In order to be able to mount a MTP device (in my case it is a Oneplus One) in thunar file manager the following packages are needed: simple-mtpfs libmtp fuse fuse-libs gvfs-mtp. After installing the previous listed packages restart the system.
Once installed the device can me be mounted with simple-mtpfs _directory_, unmounted with fusermount -u _directory_ or mounted with thunar/gigolo/etc.