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Ecological drivers of variation in the morphology of the lizard tail are understudied despite its important and varied functions in defence, locomotion, balance, climbing, and resource storage. We quantified variation in original tail shape and surface area-to-volume ratio (SA : V) in an Australian gecko clade (Oedura) and tested whether environmental variables are predictors of this variation. To use museum specimens, we developed an approach to straighten deformed preserved tails for accurate shape analysis. Tail shape varied from a relatively 'typical lizard' tail—long, tapered, and circular in cross-section—to a distinctive expanded, wide, and flat shape. Extreme versions of the latter shape seem to have evolved in parallel in two distantly related lineages. Wide tails and low SA : V ratio values occur in the Australian Monsoonal Tropics, while arid zone species all had a narrow, tapered tail with high SA : V. These data suggest expanded or bulbous tails may be analogous to succulence in plants and an adaptation for resource storage in environments with predictable peaks (wet season) and dearths (dry season) of resource availability. However, limited replicated evolution of bulbous tails precludes statistical significance in this case, and more analyses of tail anatomy in Oedura and other lizard clades are required to test this hypothesis further. [ABSTRACT FROM AUTHOR]

This contribution presents a detailed methodology for reconstructing the anterior and posterior autopodia (manus and pes elements) of the sauropod dinosaur Neuquensaurus australis. The study utilizes various techniques, including digital three-dimensional (3D) scanning, reconstruction, retrodeformation, scaling, texturing, rendering, 3D printing, and mounting, to create accurate representations of the fossil elements. Two different scanning devices were employed to capture high-resolution 3D models of the fossil elements. The scanned data was processed to align and fuse the points, resulting in detailed 3D models. Related taxa such as Argyrosaurus superbus and 3D modeling techniques were used to reconstruct missing elements. Scaling calculations were performed based on comparative analysis with other titanosaurs to estimate the size of the missing elements. Retrodeformation was applied to correct taphonomic distortion and restore the original shape of the fossil elements. Texturing and rendering techniques were also employed to enhance the visual quality of the 3D models. The 3D models were subsequently 3D printed using white polylactic acid (PLA) filament. Creating physical replicas is useful for further studies, educational purposes, and public outreach. We highlight the advantages of 3D printing in paleontology, such as cost-effectiveness and accessibility, as it creates accurate replicas without compromising the original fossils. Overall, the presented methodologies demonstrate the potential of 3D technologies in paleontological research. The combination of scanning, reconstruction, retrodeformation, scaling, texturing, rendering, and 3D printing provides a comprehensive approach to accurately reconstructing and visualizing fossil elements. These techniques contribute to a better understanding of extinct vertebrates and their biomechanics.

Accurate muscle reconstructions can offer new information on the anatomy of fossil organisms and are also important for biomechanical analysis (multibody dynamics and finite-element analysis (FEA)). For the sake of simplicity, muscles are often modelled as point-to-point strands or frustra (cut-off cones) in biomechanical models. However, there are cases in which it is useful to model the muscle morphology in three dimensions, to better examine the effects of muscle shape and size. This is especially important for fossil analyses, where muscle force is estimated from the reconstructed muscle morphology (rather than based on data collected in vivo). The two main aims of this paper are as follows. First, we created a new interactive tool in the free open access software Blender to enable interactive three-dimensional modelling of muscles. This approach can be applied to both palaeontological and human biomechanics research to generate muscle force magnitudes and lines of action for FEA. Second, we provide a guide on how to use existing Blender tools to reconstruct distorted or incomplete specimens. This guide is aimed at palaeontologists but can also be used by anatomists working with damaged specimens or to test functional implication of hypothetical morphologies.

In this study, we suggest a method adapted to the retrodeformation of asymmetrical objects - such as limb bones - by quantitatively estimating the effectiveness of the Thin-Plate Splines (TPS) interpolation function as a retrodeformation tool. To do so, taphonomic deformations were first simulated on a single horse femur. The original bone was then used as a reference in order to drive the retrodeformation using anatomical landmarks. This approach, based on a single bone, enabled us to evaluate the performance of the retrodeformation procedure. Then, the same approach was performed on a sample of rhino femora but using a different specimen (from the same species) as the reference in order to account for morphological variation. We also added sliding semi-landmarks on anatomical curves. Finally, retrodeformation was applied on a sample of sauropodomorph dinosaur femora by building a mean shape based on several well-preserved fossil specimens. Results show that entirely flattened and stretched bones are more efficiently retrodeformed than bent and twisted bones. Introduction of morphological variation increased the efficiency of retrodeformation for bent and locally stretched bones. The application to the sample of fossils produced similar results but also highlighted the difficulty of retrodeforming bones with a combination of different deformations. TPS interpolation is an efficient tool of retrodeformation for asymmetrical objects, especially for bones with only one affine deformation such as flattening or stretching. Finding a threshold of landmark number to use for this process would be the next step because it would allow us to ensure the quality of retrodeformation while keeping available a reasonable number of landmarks in order to perform shape analysis on retrodeformed bones. Twisted and bent fossils are frequently discovered and we suggest that these kinds of deformations should be studied with caution, especially when combined with other types of taphonomic distortions. [ABSTRACT FROM AUTHOR]

Taphonomic and diagenetic processes inevitably distort the original skeletal morphology of fossil vertebrate remains. Key aspects of palaeobiological datasets may be directly impacted by such morphological deformation, such as taxonomic diagnoses and phylogenetic hypotheses, interpretations of the shape and orientation of anatomical structures, and assessments of interspecific and intraspecific variation. In order to overcome these ubiquitous challenges we present a novel reconstruction workflow combining retopology and retrodeformation, allowing the original morphology of both symmetrically and asymmetrically damaged areas of fossils to be reconstructed. As case studies, we present idealised three-dimensional reconstructions of the sternum of the crownward stem-bird Ichthyornis dispar, and cervical vertebrae of the diplodocid sauropod Galeamopus pabsti. Multiple Ichthyornis sterna were combined into a single, idealised composite representation through superimposition and alignment of retopologised models, and this composite was subsequently retrodeformed. The Galeamopus vertebrae were individually retrodeformed and symmetrised. Our workflow enabled us to quantify deformation of individual specimens with respect to our reconstructions, and to characterise global and local taphonomic deformation. Our workflow can be integrated with geometric morphometric approaches to enable quantitative morphological comparisons among multiple specimens, as well as quantitative interpolation of “mediotypes” of serially homologous elements such as missing vertebrae, haemal arches, or ribs.

Digital restoration of fossils based on computed tomographic (CT) imaging and other scanning technologies has become routine in paleontology. Digital restoration includes the retrodeformation and reconstruction of a fossil specimen. The former involves modification of the original 3D model to reverse post-mortem brittle and plastic deformation; and the latter involves the infilling of fractures, addition of missing pieces, and smoothing of the mesh surface. The restoration process often involves digital editing of the specimen in ways that are difficult to document and reproduce. To record all actions taken during the digital restoration of a fossil, we outline a workflow that generates both the restored bone and the sequence of steps involved in its retrodeformation and reconstruction. Our method can also generate an animation showing the transformation of the original digital model into its final form. We applied this method to a dorsal rib and frontal bone of a small-bodied Jurassic-age armored dinosaur from Africa, the digital restoration of which engaged all modalities of deformation (translation, rotation, scaling, distortion) and reconstruction (fracture infilling, adding missing bone, surface smoothing). Each bone was CT-scanned, segmented, and imported into Blender, an open-source 3D-graphics animation program. Blender has an animation tool called an “armature” that allows for precise control over portions of a surface mesh while keeping a record of manipulations. To retrodeform a fossil, an armature is created and then linked, or “rigged,” to the fossil in order to control the displacement and distortion of its fragments. After using the armature to perform retrodeformation, we use Blender to record the movement and distortion of each fragment and also record reconstructive modifications. By ensuring documentation and reproducibility in an open-source program, our workflow and output open a window onto the heretofore largely hidden process of digital restoration in paleontology.

Sinkhole risks are becoming particularly severe in urban areas that lack careful planning and where karst depressions are frequently filled and developed. These built-up areas are the most challenging for sinkhole investigation; they are the ones that require the highest priority and the application of novel approaches aimed at reducing the epistemic uncertainties associated with hazard assessments. This work illustrates the strengths of the rarely used trenching technique for the investigation of sinkholes in mantled karst areas. The approach has been tested on a buried sinkhole in the evaporite karst of Zaragoza city, analysing and comparing data gathered by trenching, Ground Penetrating Radar (GPR) using shielded and unshielded antennas with different frequencies, Electrical Resistivity Tomography (ERT) and high-precision leveling. The sinkhole is located beneath a street and has led to the demolition of buildings, creating a risk situation that requires careful assessment and management. Trenching provided the largest amount of objective data required for hazard assessment: (1) Precise location of the sinkhole edges. (2) Internal structure, cumulative displacement, subsidence mechanisms and their contribution. The trench exposed an asymmetric structure with a minimum vertical displacement of 6.2 m, comprising a complex collapse with different generations of faults and two marginal zones affected by gentle inward tilting. Collapse faulting accommodates at least 70% of the subsidence. (3) Age of the sinkhole and average subsidence rate. The sinkhole was initiated sometime before or within 337–435 cal yr AD, indicating a long-term subsidence rate of ca. 3.7–4.2 mm/yr. (4) Kinematic style, characterised by episodic collapse events, as supported by leveling data. The retrodeformation analysis, together with geochronological data, indicates four collapse events with a recurrence of around 400 years and suggests enhanced activity since ca. 1950 AD. The performance of GPR was highly variable, depending mainly on the type of antenna and the timing of data acquisition. The best-quality data were obtained with shielded antennas and during relatively drier conditions. The rather poor performance of ERT, commonly an adequate method for resolving subsidence structures at depth, is attributed to the complex structure of the collapse sinkhole, with spatially-dense and abrupt resistivity changes in resistivity. This case study strongly substantiates the implementation of the relatively inexpensive and highly objective trenching technique in sinkhole investigations. [ABSTRACT FROM AUTHOR]

Ornithomimosaur dinosaurs evolved lightweight, edentulous skulls that possessed keratinous rhamphothecae. Understanding the anatomy of these taxa allows for a greater understanding of “ostrich-mimic” dinosaurs and character change during theropod dinosaur evolution. However, taphonomic processes during fossilisation often distort fossil remains. Retrodeformation offers a means by which to recover a hypothesis of the original anatomy of the specimen, and 3D scanning technologies present a way to constrain and document the retrodeformation process. Using computed tomography (CT) scan data, specimen specific retrodeformations were performed on three-dimensionally preserved but taphonomically distorted skulls of the deinocheirid Garudimimus brevipes Barsbold, 1981 and the ornithomimids Struthiomimus altus Lambe, 1902 and Ornithomimus edmontonicus Sternberg, 1933. This allowed for a reconstruction of the adductor musculature, which was then mapped onto the crania, from which muscle mechanical advantage and bite forces were calculated pre- and post-retrodeformation. The extent of the rhamphotheca was varied in each taxon to represent morphologies found within modern Aves. Well constrained retrodeformation allows for increased confidence in anatomical and functional analysis of fossil specimens and offers an opportunity to more fully understand the soft tissue anatomy of extinct taxa.

Accurate muscle reconstructions can offer new information on the anatomy of fossil organisms and are also important for biomechanical analysis (multibody dynamics and finite-element analysis (FEA)). For the sake of simplicity, muscles are often modelled as point-to-point strands or frustra (cut-off cones) in biomechanical models. However, there are cases in which it is useful to model the muscle morphology in three dimensions, to better examine the effects of muscle shape and size. This is especially important for fossil analyses, where muscle force is estimated from the reconstructed muscle morphology (rather than based on data collected in vivo ). The two main aims of this paper are as follows. First, we created a new interactive tool in the free open access software Blender to enable interactive three-dimensional modelling of muscles. This approach can be applied to both palaeontological and human biomechanics research to generate muscle force magnitudes and lines of action for FEA. Second, we provide a guide on how to use existing Blender tools to reconstruct distorted or incomplete specimens. This guide is aimed at palaeontologists but can also be used by anatomists working with damaged specimens or to test functional implication of hypothetical morphologies., (© 2022 The Authors.)

A simple algorithm based on the transformation equations of homogeneous deformation allows application of computer-graphic software for estimation of strain and restoration of shape of distorted fossils in a single operation. This paper gives a computer-aided digital method for the estimation of strain in situations where a single fossil, or a set of fossils, is found embedded in rocks. Because the digital method deciphers reciprocal strain ellipse by removing the effect of tectonic deformation, it is also useful in precise taxonomic identification. Several natural examples of trilobites and brachiopods are tested by the digital method, as well as by other conventional methods of strain analysis. The digital method is easy to use, rapid, and accurate in comparison to other existing methods of strain analysis and retrodeformation. [ABSTRACT FROM AUTHOR]

Strain reversal of structural/stratigraphic profiles at different scales in the western Lachlan Orogen provides a perspective on original crustal thickness estimates, the former depositional basin width of the proto-western Lachlan Orogen, the original sedimentary-fan thickness, and the possible length extent of lower crust lost by subduction. Retrodeformation using strain-reversal techniques allows basin reconstruction giving an original width of the western Lachlan Orogen basin receptor of between 800 km (minimum) and ∼⃒1150 km (maximum), depending on the amount of stratal duplication allowed in the turbidites. Crude area balancing of the regional cross-section, adding in sectional volume lost by erosion and assuming strain compatibility between the upper and lower crust, suggests that the predeformation crustal thickness ranges between 15 km and ∼⃒21 km, with a lower crustal thickness (oceanic lithosphere) of ∼⃒9 km and a turbidite fan thickness of ∼⃒6 km (minimum) and ∼⃒12 km (maximum allowable), respectively. Disparity between the calculated fan thickness and that derived from measured stratigraphic sections adjusted for strain (∼⃒6 km) indicates that some form of crustal stacking must be important in structural thickening of the turbidite crustal component. By varying shortening due to fault stacking, mass balance dictates the mismatch of the upper crustal (uc) and lower crustal (lc) retrodeformed lengths, and therefore provides an estimate of lower crustal loss by subduction. End members range from: (i) a 12 km-thick fan without fault duplication, a basin width of ∼⃒800 km where uc = lc giving no lower crustal loss by subduction; to (ii) a ∼⃒6 km fan, requiring duplication by faulting, a basin of ∼⃒1150 km where uc > lc, and ∼⃒360 km of lower crust length (∼⃒30%) lost by subduction. This suggests that the total thickness of underplated igneous material in the western Lachlan Orogen is low, probably [ABSTRACT FROM AUTHOR]

Ornithomimosaur dinosaurs evolved lightweight, edentulous skulls that possessed keratinous rhamphothecae. Understanding the anatomy of these taxa allows for a greater understanding of "ostrich-mimic" dinosaurs and character change during theropod dinosaur evolution. However, taphonomic processes during fossilisation often distort fossil remains. Retrodeformation offers a means by which to recover a hypothesis of the original anatomy of the specimen, and 3D scanning technologies present a way to constrain and document the retrodeformation process. Using computed tomography (CT) scan data, specimen specific retrodeformations were performed on three-dimensionally preserved but taphonomically distorted skulls of the deinocheirid Garudimimus brevipesBarsbold, 1981 and the ornithomimids Struthiomimus altusLambe, 1902 and Ornithomimus edmontonicusSternberg, 1933. This allowed for a reconstruction of the adductor musculature, which was then mapped onto the crania, from which muscle mechanical advantage and bite forces were calculated pre- and post-retrodeformation. The extent of the rhamphotheca was varied in each taxon to represent morphologies found within modern Aves. Well constrained retrodeformation allows for increased confidence in anatomical and functional analysis of fossil specimens and offers an opportunity to more fully understand the soft tissue anatomy of extinct taxa.