The Chinese journal Global Geology 22(4) (2019) (English language version) has papers posted from the International Symposium on Cretaceous Biota and K-Pg boundary, held in ÂJiayin, China.This journal has free pdfs.Â
Amber chemistry suggests cupressaceous trees in Late Cretaceous high latitude.
Stable isotope analyses suggest habitat distant from the Western Interior Seaway.
Relatively diverse arthropod, botanical, and vertebrate inclusions are present.
Abstract
Amber deposits and dinosaur bonebeds provide some of the most detailed sources of information on terrestrial ecosystems, but these sources have rarely been studied in tandem. The Pipestone Creek bonebed from the Campanian Wapiti Formation of Alberta, Canada, provides an opportunity to explore both data sources in the same deposit for the first time. The site has yielded an exceptional fauna dominated by abundant remains of the centrosaurine ceratopsian Pachyrhinosaurus. The initial campaigns of excavation in the 1980s led to the collateral discovery of amber, and the site became the first published source of insect-bearing amber in a dinosaur bonebed. Here we describe amber inclusions in detail and analyze the composition and geochemistry of the amber (FTIR spectroscopy and stable isotope studies) in order to draw paleoecological and paleoenvironmental inferences. We describe a feather fragment from an aquatic bird, as well as new species of Psocodea and Hymenoptera (Mymarommatidae) with ecological constraints. Indeterminate aphid and spider inclusions were also found, but preservation was not sufficient for formal description. FTIR spectroscopy suggests a botanical source among the Cupressaceae, while stable isotope data indicate that the resin-producing forest did not receive precipitation directly from the Western Interior Seaway. These initial results show that amber is a valuable source of additional information about the habitat surrounding the vertebrates found in bonebed deposits. Given the abundance and range of inclusions encountered so far, Pipestone Creek amber also appears to be a promising new source for a relatively diverse Campanian amber assemblage.
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Katherine L. LONG, ÂDonald R. PROTHERO & Valerie J.P. SYVERSON (2020)
How do small birds evolve in response to climate change? Data from the longâterm record at La Brea tar pits.
Integrative Zoology (advance online publication)
doi:
https://doi.org/10.1111/1749-4877.12426https://onlinelibrary.wiley.com/doi/10.1111/1749-4877.12426Biology textbooks describe the small changes in the beaks of the GalÃpagos finches as exemplars of how birds evolve in response to environmental changes. Yet recent studies of the abundant fossil birds at Rancho La Brea finds no evidence of evolutionary responses to the dramatic climate changes of the glacialâinterglacial cycle over the last 35,000 years: none of the large birds exhibit any change in body size or limb proportions, even during the last glacial maximum about 18,000â20,000 years ago, when the southern California chaparral was replaced by snowy coniferous forests. But these are all large birds with large ranges and broad habitat preferences, capable of living in many different environments. Perhaps the smaller birds at La Brea, which have smaller home ranges and narrower habitats, might respond to climate more like GalÃpagos finches. The only three common small birds at La Brea are the Western Meadowlark, the YellowâBilled Magpie, and the Raven. In this study, we demonstrate that these birds also show complete stasis over the last glacialâinterglacial cycle, with no statistically significant changes between dated pits. Recent research suggests that the smallâscale changes over short time scales seen in the GalÃpagos finches are merely fluctuations around a stable morphology, and rarely lead to longâterm accumulation of changes or speciation. Instead, the prevalence of stasis supports the view that longâterm directional changes in morphology are quite rare. While directional changes in morphology occur frequently over short (<1ka) timescales, in the long term such changes only rarely remain stable for long enough to appear in the fossil record.
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Free pdf:
Reconstructing the behavior of extinct species is challenging, particularly for those with no living analogues. However, damage preserved as paleopathologies on bone can record how an animal moved in life, potentially reflecting patterns of behavior. Here, for the first time, we use computed tomography (CT) to assess hypothesized etiologies of pathology in a pelvis and associated right femur of an adult Smilodon fatalis saber-toothed cat, one of the best-studied mammal species from the Pleistocene-age Rancho La Brea asphalt seeps, Los Angeles, California. The pelvis exhibits massive destruction of the right acetabulum that previously was interpreted, for nearly a century, to have resulted from trauma and infection. We evaluated this historical interpretation using CT imaging to supplement gross morphology in identifying symptoms of traumatic, infective, or degenerative arthritis. We found that the pathologic distortions are inconsistent with degenerative changes that started only later in life, as in the case of infective or traumatic arthritis. Rather, they characterize chronic remodeling that began at birth and led to degeneration of the joint over time. These findings suggest that this individual suffered from hip dysplasia, a congenital condition common in domestic dogs and cats.
The individual examined in this study reached adulthood (at least four to seven years of age) but never could have hunted properly nor defended territory on its own. As such, this individual, and other critically pathologic Smilodon like it, likely survived to adulthood by association with a social group that assisted it with feeding and protection. The pathologic specimens examined here in detail are consistent with a spectrum of social strategies in Smilodon supported by a predominance of previous studies. This application of a relatively new and interdisciplinary technique to an old question therefore informs the longstanding debate between social and solitary hypotheses for the behavior of an extinct predator.
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Highlights
Exceptionally preserved fossils are evaluated through petrography and geochemistry.
Three-dimensional preservation of bone tissue allows proposing a new LagerstÃtte.
CAMP-related magmatism and intensified chemical weathering triggered eutrophication.
Similar location and geological data suggest clusters of exceptional preservation.
Despite similar taphonomic pathways, autogenic factors control fossil diagenesis.
Abstract
Fossil bonanzas called Konservat LagerstÃtten provide geological windows to the ecology of ancient life communities. These deposits often occur as cluster of fossil localities with similar geographic locations, geological ages and facies, as the fossils were generally preserved during special periods and large-scale events in Earth history within environments with exceptional taphonomic conditions. This work applied petrological and geochemical analyses to evaluate the taphonomic pathway of a Konservat LagerstÃtten in the Muzinho Shale, Upper Jurassic-Lower Cretaceous of the ParnaÃba Basin, northeastern Brazil. These lacustrine deposits include interbedded limestones and fossiliferous black shales deposited in anoxic, non-euxinic and saline environment. Black shales contain articulated skeletons of fish fossils, characterised by three-dimensional preservation of the skeletal tissue. The polytypical assemblage includes diverse ontogenetic stages and is concentrated in a specific stratigraphic level. Mass mortality was triggered by anoxia probably established by stratified water column, high C flux and thermocline demise. The specimens are encased in kerogen-bearing siliciclastic laminae and cementstone microfacies, both microbially-induced. The fossils were cemented by eodiagenetic poikilotopic calcite that filled the skeletal articulation, including bone trabeculae and voids originally filled by bone marrow. The short distance, similar fossil assemblages, ages and coincident palaeoenvironments suggest that Muzinho Shale (ParnaÃba Basin) and Crato Formation (Araripe Basin) compose a cluster of exceptional preservation in West Gondwana. Lava flows and outgassing related to the Central Atlantic Magmatic Province (CAMP) resulted in the subaereal exposure of volcanic plains, acid rains and subsequent CO2 greenhouse crisis. CAMP-magmatism was especially voluminous in northern Brazilian basins, enhancing nutrient-rich waters and lacustrine eutrophication due to intensified chemical weathering in this area. Probably, other Konservat LagerstÃtten remain unreported in West Gondwana. Despite similar causative events, the individual taphonomic pathways of Muzinho Shale and Crato Formation are very different, suggesting that in these cases local phenomena affected authigenesis and diagenesis.
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Highlights
Description of paleosols from Cretaceous formations in Oklahoma and Texas
Chemical, mineralogic, and hydrogen-and oxygen isotope data from pedogenic clays
Mean annual temperature estimates of the Cretaceous using pedogenic clays
Temperature and precipitation estimates show temporal shifts across the Cretaceous.
Abstract
Clay mineralogy, chemistry, and stable oxygen and hydrogen-isotope compositions of 11 phyllosilicate samples from Cretaceous paleosol profiles were determined in order to evaluate Early-to-Late Cretaceous paleoenvironments and paleoclimates around north-central Texas and southern Oklahoma. Samples consist of mineralogical mixtures of illite, smectite, and kaolinite. Samples from the Albian Antlers Formation in southern Oklahoma and the Cenomanian Woodbine Formation are dominated by kaolinite, while the remaining samples are dominated by smectite and illite. Major element compositions of paleosol matrix materials are used to calculate CALMAG weathering values that range from 31 to 84 and correspond to Cretaceous paleoprecipitation estimates ranging from 270 to 1490âmm/yr. Paleosol phyllosilicate hydrogen and oxygen stable isotope values range from â50â to â67â to 18.5â to 21.7â, respectively, and in conjunction with their respective mineral and chemical compositions, correspond to in-situ soil crystallization temperatures ranging from 26âÂâ3âÂC to 31âÂâÂC. Paleoprecipitation trends exhibit two marked increases in precipitation from the Early to Late Cretaceous, in the Albian Antlers Formation and Cenomanian Woodbine Formation. Stratigraphic intervals with phyllosilicates that yield cooler temperature estimates coincide with stratigraphic intervals with markedly higher precipitation estimates based on CALMAG values. Importantly, cool, high precipitation intervals correlate with periods of extensive shallow seas upon the North American craton. Comparison of Cretaceous temperature, precipitation and meteoric water estimates to modern analogs supports the presence of climates similar to modern tropical climates during the Cretaceous at subtropical or temperate paleolatitudes in what is now Texas and Oklahoma, consistent with general circulation models and energy balance models suggesting a pervading Cretaceous greenhouse.