Adult female spiders and baby spider lings have been found trapped in Burmese amber dating back about 99 million years.
The Lagonomegopidae family of spiders is now extinct, but spiders have a long history and first appeared during the Carboniferous period between 359 to 299 million years ago.
The fossilized Burmese amber pieces tell two different stories. A study detailing the observations of the amber specimens published on Tuesday in the journal Proceedings of the Royal Society B: Biological Sciences.
One “shows a female lagonomegopid spider clutching an egg sac containing eggs about to hatch (you can see the little pre-hatchlings within the egg sac),” said study author Paul Selden, the Gulf-Hedberg Distinguished Professor Emeritus at the University of Kansas. “This is exactly how a living female spider which is nestled in a crevice in tree bark would look (in this case, right before being swamped with tree resin).”
Other pieces of amber show a group of tiny spiderlings that had just hatched. This shows that a female lagonomegopid spider guarded her egg sac from harm. Once the spiderlings hatched, they stayed together and were guarded by their mother as evidenced by the Lagonomegopidae leg fragments from the same piece of amber.
This suggests that baby spiderlings probably stuck close to their mother for a while after birth.
The researchers were pleasantly surprised by “just how everything fitted beautifully into place. We had three or so specimens which all corroborated each other in the story,” Selden said.
The researchers used CT-scanning to spot tiny eyes and other features that revealed the identity of the spider as well as the tiny spiderlings in 3D detail.
Lagonomegopidae spiders can be distinguished because they had a large pair of eyes situated at the front corners of the head. Other known fossils of these spiders has revealed that they had reflective tapetum in their eyes, similar to other nocturnal creatures, like the way a cat’s eyes flash in the dark.
These now-extinct spiders look similar to modern jumping spiders, but they aren’t related at all.