Image courtesy of Sid Mosdell, CC BY 2.0.
Joel Kontinen
It’s called the dinosaur that
never went extinct The Tuatara (Sphendon punctatus) is a special reptile that
lives only in New Zealand. It is often called a living dinosaur. Tuatara has
successfully opposed both extinction and change. Tuatara is the only surviving
reptile in the order Sphehodontia. Evolutionists believe it coincided with the
early dinosaurs in the Triassic about 250 million years ago .
Now, Scientists from the
University of Adelaide and South Australian Museum have collaborated with Otago
University, New Zealand and a global team to sequence the genome of the
tuatara—a rare reptile whose ancestors once roamed the earth with dinosaurs.
Professor David Adelson's lab
of the University of Adelaide's Department of Molecular and Biomedical Science
and Dr. Terry Bertozzi of the South Australian Museum carried out key analysis
of the tuatara genome that
revealed an unusual architecture, half-way between mammal and reptile.
"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 Professor Adelson.
The key contribution of
Professor Adelson's lab and Dr. Bertozzi was to demonstrate that some sequences
of DNA that move or jump location, referred to as 'jumping genes', found in the
tuatara are most similar to those found in platypus while others are more
similar to those in 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," said Professor Adelson.
"This was a highly
unusual observation and indicated that the tuatara genome is an odd combination
of both mammalian and reptilian components."
"The unusual sharing of
both monotreme and reptile-like repetitive elements is a clear indication of
shared ancestry albeit a long time ago," said Dr. Bertozzi.
With no close relatives, the
position of tuatara on the tree of life has long been contentious. The research
places tuatara firmly in the branch shared with lizards and snakes, but they
appear to have split off and been their own species for around 250 million
years—an enormous amount of time given primates only originated around 65
million years ago, and hominids, from which humans descend, originated
approximately six 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. 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," said Professor Adelson.
Source:
University of Adelaide Dinosaur relative's genome linked to mammals.Phys.org 5 August.
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