Abstract:
The Plotopteridae are wing-propelled, penguin-like diving birds of the order Pelecaniformes Found in mid-Tertiary deposits of the North Pacific. Much new material representing a considerable radiation of genera and species has been discovered in Japan since the basic adaptations and characters of the family were revealed. A new genus and species, Copepteryx hexeris, is named here from previously known but underscribed material upon which much of our knowledge of the family had originally been based. A second new species, C. titan, is described from a single gigantic femur from a bird that was probably larger than any known diving bird, living or fossil.
