Specimens are a critical basis for taxonomic research. They are cited in taxonomic treatments and other works. Increasingly these material citations are extracted from publications and submitted as part of data sets to GBIF and reused in studies.
As of today, GBIF includes 33,393 datasets derived from taxonomic publications and 415,858 material citations which are labeled as occurrences. 335 publications reuse this data. An estimate of 45,000 species are only represented in GBIF through material citations from publications, mainly covering new species that are extracted from the literature just after the publishing time. This cuts short the time to enter taxonomic names and re-submit datasets to GBIF.
However, the currently used term occurrence leads to confusion and discussions which need to be resolved.
Semantically, material citations are not specimens per se, but the citation of a specimen. Furthermore, material citations can be part of a specimen, a specimen, or groups of specimens. They can be very verbose or very cursory, transcription of the original label data or its interpretation.