A Tiny Fellow Joins the March of the Fossil Penguins

Reconstruction of Eudyptula wilsonae by Dr. Simone Giovanardi.

Early this year we reported the largest fossil penguin. This week, our team announces one of the smallest fossil penguins ever found. The new species is a bit over three million years old and represents a new species of little penguin (genus Eudyptula). We named it Eudyptula wilsonae after New Zealand ornithologist Dr Kerry-Jayne Wilson, who was an internationally respected researcher cofounder of the West Coast Penguin Trust, an organization dedicated to protecting seabirds and their habitat.

Eudyptula wilsonae is the second penguin species to be discovered in the Tangahoe Formation, which previously yielded the slender-billed crested penguin Eudyptes atatu. Most fossil penguins are known from flipper and leg bones, because these sturdy elements tend to survive the fossilization process more easily than the relatively delicate skull. Unusually, Eudyptula wilsonae is known only from the skull – two skulls but no other parts of the skeleton have been reported so far. Fossil hunter Karl Raubenheimer discovered the two skulls on the North Island of New Zealand. One skull belonged to an adult, but the other belonged to a juvenile as indicated by its smaller size and incompletely fused sutures. Both are smaller than any living penguin species, and smaller than all but one fossil species, the older and slightly tinier Eretiscus tonnii.

Holotype skull of Eudyptula wilsoni. Museum of New Zealand Te Papa Tongarewa NMNZ S.048855. Photo by Jean-Claude Stahl.

Eudyptula penguins are ridiculously cute. Standing about a foot tall and weighing in at two pounds, these pint-sized penguins are known for their sleek blue feathers and habit of coming ashore together in small groups known as “rafts” at dusk – an event enjoyed by sightseers at places like Oamaru and Phillip Island. Eudyptula penguins live in both New Zealand (Eudyptula minor) and Australia (considered either Eudyptula novaehollandiae or Eudyptula minor novaehollandiae), and scientists debate whether these two populations should be considered separate species or not. Individuals from New Zealand and Australia are practically impossible to tell part by eye, but their DNA suggests they have been evolving in isolation for more than a million years. Adding to the confusion, a group of Australian little penguins set up a breeding colony in New Zealand only a few hundred years ago. I personally lean towards recognizing them as separate species, but other experts on the team consider them to be subspecies.

Dr. Daniel Thomas, leader of the study, used morphometric methods to compare the juvenile and adults skulls to one another and to the skulls of modern Eudyptula penguins. The results show the new species has a more slender skull, which along with the age of the fossils suggests as a possible ancestor of modern little penguins.

Referred juvenile skull of Eudyptula wilsoni. Museum of New Zealand Te Papa Tongarewa NMNZ S.048854. Photo by Jean-Claude Stahl.

Along with Eudyptes atatu and many other seabirds like the albatross Aldiomedes angustirostris, Eudyptula wilsoni helps paint a more complete picture of the seabird fauna of New Zealand in the Pliocene. This is of great interest, as the Pliocene was a warm period with higher sea level compared to the present day. Understanding what types of animals were common under these warm conditions and what type of animals were absent can help us anticipate the way species ranges may shift with increasing global warming.

Reference

Thomas, D.B., A.J.D. Tennyson, F.G. Marx and D.T. Ksepka. 2023. Pliocene fossils support a New Zealand origin for the smallest extant penguins. Journal of Paleontology doi:10.1017/jpa.2023.30