They found it in the Illinois River near the city of Marseilles, Illinois, about 80 miles west of Lake Michigan—a strange entry point for an invasive Asian clam. The scientists who found it have no idea how it got there. But the discovery—along with genetic tests that confirm its uniqueness—means that a new species or “form” of invasive clam has made its official debut in North America. This is only the latest invasive aquatic species to settle in North America, said Illinois Natural History Survey aquatic ecologist Jeremy Tiemann, who discovered the new clam with INHS mussel field biologist Sarah Douglass in late 2015.