the seas for 60 million years of the early Palaeozoic era – approximately 420 and 360 million years ago. The ‘platypus fish’ may be a surprisingly close cousin to modern-day sharks (Image: Wikimedia) Most placoderms have less complex inner ear structures, with a large sac, called a vestibule. This is positioned in the centre and kept separate from all the other components.