Quark
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968. Accelerator experiments have provided evidence for all six flavors. The top quark, first observed at Fermilab in 1995, was the last to be discovered.
Richard Dalitz
Dalitz was directly involved in pioneering quark research since the early 1960s, at a time when leading theorists considered quarks as purely mathematical entities, and he participated in the identification of the top quark. In 1965 he began a series of lectures on the physics of quarks that became a "bible for the relatively few who then took it seriously."