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Fig. 4 in Stance and gait in theropod dinosaurs

Fig. 4. Reconstructed pelvic and hindlimb muscles of the theropod dinosaur Tyrannosaurus rex. AMB M. ambiens; CFB M. caudofemoralis brevis; CFL M. caudofemoralis longus; FTE M. flexor tibialis externus; GF M. gastrocnemius, fibular head; PIFI1 M. puboischiofemoralis internus part one; TFTE tendon of the M. flexor tibialis externus.

Fig. 1 in Stance and gait in theropod dinosaurs

Fig. 1. Various tarsal elements of archosaurs: a distal view of the right tarsus of a eusuchian crocodilian; b proximal view of the right calcaneum of the pseudosuchian Prestosuchus; c lateral view of the left calcaneum of a eusuchian crocodilian; d lateral view of the left calcaneum of a theropod dinosaur AC articular cartilage; AH anterior hollow of the astragulus; CT calcaneal tuber; DR distal roller of the astragulus; DT distal tarsal four facet of the calcaneum; F fibula; FC fibular condyle of the calcaneum; P peg of the astragalus; S socket of the calcaneum; T tongue of the calcaneum; TI tibia.

Fig. 2 in Stance and gait in theropod dinosaurs

Fig. 2. Superficial shank muscles of a eusuchian crocodilian. FTE tendon of the M. flexor tibialis externus; GF fibular head of the M. gastrocnemius; PLA plantar aponeurosis; T tibia.

Fig. 7 in Stance and gait in theropod dinosaurs

Fig. 7. Diagrammatic representation of the theropod dinosaur, Tyrannosaurus rex, during a walking gait.

Fig. 3 in Stance and gait in theropod dinosaurs

Fig. 3. Lateral view of the left shank and pes of a eusuchian crocodilian. AMB M. ambiens; C calcaneum; FTE M. flexor tibialis externus; G M. gas trocnemius, fibular head; PA M. pero neus anterior; PP peroneus posterior; TCF tendon of the M. caudofemoralis attaching to the fibula; TCFM tendon of the M. caudofemoralis, forming the main origin for the fibular head of the M. gastrocnemius; TE tendon of the M. caudofemoralis to the extensor tendon of the knee; TFTE tendon of the M. flexor tibialis externus to the fifth metatarsus.

Fig. 5 in Stance and gait in theropod dinosaurs

Fig. 5. Reconstructed pelvic and hindlimb muscles of the theropod dinosaur, Tyrannosaurus rex. FTI2 M. flexor tibialis internus part two; FTI3 M. flexor tibialis internus part three; IF M. ilio- femoralis; PIFI2 M. puboischio- femoralis internus part two.

opencc-by-4.0Jun 1998View details →

Figure 2 in A king-sized theropod coprolite

Figure 2 Photomicrograph of a thin section of the theropod coprolite, showing sand- to pebble-sized bone clasts within a microcrystalline phosphatic ground mass.The elemental composition of the ground mass is similar to that of the bone fragments, indicating that it is probably largely composed of reprecipitated bone apatite infiltrated by clay minerals from the host sediment (Table 1). The large bone fragment in the upper left portion of the image exhibits a fibrolamellar pattern, with osteocyte lacunae concentrically arranged around the vascular canals. Probe measurements of the interior of bone lacunae revealed that many of these channels are at least partially empty, whereas others exhibit variable element distributions, with generally lower concentrations of calcium and phosphorus, and higher silicon and aluminium levels (Table 2). Scale bar, 400 m.

opencc-by-4.0Jun 1998View details →

Figure 1 in A king-sized theropod coprolite

Figure 1 Large, bone-bearing theropod coprolite with some of the broken pieces that had eroded downslope. This specimen was found in Chamberry Coulee in the Frenchman River Valley, roughly 11.5 m below the Cretaceous/Tertiary boundary. Scale bar,10 cm.

opencc-zeroDec 2016View details →

Data from: Functional niche partitioning in Therizinosauria provides new insights into the evolution of theropod herbivory

Dietary specialization is generally considered to be a crucial factor in driving morphological evolution across extant and extinct vertebrates. The ability to adapt to a specific diet and to exploit ecological niches is thereby influenced by functional morphology and biomechanical properties. Differences in functional behaviour and efficiency can therefore allow dietary diversification and the coexistence of similarly adapted taxa. Therizinosauria, a group of secondarily herbivorous theropod dinosaurs, is characterized by a suite of morphological traits thought to be indicative of adaptations to an herbivorous diet. Digital reconstruction, theoretical modelling and computer simulations of the mandibles of therizinosaur dinosaurs provides evidence for functional niche partitioning in adaptation to herbivory. Different mandibular morphologies present in therizinosaurians were found to correspond to different dietary strategies permitting coexistence of taxa. Morphological traits indicative of an herbivorous diet, such as a downturned tip of the lower jaw and an expanded postdentary region, were identified as having stress mitigating effects. The more widely distributed occurrence of these purported herbivorous traits across different dinosaur clades suggests that these features also could have played an important role in the evolution and acquisition of herbivory in other groups.

opencc-zeroDec 2011View details →

Data from: Ventilatory mechanics from maniraptoran theropods to extant birds

Shared behavioural, morphological and physiological characteristics are indicative of the evolution of extant birds from non-avian maniraptoran dinosaurs. One such shared character is the presence of uncinate processes; respiratory structures in extant birds. Recent research has suggested a respiratory role for these processes found in oviraptorid and dromaeosaurid dinosaurs. By measuring the geometry of fossil rib cage morphology we demonstrate that the mechanical advantage, conferred by uncinate processes, for movements of the ribs in the oviraptorid theropod dinosaur, Citipati osmolskae, basal avialan species Zhongjianornis yangi, Confuciusornis sanctus, and the more derived ornithurine Yixianornis grabaui, is of the same magnitude as found in extant birds. These skeletal characteristics provide further evidence of a flow-through respiratory system in non-avian theropod dinosaurs and basal avialans, and indicate that uncinate processes are a key adaptation facilitating the ventilation of a lung air sac system that diverged earlier than extant birds.

opencc-zeroDec 2015View details →

Data from: Body size as a driver of scavenging in theropod dinosaurs

Theropod dinosaurs dominated Earth's terrestrial ecosystem as a diverse group of predators for over 160 million years, yet little is known about their foraging ecology. Ranging from the chicken-sized Microraptor up to the whale-sized Giganotosaurus, maintaining a balanced energy budget presented a major challenge in the face of intense competition and the demands of ontogenetic growth. Facultative scavenging, a behaviour present in almost all modern predators, may have been an important behaviour used to supplement energetically expensive lifestyles. By using agent-based models based on the allometric relationship between size and foraging behaviours, we show that theropods between 27 kg and 1044 kg would have gained a significant energetic advantage over individuals at both the small and large extremes of theropod body mass through their scavenging efficiency. These results were robust to rate of competition, primary productivity, and detection distance. Our models demonstrate the potential importance of facultative scavenging in theropods and the role of body size in defining its prevalence in Mesozoic terrestrial systems.

opencc-zeroDec 2015View details →

Data from: Topology, divergence dates, and macroevolutionary inferences vary between different tip-dating approaches applied to fossil theropods (Dinosauria)

Dated phylogenies of fossil taxa allow palaeobiologists to estimate the timing of major divergences and placement of extinct lineages, and to test macroevolutionary hypotheses. Recently developed Bayesian 'tip-dating' methods simultaneously infer and date the branching relationships among fossil taxa, and infer putative ancestral relationships. Using a previously published dataset for extinct theropod dinosaurs, we contrast the dated relationships inferred by several tip-dating approaches and evaluate potential downstream effects on phylogenetic comparative methods. We also compare tip-dating analyses to maximum-parsimony trees time-scaled via alternative a posteriori approaches including via the probabilistic cal3 method. Among tip-dating analyses, we find opposing but strongly supported relationships, despite similarity in inferred ancestors. Overall, tip-dating methods infer divergence dates often millions (or tens of millions) of years older than the earliest stratigraphic appearance of that clade. Model-comparison analyses of the pattern of body-size evolution found that the support for evolutionary mode can vary across and between tree samples from cal3 and tip-dating approaches. These differences suggest that model and software choice in dating analyses can have a substantial impact on the dated phylogenies obtained and broader evolutionary inferences.

opencc-zeroDec 2012View details →

Data from: The good, the bad, and the ugly: the influence of skull reconstructions and intraspecific variability in studies of cranial morphometrics in theropods and basal saurischians

Several studies investigating macroevolutionary skull shape variation in fossil reptiles were published recently, often using skull reconstructions taken from the scientific literature. However, this approach could be potentially problematic, because skull reconstructions might differ notably due to incompleteness and/or deformation of the material. Furthermore, the influence of intraspecific variation has usually not been explored in these studies. Both points could influence the results of morphometric analyses by affecting the relative position of species to each other within the morphospace. The aim of the current study is to investigate the variation in morphometric data between skull reconstructions based on the same specimen, and to compare the results to shape variation occurring in skull reconstructions based on different specimens of the same species (intraspecific variation) and skulls of closely related species (intraspecific variation). Based on the current results, shape variation of different skull reconstructions based on the same specimen seems to have generally little influence on the results of a geometric morphometric analysis, although it cannot be excluded that some erroneous reconstructions of poorly preserved specimens might cause problems occasionally. In contrast, for different specimens of the same species the variation is generally higher than between different reconstructions based on the same specimen. For closely related species, at least with similar ecological preferences in respect to the dietary spectrum, the degree of interspecific variation can overlap with that of intraspecific variation, most probably due to similar biomechanical constraints.

opencc-zeroDec 2010View details →

Data from: Using striated tooth marks on bone to predict body size in theropod dinosaurs: a model based on feeding observations of Varanus komodoensis, the Komodo monitor

Mesozoic tooth marks on bone surfaces directly link consumers to fossil assemblage formation. Striated tooth marks are believed to form by theropod denticle contact, and attempts have been made to identify theropod consumers by comparing these striations with denticle widths of contemporaneous taxa. The purpose of this study is to test whether ziphodont theropod consumer characteristics may be accurately identified from striated tooth marks on fossil surfaces. There are three major objectives; 1) experimentally produce striated tooth marks and explain how they form; 2) determine whether body size characteristics are reflected in denticle widths; 3) determine whether denticle characters are accurately transcribed onto bone surfaces in the form of striated tooth marks. Controlled feeding trials were conducted with the dental analogue Varanus komodoensis (the Komodo monitor). Goat (Capra hircus) carcasses were introduced to captive, isolated individuals. Striated tooth marks were then identified, and striation width, number, and degree of divergence were recorded for each. Denticle widths and tooth/body size characters were taken from photographs and published accounts of both theropod and V. komodoensis skeletal material, and regressions were compared among and between the two groups. Striated marks tend to be regularly striated with a variable degree of branching, and may co-occur with scores. Striation morphology directly reflects contact between the mesial carina and bone surfaces during the rostral reorientation when defleshing. Denticle width is primarily influenced by tooth size, and correlates well with body size displaying negative allometry in both groups regardless of taxon or position. When compared, striation widths fall within or below the range of denticle widths extrapolated for similar sized V. komodoensis individuals. Striation width is directly influenced by the orientation of the carina during feeding, and may underestimate but cannot overestimate denticle width. Although body size may theoretically be estimated solely by a striated tooth mark under ideal circumstances, many caveats should be considered. These include the influence of negative allometry across taxa and throughout ontogeny, the existence of theropods with extreme denticle widths, and the potential for striations to underestimate denticle widths. This method may be useful under specific circumstances, especially for establishing a lower limit body size for potential consumers.

opencc-zeroDec 2011View details →

Data from: Theropod forelimb design and evolution

We examined the relationship between forelimb design and function across the 230-million-year history of theropod evolution. Forelimb disparity was assessed by plotting the relative contributions of the three main limb elements on a ternary diagram. Theropods were divided into five functional groups: predatory, reduced, flying, wing-propelled diving, and flighdess. Forelimbs which maintained their primitive function, predation, are similarly proportioned, but non-avian theropods with highly reduced forelimbs have relatively longer humeri. Despite the dramatically different forces imparted by the evolution of flight, forelimb proportions of basal birds are only slighdy different from those of their non-avian relatives. An increase in disparity accompanied the subsequent radiation of birds. Each transition to flightlessness has been accompanied by an increase in relative humeral length, which results from relatively short distal limb elements. We introduce theoretical predictions based on five biomechanical and developmental factors that may have influenced the evolution of theropod limb proportions.

opencc-zeroDec 2013View details →

Data from: Egg shape changes at the theropod-bird transition, and a morphometric study of amniote eggs

The eggs of amniotes exhibit a remarkable variety of shapes, from spherical to elongate and from symmetrical to asymmetrical. We examine eggshell geometry in a diverse sample of fossil and living amniotes using geometric morphometrics and linear measurements. Our goal is to quantify patterns of morphospace occupation and shape variation in the eggs of recent through to Mesozoic birds (neornithe plus non-neornithe avialans), as well as in eggs attributed to non-avialan theropods. In most amniotes, eggs show significant deviation from sphericity, but departure from symmetry around the equatorial axis is mostly confined to theropods and birds. Mesozoic bird eggs differ significantly from extant bird eggs, but extinct Cenozoic bird eggs do not. This suggests that the range of egg shapes in extant birds had already been attained in the Cenozoic. We conclude with a discussion of possible biological factors imparting variation to egg shapes during their formation in the oviduct.

doi:10.1371/journal.pone.0157793.g016 in An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

doi:10.1371/journal.pone.0157793.g016

doi:10.1371/journal.pone.0157793.g013 in An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

doi:10.1371/journal.pone.0157793.g013

doi:10.1371/journal.pone.0157793.g015 in An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

doi:10.1371/journal.pone.0157793.g015

doi:10.1371/journal.pone.0157793.g006 in An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

doi:10.1371/journal.pone.0157793.g006