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Evolutionary drivers for flightless, wing-propelled divers in the Northern and Southern Hemispheres

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... Because extant seabirds respond quickly to changes in their environments (Trathan et al., 2007;Grémillet and Boulinier, 2009;Korczak-Abshire, 2010), we hypothesize that the changes in the fossil record of crown-group Miocene seabirds will reflect past environmental changes (Warheit, 2002). Some studies have shown that for some measures, e.g., richness through time, patterns found in seabirds closely correlate to those from marine mammals and cartilaginous fishes (Ando and Fordyce, 2014;Villafaña and Rivadeneira, 2014;Pimiento et al., 2016). Therefore, seabirds can serve as a proxy, or at least a baseline, for studying the faunal evolution of marine vertebrates and their responses to changing palaeoclimates. ...
... In addition to yielding statistically testable observations, our specimen-based methodology eliminates the influence of publication bias and ameliorates the influence of collector bias. The ease with which seabird postcranial material is identified likely is a factor in its frequent collection and its preponderance among collections (Ando and Fordyce, 2014). And by using the data from all known fossil specimens from a given timeframe to detail patterns of taxonomic change, publication bias is eliminated. ...
... The observed increase in pan-alcid abundance is likely a product of tectonic and climate changes occurring in the late Neogene (see Section 4.3), but taphonomic bias may also be a factor. Pan-alcids are wing-propelled divers that use their forelimbs to swim through water in pursuit of prey and some of the anatomical adaptations resulting for this include thickened cortical bone and shortened, compressed forelimbs that provide structural strength and ballast (Habib, 2010;Ando and Fordyce, 2014). Within this study, mancallines exemplify these morphological changes compared to alcids, procellariids and sulids, and these skeletal adaptations have been cited as evidence of a flightless lifestyle ( Fig. 8; Livezey, 1988). ...
Article
California has experienced major climate change from the early Miocene (~ 23 Ma) to the present. Fossil seabirds are useful for studying marine faunal responses to these changes because they are numerous in museum collections and easily identified to the family-level from fragmentary remains. Because extant seabirds respond quickly to environmental changes, we hypothesize that the fossil record of crown-group Miocene seabirds will reflect past environments. Previous studies of fossil seabird diversity through the Cenozoic of the North Pacific relied mainly on literature records to describe the appearance and disappearance of seabird species and correlated these patterns to geologic and climatic events. Our study uses an empirical, specimen-based approach to describe the seabird response to climate and tectonic change during ~ 12 million years of coastal California’s geologic history (middle Miocene to early Pliocene). The foundation of our dataset is 242 fossil seabird specimens from Orange County. The strata from Orange County form the basis for delineating chronostratigraphic bins used for studying 285 additional seabird fossils from other parts of California, for a total of 527 seabird fossils examined. Our results show a relationship between pelagic seabirds and offshore facies as well as a clear increase of pan-alcid abundance and decline of sulid abundance through time. This pattern may be the result of taphonomic bias combined with the effect of shallower facies preserved through time. The increase in pan-alcid abundance is also coincident with global climatic and tectonic changes and with enhanced and stable nutrient upwelling. Upwelling through this time also helps to explain morphological changes in salmon and speciation rates in marine mammals. The specimen-based methodology used here can be applied to contemporaneous taxa, such as marine mammals, to quantitatively analyze diversity during the late Neogene and further explore the relationship between physical drivers and faunal change.
... Because extant seabirds respond quickly to changes in their environments (Trathan et al., 2007;Grémillet and Boulinier, 2009;Korczak-Abshire, 2010), we hypothesize that the changes in the fossil record of crown-group Miocene seabirds will reflect past environmental changes (Warheit, 2002). Some studies have shown that for some measures, e.g., richness through time, patterns found in seabirds closely correlate to those from marine mammals and cartilaginous fishes (Ando and Fordyce, 2014;Villafaña and Rivadeneira, 2014;Pimiento et al., 2016). Therefore, seabirds can serve as a proxy, or at least a baseline, for studying the faunal evolution of marine vertebrates and their responses to changing palaeoclimates. ...
... In addition to yielding statistically testable observations, our specimen-based methodology eliminates the influence of publication bias and ameliorates the influence of collector bias. The ease with which seabird postcranial material is identified likely is a factor in its frequent collection and its preponderance among collections (Ando and Fordyce, 2014). And by using the data from all known fossil specimens from a given timeframe to detail patterns of taxonomic change, publication bias is eliminated. ...
... The observed increase in pan-alcid abundance is likely a product of tectonic and climate changes occurring in the late Neogene (see Section 4.3), but taphonomic bias may also be a factor. Pan-alcids are wing-propelled divers that use their forelimbs to swim through water in pursuit of prey and some of the anatomical adaptations resulting for this include thickened cortical bone and shortened, compressed forelimbs that provide structural strength and ballast (Habib, 2010;Ando and Fordyce, 2014). Within this study, mancallines exemplify these morphological changes compared to alcids, procellariids and sulids, and these skeletal adaptations have been cited as evidence of a flightless lifestyle ( Fig. 8; Livezey, 1988). ...
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... Ando and Fordyce (2014-in this issue) tackle this issue by examining the evolutionary his- tory of the most specialized of pelagic seabirds (flightless wing- propelled diving birds) an assemblage that comprises at least four clades of diving birds evolved during the Cenozoic. Ando and Fordyce (2014-in this issue) compiled taxonomic richness from the Paleobiology Database to test, at several geographic scales, whether flightless wing- propelled diving seabirds showed contrasting patterns of richness with marine mammals at concomitant temporal intervals. By mapping out diversity data with geographic and temporal specificity, Ando and Fordyce (2014-in this issue) were able to discern a specific window, be- tween the late Oligocene to early Miocene, when richness patterns be- tween flightless divers and marine mammals were inverted, at both global and basinal scales. ...
... Examining other marine tetrapod clades that spend substan- tial time on shore should test for a more general pattern. Ando and Fordyce (2014-in this issue) detected some evidence for biotic interac- tion in the form of possible negative correlation of marine bird diversity with marine mammal diversity. This is concordant with other contribu- tions of this volume that underscore the role of biotic interactions in shaping marine tetrapod evolution, even when these interactions are a by-product of physical changes in the Earth's ocean system. ...
... These toothed species may well have preyed on penguins and it is conceivable that dispersal of stem group cetaceans into the Subantarctic and Antarctic regions resulted in an increased selective pressure on the escape strategies of penguins. However, if predation pressure by cetaceans played a role in the evolution of the penguin flipper, it is difficult to understand why plotopterids and auks, with less specialized, Muriwaimanu-like wings, coexisted with cetaceans in the North Pacific [33]. Earlier analyses did not identify a correlation between the diversity of stem group cetaceans and stem group penguins [33], but the fossil record of both groups is continuously improving for the Subantarctic and Antarctic regions and future studies may provide new insights into competitive interactions. ...
... However, if predation pressure by cetaceans played a role in the evolution of the penguin flipper, it is difficult to understand why plotopterids and auks, with less specialized, Muriwaimanu-like wings, coexisted with cetaceans in the North Pacific [33]. Earlier analyses did not identify a correlation between the diversity of stem group cetaceans and stem group penguins [33], but the fossil record of both groups is continuously improving for the Subantarctic and Antarctic regions and future studies may provide new insights into competitive interactions. Even though it is not possible to identify a single evolutionary driver for the evolution of paddleshaped wings in penguins, the wing of CM 2018.124.4 documents an early stage in the evolution of wing-propelled diving in penguins. ...
Article
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We describe a partial skeleton of a stem group penguin from the Waipara Greensand in New Zealand, which is tentatively assigned to Muriwaimanu tuatahi. The fossil includes the first complete wing of a Paleocene penguin and informs on previously unknown features of the mandible and tibiotarsus of small-sized Sphenisciformes from the Waipara Greensand. The wing is distinguished by important features from that of all geologically younger Sphenisciformes and documents an early stage in the evolution of wing-propelled diving in penguins. In particular, the wing of the new fossil exhibits a well-developed alular phalanx and the distal phalanges are not flattened. Because the wing phalanges resemble those of volant birds, we consider it likely that the wing feathers remained differentiated into functional categories and were not short and scale-like as they are in extant penguins. Even though the flippers of geologically younger penguins may favor survival in extremely cold climates, they are likely to have been shaped by hydrodynamic demands. Possible selective drivers include a diminished importance of the hindlimbs in subaquatic propulsion, new foraging strategies (the caudal end of the mandible of the new fossil distinctly differs from that of extant penguins), or increased predation by marine mammals.
... The paleoenvironmental context of marginal marine tetrapod fossils (7,20) likewise indicates that warm, shallow marginal marine habitats provide favorable settings for terrestrial-marine transitions, especially in ectotherms. Conversely, mid-Cenozoic cooling and increases in marine productivity-particularly in the North Pacific and Southern Ocean-coincided with bird and mammal invasions (21,22), and these regions remain hotspots of marine mammal diversity (23). However, such relationships are not always rigid throughout the history of a clade: Cetaceans evolved in shallow equatorial seas (18) but now thrive in high-latitude oceans; the origin of penguins preceded Southern Hemisphere cooling by several million years (24). ...
... Near-shore communities often host more lineages with higher endemism and frequent turnover (16,(82)(83)(84). Specific spatial and temporal successions hint at competitive interactions, as among flightless seabirds and marine mammals competing for shore space (22), replacement of herbivorous desmostylians by sirenians in the North Pacific (82), and replacement of phocids by otariids in South America (83). ...
Article
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Many top consumers in today's oceans are marine tetrapods, a collection of lineages independently derived from terrestrial ancestors. The fossil record illuminates their transitions from land to sea, yet these initial invasions account for a small proportion of their evolutionary history. We review the history of marine invasions that drove major changes in anatomy, physiology, and ecology over more than 250 million years. Many innovations evolved convergently in multiple clades, whereas others are unique to individual lineages. The evolutionary arcs of these ecologically important clades are framed against the backdrop of mass extinctions and regime shifts in ocean ecosystems. Past and present human disruptions to marine tetrapods, with cascading impacts on marine ecosystems, underscore the need to link macroecology with evolutionary change. Copyright © 2015, American Association for the Advancement of Science.
... Several common structures shared convergently with penguins and auks in the wing and shoulder girdle elements, such as short, dorsoventrally compressed wing bones, or a long processus acrocoracoideus, indicate that plotopterids were flightless, wing-propelled diving birds. However, detailed discussions on their function and ecology have been limited (Howard, 1969;Olson, 1980;Ando & Fordyce, 2014). A total of 11 species in eight genera of plotopterids have been described, but the scapulae, Shimonoseki-City, Yamaguchi Prefecture, Japan. ...
... The variation of the shoulder girdle region, as indicated by a different shape of the caudal scapula in plotopterids (Mayr & Goedert, 2016), suggests that there was a morpho-functional variation in their evolutionary history. As the competition with marine mammals has been suggested as a cause of the demise of giant forms of penguins and plotopterids (Olson & Hasegawa, 1979;Ando, 2007;Ando & Fordyce, 2014), the morpho-functional variation in plotopterids could have related to such event. ...
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The discovery of a well-preserved cranial end of a plotopterid scapula from the Early Oligocene Jinnobaru Formation in southwestern Japan has provided a fine example of its bone structure and has enabled the reconstruction of the triosseal canal (canalis triosseus) of the unique extinct penguin-like bird. It is believed that plotopterids performed penguin-like underwater propulsion using wings that were similar to those of penguins. Until this discovery, the lack of well-preserved plotopterid scapulae hindered reconstruction of the canalis triosseus, which is an important structure for the wing-upstroke. We reconstructed a composite model of the canalis triosseus based on the new scapula. The reconstructed size of the canal is as large as that in Emperor Penguins ( Aptenodytes forsteri ), suggesting that the bird had a large and powerful m. supracoracoideus, which is the essential muscle for the powered upstroke required for wing-propelled diving. Plotopterids likely have had the same functional requirement as penguins, the powerful wing-upstroke in the water. They must have also been capable swimmers. This scapula accounts for the structural difference between plotopterids and penguins in terms of the canalis triosseus. The large canalis triosseus of plotopterids was composed of the elongated acromion of the scapula, while penguins have a long processus acromialis claviculae for the same function.
... The North Pacific IAR is 152 + 60.4 ich cm 22 Myr 21 in the Early Oligocene, approximately double the contemporary values of the South Pacific, and slightly lower than those of the Palaeocene North Pacific (177.3 + 21.5 ich cm 22 Myr 21 ; m 1 = m 2 , p ¼ 0.006), mirroring the observed difference in fish production between the Early Palaeogene and the Oligocene observed in the South Pacific (figure 2b). The Eocene-Oligocene transition is a time of increased diatom production in the Southern Ocean, which is thought to have driven an increase in food web efficiency, small forage fish abundance and the diversification of marine mammals and seabirds [25][26][27][28][29], which would prey on the small pelagic fish represented in our ichthyolith records. However, it appears that increased production of large phytoplankton at high latitudes did not drive an increase in ray-finned fish and elasmobranch production in the gyres, as the beginning of 'Icehouse Earth' was associated with a decrease in both fish and elasmobranch production. ...
... Notably, the Early Miocene coincides with the radiations of baleen whales [25,29,32], large pelagic ray-finned fish like tunas [33], and many sea birds [26], all of which may have been competitors for resources with elasmobranchs, either directly by targeting common prey, or indirectly by targeting lower trophic levels like krill and forage fish. Pelagic elasmobranchs obviously did not become extinct, indeed, there are numerous notable pelagic shark species, including Megalodon, that have a prominent fossil record during the Neogene [34]. ...
Article
While the history of taxonomic diversification in open ocean lineages of ray-finned fish and elasmobranchs is increasingly known, the evolution of their roles within the open ocean ecosystem remains poorly understood. To assess the relative importance of these groups through time, we measured the accumulation rate of microfossil fish teeth and elasmobranch dermal denticles (ichthyoliths) in deep-sea sediment cores from the North and South Pacific gyres over the past 85 million years (Myr). We find three distinct and stable open ocean ecosystem structures, each defined by the relative and absolute abundance of elasmobranch and ray-finned fish remains. The Cretaceous Ocean (pre-66 Ma) was characterized by abundant elasmobranch denticles, but low abundances of fish teeth. The Palaeogene Ocean (66-20 Ma), initiated by the Cretaceous/Palaeogene mass extinction, had nearly four times the abundance of fish teeth compared with elasmobranch denticles. This Palaeogene Ocean structure remained stable during the Eocene greenhouse (50 Ma) and the Eocene-Oligocene glaciation (34 Ma), despite large changes in the overall accumulation of both groups during those intervals, suggesting that climate change is not a primary driver of ecosystem structure. Dermal denticles virtually disappeared from open ocean ichthyolith assemblages approximately 20 Ma, while fish tooth accumulation increased dramatically in variability, marking the beginning of the Modern Ocean. Together, these results suggest that open ocean fish community structure is stable on long timescales, independent of total production and climate change. The timing of the abrupt transitions between these states suggests that the transitions may be due to interactions with other, non-preserved pelagic consumer groups. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
... Early pinnipedimorphs, cetaceans, and flightless seabirds.-Several studies have investigated possible evolutionary interactions between early pinnipedimorphs, cetaceans, and sea birds (Olson 1985;Olson and Hasegawa 1979;Ando and Fordyce 2014;. Most Oligocene toothed baleen whales were quite small (e.g., 2-4 m body length, Fucaia buelli; and some at least were raptorial piscivores like early pinnipedimorphs Clementz 2015, 2016), raising the possibility that they competed for prey. ...
... Pinnipedimorph diversification has been implicated in the extinction of the giant flightless wing-propelled penguin-like plotopterids and giant Oligo-Miocene penguins (Olson 1985;Olson and Hasegawa 1979). However, analyses of diversity trends find little long term evidence for competitive displacement of penguins and plotopterids by pinnipeds, instead highlighting echolocating toothed whales (Odontoceti) as competitors (Ando and Fordyce 2014). Given various differences in feeding morphology between early pinnipedimorphs and toothed Clementz 2015, 2016;Marx et al. 2016), perhaps odontocetes occupied a more competitive role that could explain the extinction of toothed mysticetes. ...
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The early pinnipedimorph Enaliarctos was a marine-adapted carnivore with dental and locomotor features intermediate between terrestrial arctoids and living pinnipeds. New specimens of Enaliarctos are described from Oligocene and Miocene deposits on the Pacific coast of North America, and include the oldest enaliarctine mandible (Yaquina Formation, 30.6–27.4 Ma), the first enaliarctine from Northern California (Skooner Gulch Formation, 23.8–22 Ma), and the stratigraphically youngest fossil of the genus (Astoria Formation, 17.3–16.6 Ma). The wide biogeographic and temporal range of Enaliarctos provided the potential for interaction or competition with plotopterid birds, odontocete whales, and crown pinnipeds such as early odobenids, early otariids, and desmatophocids. The expansion of the known ranges of Enaliarctos species and the description of additional morphology, particularly of the mandible and lower dentition, provides insight into the origins of pinniped diversity and their possible interactions with other early Neogene coastal marine organisms.
... Individual examples of faunal turnover and extinctions of large marine vertebrates (collectively known as 'marine megafauna' , which includes, but is not limited to marine mammals, seabirds, turtles, sharks and rays 10,11 ) have been observed around this period. These include a substantial drop in cetacean [12][13][14] (but see ref. 15 ) and penguin diversity 16,17 , the extinction of dugongids in the Western Atlantic and Mediterranean regions [18][19][20] , the loss of the largest shark that ever lived (Carcharocles megalodon) 21,22 and extinctions of sea turtles (for example, Psephophorus, a leatherback turtle) 23 . However, it remains unclear whether these megafauna losses were simply conspicuous background extinctions or formed part of a global marine extinction event resulting from the environmental changes of the Plio− Pleistocene 8,24 . ...
... Some genera may have only succumbed to repeated sealevel oscillations or when habitat loss coincided with other extinction drivers (for example, prey availability and/or competition) 62,63 , which may explain the continuation of elevated extinction rates in the Pleistocene. Similar mechanisms might be responsible for the previously noted decline of some megafauna groups in the late Miocene 16,43 , although such losses were not comparable in magnitude to the Pliocene losses documented here (Fig. 1a). ...
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Full text: rdcu.be/tIj5. The end of the Pliocene marked the beginning of a period of great climatic variability and sea-level oscillations. Here, based on a new analysis of the fossil record, we identify a previously unrecognized extinction event among marine megafauna (mammals, seabirds, turtles and sharks) during this time, with extinction rates three times higher than in the rest of the Cenozoic, and with 36% of Pliocene genera failing to survive into the Pleistocene. To gauge the potential consequences of this event for ecosystem functioning, we evaluate its impacts on functional diversity, focusing on the 86% of the megafauna genera that are associated with coastal habitats. Seven (14%) coastal functional entities (unique trait combinations) disappeared, along with 17% of functional richness (volume of the functional space). The origination of new genera during the Pleistocene created new functional entities and contributed to a functional shift of 21%, but minimally compensated for the functional space lost. Reconstructions show that from the late Pliocene onwards, the global area of the neritic zone significantly diminished and exhibited amplified fluctuations. We hypothesize that the abrupt loss of productive coastal habitats, potentially acting alongside oceanographic alterations, was a key extinction driver. The importance of area loss is supported by model analyses showing that animals with high energy requirements (homeotherms) were more susceptible to extinction. The extinction event we uncover here demonstrates that marine megafauna were more vulnerable to global environmental changes in the recent geological past than previously thought.
... Recent evaluation of hypotheses regarding competitive exclusion of flightless seabirds by marine mammals found support for significant interactions between marine mammals and Spheniscidae (penguins) in the Southern Hemisphere, and between the extinct flightless, wing-propelled †Plotopteridae of the Northern Pacific Ocean (Ando and Fordyce 2013). However, no significant diversity correlations were identified among marine mammals and flightless pan-alcids ( †Mancallinae and †Pinguinus) and thus, pan-alcid evolutionary drivers may be more heavily influenced by physical factors such as paleoclimate (Ando and Fordyce 2013). Our results suggest that pan-alcids have diversified during periods of relative warmth (e.g. ...
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Puffins, auks and their allies in the wing-propelled diving seabird clade Pan-Alcidae (Charadriiformes) have been proposed to be key pelagic indicators of faunal shifts in Northern Hemisphere oceans. However, most previous phylogenetic analyses of the clade have focused only on the 23 extant alcid species. Here we undertake a combined phylogenetic analysis of all previously published molecular sequence data (∼ 12 kb) and morphological data (n = 353 characters) with dense species level sampling that also includes 28 extinct taxa. We present a new estimate of the patterns of diversification in the clade based on divergence time estimates that include a previously vetted set of twelve fossil calibrations. The resultant time trees are also used in the evaluation of previously hypothesized paleoclimatic drivers of pan-alcid evolution. Our divergence dating results estimate the split of Alcidae from its sister taxon Stercorariidae during the late Eocene (∼ 35 Ma), an evolutionary hypothesis for clade origination that agrees with the fossil record and that does not require the inference of extensive ghost lineages. The extant dovekie Alle alle is identified as the sole extant member of a clade including four extinct Miocene species. Furthermore, whereas an Uria + Alle clade has been previously recovered from molecular analyses, the extinct diversity of closely related Miocepphus species yields morphological support for this clade. Our results suggest that extant alcid diversity is a function of Miocene diversification and differential extinction at the Pliocene–Pleistocene boundary. The relative timing of the Middle Miocene climatic optimum and the Pliocene–Pleistocene climatic transition and major diversification and extinction events in Pan-Alcidae, respectively, are consistent with a potential link between major paleoclimatic events and pan-alcid cladogenesis.
... Competition with large marine mammals has been frequently proposed as a driver of extinction in flightless wing-propelled divers (Olson 1985;Olson and Hasegawa 1979;Simpson 1946;Warheit and Lindberg 1988). However, temporal patterns of biodiversity suggest that no universal driver of extinction exists among giant penguins, flightless pan-alcids and plotopterids, and that competitive displacement by marine mammals was likely less important than environmental drivers (e.g., climate changes) for some taxa (Ando and Fordyce 2013). As with the increased body mass variability documented in terrestrial birds in relation to continent size, a link between the relative abundance of "large" species and continent size has also been proposed (Maurer 2013). ...
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Hypotheses regarding the evolution of many clades are often generated in the absence of data from the fossil record and potential biases introduced by exclusion of paleontological data are frequently ignored. With regard to body size evolution, extinct taxa are frequently excluded because of the lack of body mass estimates—making identification of reliable clade specific body mass estimators crucial to evaluating trends on paleontological timescales. Herein, I identify optimal osteological dimensions for estimating body mass in extinct species of Pan-Alcidae (Aves, Charadriiformes) and utilize newly generated estimates of body mass to demonstrate that the combination of neontological and paleontological data produces results that conflict with hypotheses generated when extant species data are analyzed in isolation. The wing-propelled diving Pan-Alcidae are an ideal candidate for comparing estimates of body mass evolution based only on extant taxa with estimates generated including fossils because extinct species diversity (≥31 species) exceeds extant diversity, includes examples from every extant genera, and because phylogenetic hypotheses of pan-alcid relationships are not restricted to the 23 extant species. Phylogenetically contextualized estimation of body mass values for extinct pan-alcids facilitated evaluation of broad scale trends in the evolution of pan-alcid body mass and generated new data bearing on the maximum body mass threshold for aerial flight in wing-propelled divers. The range of body mass in Pan-Alcidae is found to exceed that of all other clades of Charadriiformes (shorebirds and allies) and intraclade body mass variability is recognized as a recurring theme in the evolution of the clade. Finally, comparisons of pan-alcid body mass range with penguins and the extinct †Plotopteridae elucidate potentially shared constraints among phylogenetically disparate yet ecologically similar clades of wing-propelled divers.
... The majority of the chondrichthyan assemblage from the Santa Cruz section of the Purisima Formation -and the majority of Cenozoic strata on the west coast, for that matter -remains unpublished. Lack of published information on chondrichthyan occurrences hinders the study of faunal change in the eastern North Pacific, and as a result little is known regarding evolutionary interactions between chondrichthyans and other marine vertebrate groups in the eastern North Pacific including birds (Warheit 1992, Ando andFordyce 2014), sea turtles (Parham and Pyenson 2010), or marine mammals (Boessenecker 2013). Further study of eastern North Pacific fossil fish assemblages already present in museum collections will elucidate the recent evolution of particular sharks and fish viz. ...
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Megatoothed sharks (Family: Otodontidae) are among the most widely reported sharks in Cenozoic marine sediments worldwide, and certain species such as the famed Carcharocles megalodon are particularly abundant in Neogene deposits on the Atlantic margin of the United States. Cenozoic marine strata on the Pacific margin of North America have yielded one of the most densely sampled marine vertebrate records anywhere, but published occurrences of shark assemblages are uncommon. Rarer yet are published occurrences of C. megalodon from this region with unambiguous provenance and robust age control — critical data required for the study of recent marine vertebrate faunal evolution in the eastern North Pacific. A tooth of C. megalodon eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide. from near Santa Cruz, California, represents the first record of this species from the Purisima Formation and the geochronologically youngest occurrence (6.9–5.6 Ma, uppermost Miocene; late Messinian) of this species from northern California.
... Stem group penguins therefore reached a giant size very early in their evolution, and size increase appears to have commenced soon after flightlessness released penguins from aerodynamic constraints, with giant species existing over a period of at least 30 million years, from the mid-Paleocene to the late Oligocene. Why giant species disappeared towards the Neogene remains elusive, but the evolution of odontocete whales was considered as a factor that contributed to their demise (Ando and Fordyce 2014). ...
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We describe leg bones of a giant penguin from the mid-Paleocene Waipara Greensand of New Zealand. The specimens were found at the type locality of Waimanu manneringi and together with this species they constitute the oldest penguin fossils known to date. Tarsometatarsus dimensions indicate a species that reached the size of Anthropornis nordenskjoeldi, one of the largest known penguin species. Stem group penguins therefore attained a giant size very early in their evolution, with this gigantism existing for more than 30 million years. The new fossils are from a species that is phylogenetically more derived than Waimanu, and the unexpected coexistence of Waimanu with more derived stem group Sphenisciformes documents a previously unknown diversity amongst the world’s oldest penguins. The characteristic tarsometatarsus shape of penguins evolved early on, and the significant morphological disparity between Waimanu and the new fossil conflicts with recent Paleocene divergence estimates for penguins, suggesting an older, Late Cretaceous, origin.
... To understand size evolution in penguins we therefore must not seek an explanation for the presence of giant species throughout the Paleogene, but one for the absence of equally large species in the Neogene and today. Earlier authors proposed that feeding competition with marine mammals played a role in the extinction of giant penguins and other very large wing-propelled diving birds 7,26,27 , and competition with gregarious pinnipeds for safe breeding was also considered 28 . The disappearance of giant penguins indeed coincides with the rise of marine mammals, that is, odontocete cetaceans and pinnipeds 27 , but the exact causes and mechanisms of a competitive replacement remain poorly understood. ...
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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.
... This is one of the many reasons for the importance of specimen occurrence information. In marine mammal studies, some recent examples for the use of PBDB include ecological analysis of marine mammals versus diatoms as primary producers and that of marine mammals versus other animals [39,47], the evolution of gigantism in whales and sirenians [48,49], and reconstruction of desmostylian habitats [50]. Correct provenance data (information of locality and occurrence) are requisites for these studies. ...
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Here, we report a new ‘discovery’ of a desmostylian fossil in the geological collection at a national university in Japan. This fossil was unearthed over 60 years ago and donated to the university. Owing to the original hand-written note kept with the fossil in combination with interview investigation, we were able to reach two equally possible fossil sites in the town of Tsuchiyu Onsen, Fukushima. Through the interviews, we learned that the fossil was discovered during construction of a debris flow barrier and that it was recognized as a ‘dinosaur’ bone among the locals and displayed in the Village Hall before/until the town experienced a fire disaster in 1954. As scientific findings, the fossil was identified to be a right femur of Paleoparadoxia (Desmostylia), which shows well-preserved muscle scars on the surface. The age was estimated to be 15.9 Ma or younger in zircon-dating. This study shows an excellent case that historical and scientific significances could be extracted from long-forgotten uncatalogued specimens as long as the original information is retained with the specimens.
... The causes of extinction of Mancallinae are not clear. Ando and Fordyce (2014) analysed patterns of geographical and temporal distributions of flightless wing-propelled diving birds and marine mammals, and argued that the extinction of Mancallinae was probably caused by both physical factors like climate change and biological factors such as competitions with marine mammals, in contrast to those of Plotopteridae and stem-group Sphenisciformes where biological factors are likely to have played a primary role (see also Olson and Hasegawa 1979;Warheit 1992). In the Shiriya local fauna, Mancallinae is associated with marine mammals including several pinnipeds (Hasegawa et al. 1988), and such a cooccurrence with marine mammals is apparently not rare for Mancallinae (e.g. ...
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Seabirds are higher-order predators in the marine ecosystem and hence good indicators of the marine environment. Although the North Pacific has been the focal area for investigations of seabird faunal dynamics, the Pleistocene seabird fossil record has been scarce in the western North Pacific. Here, remains of 32 species of seabirds and related taxa (Anatidae, Podicipedidae, Gaviidae, Diomedeidae, Hydrobatidae, Procellariidae, Phalacrocoracidae, Scolopacidae, Laridae, and Alcidae) are reported from the middle–late Pleistocene Shiriya local fauna, northeastern Japan (Marine Isotope Stages 9 and 5e, ~ 320 and ~ 120 ka). This is the first substantial Pleistocene seabird fauna reported from the region so far, and includes globally first fossil records for Cepphus carbo and extant species of Aethia. The fauna also includes three extinct species, Shiriyanetta hasegawai, Mancalla? sp., and Uria onoi, the former two of which were flightless. The occurrence of immature individuals indicates that at least two species had nearby breeding sites. The seabird populations had probably been sustained by enhanced oceanic productivity in this area during their age, but oceanographic fluctuations in the subsequent glacial period, including the probable disappearance of a nearby oceanic front, would have seriously affected their subsistence, likely causing local extinctions of some species.
... Whereas competition with other penguins certainly played a major role in the attainment of a giant size, the extinction of very large-sized penguins was probably due to competition with marine mammals (Simpson 1975, Ando & Fordyce 2014, Mayr et al. 2017c). ...
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Mayr, G., De Pietri, V.L., Love, L., Mannering, A. & Scofield, R.P., 9 August 2019. Leg bones of a new penguin species from the Waipara Greensand add to the diversity of very large-sized Sphenisciformes in the Paleocene of New Zealand. Alcheringa XX, xxx–xxx. ISSN 0311-5518 We describe a new large-sized species of the Sphenisciformes (penguins) from Paleocene strata of the Waipara Greensand in New Zealand. ?Crossvallia waiparensis, sp. nov. is represented by leg bones of a single individual as well as two tentatively referred proximal humeri and resembles Crossvallia unienwillia from the late Paleocene of Antarctica in size and morphology. The new species is the fifth published species of stem group Sphenisciformes from the Waipara Greensand and the fourth one, which has been formally named. It is distinguished from a recently reported tarsometatarsus of an unnamed large-sized penguin species from the Waipara Greensand and is the oldest well-represented giant penguin. ?C. waiparensis approaches the size of the Eocene taxa Anthropornis and Palaeeudyptes and provides further evidence that penguins attained a very large size early in their evolutionary history. Gerald Mayr [gerald.mayr@senckenberg.de], Senckenberg Research Institute and Natural History Museum Frankfurt, Ornithological Section, Senckenberganlage 25, D-60325 Frankfurt am Main, Germany; Vanesa L. De Pietri [vdepietri@canterburymuseum.com], Al Mannering [alman@slingshot.co.nz], R. Paul Scofield [pscofield@canterburymuseum.com], Canterbury Museum, Rolleston Avenue, Christchurch 8050, New Zealand; Leigh Love [lvlove@xtra.co.nz], PO Box 49, Waipara 7483, New Zealand.
... Competition for food (Fordyce and Jones 1990;Williams 1995) is generally cited as the primary factor for their extinction, but competition for breeding sites with pinnipeds may have also contributed (Warheit and Lindberg 1988). Ando and Fordyce (2014) found evidence that competitive replacement between odontocetes and large flightless wing propelled divers (in addition to abiotic factors) resulted in the extinction of the latter from mid-latitude waters in the Cenozoic. ...
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The Glen Murray fossil penguin was one of the first ancient penguins to be reported from the North Island of New Zealand when it was described in 1973. However, its significance for penguin diversity has remained largely unresolved since initial description. Here we show that the Glen Murray penguin exhibits two of three traits that are autapomorphic for Kairuku: the femur is very stout with a midshaft width <15% of the total femoral length and the tibiotarsus has a distinctly convex medial border in distal view. The third trait (absence of the crista medialis hypotarsi) cannot be assessed as the proximal end of the tarsometatarsus is missing. The Glen Murray penguin is most likely a distinct species that should be assigned to the genus Kairuku, although we refer it to Kairuku sp. pending the discovery of more material. Reappraisal of local stratigraphy indicates that the Glen Murray fossil penguin is from the Dunphail Siltstone member of the Glen Massey Formation and can be assigned to the lower Whaingaroan stage (34.6–29.8 Ma).
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A review of the fossil record of birds in Asia from the Early Cretaceous to Pleistocene is provided. The main stages of the formation of the modern faunas are outlined. Ornithuromorph birds become a diverse group in the Late Cretaceous, the Paleocene – Oligocene avifaunas of the region comprise mostly representatives of the archaic lineages. Beginning with the Miocene, modern families dominate the faunas, and the formation of the modern genera has been generally completed by the late Miocene. Modern species (or complexes of species) appear in the Pliocene or, more likely, in the Pleistocene. The basic paleobiogeographic events which influenced the evolution of avian communities are outlined. It is also noted that many time intervals of the avian evolution in Asia, as well as many geographical areas of this continent, remain largely or completely unstudied.
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Despite its current low diversity, the penguin clade (Sphenisciformes) is one of the groups of birds with the most complete fossil record. Likewise, from the evolutionary point of view, it is an interesting group given the adaptations developed for marine life and the extreme climatic occupation capacity that some species have shown. In the present contribution, we reviewed and integrated all of the geographical and phylogenetic information available, together with an exhaustive and updated review of the fossil record, to establish and propose a biogeographic scenario that allows the spatial-temporal reconstruction of the evolutionary history of the Sphenisciformes, discussing our results and those obtained by other authors. This allowed us to understand how some abiotic processes are responsible for the patterns of diversity evidenced both in modern and past lineages. Thus, using the BioGeoBEARS methodology for biogeographic estimation, we were able to reconstruct the biogeographical patterns for the entire group based on the most complete Bayesian phylogeny of the total evidence. As a result, a New Zealand origin for the Sphenisciformes during the late Cretaceous and early Paleocene is indicated, with subsequent dispersal and expansion across Antarctica and southern South America. During the Eocene, there was a remarkable diversification of species and ecological niches in Antarctica, probably associated with the more temperate climatic conditions in the Southern Hemisphere. A wide morphological variability might have developed at the beginning of the Paleogene diversification. During the Oligocene, with the trends towards the freezing of Antarctica and the generalized cooling of the Neogene, there was a turnover that led to the survival (in New Zealand) of the ancestors of the crown Sphenisciform lineages. Later these expanded and diversified across the Southern Hemisphere, strongly linked to the climatic and oceanographic processes of the Miocene. Finally, it should be noted that the Antarctic recolonization and its hostile climatic conditions occurred in some modern lineages during the Pleistocene, possibly due to exaptations that made possible the repeated dispersion through cold waters during the Cenozoic, also allowing the necessary adaptations to live in the tundra during the glaciations.
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Catastrophic hypotheses for mass extinctions are commonly criticized because many taxa gradually disappear from the fossil record prior to the extinction. Presumably, a geologically instantaneous catastrophe would not cause a reduction in diversity or a series of minor extinctions before the actual mass extinction. Two types of sampling effects, however, could cause taxa to appear to decline before their actual biotic extinction. The first of these is reduced sample size provided in the sedimentary record and the second, which we examine in greater detail, is artificial range truncation. The fossil record is discontinuous in time and the recorded ranges of species or of higher taxa can only extend to their last known occurrence in the fossil record. If the distribution of last occurrences is random with respect to actual biotic extinction, then apparent extinctions will begin well before a mass extinction and will gradually increase in frequency until the mass extinction event, thus giving the appearance of a gradual extinction. Other factors, such as regressions, can exacerbate the bias toward gradual disappearance of taxa from the fossil record. Hence, gradual extinction patterns prior to a mass extinction do not necessarily eliminate catastrophic extinction hypotheses. The recorded ranges of fossils, especially of uncommon taxa or taxa in habitats not represented by a continuous record, may be inadequate to test either gradual or catastrophic hypotheses.
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Data from recent collections of Paleocene and Eocene mammals in the Western Interior of North America show marked inverse correlations both of generic diversity and relative abundance between multituberculates and rodents. The largest diminution in multituberculate diversity occurred in the latest Paleocene, near the Tiffanian-Clarkforkian boundary, not in the early Eocene as suggested previously. Reconstruction of diets, diel activity patterns, locomotor habits, and body sizes of multituberculates and rodents suggests that both groups potentially utilized similar resources. The hypothesis that competitive exclusion may have played a role in the decline of multituberculates is strengthened by recent evidence that rodents evolved in Asia, immigrating to North America in latest Pelocene time. Evidence in support of alternative hypothesis employed to account for the decline and eventual extinction of multituberculates is wanting.-from Author
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South America was isolated from other continents during most of the Cenozoic, developing a singular mammalian fauna. In contrast to North America, Europe, Asia, and Africa, up to the late Neogene, the carnivore adaptive zone in South America was populated by crocodiles (Sebecidae), large snakes (Madtsoiidae), large birds (Phorusrhacidae), and metatherian mammals (Sparassodonta). Sparassodonta were varied and comprised a wide range of body masses (≈ 2–50 kg) and food habits. Their diversity decreased towards the late Miocene (Huayquerian Stage/Age) and the group became extinct in the “middle” Pliocene (≈ 3 Ma, Chapadmalalan Stage/Age). Several authors have suggested that the cause of this decline and extinction was the ingression of carnivorans to South America (about 6–7 Ma ago), because they competed with the Sparassodonta; although this hypothesis has been criticized in recent years. With the intention of testing the hypothesis of “competitive displacement,” we review the fossil record of South American Sparassodonta and Carnivora, collect data about diversity, estimate size and diet, and determine first and last appearances. The diversity of Sparassodonta is low relative to that of Carnivora throughout the Cenozoic with the early Miocene (Santacrucian Stage/Age) showing the greatest diversity with 11 species. In the late Miocene-middle Pliocene (Huayquerian Stage/Age), the fossil record shows overlap of groups, and the Sparassodonta’s richness curve begins to decline with the first record of Carnivora. Despite this overlap, carnivorans diversity ranged from four or fewer species in the late Miocene-Pliocene to a peak of around 20 species in the early Pleistocene (Ensenadan Stage/Age). Carnivora was initially represented by small-sized, omnivorous species, with large omnivores first appearing in the Chapadmalalan Stage/Age. Over this period, Sparassodonta was represented by large and small hypercarnivores and a single large omnivorous species. From this review of the fossil record, it is suggested that factors other than competitive displacement may have caused the extinction of the Sparassodonta.
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Les activites humaines ont restreint les sites reproducteurs d'H. b. a des bandes de cotes innaccessibles et a des iles et ilots eloignes des cotes. Ces memes zones sont utilises pour la chasse et la reproduction par les pinnipedes. Cette competition reduit encore le succes reproducteur des oiseaux
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Three skeletons collected from the late Oligocene Kokoamu Greensand of New Zealand are among the most complete Paleogene penguins known. These specimens, described here as Kairuku waitaki, gen. et sp. nov., and Kairuku grebneffi, sp. nov., reveal new details of key elements of the stem penguin skeleton associated with underwater flight, including the sternum, flipper, and pygostyle. Relative proportions of the trunk, flippers, and hind limbs can now be determined from a single individual for the first time, offering insight into the body plan of stem penguins and improved constraints on size estimates for ‘giant’ taxa. Kairuku is characterized by an elongate, narrow sternum, a short and flared coracoid, an elongate narrow flipper, and a robust hind limb. The pygostyle of Kairuku lacks the derived triangular cross-section seen in extant penguins, suggesting that the rectrices attached in a more typical avian pattern and the tail may have lacked the propping function utilized by living penguins. New materials described here, along with re-study of previously described specimens, resolve several long-standing phylogenetic, biogeographic, and taxonomic issues stemming from the inadequate comparative material of several of the first-named fossil penguin species. An array of partial associated skeletons from the Eocene–Oligocene of New Zealand historically referred to Palaeeudyptes antarcticus or Palaeeudyptes sp. are recognized as at least five distinct species: Palaeeudyptes antarcticus, Palaeeudyptes marplesi, Kairuku waitaki, Kairuku grebneffi, and an unnamed Burnside Formation species.
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Living cetaceans exhibit interspecific size ranging across several orders of magnitude, and rank among the largest vertebrates ever. Details of how cetaceans evolved different body sizes, however, remain obscure, because they lack basic morphological proxies that have been traditionally used in other fossil vertebrates. Here, we reconstruct the body size of extinct crown group cetaceans (Neoceti) using different regression methods on extant skull and length data, in a phylogenetic context. Because most fossil cetaceans are fragmentary, we developed regression equations to predict total length based on cranial metrics that are preserved on most fossil crania. The resultant regression equations are based on a database of skull and length data from most extant lineages of cetaceans (n = 45 species; 272 specimens), sampling all living mysticete genera and all major clades of odontocetes. In generating predictive equations, we compared both conventional species data regression and independent contrast regression methods, as well as single trait predictors and a new approach that combines the advantages of a partial least squares (PLS) multivariate regression with independent contrasts. This last approach leverages the predictive power of using multiple correlated proxies. Lastly, we used the rare occurrences of fossil cetaceans with preserved total lengths to test the performance of our predictive equations for reconstructing body size from skull measurements alone. Our results demonstrate that incorporating information about phylogenetic relationships and multiple cranial measures in PLS scaling studies increases the accuracy of reconstructed body size, most notably by reducing prediction intervals by more than 70%. With this empirical foundation, we highlight the outline of major features in the evolution of body size for Neoceti and future opportunities to use these metrics for paleobiological questions.
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Competitive replacement has probably played a minor role in the history of tetrapods. In an assessment of the origins of 840 families of amphibians, reptiles, birds, and mammals, fewer than 26%, and probably fewer than 13%, were identified as candidate competitive replacements (CCR's). This is the pool of families that shared their geographic area of origination and their broadscale adaptations with a pre-existing family, and is thus a maximum measure of families that might have competitively displaced another. Most tetrapod families arose by expansion of the ecospace and geographic areas previously occupied by other members of the clade Tetrapoda. The numbers of CCRS through time are roughly in proportion to numbers of originations, but particular peaks in CCRS occurred after mass extinctions. Pure expansions, with no possibility of competitive replacement, were prevalent during the Late Palaeozoic (radiation of early amphibian and reptile groups, and broadening of habitats occupied and diets) and during the mid Cretaceous (radiations of frogs, turtles, lizards, snakes, and birds).
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The initial radiation of the dinosaurs in the Triassic (c.200 M yr BP) has been generally regarded as a result of successful competition with the previously dominant mammal-like reptiles. A detailed review, including estimates of relative abundance, gives a different picture of the pattern of faunal replacements. The concepts of differential survival ("competitive') and opportunistic ecological replacement of higher taxonomic categories are contrasted (the latter involves chance radiation to fill adaptive zones that are already empty), and they are applied to the fossil record. There is no evidence that either thecodontians or dinosaurs demonstrated their superiority over mammal-like reptiles in massive competitive take-overs. Throughout most of the Triassic, the thecodontians shared carnivore adaptive zones with advanced mammal-like reptiles (cynodonts) until the latter became extinct (random processes, early to late Triassic). Among herbivores, the dicynodont mammal-like reptiles were largely replaced by diademodontoid mammal-like reptiles and rhynchosaurs (differential survival, middle to late Triassic). These groups then became extinct and dinosaurs replaced them and radiated rapidly (opportunism, latest Triassic). The late Triassic extinctions may be linked with floral and climatic changes. Explanations of dinosaur success based on the competitive superiority of their thermoregulation or locomotory capability are unnecessary.-from Author
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▪ Abstract The history of carnivorous mammals is characterized by a series of rise-and-fall patterns of diversification in which declining clades are replaced by phylogenetically distinct but functionally similar clades. Seven such examples from the last 46 million years are described for North America and Eurasia. In three of the seven turnover events, competition with replacement taxa may have driven the decline of formerly dominant taxa. In the remaining four this is less likely because inferred functional similarity was minimal during the interval of temporal overlap between clades. However, competition still may have been important in producing the rise-and-fall pattern through suppression of evolution within replacement taxa; as long as the large carnivore ecospace was filled, the radiation of new taxa into that ecospace was limited, only occurring after the extinction of the incumbents. The apparently inevitable decline of incumbent taxa may reflect the tendency for clades of large carnivorous mamm...
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A recent review by Ainley et al. has suggested that recent investigations of the ecological structure and processes of the Southern Ocean have “almost exclusively taken a bottom-up, forcing-by-physical-processes approach relating individual species' population trends to climate change”. We examine this suggestion and conclude that, in fact, there has been considerable research effort into ecosystem interactions over the last 25 years, particularly through research associated with management of the living resources of the Southern Ocean. Future Southern Ocean research will make progress only when integrated studies are planned around well structured hypotheses that incorporate both the physical and biological drivers of ecosystem processes.
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Body size is an important measure in biology and especially in paleobiology. With respect to fossil penguins from the Eocene La Meseta Formation of Seymour Island (West Antarctica) the overall size has to be judged from the dimensions of single bones. The analysis based on selected measurements of hind limb bones from the Polish collection of Eocene Antarctic penguins yielded results supporting predictions published formerly. Estimated body masses and lengths indicate that mean interspecific body size of extinct Antarctic Spheniscidae exceeded that of Recent species.
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In the past decade, evolutionary paleoecology has shifted away from corroborative research of the 'me-too-ecology' type towards its proper domain - the evolutionary consequences of ecological properties, roles, and strategies at the individual, population, community, and species levels. The science of evolutionary paleoecology tests for linkage between a species' ecology and its macroevolutionary history. Do the ecological characters of species within clades influence differntial rate dynamics, particularly rates of faunal turnover and diversification? Intellectual coequality, once hampered by the misunderstanding that the role of paleoecology is to find examples of past ecology imperfectly entombed in the fossil record, is strengthened by the increasing number of evolutionary ecologists who have called for explicit paleontological contributions to resolve theoretical issues. The fossil record provides a necessary perspective to an understanding of process.-Author
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Ecologists attempt to explain species diversity within Recent seabird communities in terms of Recent oceanographic and ecological phenomena. However, many of the principal oceanographic processes that are thought to structure Recent seabird systems are functions of geological processes operating at many temporal and spatial scales. For example, major oceanic currents, such as the North Pacific Gyre, are functions of the relative positions of continents and Antarctic glaciation, whereas regional air masses, submarine topography, and coastline shape affect local processes such as upwelling. It is hypothesized that the long-term development of these abiotic processes has influenced the relative diversity and community composition of north Pacific seabirds. By affecting both the physical and biological environments, geological factors such as Antarctic glaciation, eustatic changes in sea levels, and local tectonic activities influenced and will continue to influence the structure of seabird systems in the North Pacific. -from Author
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The main changes in the distribution and abundance of marine top predators in the Antarctic in the last two centuries were caused by human over-exploitation. Hypotheses that increases in populations of krill-eating penguins and seals represent recovery from exploitation, accelerated by removal of krill-eating whales, are being re-evaluated in the light of correlations between population size and reproductive success of seabirds and seals and various features of the biological and physical environment. These correlations involve phocid and otariid seals, penguins and flying birds and sites ranging from the Antarctic continent to sub-Antarctic islands. Although the nature of, and balance between, physical and biological influences differ between sites, regions and different types of predator, processes (including potentially important links with the Southern Oscillation) involving sea-ice extent and distribution play a key role. Major uncertainties over the nature of the links between physical and biological processes and the responses of marine populations preclude any confident prediction of the potential effects of future environmental change. However, certain taxa, especially those of specialist ecology, extreme demography and restricted distribution (especially in high latitudes) are especially vulnerable to at least some of the likely environmental changes.
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Red Queen hypotheses maintain that biotic interactions are the most important drivers of evolutionary change, whereas Court Jester hypotheses regard physical-environmental perturbations, such as climate change, as most important. Tests for the biotic effects of climate change that are conducted on too large a geographic scale can falsely reject the Court Jester because climate is so complex its manifestation is in opposite directions in different geographic areas. Consequently, faunal responses vary from place to place, and lumping of data from different climate zones averages out any local faunal responses. Likewise, tests that are conducted at inappropriate temporal scales will not be effective at distinguishing between the Red Queen and Court Jester.A test at a temporal and geographic scale that takes the above considerations into account suggests a biotic response of mammals to a climatic warming event in the northern Rocky Mountains 18.5–14.0 Ma (the late-Early Miocene climatic optimum). During the environmental perturbation, mammalian species richness possibly increased, faunal turnover was pronounced, and taxa adapted to warm, arid environments became more abundant in numbers of species and density of individuals. The data are consistent with environmental change—the Court Jester—driving evolutionary change at sub-continental spatial scales and temporal scales that exceed typical Milankovitch oscillations. The Red Queen may be active at smaller temporal and geographic scales.
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The main changes in the distribution and abundance of marine top predators in the Antarctic in the last two centuries were caused by human over-exploitation. Hypotheses that increases in populations of krill-eating penguins and seals represent recovery from exploitation, accelerated by removal of krill-eating whales, are being re-evaluated in the light of correlations between population size and reproductive success of seabirds and seals and various features of the biological and physical environment. These correlations involve phocid and otariid seals, penguins and flying birds and sites ranging from the Antarctic continent to sub-Antarctic islands. Although the nature of, and balance between, physical and biological influences differ between sites, regions and different types of predator, processes (including potentially important links with the Southern Oscillation) involving sea-ice extent and distribution play a key role. Major uncertainties over the nature of the links between physical and biological processes and the responses of marine populations preclude any confident prediction of the potential effects of future environmental change. However, certain taxa, especially those of specialist ecology, extreme demography and restricted distribution (especially in high latitudes) are especially vulnerable to at least some of the likely environmental changes.
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The statistical significance of differences in evolutionary rate between major taxonomic groups is evaluated using conventional chi-square techniques on stratigraphic range data. Romer's (1966) compilation of stratigraphic ranges of fossil mammals is used to determine whether orders differ significantly from each other in generic origination and extinction rates. The evolutionary histories of 2180 genera (primarily Cenozoic in age) are analyzed. Chi-square testing shows that significantly high or low ( P ≥ 0.99) extinction or origination occurs in 15% of the testable cases. Significantly high or low evolutionary turnover in a taxon (orders in this case) we term taxotely. Significantly high turnover rate is equivalent to Simpson's tachytely and significantly low turnover is equivalent to his bradytely. In the mammal data set, taxotely is largely attributable to the influence of South American endemics. Some of the effect is interpreted as an artifact of biases in the fossil record (or its study) and some is attributed to real biological aspects of mammalian evolution.
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Many odontocetes [modern toothed whales, Early Oligocene (35 Ma) — Recent] utilise high-frequency echolocation to facilitate predation, while mysticetes (baleen whales, Early Oligocene—Recent) possess a filter-feeding system which allows cropping of plankton. These adaptations are reflected in the unique skull structure of each group. Skulls of archaeocetes [primitive toothed whales, the ancestors of odontocetes and mysticetes, Middle Eocene—Late Oligocene (45 to 25 Ma)] indicate that they possessed neither baleen nor the capacity for echolocation. Studies on Northern Hemisphere Cetacea (whales and dolphins) have suggested a paucity of Oligocene Cetacea but also have stressed that the Oligocene was an important time in cetacean evolution. The observation of some authors that cetacean diversity declined in the Oligocene has been difficult to reconcile with the origins then of odontocetes and mysticetes. Hypotheses have stressed that the “decline” reflects decreased oceanic thermal gradients, upwelling, plankton diversity and thus fewer cetacean niches. The Austral Oligocene fauna allows alternative explanations. The earliest known mysticetes and odontocetes are New Zealand Early Oligocene forms. Their appearance probably was triggered by the initiation of the psychrosphere and concomitant Austral increases in upwelling and productivity. Austral cetacean radiations in the Middle Oligocene are attributable to the influence of the Circum-Antarctic Current on regional productivity and the creation of more new niches. The decline of archaeocetes, further radiations of odontocetes and mysticetes, and the development of a cosmopolitan cetacean fauna in the Late Oligocene (25 Ma) foreshadowed the radiation of modern cetacean stocks with the establishment of major “modern” ocean patterns in the Miocene (22-5 Ma).
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The Plotopteridae are wing-propelled, penguin-like diving birds of the order Pelecaniformes found in mid-Tertiary deposits of the North Pacific. Much new material representing a considerable radiation of genera and species has been discovered in Japan since the basic adaptations and characters of the family were revealed. A new genus and species, Copepteryx hexeris, is named here from previously known but underscribed material upon which much of our knowledge of the family had originally been based. A second new species, C. titan, is described from a single gigantic femur from a bird that was probably larger than any known diving bird, living or fossil.
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The main evolutionary trend in the Mediterranean Miocene toothed whale fauna is related (1) to the change in diversity and (2) to the turnover in community structure. Diversity increases from Upper Aquitanian–Lower Burdigalian to Burdigalian–Langhian, when it reaches its maximum. Starting from this time, diversity decreases progressively. The Early Miocene (Upper Aquitanian–Lower Burdigalian) Mediterranean toothed whale fauna, as well as the extramediterranean ones, is characterised by a high number of endemic taxa and by the prevalence of longirostral forms living in estuarine-neritic environments. A more diversified fauna spreading in neritic and pelagic environments characterises the Burdigalian–Langhian age, while an increase in pelagic forms and the nearly complete disappearance of some archaic longirostral taxa is typical of the Serravallian–Messinian fauna. Decrease in diversity and disappearance of archaic longirostral taxa are also recorded, at more general scale, in the Late Miocene extramediterranean fossil bearing deposits. These events can be related to the progressive global climatic deterioration, starting from Middle Miocene. From a biogeographic point a view, we can outline some relationships between the Mediterranean and western North Atlantic Miocene faunas. Closer affinities are observed between the Baltringen fauna and the northern Atlantic one, because of the presence of the genera Pomatodelphis and Zarhachis (platanistids) in both areas. In the Miocene Mediterranean and in North Atlantic, the delphinids are apparently absent as well as other extant delphinoid groups even if erroneously recorded in the past.
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Breeding of the Cape cormorant on the South West African platforms and of the jackass penguin on islands off South Africa is coincidental with the seasonal availability of pelagic fish shoals. The largest numbers of Cape gannets and Cape cormorants occur off South West Africa where the biomass of fish is highest, though dominated by one species, the pilchard. By contrast, jackass penguins, limited in their range through flightlessness, are concentrated at the centre of the smaller but more stable South African multispecies fishery. In both South West and South Africa, densities of Cape cormorants are heaviest near the recruitment grounds for juvenile pilchard and anchovy. Island yields of guano are shown to provide reliable estimates of bird population sizes and fluctuations in these are closely related to temporal changes in fish abundance. They consequently have value in providing an understanding of fish stocks prior to exploitation and as indicators of the current state of the resources. Since the turn of the century large oscillations in the South West and South African pilchard populations were apparent but overfishing in the 1960s depressed both below their normal levels and reduced the numbers of birds.
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Strong correlations between various local and global estimates of Phanerozoic marine diversity for taxa below the ordinal level indicate a single pattern of change underlying all data on fossil density. Geological time alone seems insufficient to explain all of the significant covariation among the data sets, and it is proposed that the common pattern in diversity reflects the signal from a real evolutionary phenomenon strong enough to overcome the biases inherent in the fossil record.
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Species diversity among fossil invertebrates of the Phanerozoic is highly correlated with volume and area of sedimentary rocks. The correlations are statistically significant at the 1% level. The relationship holds even in regions (such as Canada) where the area and volume of rock do not increase through time. These results are interpreted as indicating that the apparent number of species is strongly dependent on sampling and that many of the changes in diversity seen in the Phanerozoic are artifactual. Consequently, there is no compelling evidence for a general increase in the number of invertebrate species from Paleozoic to Recent. This conclusion applies primarily to marine organisms. Diversity may have been in dynamic equilibrium throughout much of this time. A few intervals of the Phanerozoic have consistently fewer invertebrate species than would be predicted from the amount of sedimentary rock available for study. The Silurian, Permian, and Cretaceous stand out in this regard. This may result either from lower than normal diversity during these periods or from an unusual abundance of unfossiliferous rocks (evaporites, red beds, etc.).
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Fossil whales in the very rare, primitive, extinct cetacean family Aetiocetidae are small, relict, toothed mysticetes that persisted into Late Oligocene time after more highly derived baleen-bearing mysticetes had already evolved. No known aetiocetid could be ancestral to baleen-bearing mysticetes, but aetiocetid morphology is in many ways intermediate between archaeocetes and baleen-bearing mysticetes, demonstrating the probable transitional steps passed through in the evolution of baleen-bearing mysticetes. Their discovery indicates that mysticetes evolved from Archaeocetes, and supports theories of the monophyly of Cetacea. Late Oligocene aetiocetids ahve been found on both sides of the North Pacific Ocean. -from Authors
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Argues that the history of life does not necessarily record an improvement in competitive abilities through time; that the idea of large-scale competitive replacements by the appearance of key adaptations is not supported by the evidence; and that the other macroevolutionary models that involve competition as a major factor are open to question. The author criticises the assumption that competition has a central role in macroevolution, and questions the use of microevolutionary concepts in describing major events in evolution.-from Author
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We estimate the effects of three biases on the observed alpha diversity of paleocommunities from the Middle Paleozoic and Late Cenozoic. The first bias results from the preferential dissolution of aragonite relative to calcite; this bias can lower the relative abundance and preserved diversity of aragonitic taxa, potentially lowering the rarefied diversity of an entire fossil assemblage. We model the effects of this bias by analytically reinserting aragonitic specimens and taxa into Paleozoic assemblages that have been described in the literature. The aragonitic specimens are inserted using a wide range of reasonable assumptions about the original local paleocommunity composition. Although the dissolution bias is probably not as severe as has been argued by some, our analytical modeling indicates that the average Paleozoic assemblage may have lost up to 29% of its total diversity. The second bias results from the higher diversity of the tropics relative to temperate latitudes, but the Late Cenozoic collections we analyzed from the literature represent temperate assemblages whereas the Paleozoic collections were tropical in origin (the northward drift of North America and Europe through time caused this difference). On the basis of latitudinal diversity gradients in the Late Cenozoic, the diversity of the temperate Late Cenozoic samples should be at least doubled for an accurate comparison to the tropical Paleozoic samples. The third bias is environmental: our Late Cenozoic samples tend to come from more onshore, stressed habitats than the Paleozoic samples. In our study, this factor should reduce the apparent diversity of Late Cenozoic paleocommunities by about 9%. After correcting for these biases, standardized alpha diversity appears to increase by a factor of 3.0–3.7 from the Middle Paleozoic to the Late Cenozoic. Previous studies that did not correct for these biases suggested that alpha diversity increased by a factor of 2.5 times; the earlier studies produced approximately correct results because (by chance) the effects of the biases largely cancel out. In the "consensus" article on marine diversity history, an observed increase in alpha diversity was taken as powerful support for an increase in global diversity from the Paleozoic to the Cenozoic. Although we do not test all conflating factors, this study provides new rigor to this longstanding view on alpha diversity change in the Phanerozoic.