ORNITHICHNOLOGY: THE ICHNOTAXONOMIC LEGACY OF EDWARD HITCHCOCK AND THE STATUS OF THE GRALLATORID ICHNOGENERA GRALLATOR, ANCHISAURIPUS AND EUBRONTES

In 1836 Edward Hitchcock described footprints from Early Jurassic strata of the Hartford and Deerfield rift basins of Massachusetts, classifying them in 7 species within Ornithichnites ('stony bird tracks'); the type species (by page priority) is giganteus. In 1841 he replaced Ornithichnites by Ornithoidichnites ('stony bird-like tracks'), as some of these tridactyl tracks had manus prints. In an 1845 abstract he changed his approach, replacing all the track names with names of the (unknown) trackmaker animals; giganteus was made the type species of Eubrontes. In an 1847 paper he replaced the name with Brontozoum; he thought the 1845 names invalid as they were not accompanied by descriptions (although the material assigned to Eubrontes had been previously described, thus it was valid!). Until 1858 he thought all the species cogeneric; but in 1858 he erected a new genus, Grallator, for some of the (non-giganteus) species of Brontozoum. In 1904 Lull recognized that Eubrontes had priority over Brontozoum, and removed some of the species (but not giganteus) of Eubrontes (which he thought were carnivore tracks) into a new genus, Anchisauripus, thinking they were made by herbivores, although his descriptions provided no clear distinction between the genera! At present three grallatorid genera (Grallator, Anchisauripus, Eubrontes) are recognized.

According to the ICZN rules, Ornithoidichnites, Eubrontes and Brontozoum are all objective junior synonyms of Ornithichnites. Genera coined after 1836 based on species other than giganteus - for new material, or transfering material out of Ornithichnites - can be valid. Thus by strict application of ICZN rules, Eubrontes giganteus is actually Ornithichnites giganteus. A case could be made for retaining the present grallatorid genera only if some or all of their included species are generically distinct from giganteus.

Although Ornithichnites has not been used in 160 years it was never formally suppressed. Adopting it could result in instability; alternatively, given the proliferation of species names within the three currently-used grallatorid genera, using Ornithichnites for some or all of the material may be an elegant solution to what is almost certainly taxonomic oversplitting!