While some people might be less-than-pleased to share the planet with the eight-legged arachnids, spiders actually evolved way before Homo sapiens were roaming around being afraid of them. Now there are around 50,000 spider species but what did the first spiders look like, and how long ago were they crawling and climbing on planet Earth?
It is thought that the first ever spiders emerged on land around 400 million years ago, writes the Australian Museum. Before modern-day spiders evolved, thick-waisted ancestors called trigonotarbids roamed the land. They also lacked spinnerets (used to make silk) and had segmented abdomens.
One of the earliest spider-like fossils, also known as a proto-spider, dates back 380 million years and is called Attercopus fimbriunguis. Attercopus is not a true spider because the silk glands it possesses are not spinnerets; it is thought the silk was used to wrap eggs, line the burrow, or to smother prey. Attercopus also had a whip-tail similar to some scorpions.
A fossil find from Myanmar is thought to date back to the Cretaceous period, named Chimerarachne yingi. The animal is not quite a spider but thought to be a cousin, and the creature also had a tail and spinnerets. It was thought to share a common ancestor with both modern spiders and the Mesothelae, the oldest order of true spiders.
“We have known for a decade or so that spiders evolved from arachnids that had tails, more than 315 million years ago,” Dr Russell Garwood of The University of Manchester told the BBC.
Ancient spiders had their silk-producing organs under their middle rather than underneath their rear ends. These belonged to the order Mesothelae and were most likely ground-dwelling, with silk spinnerets and a venom gland.
Different spider or almost-spider fossils have turned up quite a few times. One of the oldest might be an arachnid preserved in iron carbonate for 305 million years. Idmonarachne brasieri did not possess spinnerets, and its abdomen was segmented rather than the fused abdomen seen in modern-day spiders. It’s likely this species was co-exisiting with the ancestors of modern day “true spider” species.
Not to be outdone, there is also Germany’s largest spider fossil, a similar age to Idmonarachne. Arthrolycosa wolterbeeki lived 310 to 315 million years ago and is the first true spider from the Palaeozoic in Germany.
Arthrolycosa wolterbeeki, the first Palaeozoic spider from Germany.
Modern spiders live on every continent on Earth and are successful in almost all habitats across the globe. From highly sophisticated webs to impressive mimicry, spiders have survived for the last 400 million years of Earth’s history. They could well continue for 400 million more.
Source Link: What Did The First Spiders On Earth Look Like?