The spiderlike creatures generally called daddy longlegs looked just as creepy 305 million years ago as they look today, according to a brand new computer model which shows the bugs settled into their modern forms early.
Scientists were able to create 3-D models of two ancient harvestmen species, members of groups known as the Dyspnoi and Eupnoi, using fossils discovered in mineral deposits in France more than 20 years ago.
Russell Garwood of the Natural History Museum in London said:
These fossils were “preserved in nodules of iron carbonate, or siderite,” and the mineral, well, the mineral “precipitates out early in the history of the rock, sometimes around animal remains, and prevents [the remains] from being crushed. … The animal then rots away, leaving a void in its shape.”
The new re-creations support the idea that daddy longlegs have changed remarkably little over time, even though the ancient arachnids lived at a time when their spider and scorpion relatives were still evolving into their current shapes.
For instance, spiders living 300 million years ago still bore resemblance of segments on their back halves, a trait modern spiders don’t have.
Scorpions living back then were also still relatively primitive, said Garwood, who conducted his research while at the U.K.’s Imperial College London.
Unlike modern species, ancient scorpions “had compound lateral eyes, median eyes near the front rather than the middle of their carapace, and a different position of the opening into the lungs,” he said.
The model of the Eupnoi species reveals long legs curved at the ends, a feature some modern harvestmen species use for holding vegetation while moving around from leaf to leaf.
In contrast, the Dyspnoi fossil had spikes on its back that it might have used to discourage the attention of predators.
A modern species of harvestman with spikes like these lives in moist, woody debris on the forest floor, and the team thinks the ancient Dyspnoi had a lifestyle like this.
That there were two discrete lineages of harvestmen living 305 million years ago attests to the theory that the creatures were among the earliest arachnids to take an evolutionary turn.
In another major discovery, genitals were used as important clues to identify many spider species as they can vary widely in shape and form between species. This variation in shape is thought to ensure females can only mate with males of their own species.
Fossils of both female and male harvestmen bearing genitals were originally uncovered in 2001 embedded in rocks from the village of Rhynie, near Aberdeen in Scotland. 400 million years ago, Rhynie would have resembled what Yellowstone park looks like today.
Yet another fascinating feature of the fossils is that they have large branching trachea which is the harvestmen equivalent to lungs. This is the oldest known example of air-breathing apparatus of this type found in arachnids and suggests the animals were land-living. Arachnids, along with all animal groups, started their life in the ocean.