Crustaceans including decapods, copepods, amphipods, cumaceans, tanaidaceans, ostracods, and isopods are major components of modern marine methane seeps, where they play a key role in structuring these hotspots of diversity in relatively deep waters. There is every reason to suspect they were common too in ancient seeps, but relatively few studies have focused on crustaceans from fossil seep deposits thus far. We hypothesize that crustaceans can be commonly found in Meso-Cenozoic seeps when many of the aforementioned groups were present and/or radiated. To this end, we review the global fossil record of crustaceans in seeps for the first time using the primary literature and newly collected specimens from the Late Cretaceous of South Dakota, USA. We find that seep crustaceans are much more common than previously known, are found on each continent, and occur more frequently starting in the Jurassic. Decapod crustaceans are represented by body fossils and traces (coprolites, repair scars in mollusks, and burrows), whereas only body fossils of ostracods and barnacles are known. Other groups are lacking. While modern seep decapods are dominated by galatheoid squat lobsters, alvinocaridid shrimps, king crabs, and true crabs, the fossil record is consisting primarily of callianassid ghost shrimps and true crabs thus far. Preservation and recognition are likely to have influenced this discrepancy. Finally, the relatively unexplored fossil record of seep crustaceans provides many opportunities for systematic and paleoecological research.
Crustaceans in cold seep ecosystems: fossil record, geographic distribution, taxonomic composition, and biology
