Brothers Island tuatara  (Sphenodon guntheri)

The Brothers Island tuatara is one of the oldest animals in the world today (4). It may look like a lizard but it belongs to the order Rhychocephalia, which includes ancient reptiles that existed 200 million years ago. All other species in this order, apart from the tuatara, declined and eventually became extinct about 60 million years ago. Tuatara are therefore of huge interest to biologists as they represent the only living link to these ancient reptiles. The Brothers Island tuatara is one of two species of tuatara, the other being the more common Sphenodon punctatus species, which is found on the Northern Islands (5). The Brothers Island tuatara has a lizard-like body, and a long tail, stocky legs, long claws and a large head. A crest of spines runs along its back, neck and head: a characteristic which led to its Maori name, meaning ‘peaks on the back,' (4) (5). Males are larger than females, with larger spines, though they look similar with olive green, grey, or dark pink body colouration, and speckles of grey, white or yellow. Newly hatched young are brown or grey, with pink tinges and a striped throat (5). This reptile has the unusual feature of a third pineal eye: This eye has a retina, a rudimentary lens and is connected to the brain by a nerve. While it is apparent in infants, it becomes covered by opaque scales in adults, so it is unknown whether the eye serves any function (4).