NANJING, April 10 (Xinhua) -- An international research team has unearthed a 160-million-year-old fossil in north China's Inner Mongolia Autonomous Region that provides insights into the evolution of parasitic worms.The study, conducted by researchers from the Nanjing Institute of Geology and Palaeontology under the Chinese Academy of Sciences (NIGPAS), was published in the journal Nature on Wednesday.The newly identified fossil, Juracanthocephalus, belongs to a group of parasites known as thorny-headed worms. These endoparasitic organisms inhabit both marine and terrestrial ecosystems across the globe.Measuring approximately one to two centimeters in length, Juracanthocephalus possesses a fusiform body divided into three distinct parts, including a proboscis, neck, and trunk. Researchers believe this ancient parasite likely inhabited amphibians and other hosts.Its retractable proboscis features hardened, curved hooks that would have firmly anchored it within the host's digestive tract. Its body was covered with 32 grooved ridges that acted like natural "anti-slip strips" to help it stay firmly anchored in the host's intestines.Most remarkably, researchers discovered an intricate jaw mechanism near the front of its trunk, consisting of multiple tooth-like structures that increase in size posteriorly, resembling a miniature meat grinder. Researchers speculate this jaw apparatus was primarily used to process nutrients from host tissues.Wang Bo, a researcher at the NIGPAS, said that this finding provides tangible evidence to address the longstanding mystery of acanthocephalan origins."These parasites can infect a wide range of hosts, including humans, pigs, dogs, cats and fish. Previously, how and when this bizarre group of parasites evolved from a free-living, non-endoparasitic ancestor had always been a mystery," said Wang.Wang noted that Juracanthocephalus' jaw structure resembles that of ancestral rotifers, while its hooked proboscis shows clear similarities to modern acanthocephalans. This clearly shows they evolved from free-living rotifers, developing specialized head structures to adapt to parasitic life, making them a crucial link in the evolutionary transition.Furthermore, the discovery challenges conventional wisdom about the habitat where these parasites first evolved. While modern acanthocephalans are predominantly marine, Juracanthocephalus was found in terrestrial deposits, suggesting these parasites may have first adapted to land animals before colonizing marine environments, Wang added.