Traditional taxonomy of Phocid seals of the North Atlantic

    Traditional seal taxonomy places Hooded Seals (Cystophora) in the same subfamilly as Pacific Elephant Seals (Mirounga), with which they share a distinctive morphology and dental formula. Harbor Seals (Phoca) were the first, "typical" species recognized by Linnaeus (1758) in his Systema Naturae. Early workers between 1775 - 1791 described a series of new species, which they recognized as similar to harbor seals and therefore placed them in the same genus. Later workers identified differences among the species and assigned them to new monotypic genera: this practice to emphasize differences as the basis of taxonomy can be called "splitting," as contrasted with "lumping" that uses the minimum number of necessary names.  Harp Seals and Ring Seals resemble them and are placed in the same genus. Bearded Seals and Grey Seals are morphologically distinctive and therefore placed in separate genera.

    The table shows several conventions of formal taxonomy.
(1) The First Describer of the species always remains associated with its name, as does the date. Thus Phoca vitulina L. 1758 is the so-called Linnaean "type" species of the genus; Linnaean names are always abbreviated L., and 1758 is recognized as the 'birthday' of taxonomy.

(2) The Bearded Seal was first described by Erxleben in 1777 as a member of the genus Phoca, species barbata: genus and species names must agree in Latin gender, so both end in the feminine -a. Gill in 1866 suggested elevating the species to its own genus Erignathus, which is generally accepted: use of the masculine ending -us then requires that the species name be amended to barbatus, otherwise taxonomic names cannot be changed even if misspelled or otherwise in error.

(3) To indicate that Erxleben first described the species but in a different genus, his name and reference are appended in parentheses, (Erxleben, 1777).

(4) Similar rules govern Pagophilus and Halichoerus, except that Phoca + grypus is a Latin grammatical anomaly. Phoca groenlandica remains in wide use, especially in fisheries and ecological literature, even after molecular data showed that it is only distantly related to Phoca vitulina, and should therefore be Pagophilus groendlandicus (Erxleben, 1777). This recognition fundamentally changes ideas about the behavioral evolution of Pagophilus.