scholarly journals Accretion of a large LL parent planetesimal from a recently formed chondrule population

2020 ◽  
Vol 6 (16) ◽  
pp. eaay8641
Author(s):  
Graham H. Edwards ◽  
Terrence Blackburn
Keyword(s):  
Body Size ◽  
Size Distribution ◽  
Total Duration ◽  
Parent Body ◽  
Ordinary Chondrite ◽  
Minimum Size ◽  
Thermal Models ◽  
Early Stages ◽  
Chondritic Meteorites ◽  
Chondrule Formation

Chondritic meteorites, derived from asteroidal parent bodies and composed of millimeter-sized chondrules, record the early stages of planetary assembly. Yet, the initial planetesimal size distribution and the duration of delay, if any, between chondrule formation and chondrite parent body accretion remain disputed. We use Pb-phosphate thermochronology with planetesimal-scale thermal models to constrain the minimum size of the LL ordinary chondrite parent body and its initial allotment of heat-producing 26Al. Bulk phosphate 207Pb/206Pb dates of LL chondrites record a total duration of cooling ≥75 Ma, with an isothermal interior that cools over ≥30 Ma. Since the duration of conductive cooling scales with parent body size, these data require a ≥150-km radius parent body and a range of bulk initial 26Al/27Al consistent with the initial 26Al/27Al ratios of constituent LL chondrules. The concordance suggests that rapid accretion of a large LL parent asteroid occurred shortly after a major chondrule-forming episode.

The Beginnings

2017 ◽  
Author(s):  
Raymond Pierotti ◽  
Brandy R. Fogg
Keyword(s):  
Body Size ◽  
Gene Pool ◽  
Southern Asia ◽  
Early Stages ◽  
The World ◽  
State Of Affairs ◽  
The Relationship

This introductory chapter provides an overview of the relationship between humans and wolves. The relationship began as coevolutionary, with the species cooperating at times but also capable of functioning independently. This state of affairs dominated early stages of the relationship between the two species and may have persisted for 20,000 years or longer. In other parts of the world, for example, southern Asia, humans began to shape wolves into clearly domestic forms: animals phenotypically distinct from wolves, especially in body size. This latter process involves various aspects of the wolf gene pool being essentially divided, with many individuals staying true wolves while others changed in form, becoming what people now describe as “dogs” without losing their genetic links to their wolf ancestry or their ability to interbreed with wolves.

scholarly journals Mammal body size evolution in North America and Europe over 20 Myr: similar trends generated by different processes

2017 ◽  
Vol 284 (1849) ◽  
pp. 20162361 ◽  
Author(s):  
Shan Huang ◽  
Jussi T. Eronen ◽  
Christine M. Janis ◽  
Juha J. Saarinen ◽  
Daniele Silvestro ◽  
...  
Keyword(s):  
Body Size ◽  
North America ◽  
Biological Properties ◽  
Species Selection ◽  
Minimum Size ◽  
Extinction Rate ◽  
Large Herbivores ◽  
Size Evolution ◽  
Geographical Regions ◽  
Body Size Evolution

Because body size interacts with many fundamental biological properties of a species, body size evolution can be an essential component of the generation and maintenance of biodiversity. Here we investigate how body size evolution can be linked to the clade-specific diversification dynamics in different geographical regions. We analyse an extensive body size dataset of Neogene large herbivores (covering approx. 50% of the 970 species in the orders Artiodactyla and Perissodactyla) in Europe and North America in a Bayesian framework. We reconstruct the temporal patterns of body size in each order on each continent independently, and find significant increases of minimum size in three of the continental assemblages (except European perissodactyls), suggesting an active selection for larger bodies. Assessment of trait-correlated birth-death models indicates that the common trend of body size increase is generated by different processes in different clades and regions. Larger-bodied artiodactyl species on both continents tend to have higher origination rates, and both clades in North America show strong links between large bodies and low extinction rate. Collectively, our results suggest a strong role of species selection and perhaps of higher-taxon sorting in driving body size evolution, and highlight the value of investigating evolutionary processes in a biogeographic context.

Species body size distribution patterns of marine benthic macrofauna assemblages from contrasting sediment types

1999 ◽  
Vol 79 (5) ◽  
pp. 793-801 ◽  
Author(s):  
David M. Parry ◽  
Michael A. Kendall ◽  
Ashley A. Rowden ◽  
Stephen Widdicombe
Keyword(s):  
Body Size ◽  
Size Distribution ◽  
Species Turnover ◽  
Distribution Patterns ◽  
Benthic Macrofauna ◽  
Size Spectrum ◽  
Size Spectra ◽  
Β Diversity ◽  
Sediment Types ◽  
Geometric Size

Species body size spectra have been constructed for macrofauna assemblages from four sites with contrasting sediment granulometry and heterogeneity in and around Plymouth Sound. The number of species and species turnover (β diversity) were higher on coarse sediment. While the fauna were distinct between sites, the median geometric size-class was conservative (class 14; 0.153–0.305 mg dry blotted weight). Only one site had significantly lower heterogeneity within the species size spectrum, yet this was the most heterogeneous sediment. As such, we were unable to reject the null hypothesis that species body size distribution patterns are conservative despite differences in sediment granulometry and heterogeneity.

Body size distribution in Daphnia populations as an effect of prey selectivity by planktivorous fish

Hydrobiologia ◽  
2010 ◽  
Vol 643 (1) ◽  
pp. 5-19 ◽  
Author(s):  
Z. Maciej Gliwicz ◽  
Ewa Szymanska ◽  
Dariusz Wrzosek
Keyword(s):  
Body Size ◽  
Size Distribution ◽  
Planktivorous Fish ◽  
Prey Selectivity

scholarly journals Old formation ages of igneous clasts on the L chondrite parent body reflect an early generation of planetesimals or chondrule formation

2018 ◽  
Vol 481 ◽  
pp. 372-386 ◽  
Author(s):  
Sarah A. Crowther ◽  
Michal J. Filtness ◽  
Rhian H. Jones ◽  
Jamie D. Gilmour
Keyword(s):  
Parent Body ◽  
Early Generation ◽  
Chondrule Formation

Does Body Size Optimization Result in Skewed Body Size Distribution on a Logarithmic Scale?

1999 ◽  
Vol 153 (4) ◽  
pp. 445-447 ◽  
Author(s):  
Pavel Kindlmann ◽  
Anthony F. G. Dixon ◽  
Iva Dostálková
Keyword(s):  
Body Size ◽  
Size Distribution ◽  
Size Optimization ◽  
Logarithmic Scale ◽  
Optimization Result

Clutch and egg size of the tropical lizard Tropidurus torquatus (Tropiduridae) along its geographic range in coastal eastern Brazil

2008 ◽  
Vol 86 (12) ◽  
pp. 1376-1388 ◽  
Author(s):  
M. C. Kiefer ◽  
M. Van Sluys ◽  
C. F.D. Rocha
Keyword(s):  
Body Size ◽  
Clutch Size ◽  
Female Body ◽  
Egg Size ◽  
Reproductive Investment ◽  
Geographic Range ◽  
Minimum Size ◽  
Brazilian Coast ◽  
Female Body Size ◽  
Almost All

The tropidurid lizard Tropidurus torquatus (Wied, 1820) has a set of populations inhabiting coastal sand dune habitats (“restinga”) along the eastern Brazilian coast. Despite its wide geographic range, there is no information about geographic variation in reproductive features among its populations. In the present study we compared some reproductive aspects of females in 10 coastal populations of T. torquatus, aiming to evaluate to what extension they vary geographically. The minimum size at maturity was relatively similar to most populations, but mean female body size had a considerable variation. Clutch size of almost all coastal populations of T. torquatus had little variation and was composed predominantly of two eggs. Interpopulational variation in the mean egg volume was relatively wide and strongly influenced by the variation in mean female body size. The data of the present study indicated that females of almost all coastal populations of T. torquatus produce, predominantly, clutches with two eggs and invest more energy in egg size instead of clutch size, probably as a consequence of morphological and environmental factors. The increased reproductive investment in egg size was confirmed by the values obtained for the relative clutch mass, which remained relatively constant along the coastal geographic distribution of T. torquatus.

scholarly journals Tungsten isotopic constraints on the age and origin of chondrules

2016 ◽  
Vol 113 (11) ◽  
pp. 2886-2891 ◽  
Author(s):  
Gerrit Budde ◽  
Thorsten Kleine ◽  
Thomas S. Kruijer ◽  
Christoph Burkhardt ◽  
Knut Metzler
Keyword(s):  
Planet Formation ◽  
Solar Nebula ◽  
Carbonaceous Chondrite ◽  
Critical Role ◽  
Parent Body ◽  
Uneven Distribution ◽  
Time Interval ◽  
Ordinary Chondrites ◽  
Chondrule Formation ◽  
Isotopic Constraints

Chondrules may have played a critical role in the earliest stages of planet formation by mediating the accumulation of dust into planetesimals. However, the origin of chondrules and their significance for planetesimal accretion remain enigmatic. Here, we show that chondrules and matrix in the carbonaceous chondrite Allende have complementary 183W anomalies resulting from the uneven distribution of presolar, stellar-derived dust. These data refute an origin of chondrules in protoplanetary collisions and, instead, indicate that chondrules and matrix formed together from a common reservoir of solar nebula dust. Because bulk Allende exhibits no 183W anomaly, chondrules and matrix must have accreted rapidly to their parent body, implying that the majority of chondrules from a given chondrite group formed in a narrow time interval. Based on Hf-W chronometry on Allende chondrules and matrix, this event occurred ∼2 million years after formation of the first solids, about coeval to chondrule formation in ordinary chondrites.

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