Is there any other genus that has only one living species?

The aardvark is not only the only species in its genus (plural is "genera", BTW) but the only one in its family and the only one in its order. I suspect that there may be some deep-sea animal that is the only living species in its class or even phylum.

There are many genera that include only a single species. For example, Darwin's frog, Rhinoderma darwinii is the only species in the genus Rhinoderma. The mata mata turtle, Chelus fimbriata, is another example. The green ratsnake, Senticolis triaspis, is another example. The Asian elephant (Elephas maximus), the pygmy hippo (Choeropsis liberiensis), the black vulture (Coragyps atratus), and the harpy eagle (Harpia harpyja) are other well known examples.

Generally, many genera include more than one species in the past, but because of extinction, often a single living species is left. Neanderthal man (H. neanderthalensis), and H. erectus are some of the species included in our own genus but their extinction left us the only species in our genus. Sometimes, however, a new species is so different from its closest relatives that there is little choice but to assign it to a genus of its own. The extinct Hasst's eagle, which evolved to prey on the extinct moa, Harpagornis moorei, is an example. It probably has no other close relative that can be assigned to the same genus.

Cephalotus.