Abstract
New Zealand has one of the most extensive penguin records in the world, from the oldest known penguin Waimanu (~60-62 Ma) to several extant species such as Eudyptula minor (Little Blue Penguin) and Megadyptes antipodes (Yellow-Eyed Penguin). Within this record, Platydyptes is a fossil genus that is endemic to Zealandia; it is one of the most crownward of the extinct penguins and one of the few Late Oligocene genera described. The last published work on Platydyptes was a taxonomic review by Simpson (1971), who assessed Platydyptes novaezealandiae and Platydyptes amiesi and suggested a third species (Platydyptes marplesi). This project revises and expands the understanding of the genus Platydyptes using material excavated from existing fossils and new specimens. The new material has more comprehensively revealed the body plan of the Platydyptes genus. Analysis of the morphology of Platydyptes novaezealandiae, Platydyptes amiesi and Platydyptes marplesi and a new specimen, OU22804, suggests there is a fourth species of Platydyptes (herein: Platydyptes species ‘4’ awaiting formal naming). There is comparable material for the species, including the humerus, which shows subtle differences. For example, the tricipital fossa state, Platydyptes novaezealandiae has a thin crest, whereas Platydyptes amiesi has a raised ridge dividing the fossa and Platydyptes marplesi has an undivided fossa. Due to damage, the tricipital fossa of Platydyptes sp ‘4’ was unable to be compared. Platydyptes novaezealandiae and Platydyptes amiesi now have tarsometatarsus descriptions, which improve the ability to recognise these species. A revised phylogenetic analysis contains all three named species and Platydyptes sp ‘4’, and thus provides a more comprehensive analysis of the clade compared to just the two species coded in previous analyses (Platydyptes novaezealandiae and Platydyptes marplesi). While the clade did not fully resolve, the placement of Platydyptes before crown radiation appears to be stable. The use of Linear Discriminate Analysis (LDA) on modern bone measurement datasets was found to increase understanding of intraspecies variation and variation between species within a genus. Several different bones (e.g., humerus, coracoids and tarsometatarsus) were tested within the modern groups, with results indicating that for samples with limited data the best results come from measurements of a single element’s length and width. The humerus of different Platydyptes species were used in LDA and found that the size ranges of this element between species is statistically significant and therefore helps to quantify humerus size as a useful species diagnostic. This study has elucidated the genus Platydyptes and further shown the importance of New Zealand’s fossil bird record.