Muscle scars, systematics and mode of life of the Silurian family Drahomiridae (Mollusca, Tergomya)
Radvan J. Horný
The Silurian tryblidioidean Family Drahomiridae, established as a subfamily by Knight and Yochelson (1958), was defined as to contain low spoon-shaped shells with seven pairs of muscle scars in the dorsal area. Originally it contained the genus Drahomira BARRANDE in PERNER, 1903. In 1995, Horný added a related genus, Pragamira. During the new investigation of additional material, the genus Archaeopraga HORNÝ, 1963 was studied in detail and its lateral scars were ascertained also in the genera Drahomira and Pragamira. Moreover, the typical drahomirid muscle scar pattern was found also in two additional specimens of Archaeopraga pinnaeformis (PERNER, 1903). The Family Archaeopragidae HORNÝ, 1963 is thus synonomous with the Family Drahomiridae which contains tryblidioidean genera with mostly seven sets of dorsal paired muscle scars and two long, large, lateral pedal muscle scars. The lateral scars are interpreted as a musculature assuring balance, necessary for the mode of life on shells of dead orthoconic nautiloids and may be analogous to the horseshoe-shaped scars in the archinacellid gastropods.