Mesolaria longala was named by Zhang (1986). Its type specimen is Shandong Museum Z80724, an exoskeleton, and it is a compression fossil. Its type locality is Zhouyingzi village, Luoping County (Shandong Museum collection), which is in a Callovian/Oxfordian lacustrine - large mudstone in the Jiulongshan Formation of China. It is the type species of Mesolaria.