Three species of extremely primitive spider discovered in China

Three new species of an historical, secretive group of spiders, all native to Hunan province in China, have been described. These “mesothelean” spiders diverged from different arachnid households about 300 million years in the past and have unusual, primitive options not discovered within the overwhelming majority of residing spiders.

Most spider species on Earth at this time belong to certainly one of two teams: the heavy-bodied mygalomorph spiders – corresponding to tarantulas and the notoriously venomous funnel-web spiders – and the tens of 1000’s of araneomorph spider species, lots of which spin intricate, sticky webs.

Approximately 100 spider species belong to a poorly understood third group that fall beneath the suborder Mesothelae. The mesothelean spiders diverged from different spiders again when the planet’s rainforests had been filled with large arthropods and the very first reptiles. Today, the only real remaining mesothelean spider household retains some bodily options of the primary spiders. Unlike all different spiders, mesotheleans have a segmented stomach with plates on prime, very like a shrimp tail or a bee’s rump. Their silk-spewing spinnerets are uniquely slung beneath the centre of their stomach, relatively than positioned on the rearmost tip.

All fashionable mesothelean spiders reside in East and South-East Asia, are about 1 to 2 centimetres lengthy and ambush prey from tube-shaped lairs.

Xin Xu at Hunan Normal University in China and her colleagues gathered younger, mesothelean spiders in parks and villages in western Hunan province and reared them to maturity within the lab.

Based on variations within the form of the spiders’ sexual constructions, which can be utilized to tell apart between carefully associated species, the researchers decided they had been three beforehand undescribed species, all within the genus Songthela. The species – Songthela anhua, Songthela longhui and Songthela zhongpo – are named after areas within the province the place they had been discovered.

“[Mesotheleans] are living fossils, rare in general,” says Sarah Crews on the California Academy of Sciences in San Francisco, who wasn’t concerned with the analysis. “We are learning they are more diverse than once thought.”

Cataloguing this range is essential for understanding potential environmental impacts from human exercise corresponding to constructing or mining.

“If you don’t know what you are looking at, you can’t determine anything about its range or rarity,” says Crews.

Many mesothelean spiders are present in very small geographic areas, presumably as a result of their travel-averse, burrow-dwelling way of life, which has led to totally different species inhabiting remoted areas alongside the folds of mountainous, forested terrain. These slender ranges might make some mesotheleans – such because the Batu Caves trapdoor spider (Liphistius batuensis) from Malaysia, identified from solely a handful of limestone caves – significantly weak to extinction.

But there’s extra spider life to find. New species of spider are described day-after-day, says Crews, with 977 species added to the checklist identified by scientists in 2020.

“There are 50,979 currently valid species. Spiders are one of the most diverse terrestrial arthropod orders,” she says.