THE NEW YORK TIMES - If you look around Waukesha County in Wisconsin today, it can be difficult to imagine a tropical coastline teeming with trilobites, the oldest known scorpions and jawless vertebrates. But 437 million years ago, during the Silurian period, these creatures lived and died there, some getting washed into a salty cove and entombed under mats of microbes. Soft-bodied species were preserved in remarkable detail, with some retaining traces of eyes, guts and even hearts.
A team of scientists recently described the region’s latest fossil find: the oldest known species of leech. In a paper published Wednesday in the journal PeerJ, scientists say the parasitic worm pushes back the origins of these organisms by at least 200 million years. They also highlighted its remarkable powers of suction and surprising appetite for prey.
Leeches today are both friend and foe, helping to draw blood in traditional medicine and menacing journeys through wetlands. But the evolutionary origins of leeches remain enigmatic because their soft bodies rarely fossilize.
“Leeches are an entire branch of the tree of life for which we basically have no evidence in the fossil record at all,” said Karma Nanglu, a paleontologist at the University of California, Riverside, and one of the authors of the paper.