For now, there's just one existing fossil of the bizarre bug. But that specimen shows more than just one individual. In addition to the adult bug, which was less than half an inch long, eyeless and covered in body armor, the fossil includes 10 juveniles at various stages of development. Each of them is attached to its parent by a long string.
That connection — floating along tied to a hard shell — wouldn't be favorable for a parasite trying to leech nutrients off of the bug, according to researchers. That helped them determine that the tiny passengers could conceivably be a brood of babies. Further examination showed that the little legs on the creatures were consistent with ones you might conceivably find on juveniles of the same species as the adult.
"Modern crustaceans employ a variety of strategies to protect their eggs and embryos from predators — attaching them to the limbs, holding them under the carapace, or enclosing them within a special pouch until they are old enough to be released — but this example is unique," lead author Derek Briggs, Yale's G. Evelyn Hutchinson Professor of Geology and Geophysics and curator of invertebrate paleontology at the Yale Peabody Museum of Natural History, said in a statement. "Nothing is known today that attaches the young by threads to its upper surface."
It's likely that arthropods of this era experimented with all different kinds of child rearing: everything from total neglect to methods of brooding that kept their young even closer than Aquilonifer spinosus did.
But for Aquilonifer spinosus, at least, the kite-flying method didn't prevail. The researchers don't believe the critter is a direct relation of anything alive today. "It's what we refer to as being on a stem lineage," study author David Legg of the Oxford University Museum of Natural History told BBC News. "So it belongs to a group that would have evolved and diversified before the modern groups did."
Based on analysis of its features, the team classified it as a member of the group of organisms known as Mandibulata, which includes all insects, crustaceans and millipede-type creepy crawlers. But no descendants or close cousins of Aquilonifer spinosus live today, which could explain why their method of child care seems so alien — unless you yourself were once a leash kid.