Melanopsis pachya is known only from its type locality, ‘les Sources de Mézérib' (Muzayrib), northwest of Deraa (or Daraa), a town in southern Syria. Mezerib is a small karstic spring located 5 km north-west of the city (Heller et al. 2005).
There is no population information available for this species. It has not been recorded since its original description and it may be extinct.