Marsupites is an extinct genus of crinoids from the Santonian stage of the Late Cretaceous.
Biostratigraphic significance
The International Commission on Stratigraphy (ICS) had provisionally assigned the extinction of Marsupites testudinarius as the defining biological marker for the start of the Campanian stage of the Late Cretaceous, 83.6 ± 0.2 million years ago, until a new final definition was eventually ratified in 2022, based instead primarily on magnetostratigraphy.
Distribution
Fossils of the genus have been found in: Lipnik, Poland Haslam Formation, British Columbia, Canada
References
Bibliography
Fossils (Smithsonian Handbooks) by David Ward (Page 173)