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Daniel T Ksepka - One of the best experts on this subject based on the ideXlab platform.
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bone histology in extant and fossil penguins aves Sphenisciformes
2015Co-Authors: Daniel T Ksepka, Sarah Werning, Michelle Sclafani, Zachary M BolesAbstract:Substantial changes in bone histology accompany the secondary adaptation to life in the water. This transition is well documented in several lineages of mammals and non-avian reptiles, but has received relatively little attention in birds. This study presents new observations on the long bone microstructure of penguins, based on histological sections from two extant taxa (Spheniscus and Aptenodytes) and eight fossil specimens belonging to stem lineages (†Palaeospheniscus and several indeterminate Eocene taxa). High bone density in penguins results from compaction of the internal cortical tissues, and thus penguin bones are best considered osteosclerotic rather than pachyostotic. Although the oldest specimens sampled in this study represent stages of penguin evolution that occurred at least 25 million years after the loss of flight, major differences in humeral structure were observed between these Eocene stem taxa and extant taxa. This indicates that the modification of flipper bone microstructure continued long after the initial loss of flight in penguins. It is proposed that two key transitions occurred during the shift from the typical hollow avian humerus to the dense osteosclerotic humerus in penguins. First, a reduction of the medullary cavity occurred due to a decrease in the amount of perimedullary osteoclastic activity. Second, a more solid cortex was achieved by compaction. In extant penguins and †Palaeospheniscus, most of the inner cortex is formed by rapid osteogenesis, resulting an initial latticework of woven-fibered bone. Subsequently, open spaces are filled by slower, centripetal deposition of parallel-fibered bone. Eocene stem penguins formed the initial latticework, but the subsequent round of compaction was less complete, and thus open spaces remained in the adult bone. In contrast to the humerus, hindlimb bones from Eocene stem penguins had smaller medullary cavities and thus higher compactness values compared with extant taxa. Although cortical lines of arrested growth have been observed in extant penguins, none was observed in any of the current sampled specimens. Therefore, it is likely that even these 'giant' penguin taxa completed their growth cycle without a major pause in bone deposition, implying that they did not undergo a prolonged fasting interval before reaching adult size.
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endocranial anatomy of antarctic eocene stem penguins implications for sensory system evolution in Sphenisciformes aves
2015Co-Authors: Claudia P. Tambussi, Federico Javier Degrange, Daniel T KsepkaAbstract:Fil: Tambussi, Claudia Patricia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Cordoba. Facultad de Ciencias Exactas Fisicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina
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evolution of the brain and sensory organs in Sphenisciformes new data from the stem penguin paraptenodytes antarcticus
2012Co-Authors: Daniel T Ksepka, Amy M Balanoff, Stig A Walsh, Ariel RevanAbstract:Penguins have undergone dramatic changes associated with the evolution of underwater flight and subsequent loss of aerial flight, which are manifest and well documented in the musculoskeletal system and integument. Significant modification of neurosensory systems and endocranial spaces may also be expected along this locomotor transition. However, no investigations of the brain and sensory organs of extinct stem lineage Sphenisciformes have been carried out, and few data exist even for extant species of Spheniscidae. In order to explore neuroanatomical evolution in penguins, we generated virtual endocasts for the early Miocene stem penguin Paraptenodytes antarcticus, three extant penguin species (Pygoscelis antarctica, Aptenodytes patagonicus, Spheniscus magellanicus), and two outgroup species (the common loon Gavia immer and the Laysan albatross Phoebastria immutabilis). These endocasts yield new anatomical data and phylogenetically informative characters from the brain, carotid arteries, pneumatic recesses, and semicircular canal system. Despite having undergone over 60 million years of evolution since the loss of flight, penguins retain many attributes traditionally linked to flight. Features associated with visual acuity and proprioception, such as the sagittal eminence and flocculus, show a similar degree of development to those of volant birds in the three extant penguins and Paraptenodytes antarcticus. These features, although clearly not flight-related in penguins, are consistent with the neurological demands associated with rapid manoeuvring in complex aquatic environments. Semicircular canal orientation in penguins is similar to volant birds. Interestingly, canal radius is grossly enlarged in the fossil taxon Pa. antarcticus compared to living penguins and outgroups. In contrast to all other living birds, the contralateral anterior tympanic recesses of extant penguins do not communicate. An interaural pathway connecting these recesses is retained in Pa. antarcticus, suggesting that stem penguins may still have employed this connection, potentially to enhance directional localization of sound. Paedomorphosis, already identified as a potential factor in crown clade penguin skeletal morphology, may also be implicated in the failure of an interaural pathway to form during ontogeny in extant penguins.
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multiple cenozoic invasions of africa by penguins aves Sphenisciformes
2012Co-Authors: Daniel T Ksepka, Daniel B ThomasAbstract:Africa hosts a single breeding species of penguin today, yet the fossil record indicates that a diverse array of now-extinct taxa once inhabited southern African coastlines. Here, we show that the African penguin fauna had a complex history involving multiple dispersals and extinctions. Phylogenetic analyses and biogeographic reconstructions incorporating new fossil material indicate that, contrary to previous hypotheses, the four Early Pliocene African penguin species do not represent an endemic radiation or direct ancestors of the living Spheniscus demersus (blackfooted penguin). A minimum of three dispersals to Africa, probably assisted by the eastward-flowing Antarctic Circumpolar and South Atlantic currents, occurred during the Late Cenozoic. As regional sea-level fall eliminated islands and reduced offshore breeding areas during the Pliocene, all but one penguin lineage ended in extinction, resulting in today's depleted fauna.
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The Basal Penguin (Aves: Sphenisciformes) Perudyptes devriesi and a Phylogenetic Evaluation of the Penguin Fossil Record
2010Co-Authors: Daniel T Ksepka, Julia A. ClarkeAbstract:Abstract We present the first detailed description of Perudyptes devriesi, a basal penguin from the middle Eocene (~42 Ma) Paracas Formation of Peru, and a new analysis of all published extinct penguin species as well as controversial fragmentary specimens. The Perudyptes devriesi holotype includes key regions of the skull and significant postcranial material, thus helping to fill a major phylogenetic and stratigraphic (~20 million year) gap between the earliest fossil penguins (Waimanu manneringi and Waimanu tuatahi, ~58–61.6 Ma) and the next oldest partial skeletons. Perudyptes devriesi is diagnosable by five autapomorphies: (1) an anteroventrally directed postorbital process, (2) marked anterior expansion of the parasphenoid rostrum, (3) posterior trochlear ridge of the humerus projecting distal to the middle trochlear ridge and conformed as a large, broadly curved surface, (4) convex articular surface for the antitrochanter of the femur, and (5) extremely weak anterior projection of the lateral condyl...
Paul R. Scofield - One of the best experts on this subject based on the ideXlab platform.
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A well-preserved new mid-paleocene penguin (Aves, Sphenisciformes) from the Waipara Greensand in New Zealand
2018Co-Authors: Gerald Mayr, Vanesa L. De Pietri, Leigh Love, Al A. Mannering, Paul R. ScofieldAbstract:We describe a partial skeleton of a new stem group representative of the Sphenisciformes from the mid-Paleocene Waipara Greensand in New Zealand, which represents the best-preserved and most complete Paleocene penguin found so far. Sequiwaimanu rosieae, n. gen. et sp., is the fourth penguin species from the Waipara Greensand, which previously yielded two species that were assigned to the taxon Waimanu, in addition to leg bones of an unnamed giant penguin. Among other features, the new species is characterized by an articular facet for the furcula on the apex carinae of the sternum, which is unknown from other sphenisciforms. We perform detailed comparisons with the species assigned to Waimanu and show that the type species Waimanu manneringi differs in tarsometatarsus morphology from its putative congener ‘W.’ tuatahi, which is here assigned to the new taxon Muriwaimanu. Sequiwaimanu rosieae exhibits a more derived morphology than Muriwaimanu tuatahi, but its exact affinities to W. manneringi are unresolved owing to the incompletely known osteology of the latter species. With S. rosieae being more closely related to the crown group than M. tuatahi, shared characteristics of the two taxa are likely to be plesiomorphic for sphenisciforms. Although the skeletal morphology of these sphenisciform stem species shows some similarities to plotopterids (i.e., wing-propelled diving seabirds from the North Pacific Basin) in some characters, the stem group sphenisciforms from the Waipara Greensand are clearly distinguished from plotopterids. http://zoobank.org/urn:lsid:zoobank.org:pub:86031231-EADB-45EF-930B-8E55833D32F6 SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Mayr, G., V. L. De Pietri, L. Love, A. A. Mannering, and R. P. Scofield. 2018. A well-preserved new mid-Paleocene penguin (Aves, Sphenisciformes) from the Waipara Greensand in New Zealand. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1398169.
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a paleocene penguin from new zealand substantiates multiple origins of gigantism in fossil Sphenisciformes
2017Co-Authors: Gerald Mayr, Vanesa L. De Pietri, Paul R. Scofield, Alan J D TennysonAbstract: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.
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a well preserved new mid paleocene penguin aves Sphenisciformes from the waipara greensand in new zealand
2017Co-Authors: Gerald Mayr, Vanesa L. De Pietri, Leigh Love, Al A. Mannering, Paul R. ScofieldAbstract:ABSTRACTWe describe a partial skeleton of a new stem group representative of the Sphenisciformes from the mid-Paleocene Waipara Greensand in New Zealand, which represents the best-preserved and most complete Paleocene penguin found so far. Sequiwaimanu rosieae, n. gen. et sp., is the fourth penguin species from the Waipara Greensand, which previously yielded two species that were assigned to the taxon Waimanu, in addition to leg bones of an unnamed giant penguin. Among other features, the new species is characterized by an articular facet for the furcula on the apex carinae of the sternum, which is unknown from other sphenisciforms. We perform detailed comparisons with the species assigned to Waimanu and show that the type species Waimanu manneringi differs in tarsometatarsus morphology from its putative congener ‘W.’ tuatahi, which is here assigned to the new taxon Muriwaimanu. Sequiwaimanu rosieae exhibits a more derived morphology than Muriwaimanu tuatahi, but its exact affinities to W. manneringi are ...
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multivariate skeletal analyses support a taxonomic distinction between new zealand and australian eudyptula penguins Sphenisciformes spheniscidae
2017Co-Authors: Stefanie Grosser, Paul R. Scofield, Jonathan M. WatersAbstract:ABSTRACTRecent genetic analyses have revealed evidence for the existence of two distinct lineages of Little Penguin (genus Eudyptula), one endemic to New Zealand (E. minor), and the other widespread along the coasts of Australia and south-east New Zealand (E. novaehollandiae). Here we present the first comprehensive morphometric analysis of complete Eudyptula skeletons. We show that variability in Eudyptula body and bill size is associated with sea surface temperature gradients, suggesting that thermoregulatory processes underpin morphological variation in these seabirds. More importantly, we detect osteological differentiation between New Zealand and Australian specimens, providing further support for the taxonomic separation of these behaviourally and genetically distinct lineages. Broadly, our study shows the value of multivariate osteological analyses in helping to resolve the status of genetic lineages that appear morphologically ‘cryptic’ when considering external morphometrics and plumage features ...
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Multivariate skeletal analyses support a taxonomic distinction between New Zealand and Australian Eudyptula penguins (Sphenisciformes: Spheniscidae)
2017Co-Authors: Stefanie Grosser, Paul R. Scofield, Jonathan M. WatersAbstract:Recent genetic analyses have revealed evidence for the existence of two distinct lineages of Little Penguin (genus Eudyptula), one endemic to New Zealand (E. minor), and the other widespread along the coasts of Australia and south-east New Zealand (E. novaehollandiae). Here we present the first comprehensive morphometric analysis of complete Eudyptula skeletons. We show that variability in Eudyptula body and bill size is associated with sea surface temperature gradients, suggesting that thermoregulatory processes underpin morphological variation in these seabirds. More importantly, we detect osteological differentiation between New Zealand and Australian specimens, providing further support for the taxonomic separation of these behaviourally and genetically distinct lineages. Broadly, our study shows the value of multivariate osteological analyses in helping to resolve the status of genetic lineages that appear morphologically ‘cryptic’ when considering external morphometrics and plumage features alone.
Sara Bertelli - One of the best experts on this subject based on the ideXlab platform.
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paleogene equatorial penguins challenge the proposed relationship between biogeography diversity and cenozoic climate change
2007Co-Authors: Julia A. Clarke, Mario Urbina, Daniel T Ksepka, Marcelo Stucchi, Norberto P Giannini, Sara Bertelli, Yanina Narvaez, Clint A BoydAbstract:New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4–8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude ≈14°S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper.
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fossil penguin aves Sphenisciformes cranial material from the eocene of seymour island antarctica
2006Co-Authors: Daniel T Ksepka, Sara BertelliAbstract:Our knowledge of the cranial morphology of early penguins remains poor, particularly for Paleogene taxa. This paper describes a partial penguin skull and additional isolated cranial elements from the Eocene La Meseta Formation of Seymour Island, Antarctica. These specimens cannot be assigned to named taxa at present, but there is a strong possibility they belong to La Meseta penguins known only from postcranial elements. The skull shares extensive dorsal development of the temporal fossae with extant and fossil Spheniscus and the fossil penguins Paraptenodytes and Marplesornis, indicating the adductor complex was powerful in early penguins. Partial mandibles belonging to a much larger penguin are similar to Paraptenodytes and differ from all living penguins in the lack of a hooked medial process of the articular and the presence of a foramen anterior to the mandibular cotyles. Given the rarity of penguin cranial remains, these specimens provide important new insight into early penguin evolution.
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the phylogeny of the living and fossil Sphenisciformes penguins
2006Co-Authors: Daniel T Ksepka, Sara Bertelli, Norberto P GianniniAbstract:We present the first phylogenetic analysis of the Sphenisciformes that extensively samples fossil taxa. Combined analysis of 181 morphological characters and sequence fragments from mitochondrial and nuclear genes (12S, 16S, COI, cytochrome b, RAG-1) yields a largely resolved tree. Two species of the New Zealand Waimanu form a trichotomy with all other penguins in our result. The much discussed giant penguins Anthropornis and Pachydyptes are placed in two clades near the base of the tree. Stratigraphic and phylogenetic evidence suggest that some lineages of penguins attained very large body size rapidly and early in the clade's evolutionary history. The only fossil taxa that fall inside the crown clade Spheniscidae are fossil species assigned to the genus Spheniscus. Thus, extant penguin diversity is more accurately viewed as the product of a successful radiation of derived taxa than as an assemblage of survivors belonging to numerous lineages. The success of the Spheniscidae may be due to novel feeding adaptations and a more derived flipper apparatus. We offer a biogeographical scenario for penguins that incorporates fossil distributions and paleogeographic reconstructions of the Southern continent's positions. Our results do not support an expansion of the Spheniscidae from a cooling Continental Antarctica, but instead suggest those species that currently breed in that area are the descendants of colonizers from the Subantarctic. Many important divergence events in the clade Spheniscidae can instead be explained by dispersal along the paths of major ocean currents and the emergence of new islands due to tectonic events. © The Willi Hennig Society 2006.
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a phylogeny of extant penguins aves Sphenisciformes combining morphology and mitochondrial sequences
2005Co-Authors: Sara Bertelli, Norberto P GianniniAbstract:The phylogenetic relationships among the penguins have received little attention, despite their well-known anatomy and the conspicuous nature of the group. Previous attempts have included datasets limited to few, mostly osteological characters, and one study was based on integumentary and breeding characters. We developed a morphological matrix comprising 159 morphological characters of osteology (70 characters), myology (15), digestive tract (1), integument (66), and breeding (7 characters), scored in 18 extant forms (all currently recognized species plus one distinct subspecies). A gaviiform was placed at the root, and 11 species of representative procellariiform groups completed the outgroup. A heuristic parsimony analysis under equal weights was performed. We also compiled DNA sequences available in GenBank for the mitochondrial genes 12S rDNA and cytochrome b. We included the two data partitions in a combined analysis under direct optimization. Both analyses recovered the monophyly of Sphenisciformes and all the traditional polytypic genera. Morphological characters performed optimally at the ordinal and generic nodes, also providing resolution and varying degrees of support at supra- and intrageneric nodes. The comparison of molecular and morphological results indicated that the most significant problem in the phylogeny of extant penguins is rooting the ingroup. The mutual interaction of molecular and morphological data decreases the ambiguity regarding the placement of the root, and provides a resolved, relatively well-supported phylogeny of extant penguins. Biogeographical patterns based on breeding ranges and derived from the combined analysis show that the major intercontinental vicariance events detected are consistent with cold marine current patterns of the Southern Hemisphere. � The Willi Hennig Society 2005. Penguins (Aves: Sphenisciformes) belong to a homogeneous group of marine birds of the southern oceans that exhibit the most remarkable adaptations for an aquatic life among birds. These include wings transformed into flippers for underwater propulsion, skeletal modifications for upright locomotion on land, and a highly modified plumage for insulation in critically cold conditions. Adaptations of the breeding system in all aspects (morphology, physiology, behavior) are also notable. Penguins are thought to be more closely related to other marine birds, especially the Procellariiformes (petrels and albatrosses; Stresemann, 1934; Simpson, 1946; Ho et al., 1976; Saiff, 1976; Sibley and Ahlquist,
Gerald Mayr - One of the best experts on this subject based on the ideXlab platform.
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A well-preserved new mid-paleocene penguin (Aves, Sphenisciformes) from the Waipara Greensand in New Zealand
2018Co-Authors: Gerald Mayr, Vanesa L. De Pietri, Leigh Love, Al A. Mannering, Paul R. ScofieldAbstract:We describe a partial skeleton of a new stem group representative of the Sphenisciformes from the mid-Paleocene Waipara Greensand in New Zealand, which represents the best-preserved and most complete Paleocene penguin found so far. Sequiwaimanu rosieae, n. gen. et sp., is the fourth penguin species from the Waipara Greensand, which previously yielded two species that were assigned to the taxon Waimanu, in addition to leg bones of an unnamed giant penguin. Among other features, the new species is characterized by an articular facet for the furcula on the apex carinae of the sternum, which is unknown from other sphenisciforms. We perform detailed comparisons with the species assigned to Waimanu and show that the type species Waimanu manneringi differs in tarsometatarsus morphology from its putative congener ‘W.’ tuatahi, which is here assigned to the new taxon Muriwaimanu. Sequiwaimanu rosieae exhibits a more derived morphology than Muriwaimanu tuatahi, but its exact affinities to W. manneringi are unresolved owing to the incompletely known osteology of the latter species. With S. rosieae being more closely related to the crown group than M. tuatahi, shared characteristics of the two taxa are likely to be plesiomorphic for sphenisciforms. Although the skeletal morphology of these sphenisciform stem species shows some similarities to plotopterids (i.e., wing-propelled diving seabirds from the North Pacific Basin) in some characters, the stem group sphenisciforms from the Waipara Greensand are clearly distinguished from plotopterids. http://zoobank.org/urn:lsid:zoobank.org:pub:86031231-EADB-45EF-930B-8E55833D32F6 SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Mayr, G., V. L. De Pietri, L. Love, A. A. Mannering, and R. P. Scofield. 2018. A well-preserved new mid-Paleocene penguin (Aves, Sphenisciformes) from the Waipara Greensand in New Zealand. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1398169.
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a paleocene penguin from new zealand substantiates multiple origins of gigantism in fossil Sphenisciformes
2017Co-Authors: Gerald Mayr, Vanesa L. De Pietri, Paul R. Scofield, Alan J D TennysonAbstract: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.
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a well preserved new mid paleocene penguin aves Sphenisciformes from the waipara greensand in new zealand
2017Co-Authors: Gerald Mayr, Vanesa L. De Pietri, Leigh Love, Al A. Mannering, Paul R. ScofieldAbstract:ABSTRACTWe describe a partial skeleton of a new stem group representative of the Sphenisciformes from the mid-Paleocene Waipara Greensand in New Zealand, which represents the best-preserved and most complete Paleocene penguin found so far. Sequiwaimanu rosieae, n. gen. et sp., is the fourth penguin species from the Waipara Greensand, which previously yielded two species that were assigned to the taxon Waimanu, in addition to leg bones of an unnamed giant penguin. Among other features, the new species is characterized by an articular facet for the furcula on the apex carinae of the sternum, which is unknown from other sphenisciforms. We perform detailed comparisons with the species assigned to Waimanu and show that the type species Waimanu manneringi differs in tarsometatarsus morphology from its putative congener ‘W.’ tuatahi, which is here assigned to the new taxon Muriwaimanu. Sequiwaimanu rosieae exhibits a more derived morphology than Muriwaimanu tuatahi, but its exact affinities to W. manneringi are ...
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Oligocene plotopterid skulls from western North America and their bearing on the phylogenetic affinities of these penguin-like seabirds
2015Co-Authors: Gerald Mayr, James L. Goedert, Olaf VogelAbstract:ABSTRACTPlotopterids are penguin-like, wing-propelled birds with controversial phylogenetic affinities. They are usually regarded as closely related to Suloidea (gannets, cormorants, and allies), with the penguin-like features considered to be of convergent origin. However, it has also been proposed that the similarities shared by plotopterids and penguins are due to common ancestry. An in-depth assessment of plotopterid affinities has been hampered by the fact that very little data about the skull of these birds were available. New fossils of Tonsala from the Oligocene Pysht Formation in Washington State (U.S.A.) include the first well-preserved cranial remains of this taxon. They show that although plotopterids share derived cranial features with members of Suloidea that are absent in species of Sphenisciformes (penguins), they lack diagnostic derived features of the representatives of crown group Suloidea. To assess the affinities of plotopterids, we performed a phylogenetic analysis that included, for the first time, early stem group representatives of Sphenisciformes, resulting in a sister-group relationship between Plotopteridae and Suloidea. Intriguingly, however, our reanalysis of the emended data of a more comprehensive recent analysis that supported a position of Plotopteridae within Suloidea recovered a sister-group relationship between Plotopteridae and Sphenisciformes. Although cranial morphology challenges the hypothesis of close affinities between plotopterids and penguins, more data on early stem lineage representatives of penguins are needed for a robust placement of Plotopteridae relative to Sphenisciformes. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
Norberto P Giannini - One of the best experts on this subject based on the ideXlab platform.
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paleogene equatorial penguins challenge the proposed relationship between biogeography diversity and cenozoic climate change
2007Co-Authors: Julia A. Clarke, Mario Urbina, Daniel T Ksepka, Marcelo Stucchi, Norberto P Giannini, Sara Bertelli, Yanina Narvaez, Clint A BoydAbstract:New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4–8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude ≈14°S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper.
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the phylogeny of the living and fossil Sphenisciformes penguins
2006Co-Authors: Daniel T Ksepka, Sara Bertelli, Norberto P GianniniAbstract:We present the first phylogenetic analysis of the Sphenisciformes that extensively samples fossil taxa. Combined analysis of 181 morphological characters and sequence fragments from mitochondrial and nuclear genes (12S, 16S, COI, cytochrome b, RAG-1) yields a largely resolved tree. Two species of the New Zealand Waimanu form a trichotomy with all other penguins in our result. The much discussed giant penguins Anthropornis and Pachydyptes are placed in two clades near the base of the tree. Stratigraphic and phylogenetic evidence suggest that some lineages of penguins attained very large body size rapidly and early in the clade's evolutionary history. The only fossil taxa that fall inside the crown clade Spheniscidae are fossil species assigned to the genus Spheniscus. Thus, extant penguin diversity is more accurately viewed as the product of a successful radiation of derived taxa than as an assemblage of survivors belonging to numerous lineages. The success of the Spheniscidae may be due to novel feeding adaptations and a more derived flipper apparatus. We offer a biogeographical scenario for penguins that incorporates fossil distributions and paleogeographic reconstructions of the Southern continent's positions. Our results do not support an expansion of the Spheniscidae from a cooling Continental Antarctica, but instead suggest those species that currently breed in that area are the descendants of colonizers from the Subantarctic. Many important divergence events in the clade Spheniscidae can instead be explained by dispersal along the paths of major ocean currents and the emergence of new islands due to tectonic events. © The Willi Hennig Society 2006.
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a phylogeny of extant penguins aves Sphenisciformes combining morphology and mitochondrial sequences
2005Co-Authors: Sara Bertelli, Norberto P GianniniAbstract:The phylogenetic relationships among the penguins have received little attention, despite their well-known anatomy and the conspicuous nature of the group. Previous attempts have included datasets limited to few, mostly osteological characters, and one study was based on integumentary and breeding characters. We developed a morphological matrix comprising 159 morphological characters of osteology (70 characters), myology (15), digestive tract (1), integument (66), and breeding (7 characters), scored in 18 extant forms (all currently recognized species plus one distinct subspecies). A gaviiform was placed at the root, and 11 species of representative procellariiform groups completed the outgroup. A heuristic parsimony analysis under equal weights was performed. We also compiled DNA sequences available in GenBank for the mitochondrial genes 12S rDNA and cytochrome b. We included the two data partitions in a combined analysis under direct optimization. Both analyses recovered the monophyly of Sphenisciformes and all the traditional polytypic genera. Morphological characters performed optimally at the ordinal and generic nodes, also providing resolution and varying degrees of support at supra- and intrageneric nodes. The comparison of molecular and morphological results indicated that the most significant problem in the phylogeny of extant penguins is rooting the ingroup. The mutual interaction of molecular and morphological data decreases the ambiguity regarding the placement of the root, and provides a resolved, relatively well-supported phylogeny of extant penguins. Biogeographical patterns based on breeding ranges and derived from the combined analysis show that the major intercontinental vicariance events detected are consistent with cold marine current patterns of the Southern Hemisphere. � The Willi Hennig Society 2005. Penguins (Aves: Sphenisciformes) belong to a homogeneous group of marine birds of the southern oceans that exhibit the most remarkable adaptations for an aquatic life among birds. These include wings transformed into flippers for underwater propulsion, skeletal modifications for upright locomotion on land, and a highly modified plumage for insulation in critically cold conditions. Adaptations of the breeding system in all aspects (morphology, physiology, behavior) are also notable. Penguins are thought to be more closely related to other marine birds, especially the Procellariiformes (petrels and albatrosses; Stresemann, 1934; Simpson, 1946; Ho et al., 1976; Saiff, 1976; Sibley and Ahlquist,
