An Introduction to Monotaxons

The Tree of Life

The 'Tree of Life' is a broad metaphor for the idea of a common ancestor. Every genetic difference is a new branch on the tree, signalling a new species, category, etc. from the smallest of single-celled ameobas to multi-celled bacteria, plants, bugs, fish, and animals. Through this tree, every living creature has a scientific name, through a series of taxons.

A chart of taxonomic rank, Homo Sapeins on the left and a Buttercup on the right

These are the broad taxonomic catergories of ranking most commonly used. In botany, for instance, instead of 'phylum' it's 'division.'
Some extra taxonomic divisions and terms you may see are:

Clade: a group of organisms linking and including its single ancestor.

Taxon: The name of a specific clade.

Sub- and Infra- Prefix: A further catergorization that is not signfigant enough to rank in the next taxon level

Enough with the background!

What is a Monotaxon?

Alright, alright. Hold your horses*

A Monotypic taxon, shortened to 'monotaxon,' is a taxonomic group that contains only one immediate subordinate taxon.
AKA, it is the only member of its own ~special~ taxonomic rank. Typically, they are the only genus in their own species. (or atleast, only living.)

*not a monotaxon

WHERE ARE THE ANIMALS?

Got it, got it. You don't have to shout.

Let's start with an easy one that everyone knows.

Narwhal

Indeed, the unicorn of the sea is a monolitihc taxon. Only member of the genus Monodon and one of the two living creatures in the Monodontidae family.

The other being

Beluga

Of course, the other odd foreheaded mammal of the sea would also be in this family.

Let's head to less cold waters and find...

Platypus

Indeed, our friend perry is the only member of the Ornithorhynchus genus, and recent fossil records place them as the only living memebr of the Ornithorhynchidae family.
They are also members of the funny monotreme order. (i.e. the only mammals to lays eggs O.O)