Scientists were shocked to discover a fossilized spider sporting a fully erect penis.
The organ belongs to a 99-million-year-old harvestman arachnid that was apparently aroused at the time of its death.
Its body was found in a lump of amber on a tree in Burma, according to National Geographic.
Spiders and scorpions transmit sperm through modified legs, but most species of harvestmen have actual penises.
This particular erection was nearly half the length of the arachnid's entire body and developed after months of puberty.
No female was found nearby, however.
Jason Dunlop of the Berlin Natural History Museum offered another explanation. He told National Geographic,
The unique shape of the erection also helped scientists determine what type of harvestman this spider was.
The penis is reportedly different from those of all other harvestmen species, meaning this arachnid belongs to a previously unknown but possibly extinct family, Mashable reports.
Never before has a "male copulatory organ of this nature" been recovered in an amber deposit, researchers said, making this one of the oldest and most well-preserved penises ever found.
The discovery was first announced Thursday in The Science of Nature.
Citations: Scientists discover 99millionyearold spider and his preserved erection (Mashable), Fossil Daddy Longlegs Sports a 99-Million-Year Erection (National Geographic), Penis morphology in a Burmese amber harvestman (The Science of Nature)