PubMed | Bruce Museum, State University of New York at Stony Brook and Drexel University
Type: Journal Article | Journal: Journal of anatomy | Year: 2015
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 25million 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.
PubMed | University of Texas at Austin, National Museums Scotland, Oklahoma State University, Bruce Museum and 5 more.
Type: Journal Article | Journal: Journal of anatomy | Year: 2016
The rapidly expanding interest in, and availability of, digital tomography data to visualize casts of the vertebrate endocranial cavity housing the brain (endocasts) presents new opportunities and challenges to the field of comparative neuroanatomy. The opportunities are many, ranging from the relatively rapid acquisition of data to the unprecedented ability to integrate critically important fossil taxa. The challenges consist of navigating the logistical barriers that often separate a researcher from high-quality data and minimizing the amount of non-biological variation expressed in endocasts - variation that may confound meaningful and synthetic results. Our purpose here is to outline preferred approaches for acquiring digital tomographic data, converting those data to an endocast, and making those endocasts as meaningful as possible when considered in a comparative context. This review is intended to benefit those just getting started in the field but also serves to initiate further discussion between active endocast researchers regarding the best practices for advancing the discipline. Congruent with the theme of this volume, we draw our examples from birds and the highly encephalized non-avian dinosaurs that comprise closely related outgroups along their phylogenetic stem lineage.
Ksepka D.T.,Bruce Museum |
Phillips M.J.,Queensland University of Technology
Annals of the Missouri Botanical Garden | Year: 2015
Birds represent the most diverse extant tetrapod clade, with ca. 10,000 extant species, and the timing of the crown avian radiation remains hotly debated. The fossil record supports a primarily Cenozoic radiation of crown birds, whereas molecular divergence dating analyses generally imply that this radiation was well underway during the Cretaceous. Furthermore, substantial differences have been noted between published divergence estimates. These have been variously attributed to clock model, calibration regime, and gene type. One underappreciated phenomenon is that disparity between fossil ages and molecular dates tends to be proportionally greater for shallower nodes in the avian Tree of Life. Here, we explore potential drivers of disparity in avian divergence dates through a set of analyses applying various calibration strategies and coding methods to a mitochondrial genome dataset and an 18-gene nuclear dataset, both sampled across 72 taxa. Our analyses support the occurrence of two deep divergences (i.e., the Palaeognathae/Neognathae split and the Galloanserae/Neoaves split) well within the Cretaceous, followed by a rapid radiation of Neoaves near the K-Pg boundary. However, 95% highest posterior density intervals for most basal divergences in Neoaves cross the boundary, and we emphasize that, barring unreasonably strict prior distributions, distinguishing between a rapid Early Paleocene radiation and a Late Cretaceous radiation may be beyond the resolving power of currently favored divergence dating methods. In contrast to recent observations for placental mammals, constraining all divergences within Neoaves to occur in the Cenozoic does not result in unreasonably high inferred substitution rates. Comparisons of nuclear DNA (nDNA) versus mitochondrial DNA (mtDNA) datasets and NT-versus RY-coded mitochondrial data reveal patterns of disparity that are consistent with substitution model misspecifications that result in tree compression/tree extension artifacts, which may explain some discordance between previous divergence estimates based on different sequence types. Comparisons of fully calibrated and nominally calibrated trees support a correlation between body mass and apparent dating error. Overall, our results are consistent with (but do not require) a Paleogene radiation for most major clades of crown birds.
PubMed | University of Auckland, ETH Zurich, Bruce Museum and Iowa State University
Type: | Journal: Systematic biology | Year: 2016
The total-evidence approach to divergence time dating uses molecular and morphological data from extant and fossil species to infer phylogenetic relationships, species divergence times, and macroevolutionary parameters in a single coherent framework. Current model-based implementations of this approach lack an appropriate model for the tree describing the diversification and fossilization process and can produce estimates that lead to erroneous conclusions. We address this shortcoming by providing a total-evidence method implemented in a Bayesian framework. This approach uses a mechanistic tree prior to describe the underlying diversification process that generated the tree of extant and fossil taxa. Previous attempts to apply the total-evidence approach have used tree priors that do not account for the possibility that fossil samples may be direct ancestors of other samples, that is, ancestors of fossil or extant species or of clades. The fossilized birth-death (FBD) process explicitly models the diversification, fossilization, and sampling processes and naturally allows for sampled ancestors. This model was recently applied to estimate divergence times based on molecular data and fossil occurrence dates. We incorporate the FBD model and a model of morphological trait evolution into a Bayesian total-evidence approach to dating species phylogenies. We apply this method to extant and fossil penguins and show that the modern penguins radiated much more recently than has been previously estimated, with the basal divergence in the crown clade occurring at [Formula: see text] Ma and most splits leading to extant species occurring in the last 2 myr. Our results demonstrate that including stem-fossil diversity can greatly improve the estimates of the divergence times of crown taxa. The method is available in BEAST2 (version 2.4) software www.beast2.org with packages SA (version at least 1.1.4) and morph-models (version at least 1.0.4) installed. [Birth-death process; calibration; divergence times; MCMC; phylogenetics.].
Smith N.D.,Howard University |
Smith N.D.,Smithsonian Institution |
Ksepka D.T.,Bruce Museum
Palaeontologia Electronica | Year: 2015
The "waterbird" assemblage is a group of aquatic and semi-aquatic birds that are characterized by extremely diverse morphologies, ecologies, and life histories. The group also includes fossil representatives that constitute some of the oldest records of Neoaves and are critical to calibrating the temporal diversification of modern birds. Herein, we provide a set of five well-supported fossil calibrations from the waterbird clade that will serve to provide robust temporal calibrations for the origins of: stem Phaethontes (tropicbirds); stem Threskiornithidae (ibises and spoonbills); stem Pelecanidae (pelicans); stem Fregatidae (frigatebirds); and stem Phalacrocoracidae (cormorants). We apply stringent criteria to justify both the phylogenetic placement and geochronologic context of these specimens, and discuss potentially older records to help focus future research and collection. The fossils described here affirm previous studies in recognizing that most major cladogenetic splits within the waterbird assemblage occurred by the Eocene, supporting interpretations of both rapid lineage diversification of waterbirds in the early Paleogene, and also the rapid establishment of body plans and possibly ecologically relevant morphologies during this time period. © Society for Vertebrate Paleontology April 2015.
News Article | October 30, 2015
The various skeletal pieces that researchers uncovered of the ancient bird that lived just after the age of the dinosaurs. More A teeny-tiny fossilized bird skeleton is helping researchers understand the explosive rate at which birds diversified after the dinosaur age, new research shows. The newfound skeleton dates back to about 62.5 million to 62 million years ago, making it the oldest known modern bird specimen in North America to live after the dinosaur-killing mass extinction, the researchers said. Its mere existence suggests that birds rapidly evolved in the 3 million to 4 million years after the dinosaurs died — much faster than previously thought, they said. "Birds were explosively diversifying right after the end of the Cretaceous, right after the big mass extinction," said study co-author Tom Williamson, curator of paleontology at the New Mexico Museum of Natural History and Science. [Avian Ancestors: Dinosaurs That Learned to Fly (Gallery)] Birds have a lengthy past. They began their evolutionary split from dinosaurs during the Jurassic period, about 150 million years ago. But like their scaly relatives, many bird lineages went extinct when a roughly 6-mile-long (10 kilometers) asteroid smashed into Earth about 66 million years ago. "Maybe a dozen or less lineages of birds survived," said study co-author Daniel Ksepka, curator of science at the Bruce Museum in Greenwich, Connecticut. (Today, there are about 40 lineages of birds that include more than 10,000 living species, he said.) Without dinosaurs and the other extinct animals in the way, bird diversity suddenly skyrocketed, and the newfound skeleton shows just how quickly it did so, Ksepka told Live Science. Williamson's 12-year-old twin sons found the delicate skeleton during a fossil dig in northwestern New Mexico in 2007. Williamson later excavated the fragmented bones, which are so small that the bird was likely no larger than a sparrow — smaller than the size of a human fist, he said. The tiny bones piqued Williamson's interest, so he teamed up with Ksepka and Thomas Stidham, an avian paleontologist at the Institute for Vertebrate Paleontology and Paleoanthropology in Beijing. The researchers analyzed the fossils, looking at 120 different size and shape characteristics. They found that the newfound species (which they have yet to name) is part of an extinct family of birds that is closely related to owls and mouse birds — a group of small, long-tailed birds that live only in sub-Saharan Africa. If this tiny, newfound bird was already living about 62 million years ago, it suggests that other modern birds, especially its close relatives, developed earlier than previously thought. For instance, the new evidence indicates that the mouse bird evolved some 6 million years earlier than researchers had thought, Ksepka said. "This bird has some wide implications for the timing of the radiation [diversification] of modern birds," Ksepka said. But "to pinpoint exactly when these birds are popping up, we really need the fossil record," he added. In 1980, other researchers, in New Zealand, discovered the fossilized skeleton of a penguin (Waimanu manneringi) that dates to between 60.5 million and 61.6 million years ago. "Together, the new bird and Waimanu show that the diversifications of aquatic and terrestrial birds were both well underway just a few million years after the mass extinction that hit 66 million years ago," Ksepka said. In fact, the compressed but explosive 4-million-year diversification that modern birds likely underwent after the dinosaur extinction is similar to the diversification of placental mammals, which also rapidly diversified after the nonavian dinosaurs died, he said. The researchers presented the unpublished findings earlier this month at the 75th annual Society of Vertebrate Paleontology conference in Dallas. Copyright 2015 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
News Article | February 15, 2017
At the philanthropy organization's annual meeting of the Greenwich Chapter at the Bruce Museum in Greenwich, CT, Mr. Abrams was present during an honorarium for Dr. Rick Hodes, the famed medical doctor who has worked tirelessly on behalf of those without medical care. Mr. Abrams said of the position, “I am honored to serve as a representative of my Synagogue to the UJA Greenwich Board and look forward to continuing to assist the organization in its incredibly important work both locally and around the globe. In these times especially, I believe the work done by organizations such as the UJA are critical and there is no better feeling than being a part of something that does such important work as the UJA and all of the various philanthropic board’s I have been honored to serve on.” Marcus Abrams is currently Co-President of the Greenwich Reform Synagogue in Greenwich, CT where he is responsible for overseeing the Synagogue’s operating budget and substantial endowment. His tenure has included leading the effort as Co-President to build a new Synagogue building that is the first purpose built Synagogue in Greenwich history. Mr Abrams has had a distinguished career spanning politics and finance. He served as Special Assistant to US Congressman Martin Frost(TX) and then in similar positions at the Democratic Congressional Campaign Committee. Mr. Abrams then formed Titan Advisors a political consulting firm whose clients included Congresswoman Carolyn Maloney and others. While attending law school, Mr. Abrams founded one of the most successful investment management companies in the world - responsible for over $1billion dollars in investment. Mr. Abrams left the firm to focus on philanthropic passions - previously serving as the Chair of the National Jewish Democratic Council's Economic Development Committee, and a member of AIPAC Senate Club. He additionally has been involved in the film industry as an executive producer of several documentary films. Mr. Abrams holds a B.A. from Boston University and a J.D. from New York University School of Law. He lives in Greenwich, CT with their four year old son and are twin daughters born in December of 2016.
Ksepka D.T.,Bruce Museum
Current Biology | Year: 2014
Summary Remarkable feathered dinosaur fossils have blurred the lines between early birds and their non-avian dinosaur relatives. Rapid skeletal evolution and decreasing body size along one particular lineage of theropod dinosaurs paved the way for the spectacular radiation of birds. © 2014 Elsevier Ltd.
Glass J.R.,Yale University |
Davis M.,Yale University |
Walsh T.J.,Bruce Museum |
Sargis E.J.,Yale University |
Caccone A.,Yale University
PLoS ONE | Year: 2016
Accounts of woolly mammoths (Mammuthus primigenius) preserved so well in ice that their meat is still edible have a long history of intriguing the public and influencing paleontological thought on Quaternary extinctions and climate, with some scientists resorting to catastrophism to explain the instantaneous freezing necessary to preserve edible meat. Famously, members of The Explorers Club purportedly dined on frozen mammoth from Alaska, USA, in 1951. This event, well received by the press and general public, became an enduring legend for the Club and popularized the notorious annual tradition of serving rare and exotic food at Club dinners that continues to this day. The Yale Peabody Museum holds a sample of meat preserved from the 1951 meal, interestingly labeled as a South American giant ground sloth (Megatherium), not mammoth. We sequenced a fragment of the mitochondrial cytochrome-b gene and studied archival material to verify its identity, which if genuine, would extend the range of Megatherium over 600% and alter our views on ground sloth evolution. Our results indicate that the meat was not mammoth or Megatherium but green sea turtle (Chelonia mydas). The prehistoric dinner was likely an elaborate publicity stunt. Our study emphasizes the value of museums collecting and curating voucher specimens, particularly those used for evidence of extraordinary claims. © 2016 Glass et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
PubMed | Yale University and Bruce Museum
Type: Journal Article | Journal: PloS one | Year: 2016
Accounts of woolly mammoths (Mammuthus primigenius) preserved so well in ice that their meat is still edible have a long history of intriguing the public and influencing paleontological thought on Quaternary extinctions and climate, with some scientists resorting to catastrophism to explain the instantaneous freezing necessary to preserve edible meat. Famously, members of The Explorers Club purportedly dined on frozen mammoth from Alaska, USA, in 1951. This event, well received by the press and general public, became an enduring legend for the Club and popularized the notorious annual tradition of serving rare and exotic food at Club dinners that continues to this day. The Yale Peabody Museum holds a sample of meat preserved from the 1951 meal, interestingly labeled as a South American giant ground sloth (Megatherium), not mammoth. We sequenced a fragment of the mitochondrial cytochrome-b gene and studied archival material to verify its identity, which if genuine, would extend the range of Megatherium over 600% and alter our views on ground sloth evolution. Our results indicate that the meat was not mammoth or Megatherium but green sea turtle (Chelonia mydas). The prehistoric dinner was likely an elaborate publicity stunt. Our study emphasizes the value of museums collecting and curating voucher specimens, particularly those used for evidence of extraordinary claims.