From the perspective of Latin grammar, I’m curious as to why all the family names of animals have the same ending. For instance, there are Felidae (cats), Canidae (dogs), Phasanidae (pheasants), and so on. But at other taxonomic levels there are a variety of endings. Genus names seem to be whatever the Latin word for the animal is, like Homo, Felis, or Canis. Orders seem to have a variety of plural endings, depending on the original Latin derivation–Primates, Proboscidea, Sirenia, and so on. But the families are always -idae.
So how is it that the family name endings are all so uniform?
The ending is prescribed by International Code for Zoological Nomenclature. Families are described based on a type genus. This is not necessarily the most representative genus, but may be the best known or earliest described. The name of the family is constructed from the name of the type genus with the -idae suffix. For example, the type genus for the dog family is Canis, hence the name of the family is Canidae.
Families of Animals end in -idae, but families of Plants end in -aceae. There were (some exceptions, like grasses (Graminae), that have now been given standardized family names (Poaceae)).
Orders are more regular in some groups. For example, in birds and fish Orders always end in -iformes.
You want regularity, look to the International Code of Botanical Nomenclature, which prescribes the following endings:
[ul]
[li] Phylum/Divison: -phyta (plants & algae) or -mycota (fungi)[/li][li] Subphylum: -phytina (plants & algae) or -mycotina (fungi)[/li][li] Class: -opsida (plants), -phyceae (algae) or -mycetes (fungi)[/li][li] Subclass: -idae (plants), -phycidae (algae) or -mycetidae (fungi)[/li][li] Order: -ales[/li][li] Suborder: -ineae[/li][li] Family: -aceae[/li][li] Subfamily: -oideae[/li][/ul]
There are allowed exceptions for historically well-known names, like the aforementioned Graminae.