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

   https://doi.org/10.1017/jpa.2022.88  

   Ksepka, Daniel T. ; Field, Daniel J. ; Heath, Tracy A. ; Pett, Walker ; Thomas, Daniel B. ; Giovanardi, Simone ; Tennyson, Alan J.D. ( March 2023 , Journal of Paleontology)

   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 fordycein. 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, forKumimanu fordycei. A second new species,Petradyptes stonehousein. gen. n. sp., is represented by five specimens and was slightly larger than the extant emperor penguinAptenodytes forsteri. Two small humeri represent an additional smaller unnamed penguin species. Parsimony and Bayesian phylogenetic analyses recoverKumimanuandPetradyptescrownward of the early Paleocene mainland NZ taxaWaimanuandMuriwaimanu, but stemward of the Chatham Island taxonKupoupou. These analyses differ, however, in the placement of these two taxa relative toSequiwaimanu,Crossvallia, andKaiika. The massive size and placement ofKumimanu fordyceiclose 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

    

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2. Ancient crested penguin constrains timing of recruitment into seabird hotspot

   https://doi.org/10.1098/rspb.2020.1497  

   Thomas, Daniel B. ; Tennyson, Alan J. ; Scofield, R. Paul ; Heath, Tracy A. ; Pett, Walker ; Ksepka, Daniel T. ( August 2020 , Proceedings of the Royal Society B: Biological Sciences)

   New Zealand is a globally significant hotspot for seabird diversity, but the sparse fossil record for most seabird lineages has impeded our understanding of how and when this hotspot developed. Here, we describe multiple exceptionally well-preserved specimens of a new species of penguin from tightly dated (3.36–3.06 Ma) Pliocene deposits in New Zealand. Bayesian and parsimony analyses place Eudyptes atatu sp. nov. as the sister species to all extant and recently extinct members of the crested penguin genus Eudyptes . The new species has a markedly more slender upper beak and mandible compared with other Eudyptes penguins. Our combined evidence approach reveals that deep bills evolved in both crested and stiff-tailed penguins ( Pygoscelis ) during the Pliocene. That deep bills arose so late in the greater than 60 million year evolutionary history of penguins suggests that dietary shifts may have occurred as wind-driven Pliocene upwelling radically restructured southern ocean ecosystems. Ancestral area reconstructions using BioGeoBEARS identify New Zealand as the most likely ancestral area for total-group penguins, crown penguins and crested penguins. Our analyses provide a timeframe for recruitment of crown penguins into the New Zealand avifauna, indicating this process began in the late Neogene and was completed via multiple waves of colonizing lineages. 

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3. A tale of worldwide success: Behind the scenes of Carex (Cyperaceae) biogeography and diversification

   https://doi.org/10.1111/jse.12549  

   Martín‐Bravo, Santiago ; Jiménez‐Mejías, Pedro ; Villaverde, Tamara ; Escudero, Marcial ; Hahn, Marlene ; Spalink, Daniel ; Roalson, Eric H. ; Hipp, Andrew L. ; the Global Carex Group ; Benítez‐Benítez, Carmen ; et al ( December 2019 , Journal of Systematics and Evolution)

   The megadiverse genusCarex(c. 2000 species, Cyperaceae) has a nearly cosmopolitan distribution, displaying an inverted latitudinal richness gradient with higher species diversity in cold‐temperate areas of the Northern Hemisphere. Despite great expansion in our knowledge of the phylogenetic history of the genus and many molecular studies focusing on the biogeography of particular groups during the last few decades, a global analysis ofCarexbiogeography and diversification is still lacking. For this purpose, we built the hitherto most comprehensiveCarex‐dated phylogeny based on three markers (ETS–ITS–matK), using a previous phylogenomic Hyb‐Seq framework, and a sampling of two‐thirds of its species and all recognized sections. Ancestral area reconstruction, biogeographic stochastic mapping, and diversification rate analyses were conducted to elucidate macroevolutionary biogeographic and diversification patterns. Our results reveal thatCarexoriginated in the late Eocene in E Asia, where it probably remained until the synchronous diversification of its main subgeneric lineages during the late Oligocene. E Asia is supported as the cradle ofCarexdiversification, as well as a “museum” of extant species diversity. Subsequent “out‐of‐Asia” colonization patterns feature multiple asymmetric dispersals clustered toward present times among the Northern Hemisphere regions, with major regions acting both as source and sink (especially Asia and North America), as well as several independent colonization events of the Southern Hemisphere. We detected 13 notable diversification rate shifts during the last 10 My, including remarkable radiations in North America and New Zealand, which occurred concurrently with the late Neogene global cooling, which suggests that diversification involved the colonization of new areas and expansion into novel areas of niche space.

    

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4. Holocene climate change shifted Southern Ocean biogeochemical cycling and predator trophic dynamics

   https://doi.org/10.1002/lno.12446  

   Michelson, Chantel I. ; Polito, Michael J. ; Wunder, Michael B. ; Emslie, Steven D. ; McCarthy, Matthew D. ; Patterson, William P. ; McMahon, Kelton W. ( October 2023 , Limnology and Oceanography)

   Studies of Antarctic paleo‐archives have produced conflicting hypotheses on the relative impact of long‐term climate change and historic exploitation of marine mammals on Southern Ocean krill predator foraging ecology. We disentangle these hypotheses using amino acid stable isotope analysis on a 7000‐yr Holocene archive of Adélie penguin (Pygoscelis adeliae) eggshells to differentiate variation in diet and trophic dynamics from baseline biogeochemical cycling as drivers of the rapid decline in krill predator bulk tissue δ¹⁵N values in recent centuries. Contrary to previous hypotheses suggesting solely trophic dynamic mechanisms as drivers of this decline, we identified an abrupt decline in source amino acid δ¹⁵N values, indicative of major changes in biogeochemical cycling at the base of the Southern Ocean food web that mirrored the decline in penguin bulk tissue δ¹⁵N values. These abrupt shifts in penguin δ¹⁵N values and associated biogeochemical cycling aligned with climatic events during the Little Ice Age that decreased surface δ¹⁵N_NO3−, likely connected to a proposed increase in Ekman upwelling via a southward migration of the Westerlies. This baseline shift was in addition to a long‐term, gradual decline in penguin trophic position over the Holocene that began prior to both recent anthropogenic climate change and a proposed “krill‐surplus” following historic marine mammal exploitation in the 19^thand 20^thcenturies. In resolving these outstanding hypotheses about drivers of Southern Ocean food web dynamics, this study emphasizes the fundamental importance of climate‐induced variability in biogeochemical cycling on ecological processes and improves the ability of paleo‐archives to inform the ecological consequences of future environmental change in the Southern Ocean.

    

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5. Journal of Vertebrate Paleontology, Program and Abstracts

   Bertrand, O.C. ; Brusatte, S. L. ; Shelley, S. L. ; Wible, J. R. ; Williamson, T. E. ; Chester, S. G. ; Holbrook, L. T. ; Lyson, T. R. ; Smith, T. ; Meng, J. ( October 2020 , Society of Vertebrate paleontology)

   The end-Cretaceous mass extinction, 66 million years ago, profoundly reshaped the biodiversity of our planet. After likely originating in the Cretaceous, placental mammals (species giving live birth to well-developed young) survived the extinction and quickly diversified in the ensuing Paleocene. Compared to Mesozoic species, extant placentals have advanced neurosensory abilities, enabled by a proportionally large brain with an expanded neocortex. This brain construction was acquired by the Eocene, but its origins, and how its evolution relates to extinction survivorship and recovery, are unclear, because little is known about the neurosensory systems of Paleocene species. We used high-resolution computed tomography (CT) scanning to build digital brain models in 29 extinct placentals (including 23 from the Paleocene). We added these to data from the literature to construct a database of 98 taxa, from the Jurassic to the Eocene, which we assessed in a phylogenetic context. We find that the Phylogenetic Encephalization Quotient (PEQ), a measure of relative brain size, increased in the Cretaceous along branches leading to Placentalia, but then decreased in Paleocene clades (taeniodonts,phenacodontids, pantodonts, periptychids, and arctocyonids). Later, during the Eocene, the PEQ increased independently in all crown groups (e.g., euarchontoglirans and laurasiatherians). The Paleocene decline in PEQ was driven by body mass increasing much more rapidly after the extinction than brain volume. The neocortex remained small, relative to the rest of the brain, in Paleocene taxa and expanded independently in Eocene crown groups. The relative size of the olfactory bulbs, however, remained relatively stable over time, except for a major decrease in Euarchontoglires and some Eocene artiodactyls, while the petrosal lobules (associated with eye movement coordination) decreased in size in Laurasiatheria but increased in Euarchontoglires. Our results indicate that an enlarged, modern-style brain was not instrumental to the survival of placental mammal ancestors at the end-Cretaceous, nor to their radiation in the Paleocene. Instead, opening of new ecological niches post-extinction promoted the diversification of larger body sizes, while brain and neocortex sizes lagged behind. The independent increase in PEQ in Eocene crown groups is related to the expansion of the neocortex, possibly a response to ecological specialization as environments changed, long after the extinction. 

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