The content of Pterioidea: pearl oysters and their relatives is citable because all changes to a page are archived. Every time a change in the content on a page is made, the author of the change and the date when it was made are reported in a log. The log for each page can be accessed by clicking the Revisions botton that appears next to the page's title. (Clicking the View button brings you back to the current view of the page.) A combination of web address and date allows for retrieval of any information that was featured on the page, even if a page has changed substantially since it was referenced.
An example of citing the content of the website:
Pterioidea: Pearl Oysters and their Relatives. 2007 Oct 15. CBE home page. http://pterioidea.myspecies.info. Accessed 2007 Oct 20.
An example of citing a web discussion forum posting:
Tëmkin I. 2007 Oct 15. http://pterioidea.myspecies.info/23354. Accessed 2007 Oct 16.
The author' names and dates, obviosly, should correspond to the latest on-line publication dates and the date when this information was viewed. The current publication dates are displayed at the Revision tab of every page; web form posts are automatically individually dated. Note, that for citing the web address of a forum entry, the part of the address that follows pterioidea.myspecies.info/ will be different from the given example.