Key to Families of Australian Aquatic Crustacea
This key is apart of the Keys to Australian Aquatic Macro-Invertebrates. This key attempts to cover all families of Crustacea known to occur in Australian inland waters, fresh or salt, permanent or temporary, running or still.
The first two characters enable a quick assignment to subclass or order. Use these when the higher-level taxon is determinable at a glance.
The next 13 characters together have much the same effect as character 1 or character 2 although the division of the taxa may not exactly follow conventional subclass/order boundaries. Use these characters to narrow the possibilities by summarising the individual features of a specimen when the higher-level taxon is not clear.
The remaining characters (37 in all) in effect form eight separate “sub-keys”, one to each subclass or order for which more than one family is present in Australian inland waters. These sub-keys are listed in conventional museum-drawer order from Anostraca to Decapoda, except that for convenience the two classes with bivalved carapace (Conchostraca, Ostracoda) are dealt with together. The selection of any character-state from a sub-key will cause all other subclasses/orders to be eliminated. Hence this action, too, is like making a selection from character 1.
Throughout the key we have tried to avoid using characters which are difficult to see, which require dissection, or which depend on the specimen being fully adult or of one particular sex. Dichotomous, printed keys often offer a hierarchic identification process in which successive steps represent identification to class, order, suborder, and superfamily level. A difficulty with such keys is that the characters which indicate a higher-taxon may be less immediately obvious than those which indicate a lower ranking. For example, some superfamily may be recognised by a character of the mandibular palp but the local genus may have unique, bright green antennae.Faced with situations of that sort, we have opted to mention the antennae and ignore the palps. The result is a key which should work rather readily for the known fauna, but undescribed and unrecorded species may or may not key out as well as they would in a conventional key. Further, the information content of the key in some instances will not suffice for a family or superfamily synopsis.
In other words, this key is designed for putting a name on a specimen. We have been less concerned with describing (or redescribing) higher taxa, with summarising the hierarchy of names, or with providing taxonomists with clues to where a new species might be put.
Without a thorough first-hand knowledge of every species in every sub-group of the Crustacea (an impossible requirement even for the specialist), a key such as this must rely largely on published descriptions, revisions, and previous keys. Very often, important data which would allow the easy identification of specimens are missing from such sources (taxonomists tend to write in terms of the taxonomic hierarchy). Thus, there are some places at which unnecessarily obscure characters had to been used, simply for lack of knowledge. Hopefully, the number of these instances will be reduced in later editions.
We thank the compilers of earlier keys, describers and revisors of taxon groups, for the provision of information on which this key has been based. Acknowledgement for the use of images is shown o the face of the relevant image.
Please note:
- Many juveniles of aquatic Crustacea simply cannot be identified to family. For those the key should produce a correct but incomplete result.
- New species may key correctly, incorrectly, partially, or not at all. That is in the nature of being new.
