It looks like Al's ancestors were bigger than expected!
One of the notable features of penguin evolution is the occurrence of very large species in the early Cenozoic, whose body size greatly exceeded that of the largest extant penguins. Here we describe a new giant species from the late Paleocene of New Zealand that documents the very early evolution of large body size in penguins. Kumimanu biceae, n. gen. et sp. is larger than all other fossil penguins that have substantial skeletal portions preserved. Several plesiomorphic features place the new species outside a clade including all post-Paleocene giant penguins. It is phylogenetically separated from giant Eocene and Oligocene penguin species by various smaller taxa, which indicates multiple origins of giant size in penguin evolution. That a penguin rivaling the largest previously known species existed in the Paleocene suggests that gigantism in penguins arose shortly after these birds became flightless divers. Our study therefore strengthens previous suggestions that the absence of very large penguins today is likely due to the Oligo-Miocene radiation of marine mammals.
New Zealand has yielded several fossils of Paleocene Sphenisciformes, which shed considerable light on the early evolution of penguins. All of the described specimens come from exposures of the Waipara Greensand in the Canterbury region and the two named species, Waimanu manneringi and W. tuatahi, are the oldest and phylogenetically most basal Sphenisciformes reported so far1,2,3.
Recently, remains of a very large penguin have also been found in the Waipara Greensand4. These fossils, an incomplete tarsometatarsus and associated pedal phalanges, belong to an unnamed species that is phylogenetically closer to the crown group (the clade including the extant species) than Waimanu. A definitive taxonomic assignment of the fragmentary fossils is, however, not possible and this is also true for Crossvallia unienwillia, an equally large stem group penguin from the late Paleocene of Antarctica5, 6.
Gigantism, that is, the evolution of a size exceeding that of the extant Emperor Penguin (Aptenodytes forsteri), is much better documented in post-Paleocene penguins, and the Eocene Anthropornis nordenskjoeldi and Pachydyptes ponderosus were for a long time considered to be the largest known penguin species7, 8. Pachydyptes ponderosus, from the late Eocene of New Zealand, is known only from a few wing and pectoral girdle bones7; however, numerous isolated skeletal elements as well as a few partial skeletons have been reported for A. nordenskjoeldi, from the late Eocene and early Oligocene of Antarctica9, 10. Recently, it was hypothesised that the well-preserved Kairuku grebneffi from the late Oligocene of New Zealand may have been taller, although less massive than P. ponderosus; for the largest individual of K. grebneffi, a total body length of about 1.5 m was estimated8. Based on isolated limb bones, lengths of 1.6 and 1.5 m were also calculated for Anthropornis nordenskjoeldi and the very large Palaeeudyptes klekowskii from the Eocene and Oligocene of Antarctica11. While partial skeletons of P. klekowskii indicate a somewhat shorter body length of about 1.4 m12, 13, a recently described humerus fragment and a tarsometatarsus may come from individuals with an estimated length of about 2.0 m14. A large size is reached by other Palaeeudyptes species from the Eocene and Oligocene of Antarctica and New Zealand2, 15, 16, and further, very large Sphenisciformes occurred in the late Eocene of Australia17 and the late Eocene of Peru18, 19.
Some authors assumed that penguins achieved a giant size multiple times6, but the giant taxa Anthropornis, Palaeeudyptes, Kairuku, Icadyptes, and Inkayacu were recovered as parts of subsequently branching clades and it was therefore considered more likely that extremely large size evolved only once18. Definitive conclusions about size evolution in fossil Sphenisciformes are, however, impeded by the fact that even in more recent analyses the exact interrelationships between giant sphenisciform taxa are poorly resolved8, 19, 20.
Here we report a partial skeleton of a giant stem penguin from the Paleocene Moeraki Formation at Hampden Beach in the Otago region of New Zealand, some 300 km southwest of the exposures of the Waipara Greensand in the Canterbury region. A few fragmentary bird remains from the Moeraki Formation were previously mentioned21 and the age of the Moeraki Formation has been constrained to the late Paleocene based on foraminiferal biostratigraphy22, 23. The new fossil is one of the oldest giant penguins found so far and is clearly outside a clade including the giant Eocene and Oligocene Sphenisciformes, substantiating multiple origins of gigantism in fossil penguins.
Source:
https://www.nature.com/articles/s41467-017-01959-6
Topic: A Paleocene penguin from New Zealand substantiates multiple origins of gigantism (Read 858 times)