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Virtual paleontology is the study of fossils through three-dimensional digital visualizations; it represents a powerful and well-established set of tools for the analysis and dissemination of fossil data. Techniques are divisible into tomographic (i.e., slice-based) and surface-based types. Tomography has a long predigital history, but the recent explosion of virtual paleontology has resulted primarily from developments in X-ray computed tomography (CT), and of surface-based technologies (e.g., laser scanning). Destructive tomographic methods include forms of physical-optical tomography (e.g., serial grinding); these are powerful but problematic techniques. Focused Ion Beam (FIB) tomography is a modern alternative for microfossils; it is also destructive but is capable of extremely high resolutions. Nondestructive tomographic methods include the many forms of CT, which are the most widely used data-capture techniques at present, but are not universally applicable. Where CT is inappropriate, other nondestructive technologies (e.g., neutron tomography, magnetic resonance imaging, optical tomography) can prove suitable. Surface-based methods provide portable and convenient data capture for surface topography and texture, and might be appropriate when internal morphology is not of interest; technologies include laser scanning, photogrammetry, and mechanical digitization. Reconstruction methods that produce visualizations from raw data are many and various; selection of an appropriate workflow will depend on many factors, but is an important consideration that should be addressed prior to any study. The vast majority of three-dimensional fossils can now be studied using some form of virtual paleontology, and barriers to broader adaptation are being eroded. Technical issues regarding data sharing remain problematic. Technological developments continue; those promising tomographic recovery of compositional data are of particular relevance to paleontology.
X-ray computed tomography (CT) provides a nondestructive means of studying the inside and outside of objects. It allows accurate visualization and measurement of internal features, that are otherwise impossible to obtain nondestructively, and is a lasting digital record that can be made available to future researchers, museums, and the general public. Here, an overview of CT scanning methodologies and protocol is provided, as well as some recent examples of how this technology is allowing paleontologists to make new inroads into understanding the ecology, evolution, and development of both extant and extinct organisms. Lastly, some frontiers and outstanding questions in the acquisition, processing, and storage of digital 3-D morphological data are highlighted.
Confocal laser scanning microscopy is a well-established optical technique allowing for three-dimensional (3-D) visualization of fluorescent specimens with a resolution close to the diffraction limit of light. Thanks to the availability of a wide range of fluorescent dyes and selective staining using antibodies, the technique is commonly used in life sciences as a powerful tool for studying different biological processes, often at the level of single molecules. However, this type of approach is often not applicable for specimens that are preserved in historical slide collections, embedded in amber, or are fossilized, and cannot be exposed to any form of selective staining or other form of destructive treatment. This usually narrows the number of microscopic techniques that can be used to study such specimens to traditional light microscopy or scanning electron microscopy. However, these techniques have their own limitations and cannot fully reveal 3-D structures within such barely accessible samples. Can confocal microscopy be of any help? The answer is positive, and it is due to the fact that many paleontological specimens exhibit a strong inherent autofluorescence that can serve as an excellent source of emitted photons for confocal microscopy visualizations either through reconstruction of the induced autoflourescent signal from the sample, or through reconstruction of the reflected signal from the sample surface. Here, we describe the workflow and methodology involved in acquiring confocal data from a sample and reprocessing the resulting image stack using the image-processing program imageJ before reconstructing the data using the open-source 3-D rendering program, Drishti. This approach opens new possibilities for using confocal microscopy in a nondestructive manner for visualizing complex paleontological material that has never previously been considered as suitable for this type of microscopic technique.
Laser and structured light scanners are primary tools for acquiring surface details of body and trace fossils and have been widely used to study vertebrate specimens. Comparison of different scanner types shows their relative advantages and limitations. Regardless of scanning device, the workflow from initial scan to final product involves registration and some editing for archival or research-grade products. Additional steps, including further object editing and optimization, are required to prepare a scan file for web viewing, animation, and three-dimensional (3-D) printing.
Focusing on geometric morphometrics (GMM), we review methods for acquiring morphometric data from 3-D objects (including fossils), algorithms for producing shape variables and morphospaces, the mathematical properties of shape space, especially how they relate to morphogenetic and evolutionary factors, and issues posed by working with fossil objects. We use the Raupian shell-coiling equations to illustrate the complexity of the relationship between such factors and GMM morphospaces. The complexity of these issues re-emphasize what are arguably the two most important recommendations for GMM studies: 1) always use multivariate methods and all of the morphospace axes in an analysis; and 2) always anticipate the possibility that the factors of interest can have complex, nonlinear relationships with shape.
In the last two decades, advances in computational imaging techniques and digital visualization have created novel avenues for the study of fossil organisms. As a result, paleontology has undergone a shift from the pure study of physically preserved bones and teeth, and other hard tissues, to using virtual computer models to study specimens in greater detail, restore incomplete specimens, and perform biomechanical analyses. The rapidly increasing application of these techniques has further paved the way for the digital reconstruction of soft-tissue structures, which are rarely preserved or otherwise available in the fossil record. In this contribution, different types of digital soft-tissue reconstructions are introduced and reviewed. Provided examples include methodological approaches for the reconstruction of musculature, endocranial components (e.g., brain, inner ear, and neurovascular structures), and other soft tissues (e.g., whole-body and life reconstructions). Digital techniques provide versatile tools for the reconstruction of soft tissues, but given the nature of fossil specimens, some limitations and uncertainties remain. Nevertheless, digital reconstructions can provide new information, in particular if interpreted in a phylogenetically grounded framework. Combined with other digital analytical techniques (e.g., finite element analysis [FEA], multibody dynamics analysis [MDA], and computational fluid dynamics [CFD]), soft-tissue reconstructions can be used to elucidate the paleobiology of extinct organisms and to test competing evolutionary hypotheses.
Functional analysis through computer modeling can inform on how extinct organisms moved and fed, allowing us to test long-standing paleobiological hypotheses. Many such studies are based on digital models derived from computed tomography or surface scanning, but these methods are not appropriate for all fossils. Here, we show that box modeling—3-D modeling of complex shapes based on simple objects—can be used to reconstruct the morphology of various fossil specimens. Moreover, the results of computational functional analyses utilizing such models are very similar to those for models derived from tomographic or surface-based techniques. Box modeling is more broadly applicable than alternative methods for digitizing specimens; hence, there is great potential for this approach in paleontological functional analysis. Possible applications include large-scale comparative studies, analyses of hypothetical morphologies, and virtually restoring incomplete/distorted specimens.
Body mass is a key parameter for understanding the physiology, biomechanics, and ecology of an organism. Within paleontology, body mass is a fundamental prerequisite for many studies considering body-size evolution, survivorship patterns, and the occurrence of dwarfism and gigantism. The conventional method for estimating fossil body mass relies on allometric scaling relationships derived from skeletal metrics of extant taxa, but the recent application of three-dimensional imaging techniques to paleontology (e.g., surface laser scanning, computed tomography, and photogrammetry) has allowed for the rapid digitization of fossil specimens. Volumetric body-mass estimation methods based on whole articulated skeletons are therefore becoming increasingly popular. Volume-based approaches offer several advantages, including the ability to reconstruct body-mass distribution around the body, and their relative insensitivity to particularly robust or gracile elements, i.e., the so-called ‘one bone effect.’ Yet their application to the fossil record will always be limited by the paucity of well-preserved specimens. Furthermore, uncertainties with regards to skeletal articulation, body density, and soft-tissue distribution must be acknowledged and their effects quantified. Future work should focus on extant taxa to improve our understanding of body composition and increase confidence in volumetric model input parameters.
Advancement of understanding in paleontology and biology has always been hindered by difficulty in accessing comparative data. With current and burgeoning technology, the severity of this hindrance can be substantially reduced. Researchers and museum personnel generating three-dimensional (3-D) digital models of museum specimens can archive them using internet repositories that can then be explored and utilized by other researchers and private individuals without a museum trip. We focus on MorphoSource, the largest web archive for 3-D museum data at present. We describe the site, how to use it most effectively in its current form, and best practices for file formats and metadata inclusion to aid the growing community wishing to utilize it for distributing 3-D digital data. The potential rewards of successfully crowd sourcing the digitization of museum collections from the research community are great, as it should ensure rapid availability of the most important datasets. Challenges include long-term governance (i.e., maintaining site functionality, supporting large amounts of digital storage, and monitoring/updating file to prevent bit rot, which is the slow and random corruption of electronic data over time, and data format obsolescence, which is the problem of data becoming unreadable or ineffective because of the loss of functional software necessary for access), and utilization by the community (i.e., detecting and minimizing user error in creating data records, incentivizing data sharing by researchers and institutions alike, and protecting stakeholder rights to data, while maximizing accessibility and discoverability).
MorphoSource serves as a proof-of-concept of how these kinds of challenges can be met. Accordingly, it is generally recognized as the most appropriate repository for large, raw datasets of fossil organisms and/or comparative samples. Its existence has begun to transform data transparency standards because journal reviewers, editors, and grant officers now often suggest or require that 3-D data be made available through this site.
Since the early 1990s, methods for the acquisition of three-dimensional (3-D) data and computer-assisted techniques for the visualization of such data have grown increasingly popular among biologists, paleontologists, and paleoanthropologists. However, thus far no standardized repository for complex virtual models based on 3-D digital data of specimens has emerged, whereas the need for researchers to provide access to 3-D models of specimens as well as the pressure imposed on authors by scientific journals to make original 3-D morphological data publicly available have increased. MorphoMuseuM (M3) aims to fill this gap. M3 is both a peer-reviewed scientific journal (M3 Journal) and a virtual specimen repository (M3 Repository). All scientific articles and their associated 3-D models deposited in M3 go through a formal review process. Each published model is given a DOI and a unique identifier code, which should be cited by researchers using this model in their scientific publications. In this paper, we describe the place of M3 among other online repositories for 3-D data, and explain how the growing community of biologists working with 3-D data can benefit from using M3.
Fossils and the science of paleontology provide a charismatic gateway to integrate STEM teaching and learning. With the new Next Generation Science Standards (NGSS), as well as the exponentially increasing use of three-dimensional (3-D) printing and scanning technology, it is a particularly opportune time to integrate a wider variety of fossils and paleontology into K–12 curricula. We describe a curricular prototype that integrates all four components of STEM (Science, Technology, Engineering, Math) into authentic research using dentitions of the Neogene giant shark Megalodon (Carcharocles megalodon Agassiz, 1843). This prototype has been implemented in two middle and two high schools in California and Florida. Consistent with prior evidence-based research, student engagement increases when they have hands-on experiences with fossils, particularly with a charismatic species such as Megalodon. Access to museum specimens helps students understand big ideas in ‘Deep Time.’ In addition to engaging students in authentic STEM practices and scaffolding development of content knowledge, paleontology is an integrative science that connects and informs socially relevant topics, including long-term (macro-) evolution and climate change. The application of 3-D printing and scanning to develop curricula using fossils has immense potential in K–12 schools in the U.S.