Pegomastax africana is a heterodontosaur from the early Jurassic period in South Africa. It was an exceptionally tiny dinosaur, measuring no more than 60 cm from beak to tail tip - or, about 2 feet long. With its parrot-like beak and large flat teeth it was clearly an herbivore, but it also held a pair of fangs or tusks on both the upper and lower jaws, possibly for interspecific combat or possibly for helping to pry up roots to eat. But its most remarkable feature is the dense coat of quills this dinosaur had. As should be unsurprising to any of you by now, we don't quite know what purpose they held. Were they for defense, like in today's porcupines, or perhaps for camouflage, or were they brightly colored or patterned and used in communication? Given their small size the former seems plausible, but we can't really say for sure.
The Pegomastax fossil was unearthed back in the 1960s but was never actually described and published until 2012. There are undoubtedly many other species currently suffering this same fate - sitting in museum cabinets, already collected but still waiting to truly be discovered. And dinosaurs of course aren't the only ones this happens to - new species of extant animals, as well as new anthropological discoveries, are still being found on a regular basis out of old overlooked museum collections.