PlaesiomyidaePlaesiomyidae is a family of extinct lamp shells belonging to the order Orthida.Fossil recordFossils of Plaesiomyidae are found in marine strata from the Ordovician until the Silurian .Genera†Austinella Foerste, 1909†Bokotorthis Popov et al., 2000†Campylorthis Ulrich and Copper, 1942†Chaulistomella†Dinorthis Hall and Clarke, 1892†Evenkina†Madiorthis Zuykov and Harper, 2008†Metorthis †Multicostella†Plaesiomys Hall and Clarke, 1892†Retrorsirostra Schuchert and Cooper, 1932†''Valcourea''