Bill disparity and feeding strategies amongst fossil and modern penguins

One of the most remarkable differences between Paleogene penguins and their living relatives is the shape and length of their beaks. Many of the Eocene and Oligocene penguins have a thin and elongated spear-like bill, which contrasts with the proportionally shorter and more robust bill of most living species. These differences suggest an important shift on their feeding strategies. This study explores the morphological disparity on the skull of penguins, emphasizing bill morphology and it relationship with feeding habits. For this, the skull of 118 species of aquatic birds including 21 fossil and living penguins were analysed using two-dimensional geometric morphometric. The results show that, unlike what has been reported for modern birds overall, in penguins and Aequornithes bill elongation is related to a reduction of the braincase. The discriminant analysis shows that there are significant differences between penguins that feed near or far from the coast and between those that consu...