Some thoughts on categorization:
- Organization
- The main categorization scheme for mammals should be based on taxonomy. Categories should be subdivided as needed when their size demands it. Categories should be created preferentially for orders and families and categories for other ranks should generally be avoided. Very small taxa, such as Category:Vermilingua, should not be subdivided into smaller categories.
- Don't mix taxonomic categorization with other types of categorization. Categories like Category:Marine mammals should go or be restructured.
- "Extinct" and "prehistoric" categories should be organized in a consistent and sensible way. Currently, they are not.
- Naming
- Common names should be used where available (as in Category:Shrews).
- Scientific names should be used elsewhere. Pseudo-common names directly derived from the scientific name, such as Category:Pilosans, should be avoided; they do not agree with the naming of the parent article, may be confusing, and are unnecessarily long.