Today, the only genus that has alive species in it is Castor.

It is usually treated as the only genus in the family Grossulariaceae.

It is the only genus of the family to have species which live in tropical waters.

Prestonella was considered as the only genus in the family Prestonellidae.

They are presently the only genus in the tribe Tomarini.

It is the only extant genus in the family Oxynotidae.

The only other genus in the family is Brochothrix.

They are the only genus still living in the family Amphiumidae.

Previously, it was the only genus in the family Callitrichaceae.

It is the only genus currently known in the Coriariaceae family.