Researchers recently found new fossil records for an insect from the Jurassic whose classification was vexing them. A family had been named for the insect – Strashilidae – but what was it? Was it an ectoparasite, like a tick? After all, some suggested that the mouthparts were of the biting/sucking variety. Was it part of some mysterious, extinct clade? Well – no and nope. An impression fossil, described yesterday in Nature, indicates that this insect has the wings and genitalia characteristic of flies. But it was a weird fly. It had external gills along its abdomen, which only juvenile flies have, and aquatic juveniles at that. It also had those two wings, which only adult flies have. Argh! What’s a paleo-entomologist to do? The authors concluded that the external gills were a case of paedomorphosis, and that the gills facilitated an aquatic lifestyle. The Strashilidae might be related to a non-extinct group of flies, the Nymphomyiidae (see photo). Very cool stuff.
If you’ve never heard the word “paedomorphosis,” 1) you’re not alone, and 2) say it outloud, because it’s lovely: pay-dough-morf-o-sis. This cool word refers to adult animals that have features of juveniles — like this awesome, salamander called an axlotl, which has gills (most salamanders lose their gills when they become adults).