Complex sentence: The paper setting out this taxonomy was published in the journal "Malacologia"; it encompassed all known families of living slugs and snails, and also of fossil gastropods (including fossils that may or may not have been gastropods).
Split into simpler sentences: The paper setting out this taxonomy was published in the journal "Malacologia". The system encompasses all known families of living slugs and snails, and also of fossil gastropods (including some fossils groups which may or may not have been gastropods).