Multibody dynamics analysis (MDA) as a numerical modelling tool to reconstruct the function and palaeobiology of extinct organisms

Recent advances in computer technology have substantially changed the field of palaeontology in the last two decades. Palaeontologists now have a whole new arsenal of powerful digital techniques available to study fossil organisms in unprecedented detail and to test hypotheses regarding function and behaviour. Multibody dynamics analysis (MDA) is one of these techniques and although it originated as a tool used in the engineering and automotive industry, it holds great potential to address palaeontological questions as well. MDA allows the simulation of dynamic movements in complex objects consisting of multiple linked components. As such, this technique is ideally suited to model biological structures and to obtain quantifiable results that can be used to test the function of musculoskeletal systems rigorously. However, despite these advantages, MDA has seen a slow uptake by the palaeontological community. The most likely reason for this lies in the steep learning curve and complexity of the method. This paper provides an overview of the underlying principles of MDA and outlines the main steps involved in conducting analyses. A number of recent studies using MDA to reconstruct the palaeobiology of fossil organisms are presented and the potential for future studies is discussed. Similar to other computational techniques, including finite element analysis and computational fluid dynamics, the non‐invasive and exploratory power of MDA makes it ideally suited to study the form and function in vertebrates for which no modern analogues exist

Novel track morphotypes from new tracksites indicate increased Middle Jurassic dinosaur diversity on the Isle of Skye, Scotland

Dinosaur fossils from the Middle Jurassic are rare globally, but the Isle of Skye (Scotland, UK) preserves a varied dinosaur record of abundant trace fossils and rare body fossils from this time. Here we describe two new tracksites from Rubha nam Brathairean (Brothers’ Point) near where the first dinosaur footprint in Scotland was found in the 1980s. These sites were formed in subaerially exposed mudstones of the Lealt Shale Formation of the Great Estuarine Group and record a dynamic, subtropical, coastal margin. These tracksites preserve a wide variety of dinosaur track types, including a novel morphotype for Skye: Deltapodus which has a probable stegosaur trackmaker. Additionally, a wide variety of tridactyl tracks shows evidence of multiple theropods of different sizes and possibly hints at the presence of large-bodied ornithopods. Overall, the new tracksites show the dinosaur fauna of Skye is more diverse than previously recognized and give insight into the early evolution of major dinosaur groups whose Middle Jurassic body fossil records are currently sparse

3D hindlimb joint mobility of the stem-archosaur Euparkeria capensis with implications for postural evolution within Archosauria.

Triassic archosaurs and stem-archosaurs show a remarkable disparity in their ankle and pelvis morphologies. However, the implications of these different morphologies for specific functions are still poorly understood. Here, we present the first quantitative analysis into the locomotor abilities of a stem-archosaur applying 3D modelling techniques. μCT scans of multiple specimens of Euparkeria capensis enabled the reconstruction and three-dimensional articulation of the hindlimb. The joint mobility of the hindlimb was quantified in 3D to address previous qualitative hypotheses regarding the stance of Euparkeria. Our range of motion analysis implies the potential for an erect posture, consistent with the hip morphology, allowing the femur to be fully adducted to position the feet beneath the body. A fully sprawling pose appears unlikely but a wide range of hip abduction remained feasible-the hip appears quite mobile. The oblique mesotarsal ankle joint in Euparkeria implies, however, a more abducted hindlimb. This is consistent with a mosaic of ancestral and derived osteological characters in the hindlimb, and might suggest a moderately adducted posture for Euparkeria. Our results support a single origin of a pillar-erect hip morphology, ancestral to Eucrocopoda that preceded later development of a hinge-like ankle joint and a more erect hindlimb posture

The effect of intervertebral cartilage on neutral posture and range of motion in the necks of sauropod dinosaurs

The necks of sauropod dinosaurs were a key factor in their evolution. The habitual posture and range of motion of these necks has been controversial, and computer-aided studies have argued for an obligatory sub-horizontal pose. However, such studies are compromised by their failure to take into account the important role of intervertebral cartilage. This cartilage takes very different forms in different animals. Mammals and crocodilians have intervertebral discs, while birds have synovial joints in their necks. The form and thickness of cartilage varies significantly even among closely related taxa. We cannot yet tell whether the neck joints of sauropods more closely resembled those of birds or mammals. Inspection of CT scans showed cartilage:bone ratios of 4.5% for Sauroposeidon and about 20% and 15% for two juvenile Apatosaurus individuals. In extant animals, this ratio varied from 2.59% for the rhea to 24% for a juvenile giraffe. It is not yet possible to disentangle ontogenetic and taxonomic signals, but mammal cartilage is generally three times as thick as that of birds. Our most detailed work, on a turkey, yielded a cartilage:bone ratio of 4.56%. Articular cartilage also added 11% to the length of the turkey's zygapophyseal facets. Simple image manipulation suggests that incorporating 4.56% of neck cartilage into an intervertebral joint of a turkey raises neutral posture by 15°. If this were also true of sauropods, the true neutral pose of the neck would be much higher than has been depicted. An additional 11% of zygapophyseal facet length translates to 11% more range of motion at each joint. More precise quantitative results must await detailed modelling. In summary, including cartilage in our models of sauropod necks shows that they were longer, more elevated and more flexible than previously recognised

Frozen in the Ashes

Fossil footprints are very useful palaeontological tools. Their features can help to identify their makers and also to infer biological as well as behavioural information. Nearly all the hominin tracks discovered so far are attributed to species of the genus Homo. The only exception is represented by the trackways found in the late 1970s at Laetoli, which are thought to have been made by three Australopithecus afarensis individuals about 3.66 million years ago. We have unearthed and described the footprints of two more individuals at Laetoli, who were moving on the same surface, in the same direction, and probably in the same timespan as the three found in the 1970s, apparently all belonging to a single herd of bipedal hominins walking from south to north. The estimated stature of one of the new individuals (about 1.65 m) exceeds those previously published for Au. afarensis. This evidence supports the existence of marked morphological variation within the species. Considering the bipedal footprints found at Laetoli as a whole, we can hypothesize that the tallest individual may have been the dominant male, the others smaller females and juveniles. Thus, considerable differences may have existed between sexes in these human ancestors, similar to modern gorillas