Ancient fossilised, spider-like species have been imaged in 3D using thousands of X-ray scans and imaging software.
The two species, Cryptomartus hindi and Eophrynus prestvicii, lived 300 million years ago but are closely related to modern spiders.
The 3D images show that C. hindi grasped at prey with its front legs and E. prestivicii had defensive spikes on its back.
The results are published in the journal Biology Letters.
The 3D images were obtained by using a computed tomography scanner - a device that can take X-ray images from many angles.
Some 3,000 images of each fossil were obtained, and a custom software package developed at Imperial College London was used to assemble the images into a single, detailed, 3D virtual model of the creatures.
Those 3D images revealed new detail that previous fossil studies of the animals had not revealed.
C. hindi's front pair of legs, the team found, were angled toward the front, suggesting they were used to grapple with prey.
The researchers suggest that the animal probably was an "ambush predator" like the modern-day crab spider, lying in wait for prey to come close.
Another finding from the models is that E. prestivicii had hard spikes along its back, probably as a defensive measure making it less palatable to the amphibians that would have hunted it.
"Our models almost bring these ancient creatures back to life and it's really exciting to be able to look at them in such detail," said Imperial College London researcher Russel Garwood, lead author on the research.
"Our study helps build a picture of what was happening during this period early in the history of life on land."
The technique could be used to return to fossils that have already been analysed by conventional means, the researchers said.
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