Here is a lovely little creature from Sri Lanka, Pettalus cf. cimiciformis, a member of the same lineage that includes the daddy longlegs we’re all familiar with. You could call it a daddy longlegs too, but its legs aren’t particularly long (plus it’s tiny–the size of a sesame seed.)
It may not seem like much, but it poses a fascinating riddle. It belongs to a family of daddy longlegs called Petallidae. Below is a map of where other species of Petallidae can be found. They seem to be scattered randomly across the world. But petallids are terrible at dispersing. Their ranges are small (usually less than fifty miles). And they live only on ancient continent crust. Petallids live on Sri Lanka and on Madagascar. But they live on none of the young volcanic islands in between–or anywhere else in the world, for that matter. So they couldn’t have swum or flown to their farflung locations. Yet DNA evidence clearly shows that the petallids all descend from a common ancestor. So, how did they get there? The answer lies below the fold…
Here is a picture of the southern hemisphere about 150 million years ago. Ever since the continents formed, they have been drifting slowly across the surface of the planet. Back in the Jurassic Period, South America, Africa, Antarctica, India, and Australia were all welded together. So were a few islands, such as Madagascar and Sri Lanka. And the current ranges of petallids, so fragmented today, appear to have covered the southern part of this vanished supercontinent. The lineage first evolved there, slowly spread out across a continuous landmass, and then rode across the planet on drifting continents.
The journeys of animals and plants are the subject of one of science’s lesser known branches, historical biogeography. I’ve always thought its obscurity was a shame, because it can do such a remarkable job of illuminating the history of the planet through a comparison of living things. Much to my surprise, stumpy daddy longlegs are turning out to be among the best guides to that history. The full story can be found in my article in tomorrow’s New York Times, plus an even more detailed map. (Two papers in press can be found here and here.)
Update: I’ve also posted the article on my web site.
Go Further
Animals
- These 'trash fish' are among Earth's most primitive animalsThese 'trash fish' are among Earth's most primitive animals
- These photos are works of art—and the artists are bugsThese photos are works of art—and the artists are bugs
- The epic migration of a 6-foot long, 200-pound catfishThe epic migration of a 6-foot long, 200-pound catfish
- Frans de Waal, biologist who studied animal emotion, dies at 75Frans de Waal, biologist who studied animal emotion, dies at 75
Environment
- Are synthetic diamonds really better for the planet? The answer isn't clear-cut.Are synthetic diamonds really better for the planet? The answer isn't clear-cut.
- This year's cherry blossom peak bloom was a warning signThis year's cherry blossom peak bloom was a warning sign
- The U.S. just announced an asbestos ban. What took so long?The U.S. just announced an asbestos ban. What took so long?
- The most dangerous job? Inside the world of underwater weldersThe most dangerous job? Inside the world of underwater welders
- The harrowing flight that wild whooping cranes make to surviveThe harrowing flight that wild whooping cranes make to survive
History & Culture
- Why Swedish children celebrate Easter by dressing up as witchesWhy Swedish children celebrate Easter by dressing up as witches
- Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’
- A surprising must-wear for European monarchs? Weasels.A surprising must-wear for European monarchs? Weasels.
- Meet the woman who made Polaroid into a cultural iconMeet the woman who made Polaroid into a cultural icon
Science
- LED light treatments for skin are trendy—but do they actually work?LED light treatments for skin are trendy—but do they actually work?
- NASA smashed an asteroid. The debris could hit Mars.NASA smashed an asteroid. The debris could hit Mars.
- Humans really can have superpowers—scientists are studying themHumans really can have superpowers—scientists are studying them
- Why engineers are concerned about aging infrastructureWhy engineers are concerned about aging infrastructure
Travel
- Why you should try beach-hopping by boat around Paxos, GreeceWhy you should try beach-hopping by boat around Paxos, Greece
- Mansion museums show visitors the gritty side of the Gilded AgeMansion museums show visitors the gritty side of the Gilded Age
- 2024 will be huge for astrotourism—here’s how to plan your trip2024 will be huge for astrotourism—here’s how to plan your trip