While visiting the Gallery of Natural History at the Arizona Historical Society Museum at Papago Park (1300 N. College Ave, Tempe Arizona 85281) I saw fossil specimen (AHS-NH#9854) Encope micorpora (Agassiz, 1841) sand dollar. Creatures like this are alive today and existed back to the Pliocene This one was found in El Golfo, Mexico.
Image of museum specimen taken October 2014.
Source to refer to:
http://www.nhm.ac.uk/research-curation/research/projects/echinoid-directory/taxa/taxon.jsp?id=2133
http://www.nhm.ac.uk/research-curation/research/projects/echinoid-directory/taxa/specimen.jsp?id=7192