Taxonomic status of the Eocene penguins Orthopteryx gigas Wiman, 1905 and Ichtyopteryx gracilis Wiman, 1905 from Antarctica

Traditionally, the systematics of the Seymour Island fossil penguins has been based on Wiman's groups defined by the robustness and size of isolated postcranial bones. However, current evaluations of fossil penguins necessitate that new species be established when the specimens include at least a tarsometatarsus or in some cases a humerus. Accordingly, neither of the two species reviewed herein (Orthopteryx gigas and Ichtyopteryx gracilis) are represented by remains sufficiently complete to validate a new taxon. Orthopteryx gigas is based on an isolated synsacrum lacking diagnostic characters. Ichtyopteryx gracilis is based on a tarsometatarsus but with insufficient preservational quality to justify discrimination of the species. For these reasons both Orthopteryx gigas and Ichtyopteryx gracilis should be considered nomen dubia.