There are three recognized genera in this North American Eocene fossil family: Mortonella, Periarchus, and Protoscutella. (Mortonella is problematic, and has been synonymized with Periarchus by some authors.) Osborn et al. (2013) note that one trait the Protoscutellidae share is "the presence of a fifth gonopore in the posterior interambulacrum", distinguishing them from all similar Eocene sand dollars.
Osborn et al (2013) acknowledged that the family was in need of revision, but here are some currently recognized species and where their fossils can be found. Mortonella sp. has been found in the Crystal River Formation of Florida (Oyen and Portell 2001); Periarchus lyelli in the Ocala Formation of Florida and Georgia, the Castle Hayne Limestone of North Carolina, the Santee Limestone of South Carolina, the Moodys Branch Formation of Alabama, the Caddell and Cook Mountain Formations of Texas, and in Louisiana and Mississippi (Kier 1980; Carter et al. 1989; Zachos and Molineux 2003; Zachos 2009; Osborn et al. 2016); Periarchus quinquefarius in the Tobacco Road Sand of Georgia (Huddleston and Hetrick 1979); Protoscutella conradi in the Castle Hayne Limestone of North Carolina and the Santee Limestone of South Carolina (Kier 1980; Osborn et al. 2016); Protoscutella mississippiensis in the Castle Hayne Limestone of North Carolina, the Warley Hill Formation of South Carolina, the Winona Sand of Mississippi, the Tallahatta and Lisbon Formations of Alabama, and the Weches and Mount Selman Formations of Texas (Kier 1980; Zachos and Molineux 2003; Osborn et al. 2016); Protoscutella palmeri in the Santee Limestone of South Carolina (Osborn et al. 2013); Protoscutella plana in the Santee limestone of South Carolina (Osborn et al. 2016); Protoscutella pentagonium in Florida (Zachos and Molineux 2003); and Protoscutella tuomeyi in the Castle Hayne Formation of North Carolina, the Warley Hill and Santee Formations in South Carolina, and the Weches Formation in Texas (Zachos and Molineux 2003; Osborn et al. 2016).
