You may be a little out of date there. The “particle zoo” was the term used until the 1960s to describe the bewildering array of new particle discoveries. Gell-Mann and Zweig independently came up with quark theory in 1964 and Gell-Mann got the Nobel Prize for it in 1969 after accelerator experiments confirmed the existence of quarks. Suddenly all the new particles were explicable in terms of different quark configurations.
Quarks have two types of “charge”, called colour and flavour, that govern their interactions with the strong and weak nuclear forces. They’re more complicated than electric charge, coming in three and six different varieties respectively. That’s basically why there are more configurations of them, leading to the particle zoo. (Quarks also have electric charge, in fact they’re the only particle which feels all four of the fundamental forces).
Once the quark theory arrived, the list of known (and assumed fundamental) particles started to settle down. You had six different predicted flavours of quarks (in three pairs), although it took a while to actually discover them all, and those may have been some of the new discoveries you’ve heard of. The last of them was discovered at Fermilab in 1995. You had the leptons (including electrons), which also came in three different flavours along with three associated neutrinos. (The electron was discovered by Thompson in 1897, the muon by Anderson in 1936, and the tauon by Perl in 1976).
Each of the types of particles has an associated antiparticle. Antiparticles were first posited on purely quantum theoretical grounds by Dirac and Weyl in the late 1920s, and the first of them – the positron – was discovered in 1932 by Anderson who got a Nobel for it in 1936, the same year he also discovered the muon.
Then there are the bosons which are the carriers or intermediaries of the known fundamental forces. There are photons for electromagnetism and gluons for the strong nuclear force. The picture was completed for the weak nuclear force by the discovery of electroweak theory for which Weinberg, Salaam and Glashow won the Nobel prize in 1979. This predicted three new type of bosons for the weak force. There is no known boson for the gravitational force because we don’t have a quantum theory for it, but the graviton has been named in advance in expectation of its arrival. Finally, there is one more boson – the Higgs – associated with mass.
And that’s it – all our known particles are organised into the so-called Standard Model, which reflects the beautiful symmetries that govern their arrangements and force interactions. (Actually, all “ordinary” matter of everyday experience is made out of a single flavour of quarks and leptons, the first generation column below).
So why do we think these particles and bosons are fundamental? There are a number of reasons. Firstly, we have theories dealing with a small set of quantised properties that seem to explain pretty much everything there is to explain about the fundamental particles.
Secondly, they show no sign of internal structure in high energy particle experiments. In the early 1900s, Geiger, Marsden and Rutherford demonstrated that atoms had internal structure by shooting alpha particles at a gold leaf target. The distribution of deflection angles clearly proved the existence of a tiny nucleus in a comparatively vast atom. Similar scattering experiments at much higher energies showed the existence of quarks inside nucleons in the late 1960s at SLAC. To date, the highest energy experiments show no sign of substructure in quarks or electrons. We went from from 5 MeV (million electron Volts) in the Rutherford-Geiger-Marsden experiments, to 20 GeV (giga- or billion electron Volts) in the electron-nucleon SLAC experiments. Today’s proton beam collisions at the LHC are at energies of 13 TeV (trillion eV) – a thousand times the original quark scattering energies. No additional structure has been detected, nor is expected on theoretical grounds.
Thirdly, the fundamental particles have invariant physical properties – definite charge to mass ratios, spin values, and so on. And fourthly they are stable against decay. Whereas composite particles can transmute into other particles under various force interactions, that’s not the case for the fundamental particles. Actually, it’s a bit more complicated than that – there are conservation rules which preserve the number of quarks and leptons in interactions, though certain flavour changes are allowed.
Does that mean the Standard Model is definitely the last word? Not quite. The Higgs was the final addition to the model in 2012, but different versions of it at higher energies are within the bounds of current theory. It’s conceivable – but considered very unlikely – that there is a fourth generation of quarks and leptons to be discovered at vastly higher energies. There are also various theories like supersymmetry that propose supersymmetric partners to each of the standard model particles. None have been discovered, though the proposed names are cute – squarks, selectrons, sneutrinos . Extensions to the Standard Model are required to explain how physics operated in the high energy environment close to the Big Bang, but all avenues have thus far drawn a blank. But any anticipated new particles will themselves be considered as fundamental as the existing ones.