Proto-penguins take the plunge
Waipara Greensand, Middle Palaeocene, Chatham Islands, New Zealand.
Waimanu, was a flightless, aquatic Neoave from the middle palaeocene epoch. Two species have been collected, W. tuatahi from sediments dated between 58 – 60Ma, and W. manneringi 62Ma, slightly older but less complete. Both are recognised as being basal members of the phylogenetic group the Sphenisciformes, a taxonomic order containing all modern penguins.
Evolving soon after the Cretaceous – Paleogene extinction event, Waimanu’s body morphology already exhibits the fusiform streamlined anatomy required to hunt with agility underwater, indicating that the evolution of penguins most certainly started in the Late Cretaceous but, unlike their more specialised descendants, Waimanu possessed a curious mixture of primitive and derived characteristics. Standing upright at 80 cm tall, on short legs, Waimanu would have superficially looked like a modern penguin, its terrestrial locomotion similar. However, its forelimbs, although reduced for manoeuvrability underwater, lacked the rigid elbows and compressed profile which enable modern penguin wings to cut through water like a flipper. Palaeontologists speculate that Waimanu may have swum and hunted in a manner similar to its modern close genetic relative the Loon, propelling itself through water with its feet rather than its wings.
Soft tissues have not been preserved, but Waimanu fossils were deposited in a marine environment and it is reasonable to expect that it possessed waterproof plumage similar to extant penguins, and expressing a high degree of countershading.
Waimanu evolved into a warm world lacking many of the dangerous terrestrial and aquatic predators of the late Cretaceous and, like many of the birds in New Zealand today, responded to an absence of threat by losing the power of flight. It took to water, and exploited one of the abundant ecological niches vacated by the mass extinction of the large marine reptiles and many species of shark in the world’s oceans.
Acrylic painting on board.
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