To use the bone picture database and the identification key efficiently the software "Bone Base Baltic Sea" was programmed to provide an information center combining different methods of identification under a single surface. The bone picture database is based on the database management system Microsoft Access (® Microsoft), but the user interface is a self development in the programming language Visual Basic (® Microsoft).

The bone picture data base contains about 5000 bone pictures, arranged by species. The selection of a single bone type for a known species is possible, as well as browsing the entire bone picture collection for a given species to find the suitable bone (Fig. 1). For each species basic information concerning bones and skeleton is provided. This information includes: characteristics, number of vertebrae, maximum total length, best bones to distinguish from other species, best bones to distinguish from species of the same family, similar species, regressions and osteological literature. To each bone picture additional information is attached providing primarily facts to the corresponding individual and to the occurrence (paired, single, multiple) in the species.

The identification key was basically developed as a traditional dichotomous key with drawings and corresponding descriptions (Fig. 2). With every identification step the user chooses an option and with a mouse click he enters the next step or, at the end, he jumps directly to the identified species in the bone picture data base in order to check the reliability of the identification. To evolve an interactive key including all the different bone types for all the species was not recommendable because of their variability. Nevertheless a characteristic feature of interactive keys defined by Dallwitz et al. 1998 was implemented. At each identification step the user can see which species are remaining. That means that he does not have to identify up to the species level, if not possible, but still gets a result in any case. It is possible to see the identification course, to enter every identification step individually and to bookmark them. The identification course can be saved too.

A simple way to compare bones of different species is given on the comparison tab. Therefor the software creates a HTML-Site with a set of bone pictures corresponding to the users specification (Fig. 3). Three different options are given:
     1. display of all bones belonging to one species
     2. direct comparison of the bones from two species
     3. comparison of one bone type (e. g. operculum) for all the
         species