According to a Search Engine Watch thread named Google Serps Giving Broadmatch, Google is conducting broadmatch like targeting for very detailed and obscure queries. Graywolf shows;
For example look at this serp [aardvark mastodon zosterops] I'm not sure what those files are used for or why they are available on a public webserver, but I find it pretty interesting that google will search that far across a very lengthy document to find a match.
Forum discussion at Search Engine Watch Forums.