Pliocene fossils support a New Zealand origin for the smallest extant penguins
By: Daniel B. Thomas, Alan J.D. Tennyson, Felix G. Marx, and Daniel T. Ksepka
Summarized by: Michelle Yu is a biological sciences major with a Korean studies minor at Binghamton University. Currently, she is a senior and plans to attend dental school in the hopes to become a future dentist. Outside the classroom, she can always be found in the dance studio dancing with her hip-hop and K-pop dance teams!
What data were used? Scientists discovered two new penguin fossils from New Zealand that dated from approximately three million years ago (during the Pliocene). The new fossils were found to be smaller than the smallest known penguins today, leading to an investigation to uncover if these new fossils represented a new species of small penguin. To do so, the skull measurements of the newly found fossils were taken and compared to the skull measurements of two existing small penguin species: the New Zealand small penguin species (Eudyptula minor minor) and the Australian small penguin species (Eudyptula m. novaehollandiae).
What was the hypothesis being tested? Although current data shows New Zealand as the likely origination point of the small penguin genus, Eudyptula, its sparse fossil record makes it difficult to confirm its origins and how it may have evolved in the past. Previous to this study, the scientists had found evidence of small penguins dated approximately 126,000 years ago (during the late Pleistocene). However, the new small penguin fossils found in this experiment show that small penguins existed almost three million years ago in New Zealand, marking a significant finding in the history of small penguins and where they may have evolved. To fully explore the evolution of the small penguin genus, this experiment tested the evolutionary and ancestral relationships of the new specimens and living small penguins to confirm their New Zealand origins and how they may have changed over time.
Methods: Scientists recorded the skull measurements of the newly found small penguin fossils and specimen of the existing small penguin species (some of the major measurements included were: overall skull length/width, nose bridge distance, eye socket length/width). Collected measurements were then used in a program called PAUP* (Phylogenetic Analysis Using Parsimony) which analyzed the evolutionary relationships between the new fossils and existing small penguins to ultimately determine whether the newly found fossils were of the same species as the existing small penguins or if they represented a new species.
Results: The two new fossils discovered were determined to be a new species of the little penguin genus and were named Eudyptula wilsonae by the scientists who discovered them. The new fossil species was found to have a significantly slenderer skull when compared to the existing small penguin species. However, other characteristics of the skull such as overall shape, size, and other anatomical skull features were found to be almost identical to the existing small penguin species, supporting the idea that they are closely related (Figure 1). Furthermore, because the new fossil specimens were found in New Zealand rocks that are three million years old, the discovery of the new small penguin species marks the earliest date small penguins have been found anywhere, supporting the idea that small penguins likely originated from New Zealand.
Why is this study important? The importance of this study lies with the discovery that the skull shape and body size of little penguins have not undergone significant changes for at least three million years, despite the immense changes the environment has undergone over time. By comparing environmental data from three million years ago to today, scientists hypothesized that small penguin body sizes had already evolved by this time, with the ability to survive in waters warmer than today. This is significant because it suggests that the evolutionary trait to handle a wide range of temperatures in a small body had developed in small penguins for millions of years. This is important because the maintenance of these traits can further reveal the reasons behind the evolution of character traits such as these not only in small penguins, but also other marine animals.
Broader implications beyond this study: The findings from this study can aid scientists in uncovering how birds may have evolved during warmer periods, and subsequently, how scientists relate it to what type of features certain marine species may have had during the same time that the new small penguin fossil was alive. Specifically, this finding could aid in the studies of seabirds and how they had adapted to the environment in the past and how they may adapt in the future.
Citation: Thomas, D. B., Tennyson, A. J.D., Marx, F. G., & Ksepka, D. T. (2023). Pliocene fossils support a New Zealand origin for the smallest extant penguins. Journal of Paleontology, 97(3), 711-721. doi: 10.1017/jpa.2023.30