Brush footed trapdoor spider fossil a major find in central NSW

This is the first fossil from the brush footed trapdoor spider family ever found and it five times bigger than any living relative

Untamed and ready to pounce the Megamonodontium mccluskyi brushed trapdoor spider was five times the size of any living relative and most likely far more venomous – Image: Alex Boersma

Be still, very very still, don’t make any sudden move as you are as close to a brush footed trapdoor spider, Megamonodontium mccluskyi, as anyone has been and its assumed its venom could take down a baby elephant.

There is just one saving grace, this forebear to the current day highly venomous trapdoor spider with a body length five times bigger than the current living species, is thought to have disappeared over 10 million years ago.

A team of Australian scientists led by Australian Museum (AM) and University of New South Wales (UNSW) palaeontologist Dr Matthew McCurry have formally named and described the fossil spider, Megamonodontium mccluskyi, estimated between 11 to 16 million years old.

Found at McGraths Flat in central NSW, a fossil site known for its iron-rich rock called ‘goethite’, this genus of spiders is the first ever spider fossil of the Barychelidae family to be found.

Australian Museum (AM) and University of New South Wales (UNSW) palaeontologist Dr Matthew McCurry led the expedition that has formally named and described the fossil spider Megamonodontium mcclusky

Similar to the living genus, Monodontium (a brushed trapdoor spider) but five times larger, the spider was named after Dr Simon McClusky who found the specimen. A geospatial scientist based in Canberra, McClusky volunteers his time helping on palaeontological excavations.

Dr McCurry said that there have been very few fossil spiders found in Australia and that makes the discovery very significant.

“Only four spider fossils have ever been found throughout the whole continent, which has made it difficult for scientists to understand their evolutionary history. That is why this discovery is so significant, it reveals new information about the extinction of spiders and fills a gap in our understanding of the past,” Dr McCurry continued.

“The closest living relative of this fossil now lives in wet forests in Singapore through to Papua New Guinea. This suggests that the group once occupied similar environments in mainland Australia but have subsequently gone extinct as Australia became more arid,” Dr McCurry concluded.

Queensland Museum arachnologist, Dr Robert Raven, who was the supervising author of the study said this was the largest fossil spider to be found in Australia.  

“Not only is it the largest fossilised spider to be found in Australia but it is the first fossil of the family Barychelidae that has been found worldwide,” Dr Raven confirmed.

“There are around 300 species of brush-footed trapdoor spiders alive today, but they don’t seem to become fossils very often. This could be because they spend so much time inside burrows and so aren’t in the right environment to be fossilised,” Dr Raven added

What a find inside a rock is this fossilised brushed trapdoor spider similar to the living genus, Monodontium but five times larger and now named after Dr Simon McClusky who found the specimen

University of Canberra Associate Professor Michael Frese, who used stacking microphotography to scan the fossils said that the fossils from McGraths Flat show an amazing level of detailed preservation.

“Scanning electron microscopy allowed us to study minute details of the claws and setae on the spider’s pedipalps, legs and the main body.

“Setae are hair-like structures that can have a range of functions. They can sense chemicals and vibrations, defend the spider against attackers and even make sounds,” Associate Professor Frese confirmed.

The fossil is now housed in the AM’s palaeontology collection and is available online for researchers to study.

McGraths Flat

First found in 2017, McGraths Flat is named after Nigel McGrath who discovered the first fossils from the site. The site is located near Gulgong in central NSW (Gulgong is a Wiradjuri word that means ‘deep waterhole’).

The Miocene Epoch

23 to 5 million years ago was a time of immense change in Australia. The Australian continent had separated from Antarctica and South America and was drifting northwards. When the Miocene began there was enormous richness and variety of plant and animal life in Australia.

But at around 14 million years ago an abrupt change in climate known as the “Middle Miocene Disruption” caused widespread extinctions. Throughout the latter half of the Miocene, Australia gradually became more and more arid, and rainforests turned into the dry shrublands and deserts that now characterise the landscape.

The newly discovered fossil site, McGraths Flat, provides an unprecedented look into what Australian ecosystems were like prior to this period in time.

Prof Michael Frese (right) and the dig team found that in terms of size, Megamonodontium mccluskyi is the second largest fossil spider worldwide, being rivalled only by Mongolarachne jurassica  Seldon, Shih and Ren, 2013 from the Jurassic of China, which has a slightly larger body length of 24.6 mm (Selden et al. 2013) – Image Salty Dingo

Key facts

MioceneSite revisited-(c)Alex-Boermsa

• A new fossil spider has been formally named and described Megamonodontium mccluskyi is between 11 to 16 million years old

• This is the first ever spider fossil of the Barychelidae family to be found

• Similar to the living genus, Monodontium (a brushed trapdoor spider) but five times larger, the spider was named after Dr Simon McClusky who found the specimen

• There have been very few fossil spiders found in Australia which makes the discovery very significant

How the brushed trapdoor spider measured up

Characteristicssize (mm)
Body length 23.31 
Carapace length 11.18 
Cephalothorax width 6.85 
Abdomen length 12.26 
I femur length 5.99 
I patella length 1.96 
I tibia length 5.30 
I metatarsus length 7.00 
II femur length 6.23 
II patella length 2.31 
II tibia length 4.83 
II metatarsus length 5.51 
III femur length 4.26 
III patella length 1.79 
III tibia length 2.81 
III metatarsus length 2.36 
IV femur length 5.19 
IV patella length 2.60 
IV tibia length 3.85 
IV metatarsus length 4.31