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Laser mounted on a stereo microscope. A 532 nm green laser mounted to the side of a stereo microscope. The blocking filter is mounted in front of the objective lens. No diffuser is used here for maximum effect with a smaller spot.
Source publication
Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over the last decade. Laser-stimulated fluorescence (LSF) is a next generation technique that is emerging as a way to fluoresce paleontological specimens that remain dark under typical UV. A laser’s ability to concentrate very high flux rates both at the macr...
Contexts in source publication
Context 1
... is excellent for macro photography in the field due to its portability. A laboratory setup for table-top-sized specimens would typically hold the laser on a fixed mount (Fig 1). The laser itself emits a collimated beam, which results in only a small dot of illu- mination. ...
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... indicated that specimens from both formations would indeed fluoresce under these conditions (Fig 9). A stereo micro- scope was set up with a longpass filter attached to the objective, and a laser beam was directed to the middle of the visual field (Fig 1). A one layer deep pan of concentrate was then raster scanned by hand under the microscope in search of specimens that fluoresced. ...
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... success of the manual method was followed by an experimental setup to automatically sort fluorescing fossils from concentrate without human intervention [24]. The entire experi- mental apparatus consisted of an industrial feeder bowl, green laser, video camera, computer- controlled air puff, and two bins for reject material and candidate specimens (Fig 10). See Sup- plemental Information for a more detailed description of the system (S1 Fig). ...
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... example focuses on the use of minimal equipment for in situ evaluation of a difficult-to- examine specimen. A mid-Holocene-aged skeleton of a young girl from the Sahara desert of Gobero, Niger (Fig 11) was found with an intact bracelet around her arm (G1B2; ~2835 B.C.E.) [25]. It was not possible to move the skeleton or remove the artifact. ...
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... 532 nm green laser was raster scanned by hand over the artifact in a dark room during a timed exposure of a DSLR camera fitted with a yellow longpass filter. The resulting fluorescence exposed a crack pattern (Fig 12) that was one of sev- eral lines of evidence used to identify the bracelet material as coming from a hippopotamus tusk (hippo ivory). ...
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... skull of a Microraptor specimen (IVPP V13320 [21]) was first examined under white light conditions. Although there are subtle color differences in the fossil, nothing unusual stands out on first inspection (Fig 13A). Subsequent imaging using LSF reveals dramatic differences in fluorescence between the proximal and distal portions of the skull prompting further investiga- tion ( Fig 13B). ...
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... there are subtle color differences in the fossil, nothing unusual stands out on first inspection (Fig 13A). Subsequent imaging using LSF reveals dramatic differences in fluorescence between the proximal and distal portions of the skull prompting further investiga- tion ( Fig 13B). ...
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... results could relate to different skull ossification centers as theropods show postnatal elongation of the rostrum [26][27][28]. However, this hypothesis is discounted because the fluores- cence pattern does not follow bone boundaries, but a break in the slab (Fig 13B). These miner- alogical differences may instead reflect variability in the specimen's depositional environment (source minerals and pore water composition) and taphonomic history (microbial activity and diagenesis). ...
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... miner- alogical differences may instead reflect variability in the specimen's depositional environment (source minerals and pore water composition) and taphonomic history (microbial activity and diagenesis). At a finer scale within the proximal and distal portions of the skull, cartilage and different bone types all fluoresce with different colors e.g. the scleral ring and some premaxil- lary tooth roots have a lighter fluorescence color than the rest of the darker-colored proximal portion of the skull (Fig 13B). ...
Context 10
... the proximal and distal skull portions belong to Microraptor (see Supporting Informa- tion for more details, S2 Fig), but a shared dorsal margin for the frontal and most of the teeth as well as a shared ventral margin for the suspected postorbital, splenial and prearticular, sug- gests that the ventral margin of the proximal skull portion is strangely positioned dorsally. Taken together with the fluorescence results, these observations indicate that the skull of IVPP Fig 11. In situ investigation. ...
Citations
... hidden soft tissues, providing key new insights beyond existing evidence [1], especially in early flight studies [2]. Another example is dental microwear analysis to study extinct species, which has improved with methodological developments and data from modern animals. ...
Recent developments, including new imaging and ancient environmental DNA (aeDNA) technologies, are providing unprecedented insights into the past, which can also help researchers predict future ecological change. BMC Ecology and Evolution has launched a new article Collection on the “Paleoecology of extinct species” to provide an open-access resource for all interested in this multidisciplinary field.
... Fossil specimens were imaged under LSF to reveal additional soft tissue details that were not visible under white light conditions, following the methodology of Wang et al. 15 based on Kaye et al. 40 . A 405 nm violet near-UV laser diode was used to fluoresce the specimen according to standard laser safety protocol. ...
Morphology of keratinised toe pads and foot scales, hinging of foot joints and claw shape and size all inform the grasping ability, cursoriality and feeding mode of living birds. Presented here is morphological evidence from the fossil feet of early theropod flyers. Foot soft tissues and joint articulations are qualitatively assessed using laser-stimulated fluorescence. Pedal claw shape and size are quantitatively analysed using traditional morphometrics. We interpret these foot data among existing evidence to better understand the evolutionary ecology of early theropod flyers. Jurassic flyers like Anchiornis and Archaeopteryx show adaptations suggestive of relatively ground-dwelling lifestyles. Early Cretaceous flyers then diversify into more aerial lifestyles, including generalists like Confuciusornis and specialists like the climbing Fortunguavis . Some early birds, like the Late Jurassic Berlin Archaeopteryx and Early Cretaceous Sapeornis , show complex ecologies seemingly unique among sampled modern birds. As a non-bird flyer, finding affinities of Microraptor to a more specialised raptorial lifestyle is unexpected. Its hawk-like characteristics are rare among known theropod flyers of the time suggesting that some non-bird flyers perform specialised roles filled by birds today. We demonstrate diverse ecological profiles among early theropod flyers, changing as flight developed, and some non-bird flyers have more complex ecological roles.
... Tissues. LSF imaging is based on the original protocol of Kaye et al. (60). A 0.5 W 405-nm laser diode was used to fluoresce the fossil specimens according to standard laser safety protocol. ...
Modern birds power their flight stroke using chest muscles. This evolved from an ancestral flight system thought to be divided between shoulder muscles powering the upstroke and chest muscles powering the downstroke. This is inferred from bony fossil anatomy and extant comparative anatomy, but validation from preserved soft anatomy has remained elusive. Here we reveal soft anatomy body profiles of the earliest theropod flyers preserved as residual skin chemistry covering the body and delimiting its margins. These data independently validate the ancestral shoulder/chest divided flight system, and allowed us to identify the first upstroke-enhanced flight stroke and explain early sternum losses. This study fills important gaps in our understanding of early paravian flight prior to the modern chest-driven flight system.
... In recent years, laser-stimulated fluorescence (LSF) has become a powerful tool in paleontology for highlighting and/or revealing additional soft tissue details in fossils that are otherwise unseen under white light conditions 28,29 . The application of this technology to Psittacosaurus SMF R 4970 has quite literally illuminated new aspects of the tail bristles 23 and color patterns 19 and permitted the identification of the cloaca 25 and umbilical scar 24 . ...
... We therefore interpret the scales in SMF R 4970 as true, undistorted representations of the original keratinous integument (see also Vinther et al. 19 , Supplementary Information). SMF R 4970 was photographed using LSF performed using an updated version of the methodology proposed by Kaye et al. 28 and refined in Wang et al. 29 . A 405 nm blue near-UV laser diode was used to fluoresce the specimen following standard laser safety protocol. ...
The Frankfurt specimen of the early-branching ceratopsian dinosaur Psittacosaurus is remarkable for the exquisite preservation of squamous (scaly) skin and other soft tissues that cover almost its entire body. New observations under Laser-Stimulated Fluorescence (LSF) reveal the complexity of the squamous skin of Psittacosaurus, including several unique features and details of newly detected and previously-described integumentary structures. Variations in the scaly skin are found to be strongly regionalized in Psittacosaurus. For example, feature scales consist of truncated cone-shaped scales on the shoulder, but form a longitudinal row of quadrangular scales on the tail. Reexamined through LSF, the cloaca of Psittacosaurus has a longitudinal opening, or vent; a condition that it shares only with cro-codylians. This implies that the cloaca may have had crocodylian-like internal anatomy, including a single, ventrally-positioned copulatory organ. Combined with these new integu-mentary data, a comprehensive review of integument in ceratopsian dinosaurs reveals that scalation was generally conservative in ceratopsians and typically consisted of large subcircular-to-polygonal feature scales surrounded by a network of smaller non-overlapping polygonal basement scales. This study highlights the importance of combining exceptional specimens with modern imaging techniques, which are helping to redefine the perceived complexity of squamation in ceratopsians and other dinosaurs.
... Specimen SMF R 4970 was examined first hand and photographed by M.P. and T.G.K. in 2016 using an updated version of the methodology proposed by Kaye et al. [34] and refined in Wang et al. [35]. A 405-nm violet near-UV laser diode was used to fluoresce the specimen following standard laser safety protocol. ...
Background
In egg-laying amniotes, the developing embryo is tethered to a number of the extraembryonic membranes including the yolk sac and allantois that deliver oxygen and nutrients and remove metabolic waste products throughout embryonic development. Prior to, or soon after hatching, these membranes detach from the animal leaving a temporary or permanent umbilical scar (umbilicus) equivalent to the navel or ‘belly button’ in some placental mammals, including humans. Although ubiquitous in modern mammals and reptiles (including birds), at least early in their ontogeny, the umbilicus has not been identified in any pre-Cenozoic amniote.
Results
We report the oldest preserved umbilicus in a fossil amniote from a ~130-million-year-old early-branching ceratopsian dinosaur, Psittacosaurus . Under laser-stimulated fluorescence (LSF), the umbilicus is revealed as an elongate midline structure delimited by a row of paired scales on the abdomen. The relatively late ontogenetic stage (close to sexual maturity) estimated for the individual indicates that the umbilicus was probably retained throughout life.
Conclusions
Unlike most extant reptiles and birds that lose this scar within days to weeks after hatching, the umbilicus of Psittacosaurus persisted at least until sexual maturity, similar to some lizards and crocodylians with which it shares the closest morphological resemblance. This discovery is the oldest record of an amniote umbilicus and the first in a non-avian dinosaur. However, given the variability of this structure in extant reptilian analogues, a persistent umbilical scar may not have been present in all non-avian dinosaurs.
... Future work using techniques designed to identify soft tissue remains, e.g. laser-stimulated fluorescence [77], could help to evaluate the authenticity of these sheath impressions. While only small datasets for lepidosaurs have been examined, it does generally seem that birds and lepidosaurs have similar differences between ungual and claw sheath curvature ( fig. 4 in [26]), meaning unguals should be reliable predictors of claw shape for a large extant phylogenetic bracket around Longipterygidae. ...
Background
Birds are key indicator species in extant ecosystems, and thus we would expect extinct birds to provide insights into the nature of ancient ecosystems. However, many aspects of extinct bird ecology, particularly their diet, remain obscure. One group of particular interest is the bizarre toothed and long-snouted longipterygid birds. Longipterygidae is the most well-understood family of enantiornithine birds, the dominant birds of the Cretaceous period. However, as with most Mesozoic birds, their diet remains entirely speculative.
Results
To improve our understanding of longipterygids, we investigated four proxies in extant birds to determine diagnostic traits for birds with a given diet: body mass, claw morphometrics, jaw mechanical advantage, and jaw strength via finite element analysis. Body mass of birds tended to correspond to the size of their main food source, with both carnivores and herbivores splitting into two subsets by mass: invertivores or vertivores for carnivores, and granivores + nectarivores or folivores + frugivores for herbivores. Using claw morphometrics, we successfully distinguished ground birds, non-raptorial perching birds, and raptorial birds from one another. We were unable to replicate past results isolating subtypes of raptorial behaviour. Mechanical advantage was able to distinguish herbivorous diets with particularly high values of functional indices, and so is useful for identifying these specific diets in fossil taxa, but overall did a poor job of reflecting diet. Finite element analysis effectively separated birds with hard and/or tough diets from those eating foods which are neither, though could not distinguish hard and tough diets from one another. We reconstructed each of these proxies in longipterygids as well, and after synthesising the four lines of evidence, we find all members of the family but Shengjingornis (whose diet remains inconclusive) most likely to be invertivores or generalist feeders, with raptorial behaviour likely in Longipteryx and Rapaxavis.
Conclusions
This study provides a 20% increase in quantitatively supported fossil bird diets, triples the number of diets reconstructed in enantiornithine species, and serves as an important first step in quantitatively investigating the origins of the trophic diversity of living birds. These findings are consistent with past hypotheses that Mesozoic birds occupied low trophic levels.
... Thus, the same wavelength laser would produce a stronger fluorescent signal than a regular UV lamp, revealing details and hidden features more vividly or showing new details that are otherwise too faint to see using a UV lamp. Similar benefits of using a laser instead of a UV lamp have been documented in the study of fossils (Kaye et al., 2015;Wang et al., 2017;Kaye et al., 2019a;Kaye et al., 2019b;Barlow et al., 2021) and cave formations (Kaye et al., 2019c;Kaye and Garcia, 2017). As a nondestructive technique, LSF is ideal for use with archaeological specimens. ...
... These objects were all handled according to standard archaeological practices. LSF involved scanning a high-power violet (near-UV) laser diode (wavelength = 405 nm, power = 0.75 W) over the study objects in a darkened room ( Fig. 1) according to the protocol of Kaye et al. (2015). The LSF module was custom built by TGK and MP using off-the-shelf parts and can be reproduced in a standard institutional machine shop. ...
... LSF has three main modes of operation that are optimised for specific imaging tasks (Fig. 2). For additional information see Kaye et al. (2015) and Wang et al. (2017). LSF setup shown in Fig. 1. ...
Laser-Stimulated Fluorescence (LSF) is a non-destructive imaging technique in which high- power lasers cause fluorescence on or just below the surface of an object, which is then imaged as a qualitative chemical map. The LSF technique has successfully revealed hidden soft tissues preserved in fossils, been applied to find fossils in the field and used to study cave formations. In this study, we detail a range of LSF applications in archaeology for the first time, using case studies from prehistory to English medieval times. Five applications are detailed: 1) Investigating active and completed excavations; 2) Analysing large-scale and hard-to-reach objects; 3) Aiding identification; 4) Understanding production processes; 5) Documenting and evaluating conservation interventions. These LSF applications promise to deliver tangible benefits to the wider archaeological community, underscoring the value of developing new technologies in the field of archaeology.
... As for CL, the wavelength of the emission is related to a specific chemical species. Only a few studies addressed the application of the technique to palaeontological specimens (Croft et al., 2004;Kaye et al., 2015) despite providing sensitive, non-destructive qualitative analyses using a remote and portable instrument. The fluorescence in minerals is sensitive to activator elements, impurity ions, defects, chemical composition, and crystal lattice (Gaft et al., 1998(Gaft et al., , 2001, and allows detecting trace elements in minerals (Bozlee et al., 2005;MacRae and Wilson, 2008). ...
Teeth are usually targeted for dating archaeological sites because they are the least prone to dissolution, in comparison with bones. However, despite this apparent resistance, teeth do undergo diagenesis, which needs to be accounted for in order to obtain accurate ages. In particular, the uptake of trace elements such as uranium in dental tissues needs to be considered for dose rate determination when dated using electron spin resonance (ESR). Characterising the mineralogy and structural integrity of samples prior to dating may thus provide important information related to their state of preservation, especially in the case of teeth whose U content can significantly affect the dose rate.
In this study, we dated five teeth of small-sized bovids using combined ESR/U-series dating. They were collected at the Middle Stone Age site of Lovedale, located in the central interior of South Africa. Micromorphology provided sedimentary context to the samples, which were recovered from a layer of gravel rich in faunal remains. Using cathodoluminescence, laser-induced fluorescence, Fourier transform infrared spectroscopy and Raman micro-spectroscopy we assessed the degree of preservation of the enamel. Results reveal that carbonate hydroxyapatite underwent post-depositional alteration, based on its molecular structure and elemental composition. Although the teeth all originate from the same layer and were sampled in the same 1-m square and at a similar elevation, U-content in the enamel differs highly from one tooth to the other, with values ranging from 1.7 to 29.6 ppm. These values are correlated with equivalent doses (De) from 228 to 923 Gy and are consistent with variations in crystallinity determined with vibrational spectroscopy. We also investigated the possible saturation of the ESR signal, by repeating measurements with microwave power values from 1 to 20 mW.
Despite such diversity in U-content, the ages calculated assuming an early uptake of U all fall within the same range, from 63 ± 8 ka to 68 ± 15 ka and may only represent a minimum estimate.
... In recent years, laser-stimulated fluorescence (LSF) has become a powerful tool in paleontology for highlighting and/or revealing additional soft tissue details in fossils that are otherwise unseen under white light conditions 28,29 . The application of this technology to Psittacosaurus SMF R 4970 has quite literally illuminated new aspects of the tail bristles 23 and color patterns 19 and permitted the identification of the cloaca 25 and umbilical scar 24 . ...
... We therefore interpret the scales in SMF R 4970 as true, undistorted representations of the original keratinous integument (see also Vinther et al. 19 , Supplementary Information). SMF R 4970 was photographed using LSF performed using an updated version of the methodology proposed by Kaye et al. 28 and refined in Wang et al. 29 . A 405 nm blue near-UV laser diode was used to fluoresce the specimen following standard laser safety protocol. ...
The Frankfurt specimen of the early-branching ceratopsian dinosaur Psittacosaurus is remarkable for the exquisite preservation of squamous (scaly) skin and other soft tissues that cover almost its entire body. Newly detected details revealed under Laser-Stimulated Fluorescence (LSF) reveals the complexity of the squamous skin of Psittacosaurus , including several unique features and details of newly detected and previously-described integumentary structures. Variations in the scaly skin are found to be strongly regionalised in Psittacosaurus . For example, feature scales consist of truncated cone-shaped scales on the shoulder, but form a longitudinal row of quadrangular scales on the tail. Re-examined through LSF, the cloaca of Psittacosaurus has a longitudinal opening, or vent; a condition that it shares only with crocodylians. This implies that the cloaca had crocodylian-like internal anatomy, including a single, ventrally-positioned copulatory organ. Combined with these new integumentary data, a comprehensive review of integument in ceratopsian dinosaurs reveals that scalation was generally conservative in ceratopsians and typically consisted of large subcircular-to-polygonal feature scales surrounded by a network of smaller non-overlapping polygonal basement scales. This study highlights the importance of combining exceptional specimens with modern imaging techniques, which are helping to redefine the perceived complexity of squamation in ceratopsians and other dinosaurs.
... Additional morphological details of NHMUK R1868 have remained undescribed, because these are only visible using more sophisticated imaging methods. Laser-stimulated fluorescence (LSF), in particular, has emerged as an imaging technique that can highlight and/or reveal additional structural details in some fossils that are otherwise unseen under white light conditions 8,9 . ...
... Laser-stimulated fluorescence (LSF). The LSF imaging protocol is based on the original protocol of Kaye et al. 8 that was refined in Wang et al. 9 . A 0.5 W 405 nm laser diode was used to fluoresce the fossil specimens according to standard laser safety protocol. ...
Discovered in 1852, the scaly skin belonging to Haestasaurus becklesii was the first to be described in any non-avian dinosaur. Accordingly, it has played a crucial role in the reconstruction of sauropod integument and dinosaurs more broadly. Here, we reassess this historic specimen using Laser-Stimulated Fluorescence (LSF), revealing extensive, previously unknown regions of skin that augment prior interpretations of its integumentary morphology and taphonomy. Under white light, polygonal-subrounded, convex scales are visible on one side of the block ('side A'), but LSF reveals extensive smaller and more flattened scales, which are diagenetically fragmented, on the reverse block surface ('side B'). Contrary to the prior interpretation that the visible scales are the epidermal undersides, the presence of convex, intrascale papilliform textures on side A suggests that the external skin surface is exposed. We define intrascale papillae and provide a review of sauropod skin morphology, which clarifies that intrascale papillae are unique to and widespread across stem Neosauropoda, and likely have an evolutionary origin in the Early Jurassic. Intrascale papillae may ultimately have been integral to the evolution of gigantism in this charismatic clade.
