New Zealand's tuataras look like iguanas. The spiny reptiles are not lizards. They are the last remnant of the Rhynchocephalians, a group of lizards that disappeared after their heyday.
They are not normal members of the reptile family. Tuataras can live for more than a century in cold climates and can shear through insects and seabirds with their jaws. They have a third eye below the scales on the top of their heads that can help them track the sun.
Tuatara is an evolutionary enigma, and a spotty fossil record of its long- lost kin has confounded paleontologists. The Rhynchocephalians went extinct at the end of the Mesozoic Era. Many left little more than the remnants of their teeth and jaws.
A piece of this puzzle has been in a drawer for decades. The nearly complete skeleton of a lizardlike animal was found on a slab of stone small enough to fit in a suitcase, by the museum's curator of vertebrate paleontology and her team.
The fossil was discovered during an expedition to the Kayenta Formation. The band of red rock was deposited during the early days of the dinosaurs. Early dinosaurs like the Dilophosaurus mingled with fearsome, crocodile-like creatures encased in armor around this primeval floodplain. This strange new reptile is scurried primitive, shrew-like mammals.
While fossils of the site's early mammals attracted a lot of attention, Dr. Pierce and Simo have finally studied this specimen in depth.
The scientists named the new animal after it. The tribe who live in the area where the fossil was found are the Navajo.
The scientists used micro-CT scans to look at the fossil in three dimensions and pieced it together.
The structure of its skull was similar to a tuatara. It had similar rows of teeth. There were two holes behind the animal's eye. Tuataras are different from lizards who only have one hole because of this configuration. As the tuatara bites down and seess prey, the extra hole in the skull helps.
Dr. Simo said that all of these features are unlike what other modern reptiles have. After a lot of testing, the team decided to take a look at the base of the tuatara lineage.
The fossil shows that the tuataras have not changed much in 190 million years. The differences between the tuatara jaws and those of modern crocodiles were emphasized by Dr. Simo.
Many Rhynchocephalians had little change throughout their history according to a PhD student at Yale who specializes in early reptile evolution. The study states that 200 million years is extreme.
Dr. Simo said that slow rates of evolution don't necessarily mean absence of evolution. It's the evolutionary equivalent of the adage "If it ain't broke, don't fix it."
Much of the reptile's back story is hazy, even though the discovery of Navajosphenodon helps flesh out a crucial chapter in tuatara evolution. Without more fossil discoveries, it will be difficult for scientists to understand why these lone survivors seem to possess evolutionary cheat codes.
The evolution of the modern tuataras is a bigger question and a bit harder to answer.
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