Ben Creisler
Some new non-dino papers:
Free pdf:
Joyce C. Havstad & N. Adam Smith (2019)
Fossils with Feathers and Philosophy of Science.
Systematic Biology, syz010 (advance online publication)
The last half century of paleornithological research has transformed the way that biologists perceive the evolutionary history of birds. This transformation has been driven, since 1969, by a series of exciting fossil discoveries combined with intense scientific debate over how best to interpret these discoveries. Ideally, as evidence accrues and results accumulate, interpretive scientific agreement forms. But this has not entirely happened in the debate over avian origins: the accumulation of scientific evidence and analyses has had some effect, but not a conclusive one, in terms of resolving the question of avian origins. Although the majority of biologists have come to accept that birds are dinosaurs, there is lingering and, in some quarters, strident opposition to this view. In order to both understand the ongoing disagreement about avian origins and generate a prediction about the future of the debate, here we use a revised model of scientific practice to assess the current and historical state of play surrounding the topic of bird evolutionary origins. Many scientists are familiar with the meta-scientific scholars Sir Karl Popper and Thomas Kuhn, and these are the primary figures that have been appealed to so far, in prior attempts to assess the dispute. But we demonstrate that a variation of Imre Lakatos's model of progressive versus degenerative research programmes provides a novel and productive assessment of the debate. We establish that a refurbished Lakatosian account both explains the intractability of the dispute and predicts a likely outcome for the debate about avian origins. In short, here we offer a meta-scientific tool for rationally assessing competing theoriesâone that allows researchers involved in seemingly intractable scientific disputes to advance their debates.
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Free pdf:
E. M. Kelly, J. D. Marcot, L. Selwood & K. E. Sears (2019)
The Development of Integration in Marsupial and Placental Limbs.
Integrative Organismal Biology 1(1): oby013
The morphological interdependence of traits, or their integration, is commonly thought to influence their evolution. As such, study of morphological integration and the factors responsible for its generation form an important branch of the field of morphological evolution. However, most research to date on post-cranial morphological integration has focused on adult patterns of integration. This study investigates patterns of correlation (i.e., morphological integration) among skeletal elements of the fore- and hind limbs of developing marsupial and placental mammals. The goals of this study are to establish how patterns of limb integration vary over development in marsupials and placentals, and identify factors that are likely responsible for their generation. Our results indicate that although the overall pattern of correlation among limb elements is consistent with adult integration throughout mammalian development, correlations vary at the level of the individual element and stage. As a result, the relative integration among fore- and hind limb elements varies dynamically between stages during development in both marsupial and placental mammals. Therefore, adult integration studies of the limbs may not be indicative of developmental integration. Results are also consistent with integration during early limb development being more heavily influenced by genetic and developmental factors, and later by function. Additionally, results are generally consistent with a constraint on marsupial forelimb evolution caused by the functional requirements of the crawl to the teat that operates by limiting morphological variation before and at the time of birth, and not after.
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Masaya Iijima & Tai Kubo (2019)
Comparative morphology of presacral vertebrae in extant crocodylians: taxonomic, functional and ecological implications.
Zoological Journal of the Linnean Society, zly096 (advance online publication)
Despite its systematic and functional relevance, the axial skeleton of crocodylians has received considerably less attention than the cranial and appendicular skeleton due to the assumed evolutionary conservativeness. The current study provides comprehensive comparisons of presacral vertebrae in extant crocodylians to demonstrate: (1) taxonomic variation, (2) size-dependent shape changes and (3) potential integration between vertebrae and skull functional modules. Our comparisons highlighted the uniqueness of the Indian gharial, Gavialis gangeticus, among extant crocodylians. The presacral vertebrae of G. gangeticus are characterized by reduced level of regionalization and increased intervertebral mobility in the neck (more narrowly placed zygapophyses and short vertebral processes), which would help lateral head sweeping under water for foraging. The scaling relationships of vertebral dimensions against the body size proxy indicate that dorsal vertebrae become stiffer with increasing body size: positive allometries were observed in areas and heights of inter-central joints, and lengths of vertebral processes (neural spines and transverse processes). These structural changes presumably serve to resist increasing compression loads and dorsiflexion bending moment on dorsal vertebrae of larger individuals during terrestrial locomotion. The analyses of correlation between vertebral dimensions and snout shape revealed that slender-snouted species tend to have more laterally mobile necks (specifically narrow zygapophyses), implying the potential integration of cranial and neck modules to optimize the foraging strategy.
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Florian Witzmann & Marcello Ruta (2019)
Evolutionary changes in the orbits and palatal openings of early tetrapods, with emphasis on temnospondyls.
Earth and Environmental Science Transactions of The Royal Society of Edinburgh (advance online publication)
Open palates with large interpterygoid vacuities are a diagnostic characteristic of temnospondyl amphibians, the most species-rich group of early tetrapods. Aside from their functional roles, several other aspects of such vacuities, such as their variation and spatial relationships relative to the orbits, have received only scarce attention. The present work examines patterns of shape and size changes in the orbits and vacuities of temnospondyls using a time-calibrated phylogeny of 69 temnospondyl taxa and 13 additional early tetrapod 'outgroups' (colosteids, an embolomere, 'microsaurs' and nectrideans). Orbit and vacuity outlines are quantified in a comparative framework using standard eigenshape analyses. In addition, we employ a series of ratios of linear measurements of both orbits and vacuities, and subject them to a phylogenetic principal component analysis in order to evaluate their proportional changes relative to the skull and to one another. Finally, we examine rates of evolutionary change and their associated shifts for shape and size for both structures, and assess the strength and significance of the correlations between these two variables using phylogenetic generalised least squares analyses. Although orbits and vacuities have fairly simple outlines, they both reveal complex models of proportional change across the temnospondyl phylogeny. These changes exhibit strong phylogenetic signal, that is, trait covariance among taxa is predicted by tree topology. We discuss the hypothesis that, early in tetrapod evolution, the functional role of the vacuities was related to the accommodation of the anterior jaw muscles. Only later in evolution did such vacuities serve to accommodate the eye muscles only.