Ben Creisler
A new papers:
======
Highlights
The Lower Cretaceous Dabeigou Formation represents three depositional stages.
In 1st and 2nd stages, volcanic activity was frequent and the climate was cold and humid.
Cold climate in 2nd stage coincides with the cooling event during the Weissert Event.
In 3rd stage, decreased volcanism and warm climate favored lacustrine productivity.
Improved environmental conditions enabled the diversification of the Jehol Biota.
Abstract
The Jehol Biota of northern China provides a new and unmatched window for the reconstruction and understanding of Early Cretaceous terrestrial ecosystems. Previous studies on the paleoenvironmental and paleoclimatic background of the Jehol Biota have mainly focused on middleâlate evolutionary stages while the less diverse and more narrowly distributed early Jehol Biota remains less understood. The Lower Cretaceous (ValanginianâHauterivian) Dabeigou Formation in the Luanping Basin (North China), preserves the early stages of the Jehol Biota and can be subdivided into three members. To reconstruct the living environment of the early Jehol Biota, we explored the geochemistry, bulk mineralogy, total organic carbon, sedimentology, and paleoecology of the Dabeigou Formation from the Yushuxia section of the Luanping Basin. Decreased volcanic activity during the deposition of the Dabeigou Formation resulted in changes in its source material from felsic to mafic. The Luanping palaeolake reached its deepest water depth during deposition of the Member 2, and generally exhibited low salinity, while a short time of high salinity occurred during deposition of the Member 3. Analysis on the paleoweathering indices and other evidences, indicate that the Luanping area was generally in cold and humid climate conditions during deposition of the members 1 and 2 (correlated to the Weissert Event), but changed to warm climate conditions during deposition of the Member 3, which coincides with an increasing trend of biotic diversity. Consequently, our results suggest that the increasingly warm paleoclimate and lacustrine productivity, associated with decreasingly volcanic activity in North China, have contributed to the early evolution of the Jehol Biota.
Â.
====
Birds are the most diversified terrestrial vertebrates due to highly diverse integumentary organs that enable robust adaptability to various eco-spaces. Here we show that this complexity is built upon multi-level regional specifications. Across-the-body (macro-) specification includes the evolution of beaks and feathers as new integumentary organs that are formed with regional specificity. Within-an-organ (micro-) specification involves further modifications of organ shapes. We review recent progress in elucidating the molecular mechanisms underlying feather diversification as an example. (1) Î-Keratin gene clusters are regulated by typical enhancers or high order chromatin looping to achieve macro- and micro-level regional specification, respectively. (2) Multi-level symmetry-breaking of feather branches confers new functional forms. (3) Complex color patterns are produced by combinations of macro-patterning and micro-patterning processes. The integration of these findings provides new insights toward the principle of making a robustly adaptive bio-interface.
===
Fossil eggshells can preserve thermally altered carbonaceous material
Maximum paleotemperature that fossil eggshells experienced can be estimated from RSCM
Paleotemperature estimates from RSCM is further supported by FTIR and EBSD
Paleothermometry using eggshells can be applicable to diverse geological questions
Abstract
Raman spectroscopic analyses of thermally altered organic materials can be used to assess the paleothermometry of the sedimentary deposits. Although this technique has been widely applied to diverse microfossils, macroscopic vertebrate fossils have been neglected. In this paper, we show that fossil eggshells can be used for this purpose by demonstrating the paleothermometric potential of diverse amniotic eggshells from the Wido Volcanics (Upper Cretaceous, South Korea) that contain thermally altered organic material. We estimate the maximum paleotemperature recorded in the eggshells using Raman spectroscopic data and the spectrum deconvolution technique, which was invented and developed by organic geochemists. The results show that the same type of eggshells record different paleotemperature gradients depending on their spatial distribution in the fossil locality, whereas different types of eggshells from similar locations show similar paleotemperature gradients (except for one specimen with a peculiar microstructure). These findings are further supported by Fourier transform infrared spectroscopic results, which focus on thermally altered organic materials, and electron backscatter diffraction data, which focus on calcite twinning. This study suggests that fossil eggshells are useful and reliable materials for paleothermometry because thermally altered organic materials and calcites of eggshells provide independent opportunities to assess paleothermometry. We propose that fossil eggshells may be useful for evaluating the thermal evolution of sedimentary basins.
===
Alistair R. Evans, Tahlia I. Pollock, Silke G. C. Cleuren, William M. G. Parker, Hazel L. Richards, Kathleen L. S. Garland, Erich M. G. Fitzgerald, Tim E. Wilson, David P. Hocking & Justin W. Adams
A universal power law for modelling the growth and form of teeth, claws, horns, thorns, beaks, and shells.
BMC Biology 19:58
doi:
https://doi.org/10.1186/s12915-021-00990-whttps://link.springer.com/article/10.1186/s12915-021-00990-w
A major goal of evolutionary developmental biology is to discover general models and mechanisms that create the phenotypes of organisms. However, universal models of such fundamental growth and form are rare, presumably due to the limited number of physical laws and biological processes that influence growth. One such model is the logarithmic spiral, which has been purported to explain the growth of biological structures such as teeth, claws, horns, and beaks. However, the logarithmic spiral only describes the path of the structure through space, and cannot generate these shapes.
Results
Here we show a new universal model based on a power law between the radius of the structure and its length, which generates a shape called a âpower coneâ. We describe the underlying âpower cascadeâ model that explains the extreme diversity of tooth shapes in vertebrates, including humans, mammoths, sabre-toothed cats, tyrannosaurs and giant megalodon sharks. This model can be used to predict the age of mammals with ever-growing teeth, including elephants and rodents. We view this as the third general model of tooth development, along with the patterning cascade model for cusp number and spacing, and the inhibitory cascade model that predicts relative tooth size. Beyond the dentition, this new model also describes the growth of claws, horns, antlers and beaks of vertebrates, as well as the fangs and shells of invertebrates, and thorns and prickles of plants.
Conclusions
The power cone is generated when the radial power growth rate is unequal to the length power growth rate. The power cascade model operates independently of the logarithmic spiral and is present throughout diverse biological systems. The power cascade provides a mechanistic basis for the generation of these pointed structures across the tree of life.