A Taste For Bigger Things 

Leeches have long had a reputation for being the bloodsuckers of the animal kingdom. But a newly discovered fossil from Wisconsin suggests their ancient ancestors had a wider palate.  

A research team recently uncovered the world’s first known fossilized leech, preserved for some 430 million years in a rare geological formation known as the Waukesha Biota.  

The find pushes back the origins of the species by at least 200 million years, showing that leeches existed long before the rise of dinosaurs – and that their earliest relatives may have thrived in the sea rather than on land. 

“This is the only body fossil we’ve ever found of this entire group,” Karma Nanglu, co-author of a new study, wrote in a statement. 

The ancient specimen had a large tail sucker and a segmented, teardrop-shaped body, which are also found in modern leeches.  

However, this prehistoric creature lacked the forward sucker used by many of today’s species to pierce skin and draw blood. The team believes this absence hints that early leeches weren’t blood-feeders at all. 

“Blood-feeding takes a lot of specialized machinery,” Nanglu noted. “Anticoagulants, mouthparts, and digestive enzymes are complex adaptations.” 

Instead, Naglu proposed that early leeches swallowed small, soft-bodied marine invertebrates – or possibly sucked their bodily fluids. 

Modern leeches can be found everywhere and they have different feeding behaviors that range from scavenging to parasitic blood sucking.  

The discovery is significant because finding their fossils is nearly impossible: Leeches lack bones or shells that would make it easier to fossilize, explained Smithsonian Magazine. 

The authors added that the new study can help better understand the origin of these soft-bodied bloodsuckers. 

“We don’t know nearly as much as we think we do,” Nanglu said. “This paper is a reminder that the tree of life has deep roots, and we’re just beginning to map them.”