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The Rise of Spiders and Roaches

The 100-million-year-old spider Chimerarachne preserved in Burmese amber. Credit: Dr Diying Huang, Nanjing Institute of Geology and Palaoentology

The 100-million-year-old spider Chimerarachne preserved in Burmese amber. Credit: Dr Diying Huang, Nanjing Institute of Geology and Palaoentology

By John Long

Tiny fossils preserved in amber reveal when spiders evolved their ability to spin webs and cockroaches first spread across the globe.

While it’s true that dinosaurs always take up the oxygen in the room when it comes to media coverage of palaeontology, it’s great to see that tiny fossils beautifully preserved in amber can also share the limelight. Recent finds of a remarkable fossil spider named Chimerarachne perfectly preserved in 100-million-year-old Cretaceous Burmese amber are able to add to the story of how spiders evolved their incredible ability to spin webs. The new discoveries were made by a team of scientists led by Diying Huang of the Nanjing Institute of Geology and Palaeontology in China (https://goo.gl/ekh2AA).

Chimerarachne, meaning “chimera spider”, is a bizarre-looking spider with very long segmented tail that tapers into a flexible appendage – a primitive condition for spiders that is also found in an ancient group called the uraneid spiders, and to a much smaller degree in living spiders called mesotheles. These include spiders with segmented abdomens such as

Liphistius and Heptathela. Fossil mesotheles go back to the Carboniferous of France, around 295 million years ago.

A phylogenetic analysis of Chimerarachne suggests that the spinnerets used to make webs evolved more basally in the tree of spiders than previously thought. This discovery also extends the known range of the uraneid spiders by another 170 million years from when they were thought to have become extinct.

Burmese amber is remarkable for hosting the greatest diversity known of spiders and other arachnids from anywhere in the world, with 244 species described so far, mostly spiders. This indicates how ecologically complex the Cretaceous forests were in Asia at the time.

Also found in Cretaceous Burmese amber is a bizarre fossil cockroach named Manipulator. It had a body shaped like a praying mantis with an extra set of eyes on top of its head, and was undoubtedly a predator equipped with very large mouthparts and flexible neck joint to move its head around. In fact, praying mantises are close relatives of cockroaches.

When did cockroaches first become widespread across the globe? Probably during the age of dinosaurs. Recent work published in Molecular Biology and Evolution (https://goo.gl/FQGWv3) by Thomas Bourguinon of the University of Sydney has determined that most of the modern families of cockroaches evolved and dispersed during the break-up of the supercontinent of Pangaea between 200 million and 135 million years ago.

The evidence for this comes from a phylogenomic study of the mitochondrial genomes of 119 cockroach species to estimate their divergence times. At least our domestic cockroaches today are mostly small. The largest known cockroaches were mouse-sized creatures that lived about 300 million years ago when global oxygen levels were very close to 30%.


John Long is Strategic Professor in Palaeontology at Flinders University, and is current President of the Society of Vertebrate Paleontology.