Ben Creisler
Some recent non-dino papers that may be of interest:
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Free pdf:
Abigail L. Lind, Yvonne Y. Y. Lai, Yulia Mostovoy, Alisha K. Holloway, Alessio Iannucci, Angel C. Y. Mak, Marco Fondi, Valerio Orlandini, Walter L. Eckalbar, Massimo Milan, Michail Rovatsos, Ilya G. Kichigin, Alex I. Makunin, Martina Johnson PokornÃ, Marie AltmanovÃ, Vladimir A. Trifonov, Elio Schijlen, LukÃÅ KratochvÃl, Renato Fani, Petr VelenskÃ, Ivan RehÃk, Tomaso Patarnello, Tim S. Jessop, James W. Hicks, Oliver A. Ryder, Joseph R. Mendelson III, Claudio Ciofi, Pui-Yan Kwok, Katherine S. Pollard, and Benoit G. Bruneau (2019)
Genome of the Komodo dragon reveals adaptations in the cardiovascular and chemosensory systems of monitor lizards.
Nature Ecology & Evolution (2019)
doi:
https://doi.org/10.1038/s41559-019-0945-8https://www.nature.com/articles/s41559-019-0945-8Free pdf:
https://www.nature.com/articles/s41559-019-0945-8.pdfMonitor lizards are unique among ectothermic reptiles in that they have high aerobic capacity and distinctive cardiovascular physiology resembling that of endothermic mammals. Here, we sequence the genome of the Komodo dragon Varanus komodoensis, the largest extant monitor lizard, and generate a high-resolution de novo chromosome-assigned genome assembly for V. komodoensis using a hybrid approach of long-range sequencing and single-molecule optical mapping. Comparing the genome of V. komodoensis with those of related species, we find evidence of positive selection in pathways related to energy metabolism, cardiovascular homoeostasis, and haemostasis. We also show species-specific expansions of a chemoreceptor gene family related to pheromone and kairomone sensing in V. komodoensis and other lizard lineages. Together, these evolutionary signatures of adaptation reveal the genetic underpinnings of the unique Komodo dragon sensory and cardiovascular systems, and suggest that selective pressure altered haemostasis genes to help Komodo dragons evade the anticoagulant effects of their own saliva. The Komodo dragon genome is an important resource for understanding the biology of monitor lizards and reptiles worldwide.
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News:
Komodo dragon genome reveals clues about its evolution
How Komodo dragons survive deadly bites from other Komodos
What makes this dragon fierce
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Free pdf:
Donald G. Cerio & Lawrence M. Witmer (2019)
Intraspecific variation and symmetry of the inner-ear labyrinth in a population of wild turkeys: implications for paleontological reconstructions.
PeerJ 7:e7355
doi:
https://doi.org/10.7717/peerj.7355https://peerj.com/articles/7355/Free pdf:
https://peerj.com/articles/7355.pdfThe cochlea and semicircular canals (SCCs) of the inner ear are vital neurosensory devices. There are associations between the anatomy of these sensorineural structures, their function, and the function of related biological systems, for example, hearing ability, gaze stabilization, locomotor agility, and posture. The endosseous labyrinth is frequently used as a proxy to infer the performance of the hearing and vestibular systems, locomotor abilities, and ecology of extinct species. Such fossil inferences are often based on single specimens or even a single ear, representing an entire species. To address whether a single ear is representative of a population, we used geometric morphometrics to quantitatively assess the variation in shape and symmetry in a sample of endosseous labyrinths of wild turkeys Meleagris gallopavo of southern Ohio. We predicted that ears would be symmetrical both within individuals and across the sample; that labyrinth shape and size would covary; that labyrinth shape would vary with the size of the brain, measured as width of the endocranium at the cerebellum; and that labyrinths would be morphologically integrated. To test these predictions, we microCT-scanned the heads of 26 cadaveric turkeys, digitally segmented their endosseous labyrinths in Avizo, and assigned 15 manual landmarks and 20 sliding semilandmarks to each digital model. Following Procrustes alignment, we conducted an analysis of bilateral symmetry, a Procrustes regression analysis for allometry and other covariates including side and replicate, and analyses of global integration and modularity. Based on Procrustes distances, no individualâs left and right ears were clearly different from each other. When comparing the ears of different specimens, statistically clear differences in shape were found in only 66 of more than 1,300 contrasts. Moreover, effects of both directional and fluctuating asymmetry were very small--generally, two orders of magnitude smaller than the variance explained by individual variation. Statistical tests disagreed on whether these asymmetric effects crossed the threshold of significance, possibly due to non-isotropic variation among landmarks. Regardless, labyrinths appeared to primarily vary in shape symmetrically. Neither labyrinth size nor endocranial width was correlated with labyrinth shape, contrary to our expectations. Finally, labyrinths were found to be moderately integrated in a global sense, but four weakly separated modules--the three SCCs and cochlea--were recovered using a maximum-likelihood analysis. The results show that both fluctuating and directional asymmetry play a larger role in shape variation than expected--but nonetheless, endosseous labyrinths are symmetrical within individuals and at the level of the population, and their shape varies symmetrically. Thus, inferences about populations, and very possibly species, may be confidently made when only a single specimen, or even a single ear, is available for study.
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The mechanical performance of limb bones is closely associated with an animal's locomotor capability and is thus important to our understanding of animal behaviour. This study combined a geometrical analysis and threeâpoint bending tests to address the question of how the mechanical performance of the femurs of Japanese quail (Coturnix coturnix japonica) and pigeon (Columba livia domestica) respond to changing functional demands during ontogeny. Results showed that hatchling quails had stiff bone tissues, and the femoral ultimate loads scaled negatively with body mass, corresponding to high functional demands during early growth. The hatchling pigeon femora had weak material properties but they showed a dramatic increase in Young's modulus during growth. Consequently, although femoral crossâsectional geometry showed negative allometry, the ultimate loads scaled positively with body mass. Older pigeons had more circular bone crossâsections than younger pigeons, probably due to load stimulation changes occurred shortly after the onset of locomotion. Negative allometry and isometry of the crossâsectional geometry of hind limb bones were observed in flying birds and groundâdwelling birds, respectively. The correspondence between geometrical change and locomotor pattern suggests that ontogenetic changes in crossâsectional geometry may be an effective indicator of avian locomotor behaviour.
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Raw Xâray microtomographic data files are archived at the Naturhistorisches Museum Basel; additional data for this study are available in the Dryad Digital Repository:
https://doi.org/10.5061/dryad.rt1385v and on the MorphoMuseuM website:
https://doi.org/10.18563/journal.m3.74.
We describe the first endocast reconstruction of a hyaenodont mammal based on Xâray microtomography. The endocast belongs to the type material of the European hyaenodont Proviverra typica. We performed phylogenetic analysis to contextualize the evolution of endocranial size and complexity in Hyaenodonta. We added several European hyaenodonts and modified several codings of the most recent characterâtaxon matrix established to question the relationships within Hyaenodonta. Including these new species in a phylogenetic analysis reveals a new clade: Hyaenodontoidea. Comparisons with several previously described endocasts show that there was an increase in complexity in the convolutions of the encephalon within Hyaenodontidae history. Moreover, the analysis of the encephalization quotient reveals that the endocranium of the Hyaenodonta is not smaller than those of fossil Carnivora or some extant Carnivora. Therefore, the extinction of Hyaenodonta may not be linked to the relative size of hyaenodont brains.
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Jacob D. Gardner, Michel Laurin & Chris L. Organ (2019)
The Relationship Between Genome Size and Metabolic Rate in Extant Vertebrates.
bioRxiv
doi:
https://doi.org/10.1101/659094https://www.biorxiv.org/content/10.1101/659094v1free pdf:
https://www.biorxiv.org/content/biorxiv/early/2019/07/25/659094.full.pdfGenome size has long been hypothesized to affect metabolic rate in various groups of animals. The mechanism behind this proposed association is the nucleotypic effect, in which large nucleus and cell sizes influence cellular metabolism through surface-to-volume ratios. Here, we provide a review of the recent literature on the relationship between genome size and metabolic rate. We also conduct an analysis using phylogenetic comparative methods and a large sample of extant vertebrates. We find no evidence that the effect of genome size improves upon models in explaining metabolic rate variation. Not surprisingly, our results show a strong positive relationship between metabolic rate and body mass, as well as a substantial difference in metabolic rate between endothermic and ectothermic vertebrates, controlling for body mass. The presence of endothermy can also explain elevated rate shifts in metabolic rate. We further find no evidence for a punctuated model of evolution for metabolic rate. Our results do not rule out the possibility that genome size affects cellular physiology in some tissues, but we find little support for a direct functional connection between genome size and overall metabolism in extant vertebrates.