| 1. |
- Bonnevier Wallstedt, Ida, et al.
(författare)
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Skin Anatomy, Bone Histology and Taphonomy of a Toarcian (Lower Jurassic) Ichthyosaur (Reptilia : Ichthyopterygia) from Luxembourg, with Implications for Paleobiology
- 2024
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Ingår i: Diversity. - : Multidisciplinary Digital Publishing Institute (MDPI). - 1424-2818. ; 16:8
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Tidskriftsartikel (refereegranskat)abstract
- A partial ichthyosaur skeleton from the Toarcian (Lower Jurassic) bituminous shales of the ‘Schistes Carton’ unit of southern Luxembourg is described and illustrated. In addition, associated remnant soft tissues are analyzed using a combination of imaging and molecular techniques. The fossil (MNHNL TV344) comprises scattered appendicular elements, together with a consecutive series of semi-articulated vertebrae surrounded by extensive soft-tissue remains. We conclude that TV344 represents a skeletally immature individual (possibly of the genus Stenopterygius) and that the soft parts primarily consist of fossilized skin, including the epidermis (with embedded melanophore pigment cells and melanosome organelles) and dermis. Ground sections of dorsal ribs display cortical microstructures reminiscent of lines of arrested growth (LAGs), providing an opportunity for a tentative age determination of the animal at the time of death (>3 years). It is further inferred that the exceptional preservation of TV344 was facilitated by seafloor dysoxia/anoxia with periodical intervals of oxygenation, which triggered phosphatization and the subsequent formation of a carbonate concretion.
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| 2. |
- De La Garza, Randolph G., et al.
(författare)
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Preservational modes of some ichthyosaur soft tissues (Reptilia, Ichthyopterygia) from the Jurassic Posidonia Shale of Germany
- 2023
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Ingår i: Palaeontology. - : John Wiley and Sons Inc. - 0031-0239 .- 1475-4983. ; 66:4
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Tidskriftsartikel (refereegranskat)abstract
- Konservat-Lagerstätten, such as the Toarcian (Early Jurassic) Posidonia Shale of southwestern Germany, are renowned for their spectacular fossils. Ichthyosaur skeletons recovered from this formation are frequently associated with soft tissues; however, the preserved material ranges from three-dimensional, predominantly phosphatized structures to dark films of mainly organic matter. We examined soft-tissue residues obtained from two ichthyosaur specimens using an integrated ultrastructural and geochemical approach. Our analyses revealed that the superficially-looking ‘films’ in fact comprise sections of densely aggregated melanosome (pigment) organelles sandwiched between phosphatized layers containing fibrous microstructures. We interpret this distinct layering as representing condensed and incompletely degraded integument from both sides of the animal. When compared against previously documented ichthyosaur fossils, it becomes readily apparent that a range of preservational modes exists between presumed ‘phosphatic’ and ‘carbonized’ soft-tissue remains. Some specimens show high structural fidelity (e.g. distinct integumentary layering), while others, including the fossils examined in this study, retain few original anatomical details. This diversity of soft-tissue preservational modes among Posidonia Shale ichthyosaurs offers a unique opportunity to examine different biostratinomic, taphonomic and diagenetic variables that potentially could affect the process of fossilization. It is likely that soft-tissue preservation in the Posidonia Shale was regulated by a multitude of factors, including decay efficiency and speed of phosphatic mineral nucleation; these in turn were governed by a seafloor with sustained microbial mat activity fuelled by high organic matter input and seasonally fluctuating oxygen levels. © 2023 The Authors.
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| 3. |
- Rezasson, Reza, 1985-, et al.
(författare)
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A fast and non-destructive alternative to the burnout method for paperboard quality inspections using phase-contrast X-ray imaging
- 2023
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Ingår i: TAPPI Journal. - : TAPPI. - 0734-1415. ; 22:2, s. 99-106
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Tidskriftsartikel (refereegranskat)abstract
- An X-ray based quality inspection method for paperboard was implemented and tested as a fastand non-destructive alternative to the burnout method. An argument against X-ray imaging for inspection of paperand paperboard has been that X-ray absorption is low in paper. To overcome this limitation, we used phase-contrastX-ray imaging (PCXI), which gives higher contrast than conventional attenuation-based imaging for low-absorbingmaterials such as paper. The suggested PCXI method was applied to previously prepared and quality rated samplesusing the burnout method.A strong similarity between the burnout images and the PCXI images was observed. In conclusion, further devel-opment of the phase-contrast X-ray method would provide an interesting option for replacing or complementing thestandard burnout method.
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| 4. |
- Slater, Tiffany S., et al.
(författare)
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Taphonomic experiments reveal authentic molecular signals for fossil melanins and verify preservation of phaeomelanin in fossils
- 2023
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Ingår i: Nature Communications. - : Nature Research. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Melanin pigments play a critical role in physiological processes and shaping animal behaviour. Fossil melanin is a unique resource for understanding the functional evolution of melanin but the impact of fossilisation on molecular signatures for eumelanin and, especially, phaeomelanin is not fully understood. Here we present a model for the chemical taphonomy of fossil eumelanin and phaeomelanin based on thermal maturation experiments using feathers from extant birds. Our results reveal which molecular signatures are authentic signals for thermally matured eumelanin and phaeomelanin, which signatures are artefacts derived from the maturation of non-melanin molecules, and how these chemical data are impacted by sample preparation. Our model correctly predicts the molecular composition of eumelanins in diverse vertebrate fossils from the Miocene and Cretaceous and, critically, identifies direct molecular evidence for phaeomelanin in these fossils. This taphonomic framework adds to the geochemical toolbox that underpins reconstructions of melanin evolution and of melanin-based coloration in fossil vertebrates.
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| 5. |
- De La Garza, Randolph Glenn, et al.
(författare)
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An ancestral hard-shelled sea turtle with a mosaic of soft skin and scutes
- 2022
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The transition from terrestrial to marine environments by secondarily aquatic tetrapods necessitates a suite of adaptive changes associated with life in the sea, e.g., the scaleless skin in adult individuals of the extant leatherback turtle. A partial, yet exceptionally preserved hard-shelled (Pan-Cheloniidae) sea turtle with extensive soft-tissue remains, including epidermal scutes and a virtually complete flipper outline, was recently recovered from the Eocene Fur Formation of Denmark. Examination of the fossilized limb tissue revealed an originally soft, wrinkly skin devoid of scales, together with organic residues that contain remnant eumelanin pigment and inferred epidermal transformation products. Notably, this stem cheloniid—unlike its scaly living descendants—combined scaleless limbs with a bony carapace covered in scutes. Our findings show that the adaptive transition to neritic waters by the ancestral pan-chelonioids was more complex than hitherto appreciated, and included at least one evolutionary lineage with a mosaic of integumental features not seen in any living turtle. © 2022, The Author(s).
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| 6. |
- Eriksson, Mats E., et al.
(författare)
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A review of ichthyosaur (Reptilia, Ichthyopterygia) soft tissues with implications for life reconstructions
- 2022
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Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252. ; 226
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Forskningsöversikt (refereegranskat)abstract
- The dolphin-like ichthyosaurs – also known as ‘fish lizards’ – are extinct marine reptiles that roamed the Mesozoic oceans for some 160 million years. As for most ancient vertebrates, our knowledge of these iconic animals largely derives from biomineralized hard parts (teeth and bones). However, soft tissues are also known from a number of Lagerstätte specimens, and have opened up new avenues for deciphering their biology and ecology. Herein, we present a review of ichthyosaur research and life style iconography with particular focus on soft-tissue structures and inferences made from these, including aspects of coloration and thermoregulation. We then distill novel insights on ichthyosaur anatomy and physiology gained from an exceptionally preserved, sub-adult specimen of the parvipelvian Stenopterygius from the Jurassic Posidonia Shale in Germany, and describe the process in which a detailed, three-dimensional reconstruction in scale 1:1 was produced. Our new sculpture is based on empirical evidence obtained directly from the fossil record, including uniquely preserved soft-tissue structures (e.g., original pigments and blubber), resulting in the scientifically most up-to-date reconstruction of an ichthyosaur currently available.
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| 7. |
- Heingård, Miriam, et al.
(författare)
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Preservation and Taphonomy of Fossil Insects from the Earliest Eocene of Denmark
- 2022
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Ingår i: Biology. - : MDPI. - 2079-7737. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Marine sediments of the lowermost Eocene Stolleklint Clay and Fur Formation of north-western Denmark have yielded abundant well-preserved insects. However, despite a long history of research, in-depth information pertaining to preservational modes and taphonomic pathways of these exceptional animal fossils remains scarce. In this paper, we use a combination of scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to assess the ultrastructural and molecular composition of three insect fossils: a wasp (Hymenoptera), a damselfly (Odonata) and a pair of beetle elytra (Coleoptera). Our analyses show that all specimens are preserved as organic remnants that originate from the exoskeleton, with the elytra displaying a greater level of morphological fidelity than the other fossils. TEM analysis of the elytra revealed minute features, including a multilayered epicuticle comparable to those nanostructures that generate metallic colors in modern insects. Additionally, ToF-SIMS analyses provided spectral evidence for chemical residues of the pigment eumelanin as part of the cuticular remains. To the best of our knowledge, this is the first occasion where both structural colors and chemical traces of an endogenous pigment have been documented in a single fossil specimen. Overall, our results provide novel insights into the nature of insect body fossils and additionally shed light on exceptionally preserved terrestrial insect faunas found in marine paleoenvironments. © 2022 by the authors.
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| 8. |
- Hörnqvist, Magnus, 1966-, et al.
(författare)
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Från existentiell strävan till politisk kamp
- 2022
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Ingår i: Fronesis. - Malmö. - 1404-2614. ; :74-75, s. 8-27
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Ambitionen med det här numret av Fronesis är att fördjupa förståelsen av erkännande genom att belysa olika aspekter av denna komplexa erfarenhet hela vägen från oupphörlig existentiell strävan till politisk kamp. Som redaktörer har vi ansträngt oss att samla några av de mest centrala analyserna av erkännandets dynamik. Anslaget är brett: tillsammans täcker texterna in ett långt tidsperspektiv och flera motstridiga tolkningar och positioner. Förhoppningen är att etablerade dikotomier och vissheter efter läsningen ska framstå i ett annat ljus, som mindre självklara, och att nya politiska slutsatser ska bli möjliga att dra. Texterna rör sig genomgående kring det som är svårt med erkännande, kring dess antinomier och ambivalenser, utan tanke på den politiska tillämpningen. De är skrivna på ett sätt som kräver mycket av sina läsare, och i vissa fall balanserar de på begriplighetens gräns. Det är lika bra att säga det med en gång: möjligen förstod vi inte riktigt hur svårtillgängliga vissa texter var när vi valde ut dem till numret. För att göra texterna lättare att ta till sig och för att i någon mån anknyta till politiken sammanfattar vi huvuddragen här i inledningen. För allt rör politikens förutsättningar! Gemensamt för alla politiska mobiliseringar som ska kunna nå framgång är följande imperativ (tror vi): de måste knyta an till den under ytan pågående kampen hos människor att fullt ut bli en del av samhället utifrån en förståelse om att detta i sig är ett rörligt mål. Eller sagt på ett annat sätt: politiken måste erbjuda erkännande utöver resurser, rättigheter och trygghet.
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| 9. |
- Thuy, Ben, et al.
(författare)
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Miniaturization during a Silurian environmental crisis generated the modern brittle star body plan
- 2022
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Pivotal anatomical innovations often seem to appear by chance when viewed through the lens of the fossil record. As a consequence, specific driving forces behind the origination of major organismal clades generally remain speculative. Here, we present a rare exception to this axiom by constraining the appearance of a diverse animal group (the living Ophiuroidea) to a single speciation event rather than hypothetical ancestors. Fossils belonging to a new pair of temporally consecutive species of brittle stars (Ophiopetagno paicei gen. et sp. nov. and Muldaster haakei gen. et sp. nov.) from the Silurian (444–419 Mya) of Sweden reveal a process of miniaturization that temporally coincides with a global extinction and environmental perturbation known as the Mulde Event. The reduction in size from O. paicei to M. haakei forced a structural simplification of the ophiuroid skeleton through ontogenetic retention of juvenile traits, thereby generating the modern brittle star bauplan.
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| 10. |
- De La Garza, Randolph Glenn, et al.
(författare)
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A fossil sea turtle (Reptilia, Pan-Cheloniidae) with preserved soft tissues from the Eocene Fur Formation of Denmark
- 2021
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Ingår i: Journal of Vertebrate Paleontology. - : Informa UK Limited. - 0272-4634 .- 1937-2809. ; 41:3
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Tidskriftsartikel (refereegranskat)abstract
- A new hard-shelled sea turtle (Pan-Cheloniidae) with vestigial soft tissues from the lower Eocene (Ypresian) Fur Formation of Denmark is described and illustrated. The fossil (DK 807) comprises a partial, yet fully articulated carapace (estimated original length ∼50 cm) where the individual bones mostly are preserved in three dimensions, together with an intact sacrum, a consecutive series of articulated caudal vertebrae, a complete pelvic girdle, and both hind limbs. Primitive characters in the pelvis and limbs, along with free ribs that contact the posterior peripherals suggest affinity with the extinct pan-cheloniid Eochelone; however, because of the incomplete nature of the fossil, DK 807 is kept in open nomenclature. Associated with the skeletal elements are soft-tissue residues that include remnant epidermal scutes and a nearly complete outline of a rear paddle. The flipper-shaped halo likely represents traces of skin preserved as a dark bedding-parallel film. Its wrinkled and striated surface texture attests to an originally scaleless configuration comparable to the soft integument of living adult dermochelyid (leatherback) turtles, and unlike that of extant cheloniids. Scratches, scars and indentations on the bony carapace likely represent incompletely healed bite marks inflicted by a crocodylian or another large-sized seagoing tetrapod.
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