Hystrix africaeaustralis, Crested Porcupine
Crested porcupines are very strange. They are the name sake for Hystricomorpha, the large clade of rodents that includes some Old World groups such as the hystricid porcupines, the gundis, mole rats, and cane rats, as well as the wonderful New World clade Caviomorpha, including chinchillas, guinea pigs, capybaras, pacas, new world porcupines, and the tuco-tucos (mole rat analogues). All of these hysticomorphs are distinguished (formly thought to be a strict synapomorphy) by their hysticomorphous jaw configuration, where the medial masseter penetrates the enlarged infraorbital foramen (whole anterior to the orbit for the eye above). What makes crested porcupines so interesting, however, other than their massive spines an quills and being the second largest rodents in the world, are their highly inflated nasal sinuses that give them their distinctive convex, domed skulls. While this morphology is currently unexamined and unexplained, a similar, convergent morphology is seen in the New World porcupine Coendou prehensilis, the Brazilian Porcupine. Why? Who knows, but it's an interesting question.