Tuatara: halfway between mammals and reptiles

Hyperaxion Aug 7, 2020

A new study shows that this animal, endemic to New Zealand, has genetic material common to reptiles and mammals.

A team of scientists from Australia, New Zealand, and the United States worked together to sequence the DNA of the tuatara, a reptile that is the only living representative of the Sphenodontidae family.

Tuatara: halfway between mammals and reptiles
(Credit: Nicola Nelson).

According to an article published in the journal Nature this week, the species appeared in the Triassic period, 250 million years ago, and is endemic to New Zealand.

Genomic analysis revealed unexpected features in the animal’s DNA: it is halfway between mammals and reptiles.

“The tuatara is the last surviving species of a reptile group that roamed the earth with the dinosaurs and remarkably, its genome shares features with those of mammals such as the platypus and echidna,” said David Adelson, co-author of the article and professor at the University of Adelaide’s Department of Molecular and Biomedical Science, Australia.

In genetics, it is known that some DNA sequences can “move” or “jump” between species. These so-called “jumping genes” are found in tuatara – some are similar to those found in the platypus, while others are similar to those of lizards.

“The tuatara genome contained about 4% jumping genes that are common in reptiles, about 10% common in monotremes (platypus and echidna) and less than 1% common in placental mammals such as humans,” Adelson explained. “This was a highly unusual observation and indicated that the tuatara genome is an odd combination of both mammalian and reptilian components.”

With no living close relatives, the tuatara’s position on the tree of life has been controversial. The new research, however, places it in the branch shared by lizards and snakes and indicates that it separated and became a species of its own some 250 million years ago.

“It has been a privilege to be part of this project, which has been a true, historic collaboration with local iwi (Māori indigenous tribe) Ngātiwai,” Adelson said. “While this is largely fundamental science, I expect it to yield new ways of thinking about our own genome structure that may have relevance to our health.”

Related topics:

New Zealand Tuatara


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