Experimental evidence that clay inhibits bacterial decomposers: Implications for preservation of organic fossils

Exceptionally preserved organic fossils are commonly associated with clay-rich horizons or directly with clay minerals. It has been posited that interactions between clay minerals and organic tissues inhibit enzymatic reactions or protect carcasses in such a way that decay is impeded. However, interactions between clay minerals and the biological agents of decay, especially bacteria, may be at least as important to preservation potential. Here we show that clays of particle size <2 μmm in suspensions exceeding 10 mg/ml in concentration inhibit the growth of Pseudoalteromonas luteoviolacea, a marine heterotrophic bacterium involved in the decay of marine animals. Such clay-microbe interactions can contribute to exceptional preservation, and specific examples may play a role in shaping the distribution of Konservat- Lagerstätten through time.</p

Crab in Amber Reveals an Early Colonization of Nonmarine Environments During the Cretaceous

Amber fossils provide snapshots of the anatomy, biology, and ecology of extinct organisms that are otherwise inaccessible. The best-known fossils in amber are terrestrial arthropods—principally insects—whereas aquatic organisms are rarely represented. Here, we present the first record of true crabs (Brachyura) in amber—from the Cretaceous of Myanmar [~100 to 99 million years (Ma)]. The new fossil preserves large compound eyes, delicate mouthparts, and even gills. This modern-looking crab is nested within crown Eubrachyura, or “higher” true crabs, which includes the majority of brachyuran species living today. The fossil appears to have been trapped in a brackish or freshwater setting near a coastal to fluvio-estuarine environment, bridging the gap between the predicted molecular divergence of nonmarine crabs (~130 Ma) and their younger fossil record (latest Cretaceous and Paleogene, ~75 to 50 Ma) while providing a reliable calibration point for molecular divergence time estimates for higher crown eubrachyurans

A 520 million-year-old chelicerate larva

An important survival strategy for animal species is the so-called niche differentiation between larva and adult. Different developmental stages of the same animal occupy different ecological niches to avoid competing for food or other essential resources. Here, we describe an exceptionally preserved larval stage of the short great appendage (SGA) arthropod (megacheiran) Leanchoilia illecebrosa from the early Cambrian Chengjiang biota of China. The larval specimen preserves fine details of the main feeding limb, the SGA, which are unknown in the adult of the same species. This discovery demonstrates that niche differentiation during ontogeny was developed in this species of megacheiran-a group of fossil arthropods that has been considered to be early representatives of Chelicerata, which includes horseshoe crabs and arachnids. Hence, this type of niche differentiation, which is common today, originated from the early Cambrian

Evaluation of university library impact on students’ academic success

U radu se iznosi teorijski okvir vrednovanja knjižnica, a posebno se govori o mogućnostima istraživanja utjecaja zbirki i usluga sveučilišnih knjižnica na akademski uspjeh studenata. Ukazuje se na terminološke probleme vezane uz vrednovanje knjižnica, o važnosti vrednovanja za poslovanje knjižnica, o knjižničnoj statistici, a posebno o mjerenju utjecaja knjižničnih zbirki i usluga na korisnike. U Hrvatskoj se do sada nisu provodila istraživanja utjecaja sveučilišnih knjižnica na korisnike, a istraživanja vezanih uz utjecaj knjižnice na obrazovanje studenata jako je malo i u svijetu. Razlog tome je činjenica da je utjecaje relativno teško izmjeriti, no oni su veoma važni pokazatelji uspješnosti poslovanja određene akademske knjižnice.The paper gives a theoretical framework for library evaluation, and indicates possible effects the library collections and services might have on students’ academic achievement. The paper discusses terminological problems, the importance of evaluation for library performance, library statistics, and focuses on the measurement of impact of library collections and services on their users. So far, there has been no research in Croatia about the impact of university libraries on student academic achievement, and the studies that deal with this topic are rare even around the world. The reason for this lies in the fact that the outcomes are very difficult to measure, and are therefore avoided in measurements. However, they represent extremely important indicators of university library impact on students’ academic performance

Doushantuo-type microfossils from latest Ediacaran phosphorites of northern Mongolia

Phosphorites of the latest Ediacaran upper Khesen Formation in the Khuvsgul Group of northern Mongolia preserve a newly discovered, three-dimensionally phosphatized Doushantuo-type microfossil assemblage. Eight genera include the second occurrence of the putative multicellular fossil animal embryo Megasphaera outside South China, the Doushantuo-Pertatataka–type acanthomorphic acritarchs Appendisphaera, Cavaspina, and Variomargosphaeridium, and the possible alga Archaeophycus yunnanensis. The assemblage occurs in the lowermost phosphorite horizon in foreland basin deposits on the Khuvsgul terrane; lithostratigraphic and δ13C correlation with the Zavkhan terrane of southwestern Mongolia establishes a latest Ediacaran age for the fossiliferous phosphorites. Thus, this is the youngest Doushantuo-type assemblage yet reported. It extends the range of Megasphaera, filling a gap in the record of phosphatized embryo-like forms between the ca. 600 Ma Doushantuo Weng’an biota and Cambrian examples. The Khesen fossil assemblage emphasizes the potential of Mongolian phosphorites to provide new paleontological data on the Ediacaran-Cambrian transition, and to resolve the phylogenetic debate surrounding Megasphaera embryo-like taxa

Heterogeneity of free and occluded bitumen in a natural maturity sequence from Oligocene Lake Enspel

Sedimentation in Oligocene Lake Enspel was rapidly terminated by a basaltic lava flow. This introduced a preservational barrier while imparting a ‘natural flash pyrolysis’, during which the organic matter in underlying stratigraphic units was subjected to rapid thermal maturation resulting in hydrocarbon generation. Samples from these strata exhibit a steep maturity gradient (0.25–1.07% optical vitrinite reflectance, or RO) over uniform organofacies. This offers the opportunity to investigate bitumen generation during rapid thermal maturation mechanistically, in particular the nature of Bitumen 2—occluded bitumen, which is only recoverable after the digestion of the mineral matrix and was frequently dismissed as an artifact of incomplete extraction. Elaborate sequential extraction of the contact metamorphic sequence of oil shales at Enspel revealed systematic changes in bitumen composition. These trend progressively towards those of occluded bitumen, which exhibits a systematically elevated thermal maturity, a higher degree of catalytic biomarker-rearrangement and the conspicuous absence of molecular signatures from vascular plants that are present in the free bitumen. One plausible explanation involves a contribution of allochthonous clay-adsorbed organic matter to Bitumen 2. This could represent a mixture of older reworked bitumen and an early-diagenetic snapshot of clay adsorbed organic matter. Alternatively, a close association of early-generated bitumen with clay minerals may have led to enhanced isomerization and catalytically influenced ‘uniformization’ of alkane signatures. Deviations from the expected relationships between various thermal maturity parameters suggest variable dependence on the time-pressure-temperature pathway (i.e. metamorphic facies). The maturation of organic matter likely behaves differently under a contact metamorphic regime or during rapid subsidence and exhumation, as compared to slow maturation during regional subsidence. Our data also suggest that geologically brief shallow intrusive or extrusive magmatism might not be as destructive to the sedimentary hydrocarbon inventory as hitherto thought. This study draws attention to the small-scale compositional heterogeneity of bitumen that can be studied using sequential extraction methods. More importantly, it suggests that occluded bitumen could potentially harbor information on organic matter that pre-dates in situ primary productivity and may be derived from allochthonous biomass and detrital input

The implications of a Silurian and other thylacocephalan crustaceans for the functional morphology and systematic affinities of the group

Background: Thylacocephala is a group of enigmatic extinct arthropods. Here we provide a full description of the oldest unequivocal thylacocephalan, a new genus and species Thylacares brandonensis, which is present in the Silurian Waukesha fauna from Wisconsin, USA. We also present details of younger, Jurassic specimens, from the Solnhofen lithographic limestones, which are crucial to our interpretation of the systematic position of Thylacocephala. In the past, Thylacocephala has been interpreted as a crustacean ingroup and as closely related to various groups such as cirripeds, decapods or remipeds. Results: The Waukesha thylacocephalan, Thylacares brandonensis n. gen. n. sp., bears compound eyes and raptorial appendages that are relatively small compared to those of other representatives of the group. As in other thylacocephalans the large bivalved shield encloses much of the entire body. The shield lacks a marked optical notch. The eyes, which project just beyond the shield margin, appear to be stalked. Head appendages, which may represent antennulae, antennae and mandibles, appear to be present. The trunk is comprised of up to 22 segments. New details observed on thylacocephalans from the Jurassic Solnhofen lithographic limestones include antennulae and antennae of Mayrocaris bucculata, and endites on the raptorial appendages and an elongate last trunk appendage in Clausocaris lithographica. Preserved features of the internal morphology in C. lithographica include the muscles of the raptorial appendage and trunk. Conclusions: Our results indicate that some `typical' thylacocephalan characters are unique to the group; these autapomorphies contribute to the difficulty of determining thylacocephalan affinities. While the new features reported here are consistent with a eucrustacean affinity, most previous hypotheses for the position of Thylacocephala within Eucrustacea (as Stomatopoda, Thecostraca or Decapoda) are shown to be unlikely. A sister group relationship to Remipedia appears compatible with the observed features of Thylacocephala but more fossil evidence is required to test this assertion. The raptorial appendages of Thylacocephala most likely projected 45 degrees abaxially instead of directly forward as previously reconstructed. The overall morphology of thylacocephalans supports a predatory mode of life

Fossilized Biophotonic Nanostructures Reveal the Original Colors of 47-Million-Year-Old Moths

Original structural colors reconstructed in fossil moths had a dual defensive function and illuminate the evolution of communication strategies in insects

Early Social Cognition: Alternatives to Implicit Mindreading

According to the BD-model of mindreading, we primarily understand others in terms of beliefs and desires. In this article we review a number of objections against explicit versions of the BD-model, and discuss the prospects of using its implicit counterpart as an explanatory model of early emerging socio-cognitive abilities. Focusing on recent findings on so-called ‘implicit’ false belief understanding, we put forward a number of considerations against the adoption of an implicit BD-model. Finally, we explore a different way to make sense of implicit false belief understanding in terms of keeping track of affordances