Ben Creisler
Some recent mainly mammal papers:
A. V. Lopatin, A. O. Averianov, I. T. Kuzmin, E. A. Boitsova, P. G. Saburov, S. V. Ivantsov & P. P. Skutschas (2020)
A new finding of a docodontan (Mammaliaformes, Docodonta) in the Lower Cretaceous of western Siberia.
REPORTS OF THE RUSSIAN ACADEMY OF SCIENCES. EARTH SCIENCES 494(1): 5-8 (in Russian)
DOI:10.31857/S2686739720090121ÂÂÂÂÂ
https://elibrary.ru/item.asp?id=43928209Â Â
The first finding of the docodontan in the Bol'shoi Kemchug 3 locality (Ilek Formation, Lower Cretaceous) in the Krasnoyarsk Territory -- the lower molar of Sibirotherium sp. Sibirotherium rossicum, one of the youngest docodontans in the geological record, is known from the Ilek Formation of the Shestakovo 1 locality (Kemerovo Region). Previously, only indeterminable remains of docodontans were found in the localities of the Ilek Formation in the Krasnoyarsk Territory (Bol'shoi Terekhtyul' 2 and Bol'shoi Ilek).ÂÂ
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Ruslan I. Belyaev, Alexander N. Kuznetsov & Natalya E. Prilepskaya (2020)
A mechanistic approach for the calculation of intervertebral mobility in mammals based on vertebrae osteometry.
Journal of Anatomy (advance online publication)
doi:
https://doi.org/10.1111/joa.13300https://onlinelibrary.wiley.com/doi/10.1111/joa.13300In this paper, we develop and validate an osteometryâbased mechanistic approach to calculation of available range of motion (aROM) in presacral intervertebral joints in sagittal bending (SB), lateral bending (LB), and axial rotation (AR). Our basic assumption was the existence of a mechanistic interrelation between the geometry of zygapophysial articular facets and aROM. Trigonometric formulae are developed for aROM calculation, of which the general principle is that the angle of rotation is given by the ratio of the arc length of motion to the radius of this arc. We tested a number of alternative formulae against available in vitro data to identify the most suitable geometric ratios and coefficients for accurate calculation. aROM values calculated with the developed formulae show significant correlation with in vitro data in SB, LB, and AR (Pearson r = 0.900) in the reference mammals (man, sheep, pig, cow). It was found that separate formulae for different zygapophysial facet types (radial (Rf), tangential (Tf), radial with a lock (RfL)) give significantly greater accuracy in aROM calculation than the formulae for the presacral spine as a whole and greater accuracy than the separate formulae for different spine regions (cervical, thoracic, lumbar). The advantage of the facetâspecific formulae over the regionâspecific ones shows that the facet type is a more reliable indicator of the spine mobility than the presence or absence of ribs. The greatest gain in calculation accuracy with the facetâspecific formulae is characteristic in AR aROM. The most important theoretical outcome is that the evolutionary differentiation of the zygapophysial facets in mammals, that is the emergence of Tf joints in the rib cage area of the spine, was more likely associated with the development of AR rather than with SB mobility and, hence, with cornering rather than with forward galloping. The AR aROM can be calculated with the formulae common for man, sheep, pig, and cow. However, the SB aROM of the human spine is best calculated with different coefficient values in the formulae than those for studied artiodactyls. The most suitable coefficient values indicate that the zygapophysial articular facets tend to slide past each other to a greater extent in the human thoracolumbar spine rather than in artiodactyls. Due to this, artiodactyls retain relatively greater facet overlap in extremely flexed and extremely extended spine positions, which may be more crucial for their quadrupedal gallop than for human bipedal locomotion. The SB, LB, and AR aROMs are quite separate in respect of the formulae structure in the cervical region (radial facet type). However, throughout the thoracolumbar spine (tangential and radial with lock facets), the formulae for LB and AR are basically similar differing in coefficient values only. This means that, in the thoracolumbar spine, the greater the LB aROM, the greater the AR aROM, and vice versa. The approach developed promises a wide osteological screening of extant and extinct mammals to study the sex, age, geographical variations, and disorders.
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Danielle Fraser and S. Kathleen Lyons (2020)
Mammal Community Structure through the Paleocene-Eocene Thermal Maximum.
The American Naturalist 196(3): 271-290
DOI:
https://doi.org/10.1086/709819https://www.journals.uchicago.edu/doi/10.1086/709819Human-mediated species invasion and climate change are leading to global extinctions and are predicted to result in the loss of important axes of phylogenetic and functional diversity. However, the long-term robustness of modern communities to invasion is unknown, given the limited timescales over which they can be studied. Using the fossil record of the Paleocene-Eocene thermal maximum (PETM; â56 Ma) in North America, we evaluate mammalian community-level response to a rapid global warming event (5Â-8ÂC) and invasion by three Eurasian mammalian orders and by species undergoing northward range shifts. We assembled a database of 144 species body sizes and created a time-scaled composite phylogeny. We calculated the phylogenetic and functional diversity of all communities before, during, and after the PETM. Despite increases in the phylogenetic diversity of the regional species pool, phylogenetic diversity of mammalian communities remained relatively unchanged, a pattern that is invariant to the tree dating method, uncertainty in tree topology, and resolution. Similarly, body size dispersion and the degree of spatial taxonomic turnover of communities remained similar across the PETM. We suggest that invasion by new taxa had little impact on Paleocene-Eocene mammal communities because niches were not saturated. Our findings are consistent with the numerous studies of modern communities that record little change in community-scale richness despite turnover in taxonomic composition during invasion. What remains unknown is whether long-term robustness to biotic and abiotic perturbation are retained by modern communities given global anthropogenic landscape modification.
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Free pdf:
Gary Dougill, Eugene L. Starostin, Alyx O. Milne, Gert H. M. van der Heijden, Victor G. A. Goss Â& Robyn A. Grant (2020)
Ecomorphology reveals Euler spiral of mammalian whiskers.
doi:
https://doi.org/10.1002/jmor.21246https://onlinelibrary.wiley.com/doi/full/10.1002/jmor.21246Free pdf:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmor.21246Whiskers are present in many species of mammals. They are specialised vibrotactile sensors that sit within strongly innervated follicles. Whisker size and shape will affect the mechanical signals that reach the follicle, and hence the information that reaches the brain. However, whisker size and shape have not been quantified across mammals before. Using a novel method for describing whisker curvature, this study quantifies whisker size and shape across 19 mammalian species. We find that gross twoâdimensional whisker shape is relatively conserved across mammals. Indeed, whiskers are all curved, tapered rods that can be summarised by Euler spiral models of curvature and linear models of taper, which has implications for whisker growth and function. We also observe that aquatic and semiâaquatic mammals have relatively thicker, stiffer, and more highly tapered whiskers than arboreal and terrestrial species. In addition, smaller mammals tend to have relatively long, slender, flexible whiskers compared to larger species. Therefore, we propose that whisker morphology varies between larger aquatic species, and smaller scansorial species. These two whisker morphotypes are likely to induce quite different mechanical signals in the follicle, which has implications for follicle anatomy as well as whisker function.
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Also:
Free pdf:
Free pdf:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmor.21262The avian yolk sac is a multifunctional extraembryonic organ that serves not only as a site of nutrient (yolk) absorption, but also for early hemopoiesis, and formation of blood vessels. Although the yolk sac membrane being specialized to function as an extraembryonic absorptive organ, it is neither morphologically nor functionally part of the embryonic gut. Yolk absorption is by the phagocytic activity of the extraembryonic endoderm. I used cryohistology and resin embedding histology of complete developmental series of Japanese quail to document the development of the avian yolk sac and changes of the microscopic anatomy throughout development. This material is complemented by complete series of MRTâscans of live ostrich embryos from beginning of incubation through hatching. Considerable changes of size and shape of the yolk mass are documented and discussed as resulting from water flux from albumen to yolk associated with the biochemical activation of yolk sac proteins. During embryogenesis, the yolk sac endoderm forms villi that increase the absorptive surface and reach into the yolk ball. The histology of the absorptive epithelium is specialized for phagocytic absorption of yolk. During early developmental stages, the extraembryonic endoderm is single layered, but it eventually becomes several layers thick during later stages. The extraembryonic mesoderm forms an extensive layer of hematopoietic tissue; deep in this tissue lie the yolk sac vessels. During late stages of development, the erythropoietic tissue disappears, blood vessels are obliterated, and the yolk sac epithelium becomes apoptotic. Results are discussed in the light of the evolutionary history and phylogeny of the amniote egg.
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