A chondrophorine (Medusoid hydrozoan) from the Lower Cretaceous of Chile

Aysenspriggia apelegensis is a new genus and species of a chondrophorine (j ellyfish-like hydrozoan) from the Lower Cretaceous Apeleg Formation of sout hern Chile. Despite their modern abundance chondrophorines are rare in the fossil record. The Apeleg Formation was deposited in a deep-water environme nt characterised by strong tidal currents. The fossils resulted from water- logged pelagic floats settling to the sea bed during periods of tidal slack water. Burial of the rigid three-dimensional chitinoid float resulted in p reservation as imprints on the base of the overlying sandstone. Soft parts of the animal were not preserved. The palaeoenvironmental interpretation is in accordance with that of other records of chondrophorines, including tho se from the Ediacaran fauna, which are apparently characterised by a bimoda l depth distribution. Like much of the Ediacaran fauna most chondrophorines are preserved as impressions on the base of sandstone beds.