ABSTRACT
The phylogenetic relationships among the major groups of Pulmonata were studied by the information derived from a concatenated dataset consisting of mitochondrial (16S and COI) and nuclear (18S and 28S) markers. Heterobranchia are recovered as monophyletic. Euthyneura as paraphyletic due to the emergence of taxa from Opisthobranchia and lower Heterobranchia. The major groups of Pulmonata, namely Stylommatophora, Veronicellidae, Onchidiidae, Otinoidea, Siphonarioidea and Hygrophila are recovered as monophyletic. Monophyly of Basommatophora was not confirmed due to the variable position of Siphonarioidea and Amphiboloidea. Evolutionary divergence times for different taxa were also estimated using a relaxed molecular clock method in Bayesian evolutionary analysis by sampling trees (BEAST). The common ancestor of Heterobranchia and Caenogastropoda was originated in the Silurian period and the common ancestors of Euthyneura and Pulmonata were originated in the Carboniferous and lower Triassic periods, respectively.