Study reveals chewing ability of ancient lizard
Researchers in the United Kingdom have discovered that the tuatara of New Zealand has a distinctive way of chewing its food, using a 'steak-knife' sawing motion to break down the prey it consumes. The results of the study, presented in The Anatomical Record journal, may help shed light on how this creature has evolved over more than 200 million years, challenging the theory that a strong connection exists between the lizard's complex chewing ability and high metabolism. No other terrestrial animals chew like the tuatara. Scientists at University College London and the University of Hull used a state-of-the-art computer model to show the creatures' steak-knife chewing ability. Dr Neil Curtis of the University of Hull, one of the authors of the study, says the virtual model helped the team develop the most detailed musculoskeletal model of a skull ever developed. 'It allows us to investigate movements within skulls that would be impossible to monitor in a live animal without using harmful X-rays, which is not an option for protected species like the tuatara,' he says. The tuatara (Sphenodon) is the sole survivor of a group of a lizard-like reptile that was prevalent during the dinosaur era. Currently, the tuatara makes its home on 35 islands around the coast of New Zealand. Having made its way to the mainland in recent times, this creature survives by eating beetles, crickets, spiders, small lizards and sea birds. The researchers observed that the lower jaw of the reptile closes between two rows of upper teeth when the tuatara munches away. According to the scientists, once closed, the lower jaw slides forward a few millimetres to cut food between sharp edges on the teeth, sawing the food apart. 'Some reptiles, such as snakes, are able to swallow their food whole, but many others use repeated bites to break food down,' explains lead author Dr Marc Jones from the Cell and Developmental Biology research department at University College London. 'The tuatara also slices up its food, much like a steak knife. Because mammals show the most sophisticated form of chewing, chewing has been linked to high metabolism. However, the tuatara chews food in a relatively complex way, but its metabolism is no higher than that of other reptiles with simpler oral food processing abilities,' he adds. 'Therefore, the relationship between extensive food processing and high metabolism has perhaps been overstated.' The forward movement of the jaws triggers the slight rotation of the jaws about their long axes, a result of the jaw joint's shape. Because of this, the shearing action has a stronger effect. What is also clear is that the left and right lower jaws are not fused together at the front, as they are in people. The researchers' work identified how a specialisation of the feeding mechanism seems to enable the creature to have a broader diet. 'The slicing jaws of the tuatara allow it to eat a wide range of prey including beetles, spiders, crickets, and small lizards,' Dr Jones says. 'There are also several grizzly reports of sea birds being found decapitated following predation by tuatara. Although the tuatara-like chewing mechanism is rare today, fossils from Europe and Mexico show us that during the time of the dinosaurs (about 160 million years ago) some fossil relatives of the tuatara used a similar system and it was much more widespread.'For more information, please visit: University College London:http://www.ucl.ac.uk/To watch a video describing the research, click:http://www.youtube.com/watch?v=4Aeu5iBJ5zY (here)The Anatomical Record:http://goo.gl/I7CfZ
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