Sydney, Dec 21 (IANS): Scientists have discovered two critically endangered species of sea snakes, previously thought to be extinct, off the coast of Western Australia.

It is the first time the snakes have been spotted alive and healthy since disappearing from their only known habitat on Ashmore Reef in the Timor Sea more than fifteen years ago, the researchers said.

"This discovery is really exciting, we get another chance to protect these two endemic Western Australian sea snake species," said study lead author Blanche D'Anastasi from the James Cook University in Townsville, Queensland.

"But in order to succeed in protecting them, we will need to monitor populations as well as undertake research into understanding their biology and the threats they face," D'Anastasi said.

The discovery of the critically endangered short nose sea snake was confirmed after a Western Australia Parks and Wildlife officer, Grant Griffin, sent a photo of a pair of snakes taken on Ningaloo Reef to D'Anastasi for identification.

"We were blown away, these potentially extinct snakes were there in plain sight, living on one of Australia's natural icons, Ningaloo Reef," D'Anastasi said.

"What is even more exciting is that they were courting, suggesting that they are members of a breeding population," D'Anastasi noted.

The researchers also made another unexpected discovery, uncovering a significant population of the rare leaf scaled sea snake.

The discovery was made 1700 kilometres south of the snakes only known habitat on Ashmore Reef.

"We had thought that this species of sea snake was only found on tropical coral reefs. Finding them in seagrass beds at Shark Bay was a real surprise," D'Anastasi noted.

Both leaf scaled and short nosed sea snakes are listed as Critically Endangered under Australia's threatened species legislation, which means they have special protection.

The findings were detailed in the journal Biological Conservation.