no smaller fundamental particles than neutrinos have been discovered. Neutrinos are considered elementary particles with extremely small masses and no electric charge. They were first postulated in the 1930s and were experimentally detected in the following decades. Neutrinos are known to have a tiny mass compared to other elementary particles, but they are not considered point-like particles and do have a non-zero size.
However, it's important to note that scientific discoveries and advancements continue to occur. There may have been developments in the field since then that I'm unaware of. To stay updated on the latest scientific discoveries, I recommend referring to reputable scientific sources or news outlets.