Largest-known fossil penguin provides insight into the early evolution of sphenisciform body size and flipper anatomy

Abstract

Recent fossil discoveries from New Zealand have revealed a remarkably diverse assemblage of Paleocene stem group penguins. Here, we add to this growing record by describing nine new penguin specimens from the late Paleocene (upper Teurian local stage; 55.5–59.5 Ma) Moeraki Formation of the South Island, New Zealand. The largest specimen is assigned to a new species, Kumimanu fordycei n. sp., which may have been the largest penguin ever to have lived. Allometric regressions based on humerus length and humerus proximal width of extant penguins yield mean estimates of a live body mass in the range of 148.0 kg (95% CI: 132.5 kg–165.3 kg) and 159.7 kg (95% CI: 142.6 kg–178.8 kg), respectively, for Kumimanu fordycei. A second new species, Petradyptes stonehousei n. gen. n. sp., is represented by five specimens and was slightly larger than the extant emperor penguin Aptenodytes forsteri. Two small humeri represent an additional smaller unnamed penguin species. Parsimony and Bayesian phylogenetic analyses recover Kumimanu and Petradyptes crownward of the early Paleocene mainland NZ taxa Waimanu and Muriwaimanu, but stemward of the Chatham Island taxon Kupoupou. These analyses differ, however, in the placement of these two taxa relative to Sequiwaimanu, Crossvallia, and Kaiika. The massive size and placement of Kumimanu fordycei close to the root of the penguin tree provide additional support for a scenario in which penguins reached the upper limit of sphenisciform body size very early in their evolutionary history, while still retaining numerous plesiomorphic features of the flipper. UUID: https://zoobank.org/15b1d5b2-a5a0-4aa5-ba0a-8ef3b8461730

Pliocene fossils support a New Zealand origin for the smallest extant penguins

“…Phylogenetic analysis.-We scored the newly-described fossils into a combined morphological and molecular matrix modified from Ksepka et al (2023). Anatomical terminology is consistent with terminology used in other recent descriptions of fossil penguins (e.g., Ksepka et al, 2023) and originally adapted from Baumel and Witmer (1993). We added one morphological character: (98) lacrimal, descending process: (0) smoothly contacts jugal bar along dorsal edge of latter, (1) ends in a flange formed by laterally deflected and widened ventral extremity.…”

“…Phylogenetic analysis. —We scored the newly-described fossils into a combined morphological and molecular matrix modified from Ksepka et al (2023). Anatomical terminology is consistent with terminology used in other recent descriptions of fossil penguins (e.g., Ksepka et al, 2023) and originally adapted from Baumel and Witmer (1993).…”

“…The morphological dataset originated with the extant penguin matrix of Bertelli and Giannini (2005), which was extended to included fossil taxa by Ksepka et al (2006) and expanded iteratively over many analyses. Studies that contributed characters include O'Hara (1989), Giannini and Bertelli (2004), Bertelli and Giannini (2005), Ksepka et al (2006, 2012, 2023), Acosta Hospitaleche et al (2007), Ando (2007), Clarke et al (2007, 2010), Ksepka and Clarke (2010), Ksepka and Thomas (2012), Chávez Hoffmeister et al (2014), Blokland et al (2019), Thomas et al (2020), and Giovanardi et al (2021).…”

Decision: The extinct marine megafauna of the Phanerozoic — R2/PR9

“…(Figure 1; Blieck et al, 2002;Mark-Kurik, 2000;Moloshnikov, 2001;Sallan and Galimberti, 2015). It is worth noting that potentially larger seabirds are known, for example, the 160 kg Kumimanu fordycei, which has been proposed to be the largest-known fossil penguin (Ksepka et al, 2023). However, given the lack of body length measurements available for this and potentially other birds, it was not included in our dataset.…”

The extinct marine megafauna of the Phanerozoic

“…1; Blieck et al 2002;Mark-Kurik 2000;Moloshnikov 2001;Sallan and Galimberti 2015). It is worth noting that potentially larger seabirds are known, for example, the 160 kg Kumimanu fordycei, which has been proposed to be the largest-known fossil penguin (Ksepka et al 2023). However, given the lack of body length measurements available for this and potentially other birds, it was not included in our dataset.…”