Monday, December 18, 2017

[PaleoOrnithology • 2017] Kumimanu biceae • A Paleocene Penguin from New Zealand Substantiates Multiple Origins of Gigantism in Fossil Sphenisciformes

Kumimanu biceae
Mayr, Scofield, De Pietri & Tennyson, 2017

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.

Systematic paleontology
Aves Linnaeus, 1758
Sphenisciformes Sharpe, 1891

Kumimanu biceae, n. gen. et sp.

  Holotype. NMNZ S.45877: partial skeleton of a single individual including cranial end of left scapula, incomplete right coracoid, cranialmost portion of sternum, partial left humerus, incomplete proximal end of left ulna, right femur, right tibiotarsus lacking proximal end, partial synsacrum, three vertebrae, and various bone fragments.

  Etymology. From kumi (Maori), a large mythological monster, and manu (Maori), bird. The species epithet honors Beatrice (“Bice”) A. Tennyson, the mother of AJDT, who fostered his interest in natural history (pronounced “bee-chee-ae”).

  Type locality and horizon. Hampden Beach, Otago, New Zealand (NZ Fossil Record Number J42/f0956; precise locality information is recorded at NMNZ); Moeraki Formation, late Paleocene (late Teurian, local stratigraphic level NZP522, which has an absolute age of 55.5.-59.5 million years23; a matrix sample taken from the fossil (GNS Science sample L29126) contained a specimen of the dinoflagellate Palaeocystodinium australinum and an unnamed dinoflagellate taxon that support a Teurian age for this sample; C. Clowes, pers. comm.).

  Diagnosis. A very large-sized sphenisciform species, which is characterized by proximodistally low and widely spaced condyles of the tibiotarsus. Distinguished from the late Paleocene Crossvallia and all post-Paleocene Sphenisciformes of which humeri are known in the dorsoventrally narrower humerus shaft, with ratio of maximum width of proximal end of humerus to minimum width of shaft being 2.4 (less than this value in Crossvallia and all post-Paleocene Sphenisciformes of which the humerus is known). Distinguished from Waimanu tuatahi in having the bicipital crest of humerus not forming a distally directed bulge. Distinguished from Waimanu manneringi (the humerus of which is unknown) in having the tibiotarsus with proximodistally lower and more widely spaced condyles.

The humerus (top) and a bone from the shoulder girdle (coracoid, bottom) of the Paleocene giant penguin Kumimanu biceae, compared to the corresponding bones of one of the largest fossil penguins known to date (Pachydyptes ponderosus from the Eocene in New Zealand) and those of an Emperor Penguin (Aptendodytes forsteri).

photo: G. Mayr/Senckenberg Research Institute.

Gerald Mayr, R. Paul Scofield, Vanesa L. De Pietri and Alan J. D. Tennyson. 2017. A Paleocene Penguin from New Zealand substantiates multiple origins of gigantism in fossil Sphenisciformes. Nature Communications. 8, Article number: 1927. DOI:  10.1038/s41467-017-01959-6

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