Platydyptes: fossil penguins of Oligocene New Zealand

Platydyptes was a genus of fossil penguins from late Oligocene and earliest Miocene deposits of New Zealand. Its remains are known from Oamaru, Hakataramea and nearby localities, where several individuals preserve wing and leg bones. The shoulder bone, or humerus, helped distinguish the genus, but recent anatomical work shows that species identification depends on more subtle features than overall size or width. Three named species are commonly discussed, while the placement of P. marplesi remains doubtful and a fourth form awaits formal description. The extinct bird catalogue places these penguins in the wider record of New Zealand’s ancient seabirds.

Quick facts

From Pachydyptes to Platydyptes

Walter Reginald Brook Oliver described a New Zealand fossil penguin as Pachydyptes novaezealandiae in 1930. Brian Marples later recognised that its broad, flattened humerus differed from the type of Pachydyptes and created Platydyptes for it in 1952. The name refers to the proportions of a bone in the flipper, not to a wing that was literally a flat plate. Marples also named P. amiesi.

George Gaylord Simpson reviewed the genus in 1971 and proposed P. marplesi from a set of bones attributed to one individual. Simpson himself questioned whether that species truly belonged in Platydyptes. The current New Zealand fossil-bird checklist retains the caution. The genus is therefore most securely anchored by its type species and P. amiesi; P. marplesi is useful to discuss as a proposed assignment, not as a settled fact.

The named species are tied to different specimens and localities. The holotype of P. novaezealandiae is an isolated humerus from the Oamaru district. Additional bones have been referred to it, but the type itself is not an articulated skeleton. The holotype of P. amiesi includes humerus and radius material from the Hakataramea Valley and is associated with the name of A. C. Amies, who collected the first specimen. Later material from near Duntroon provides a more complete anatomical picture.

The collection history for P. amiesi illustrates the limits of old locality records. A museum label associates the type with Hakataramea and a date in 1899, whereas a later biographical note says that Amies found the first specimen near White Rocks, close to Duntroon, in 1946. Those accounts cannot both describe the same discovery event as written. Until original field labels and catalogues are reconciled, the safest statement is that the name honours Amies and that the type is recorded from the Hakataramea area.

What recent comparisons add

A 2022 University of Otago thesis re-examined the named species and a further specimen, OU22804. It found potentially diagnostic differences in the tricipital fossa of the humerus: the reported conditions include a thin crest in P. novaezealandiae, a raised dividing ridge in P. amiesi, and an undivided fossa in the material assigned to P. marplesi. The corresponding region of OU22804 is damaged, so that character cannot be checked there.

The study also provided tarsometatarsus descriptions for P. novaezealandiae and P. amiesi, broadening the anatomical basis for comparisons beyond the wing. Its revised phylogenetic analysis included all three named species and the proposed fourth form. This is a thesis-based revision and hypothesis, not a formal new species description. The possible fourth species remains unnamed pending fuller diagnosis and publication.

Measurements overlap and bones can be incomplete. A character combination across several elements is more reliable than assigning species from an unusually large or small bone alone. The fossil record does not show that all referred bones came from the same time or one population; late Oligocene to earliest Miocene ages are assembled from local geological correlations. For OU22804, the fourth-form interpretation rests on comparison with the named material as a whole, not on the damaged fossa alone. The distinction is preliminary until additional specimens and a formal diagnosis make the character combination testable by other researchers.

A flippered bird in an island sea

The humerus, radius, ulna and other wing bones show a forelimb transformed into a penguin flipper. The shape supports underwater propulsion and a marine lifestyle. It does not preserve the muscles in action, the exact swimming speed or how deep these penguins dived. Modern penguins provide a useful comparative framework, but their specialised behaviours cannot automatically be assigned to every extinct species.

During the late Oligocene and earliest Miocene, Zealandia consisted of islands and shallow marine settings unlike the modern outline of New Zealand. Fossils from the Oamaru and Hakataramea areas record penguins within these coastal systems. Localities and associated rocks constrain age and habitat, but a collection assembled over multiple sites is not one colony or a direct snapshot of a single ecosystem. The interval of roughly 27.3 to 21.7 million years is based on the local stages assigned to the formations yielding the named records; it is not a direct date measured on each penguin bone.

The known bones do not preserve feather colour, vocalisations, breeding behaviour or a complete soft-tissue outline. Illustrations may show a penguin on a shore, but details beyond the skeletal evidence are artistic reconstruction.

What remains unresolved

The taxonomy of Platydyptes has not received a comprehensive peer-reviewed revision since the twentieth century, and newer anatomical comparisons are still developing. The placement of P. marplesi has long been questioned. OU22804 may represent an additional species, but its damaged humerus prevents comparison of a key feature, and it has not received a formal species name.

There are also historical uncertainties in the collection data. Published accounts connect specimens with Oamaru, Duntroon and Hakataramea, while some exact collection histories differ between museum labels and later narratives. Without the original field records, a more precise account would create false certainty. These limits do not erase the useful evidence: several distinct late Oligocene penguin forms occupied New Zealand waters, and their bones record variation in the evolving flipper.

Species names are practical tools for describing recurring anatomical patterns, but they can hide uncertainty when the underlying specimens differ in completeness. For this genus, the most transparent account separates named types, referred material and proposed additions. As better-associated skeletons become available, researchers can test whether the character combinations track distinct lineages or fall within variation of fewer species.