SINGAPORE - A snake not seen in Singapore for over 172 years was spotted in Bukit Timah Nature Reserve last month, according to a report filed on Thursday (Oct 31).

Dr John van Wyhe, a senior lecturer at the National University of Singapore, found the lined blind snake, also known by its scientific name Ramphotyphlops lineatus, dead on a bike trail at the nature reserve on Sept 16.

Striped and worm-like, but over 50cm in length, the black snake's discovery changes its previous status of "indeterminate" - or in need of verification - to "extant", now that its existence has been definitively recorded here in modern times.

"It was quite unexpected to find it in Singapore since it is an uncommonly seen species even in Malaysia," said Mr Law Ing Sind, who helped identify the snake. "We still don't know the current population size or how that population is distributed in Singapore."

The 23-year-old co-founder of the Herpetological Society of Singapore, an enthusiast group for the study of reptiles and amphibians, said the features and habits of the lined blind snake could explain its elusiveness.

"The (snake) tends to burrow into the soft tropical soil in search of invertebrate prey, and so spends its entire life underground," he explained.

"They also have a great deal of superficial similarity with worms, so the public may just dismiss this as another worm when they encounter one."

Last seen in 1847, the lined blind snake has been so difficult to find that a 2015 National Parks Board (NParks) survey for reptiles and amphibians at Bukit Timah failed to detect it.

The recent rediscovery of the snake was documented in a Thursday report by Mr Law, Dr van Wyhe, and Ms Rachel Seah in the Singapore Biodiversity Records, which is hosted by Lee Kong Chian Natural History Museum for local sightings. The trio noted in the report that the specimen found was the longest one of the species.

They wrote: "The featured specimen is also of interest in that it is about 4cm longer than the maximum total length recorded for the species, which is 48cm total length."

Due to its long 172-year absence from official records, "the featured specimen would, therefore, represent a significant re-discovery in Singapore", they added.

Following Dr van Wyhe's discovery of the snake last month, the dead reptile was moved to the Lee Kong Chian Natural History Museum with NParks permission.

Taking a live animal from the wild without permits or permission by NParks is an offence here.

In May, NParks said it found more than 40 of what could turn out to be potentially new species to Singapore following a multi-year survey of the Bukit Timah Nature Reserve between 2014 and last year.

The new species included a six-eyed spider with shiny, hardened and dark-coloured plates over the front part of its body, which has been named Paculla bukittimahensis after the reserve.

The lined blind snake, however, was not detected then.

Mr Law said this was not surprising since there are about 55 terrestrial species of snakes in Singapore.

"Given that Bukit Timah hosts Singapore's oldest and largest patch of primeval forest, there is a potential to discover more surprising records and even potentially new species in the area," he said.

Several animals have been rediscovered - and even newly discovered - in Singapore in the past few years.

In August, it was reported that two species of flower flies were sighted again after they were last seen in Singapore almost 200 years ago.

One, a wasp-mimic, was rediscovered on Pulau Ubin this year, while the other flower fly was rediscovered in 2017 at Bukit Timah Nature Reserve.

In 2014, two species of non-poisonous snakes new to Singapore were identified by researchers - a blackwater mud snake and a smooth slug snake.

Then back in 2011, two neptune's cup sponges - once thought to be globally extinct - were found in Singapore waters.