Fossil parasitic copepods from a lower cretaceous fish.

Well-preserved Lower Cretaceous fossil copepods related to the super-family Dichelesthioidea have been collected from the gill chamber of the ichthyodectid fish Cladocyclus gardneri. The fossils provide conclusive evidence suporting recent theories that link caligid copepods, which are parasitic on fish, to the invertebrate-associated siphonostomes. This is the first discovery of fossil parasitic copepods, and they are by far the oldest copepods of any sort known.