According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal family-group taxon is a nominal genus called the 'type genus'; the family-group name is based upon that of the type genus."
Any family-group name must have a type genus (and any genus-group name must have a type species, but any species-group name may, but need not, have one or more type specimens).
The type genus for a family-group name is also the genus that provided the stem to which was added the ending -idae (for families).
In botanical nomenclature, the phrase "type genus" is used, unofficially, as a term of convenience.
In the ICN this phrase has no status.
The code uses type specimens for ranks up to family, and types are optional for higher ranks.
The Code does not refer to the genus containing that type as a "type genus".
- Example: "Poa is the type genus of the family Poaceae and of the order Poales" is another way of saying that the names Poaceae and Poales are based on the generic name Poa.
Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Type genus.