Fossils sparked controversy over New Zealand's engulfment

The fossil of a lizard-like New Zealand reptile has been identified by a team of scientists from UCL (University of London), University of Adelaide, and the Museum of Zealand Te Papa Tongarewa. The fossil, dating back to 18 million years ago, created new arguments about whether the continent was under the sea 25 million years ago.

Today, New Zealand's endangered tuatara (Sphenodon) is a lizard-like reptile who is the only survivor of a group of animals present globally in the period of the dinosaurs. Tuatara lives on 35 islands scattered around the waters of New Zealand, this species has become extinct in the main land due to the presence of humans and related species 750 years ago.

The oldest Sphenodon fossil dates from the Pleitocene century (about 34,000 years ago), while the new discovery dates from 19 to 16 million years ago. Fossils, jaws and teeth are similar to today's tuatara, covering a period of 70 million years in the fossil record of the mid-Pleistocene animal group in New Zealand and at the end of the Cretaceous period in Argentina.

In a paper published in the Proceedings of the Royal Society B, the team said the findings provide evidence that the ancestors of the tuatara have appeared in a wide area since it separated from the southern continent ( Gondwana).

Funny illustration An ancestral tuatara (Sphenodon) is located on a small piece of land during the New Zealand period under the sea. (Photo: Alan JD Tennyson, Marc EH Jones.)

The main author, Dr. Marc Jones of UCL's Department of Cell Biology and Development, said: 'There has been much controversy that New Zealand is completely submerged under sea level during the sinking of the Oligo-Miocence continent 25. 22 million years ago (Mya). However, the diversity of fossils from the Miocene period (St Bathans Fauna of the Manuherikia group) shows that it seems that a part of land remains on the water level to ensure the survival of some animals and purses. Such as frogs, caori trees and some freshwater insects, as well as tuatara '.

'Fossils also provide the first evidence that the ancestors of tuatara survived in New Zealand despite significant climate and environmental changes, such as a global temperature drop of 8 degrees Celsius about 14 million years ago ( Central Miocene) ".

Between the late Oligocence period and the early Miocene (35 to 22 Mya) global sea level rose and engulfed New Zealand, but the question was: how much? If the continent of Zealandia is completely submerged, Sphenodon must resettle on this continent from the sea. But if we look at modern Sphenodon, it can swim, but with only a short distance, it can survive without food for a few tahngs, but dehydration is a serious problem for a Long trip because of high rate of dehydration through the skin. In addition, there is no evidence of a subspecies of this species outside New Zealand at that time.

It seems that some of the land surfaces still exist during the continent were submerged and allowed the ancestors of the tuatara along with the frogs, birds and mammals to survive the process of encroachment, despite the amount of land remaining. At that time has not been determined. However, even if Zealandia is reduced to 1% of today's surface area, there are still 2,500 square kilometers, 1,000 times the surface area of ​​Island Stephen (1.5 square kilometers), where more than 30,000 tuatara currently living

Refer:

Marc Jones, Alan Tennyson, Jennifer Worthy, Susan Evans and Trevor Worthy.A sphenodontine (Rhynchocephalia) from the New Miocene of New Zealand and palaeobiogeography of the tuatara (Sphenodon. Proceedings of the Royal Society B, 21 January 2009