Ben Creisler
Some recent mainly non-dino papers that may be of interest on National Fossil Day:
The transition between the Devonian and Carboniferous is important for tetrapod vertebrates. By the end of the Devonian the first limbs are present in aquatic animals, and by the mid Carboniferous fully terrestrial tetrapods have diversified. Knowledge of the fin-to-limb transition is sparse because few fossils from the earliest Carboniferous (Tournaisian) are known. Blue Beach Nova Scotia, in addition to a small number of sites in Scotland and Australia, is an exception to this global trend. Previous reports from Blue Beach identified fossils from a variety of Devonian-like and Carboniferous-like tetrapod body forms, making it a valuable site for studying the fin-to-limb transition. Here we report on a new left fibula from Blue Beach, which we attribute to the later occurring Visean-aged (early Carboniferous) Crassigyrinidae. Recent investigations of deposits in Scotland, similar in age to the Tournaisian exposed at Blue Beach, have found Crassigyrinus-like elements as well, reinforcing this 20-million-year lineage extension.
====
Free pdf:
Long time perspectives can help us to better understand the response of high northern latitude environments to the consequences of climate forcing in the future. Sediment and bedrock archives can inform us of past conditions of climate, sea level, and fauna and flora that existed and even thrived in Arctic regions despite the long polar night. The Mesozoic Era, in particular, offers a view into the fascinating world of the past, when dinosaurs and diverse forests existed in polar regions during a time typically thought of as a climatic greenhouse. During the Mesozoic, atmospheric CO2 concentrations were much higher than today, over 1000 ppm (as compared to the pre-industrial average of 280 ppm). Sea-surface temperatures may have exceeded 32ÂC at 15â20Â N, while averaging 26ÂC at â53Â S (Littler et al.2011). Thus, looking to the past offers the potential for insight into what the planet may look like in the future if greenhouse gas emissions continue unabated.
In this special issue we have collected an eclectic set of papers on Mesozoic sedimentary archives stretching from Ellesmere Island in Canada to eastern Siberia in Russia, and ranging in age from the Early Triassic to the Late Cretaceous.Â
***********
With some free pdfs:
Geological Magazine 157(10) (October 2020 special issue)
Mesozoic of the Arctic
=====
Free pdf:
A large number of fossil-rich beds have been located from over 30âkm along the Tours-Poitiers High Speed Line (LGV) during earthworks prior to its construction, and in particular amber was collected from ScorbÃ-Clairvaux (locality of La Bergeonneau) to the north of Poitiers. The paper describes also amber pieces from ChÃtellerault (locality of La DÃsirÃe) discovered during the development of sewage treatment plant along the Vienne river. Lower Cenomanian shelly sandstones and siltstones of ScorbÃ-Clairvaux contain rare amber pieces associated with seed plants (Frenelopsis sp., Nehvizdya sp., and angiosperm seeds) and a diversified fauna, composed of micro-remains of 27âtaxa, comprising elasmobranchs (Haimirichia amonensis Cappetta and Case, 1975, Protolama sp. and Squalicorax sp.), actinopterygians (Enchodus sp. and Pycnodontidae), reptiles including vertebrae the marine snake Simoliophis rochebrunei Sauvage, 1880, some rare helochelydrid plates (cf.Plastremys), teeth of three crocodilian families (Atoposauridae, Goniopholididae and Bernissartiidae) and an undetermined dinosaurian long bone fragment.
====
Free pdf:
Modern day investigation in fields of archaeology and palaeontology can be greatly characterised by an exponential growth of integrated new technologies, nevertheless, while these advances are of great significance to multiple lines of research, their evaluation and update over time is equally as important. Here we present an application of inter and intra-observer analysis in taphonomy based geometric morphometrics, employing robust non-parametric statistical analyses for the study of experimental carnivore tooth pit morphologies. To fully understand the influence of measurement errors in the collection of this data, our statistical assessment was performed on fully superimposed, partially superimposed and raw landmark coordinates collected from 3D surface scanning. Experimental samples used to assess these errors includes wolf and dog tooth pits used in modern day ecological livestock predation analysis. Results obtained from this study highlight the importance of landmark type in the assessment of error, emphasising the value of semi-landmark models over the use of ambiguous Type III landmarks. In addition to this, data also reveals the importance of observer experience for the collection of data alongside an interesting increase in error when working with fully superimposed landmarks due to the "Pinocchio Effect". Through this study we are able to redefine the geometric morphometric models used for tooth pit morphological analyses. This final hybrid Type II fixed landmark and semi-landmark model presents a significant reduction in human induced error, generating a more metrically reliable and replicable method that can be used for data pooling in future inter-institutional research. These results can be considered a fundamental step forward for carnivore inspired studies, having an impact on archaeological, palaeontological, modern-day ecological research as well as applications in other forensic sciences.
====
Free pdf:
Evolution has shaped the limbs of hoofed animals in specific ways. In artiodactyls, it is the common assumption that the metatarsal is composed of the fusion of digits III and IV, whereas the other three digits have been lost or are highly reduced. However, evidence from the fossil record and internal morphology of the metatarsal challenges these assumptions. Furthermore, only a few taxonomic groups have been analysed. In giraffes, we discovered that all five digits are present in the adult metatarsal and are highly fused and modified rather than lost. We examined high-resolution micro-computed tomography scans of the metatarsals of two mid and late Miocene giraffid fossils and the extant giraffe and okapi. In all the Giraffidae analysed, we found a combination of four morphologies: (1) four articular facets; (2) four or, in most cases, five separate medullary cavities internally; (3) a clear, small digit I; and (4) in the two fossil taxa of unknown genus, the presence of external elongated grooves where the fusions of digits II and V have taken place. Giraffa and Okapia, the extant Giraffidae, show a difference from all the extinct taxa in having more flattened digits tightly packed together, suggesting convergent highly fused digits despite divergent ecologies and locomotion. These discoveries provide evidence that enhances our understanding of how bones fuse and call into question current hypotheses of digit loss.
=====
Free pdf:
Free pdf:
https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2020.1919The shells of ammonoid cephalopods are among the most recognizable fossils, whose fractally folded, internal walls (septa) have inspired many hypotheses on their adaptive value. The enduring explanation for their iterative evolution is that they strengthen the shell against pressure at increasing water depths. The fossil record does not definitively support this idea and much of the theoretical mechanical work behind it has suffered from inaccurate testing geometries and conflicting results. By using a different set of mathematical methods compared with previous studies, I generate a system of finite-element models that explore how different parameters affect the shell's response to water pressure. Increasing the number of initial folds of the septa ultimately has little to no effect on the resulting stress in the shell wall or the septum itself. The introduction of higher-order folds does reduce the tensile stress in the shell wall; however, this is coupled with a higher rate of increase of tensile stress in the septum itself. These results reveal that the increase in complexity should not be expected to have a significant effect on the shell's strength and suggests that the evolution of ammonitic septa does not reflect a persistent trend towards deeper-water habitats.
The fossil record of behaviour in deep time richly complements the modern.
A diversity of behaviours is represented in the paleontological literature.
Surveying this record can reveal how behaviours originated and evolved over time.
Understanding how behavioural evidence preserves is important for this goal.
Abstract
Paleontologists and biologists generally utilize different lines of evidence and approaches to study, conceptualize and categorize animal behaviour, which has led to a divide between the two disciplines and lack of integration of their data. Numerous filters impact the preservation of behaviour in the fossil record. Here, we utilize 13 broad categories of behaviour representing the range of modern studies of animal behaviour and assess how they are represented in the fossil record. The data summarized in an existing compilation of âfossil behavioursâ is used to estimate the relative occurrence of each category. We also examine the taxonomic coverage of fossil animal behaviour using the same source. We found that feeding and habitat selection-related behaviours were disproportionately represented. Examples of other behavioural categories, especially social ones, such as mating, communication or parenting were considerably rarer, whereas personality or play were not represented at all. Arthropods tended to be most well represented, including insects in amber, followed by vertebrates. Taxonomic coverage was overall fairly diverse. A broader literature search was used to identify the oldest paleontological evidence of each behavioural category. We found that most categories probably appeared by the end of the Cambrian radiation. Finally, we suggest that the preservation of behaviour in fossils can be estimated from first principles, such as the amount of time animals engage in a behaviour or which behaviours impact a substrate. Reconstructing the evolution of behaviour in deep time requires understanding how the fossil record captures behavioural information. We strongly encourage paleontologists and biologists studying behaviour to work together to help complete our understanding of animal behaviour across the entirety of its evolutionary history.
====
====
Varifructus lingyuanensis gen. et sp. nov.ÂÂ
Free pdf:
Free pdf:
https://www.tandfonline.com/doi/pdf/10.1080/08912963.2020.1825411?needAccess=trueThe Yixian Formation (Barremian to Aptian, Lower Cretaceous) of China has yielded many fossils of early angiosperms, but not all of these angiosperms are completely understood. The seeds of angiosperms are attached at different positions in the fruits than those previously reported from the Early Cretaceous, which suggests various provenances for these carpels and indicates the necessity of further investigation of the angiosperms present in the formation to elucidate the diversity and evolution of early angiosperm flowers. Here, we report a novel fossil angiosperm, Varifructus lingyuanensis gen. et sp. nov, which has seeds attached on the dorsal sides of its fruits. The fossils are rendered more intriguing by the fact that there appear to be perianths in the flowers, the fruits are frequently arranged in asymmetrical pairs, and two branching patterns are seen in this single specimen. This unique combination of characteristics provides a rare raw material for evaluating flower evolution in the Early Cretaceous.
===
Plant wax records of Cretaceous-Paleogene (K-Pg) boundary environmental change
A shift to more terrestrial sources of plant waxes after the K-Pg extinction event
The mixing of different carbon sources masked the carbon isotope excursion signal
Carbon and water cycles recovered in less than 10,000âyears after extinction event
Steady increase in n-alkane Î13C values of 2â spanning the K-Pg boundary
Abstract
Changes in terrestrial environments across the Cretaceous-Paleogene boundary, including plant ecology and carbon and water-cycling, remain poorly defined. Fluvial sediments spanning the Cretaceous-Paleogene (K-Pg) boundary of southern Saskatchewan, Canada contain well preserved plant wax n-alkanes that provide a means of reconstructing changes to plant ecology and carbon and water cycling during this mass extinction event. We measured n-alkane carbon (Î13C) and hydrogen (Î2H) isotope ratios in two sedimentary sections and applied established fractionation factors to estimate the isotopic compositions of precipitation and bulk sedimentary organic matter sources. We also analyzed the distribution of n-alkanes as an indicator of the relative abundance of aquatic and terrestrial plants. We find a consistent shift towards a greater relative abundance of longer-chain n-alkanes across the boundary, implying a persistent increase in the relative abundance of terrestrial plants in the sedimentary basin. This is consistent with an increase in birch and elm palynomorphs immediately above the boundary. We hypothesize the extinction of all large herbivores at the boundary may have facilitated this transition to a terrestrial angiosperm dominated flora immediately after the boundary. We also find that the region was characterized by isotopically light precipitation, with Î2H values between â95â to â160â but do not observe evidence for major millennial-scale changes in regional precipitation isotopic composition spanning the boundary. n-Alkanes derived from both aquatic and terrestrial plants at one site display an upward trend in Î13C values of approximately 2â across the K-Pg boundary. This suggests millennial-scale local or global carbon-cycle variability altering either plant carbon isotope fractionation or the carbon isotope composition of dissolved inorganic carbon and atmospheric CO2. Overall our results suggest that carbon and water cycle changes associated with the K-Pg impact in terrestrial environments in western Canada were short-lived, but ecological shifts in plant communities were longer-lasting.