Coming Onto the Land

When you consider the years paleontologists often spend in daily and intimate contact with their fossils, it’s not very surprising that they come to regard their long-gone animals as pets. Some work on the show dogs of the fossil world; they brag about how fast their velociraptor ran or how efficiently their saber-toothed tiger could sever a spinal cord. But when you listen to Jenny Clack talk about her pet, a fossil creature named Acanthostega that she has been working on for seven years, she sounds like the owner of a sweet, homely mongrel. It wasn’t very smart, she says. It probably spent a lot of its time sitting at the bottom of lagoons, hidden in the muck, waiting for something to come by it could eat. Clack has helped make a reconstruction of it; its salamander-like body has big glassy eyes sitting on top of a flat, Muppet-style head, ...