Tusoteuthis is a genus of Cretaceous cephalopod molluscs. One species, T. longa, has been identified so far, and examination of gladius remains has yielded an estimated mantle length close to or equal to that of the modern giant squid. Recent studies have seen the vampire squid as a more likely descendant than modern day giant squid.
Despite Tusoteuthis' size, which was around 20 to 35 feet (6 to 11 meters) long with tentacles fully outstretched, it was still preyed on by other animals, especially the many, various predatory fish of the Western Interior Seaway. A fossil of the predatory salmonid, Cimolichthys nepaholica, was found with the gladius of T. longa in its gullet. The back portion of the gladius was in the stomach region, while the mouth of C. nepaholica had remained opened, suggesting that the fish had died in the middle of swallowing the squid, tail first. Researchers strongly suspect that as the fish was swallowing Tusoteuthis, the head and or tentacles remained outside the mouth, thus blocking the gills of the fish, and suffocating it as it swallowed its prey
It was also eaten by Hainosaurus