A fossil specimen misidentified since its discovery during the Civil War and correctly identified by a University of Michigan researcher reveals an evolutionary leap: It marks the first time this line of sea creatures is known to have left the ocean.
U-M postdoctoral fellow Richard J. Knecht found that the specimen, identified as a seaworm for well over a century, is actually a kind of invertebrate called a lobopod. Lobopods are soft-bodied invertebrates that closely resemble a “worm with legs,” according to Knecht, who led the work as a researcher at Harvard University.
Lobopods are considered the ancestor to all arthropods—all insects, spiders and crustaceans—and scientists have long thought that lobopods, which first appeared in the fossil record more than 500 million years ago, only lived in marine environments.
Now, Knecht suggests that the specimen, named Palaeocampa anthrax, likely lived in a freshwater environment. Knecht also found the specimen likely had chemical defenses that suggest it may have spent at least part of its time on land. The study, which was supported by the National Science Foundation, was published in Communications Biology.
“This is the first evidence that we have that this group actually did leave the ocean. Transitioning from a saltwater environment, even to a freshwater environment, is a major evolutionary step,” Knecht said. “Any time you find a group that made this transition, it’s not just insightful, it’s really important evolutionarily to try to understand how this happened.”
