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Fig. 27 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 27. Daspletosaurus sp. (TMP 94.143.1). Middle ear region of left side of braincase in ventrolateral view.

Fig. 18 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 18. Daspletosaurus sp. (TMP 94.143.1). Front of skull in lateral (A), dorsal (B) and anterior views.

Fig. 12 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 12. Albertosaurus sarcophagus (TMP 81.10.1). Left ectopterygoid in dorsal (A) and ventral (B) views.

Fig. 4 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 4. Gorgosaurus libratus (TMP 91.36.500). Dorsal view of back of left mandible showing articular and part of surangular.

Fig. 11 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 11. Albertosaurus sarcophagus (TMP 81.10.1). Right palatine in lateral (A) and medial (B) views.

Fig. 9 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 9. Albertosaurus sarcophagus (TMP 81.10.1). Left quadratojugal in lateral (A) and medial (B) views.

Fig. 14 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 14. Albertosaurus sarcophagus (TMP 81.10.1). Left surangular in lateral (A) and medial (B) views.

Fig. 21 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 21. Daspletosaurus sp. (TMP 94.143.1). Parietals in dorsal (A), left lateral (B), ventral (C), and posterior (D) aspects.

Fig. 7 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 7. Albertosaurus sarcophagus (TMP 81.10.1). Specimen drawing of top of skull in dorsal (A), lateral (B), and ventral (C) views.

opencc-zeroApr 2020View details →

Data from: Chemical preservation of tail feathers from Anchiornis huxleyi, a theropod dinosaur from the Tiaojishan Formation (Upper Jurassic, China)

A panel of geochemical techniques is used here to investigate the taphonomy of fossil feathers preserved in association with the skeleton of the Jurassic theropod Anchiornis huxleyi. Extant buzzard feathers were analysed in parallel to test whether the soft tissues morphologically preserved in the fossil also exhibit a high degree of chemical preservation. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicate that clays and iron oxide pseudomorphs occur in the surrounding sediment and also reveal the preservation of melanosome-like microbodies in the fossil. Carbon gradient along a depth profile and co-occurrence of carbon and sulphur was shown in the fossil by elastic backscattering (EBS) and particle-induced X-ray emission (PIXE). The molecular composition of modern and fossil soft tissues was assessed from micro-Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (micro-ATR FTIR), solid-state 13C nuclear magnetic resonance (13C CP-MAS NMR) and pyrolysis- gas chromatography-mass spectrometry in the presence of TMAH (TMAH-Py-GC-MS). Results show that the proteinaceous material that comprises the modern feathers is not present in the fossil feathers. The latter and the embedding sediment exhibit a highly aliphatic character. However, substantial differences could be evidenced between these samples, revealing that the organic matter of the fossil feathers is, at least partially, derived from original constituents of the feathers. The preservation of the fossil feathers, primarily expressed by the preservation of their morphology, seems to be associated with in situ polymerization of endogenous lipids. Sulphur probably played a role in the fossil preservation although no natural sulphurization took place.

Fig. 11 in Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics

Fig. 11. Top and side views of theropod crania used to reconstruct crosssectional shapes, and oblique views of reconstructed plinge cross−sections for each cranium. Second moments of area of the plinges were calculated as indices of bending and torsional cranium strengths. A–D, carnosaurs; E–G, tyrannosaurids.

Fig. 7 in Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics

Fig. 7. CT−scanned cross−sections of fused tyrannosaurid nasals, showing greater vaulting and higher cross−sectional areas of bone in larger individuals. A. Gorgosaurus libratus (juvenile: TMP 86.144.1). B. Gorgosaurus libratus (subadult: TMP 86.64.1). C. Daspletosaurus torosus (adult: TMP 98.48.1). Numbers 1–4: cross−sections at topologically similar positions, from posterior to anterior.

Fig. 3 in Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics

Fig. 3. Comparisons of mediolateral (A, B) and anteroposterior (C, D) strengths of tyrannosaurid and non−tyrannosaurid theropod maxillary teeth, plotted against skull length. Regressions are by least squares, on log transformed data for the tyrannosaurids. Trend lines are allometric in the tyannosaurids but linear in non−tyrannosaurids. Tooth strengths of Tyrannosaurus rex are much higher than in any other examined taxon. Starting points of the small arrows indicate the position of the juvenile T. rex (TrJ). See Appendix 1 for other specimen labels.

Fig. 8 in Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics

Fig. 8. Average strengths of nasal cross−sections in tyrannosaurids and Allosaurus fragilis, plotted against nasal length. A. Cross−sectional areas, proportional to compression strengths. B. Second moment of area, proportional to vertical bending strength. C. Second moment of area, proportional to lateral bending strength. Values for the A. fragilis nasals are uncorrected for the hollowness of the sections, which would reduce their strengths. Lines fitted to the tyrannosaurid values are derived from log transformed data. See Appendix 1 for labels.

opennotspecifiedFeb 2004View details →

Figure 2 in Tyrannosaurus en pointe: allometry minimized rotational inertia of large carnivorous dinosaurs

Figure 2. RI versus body mass in carnivorous archosaurs. Grey bands indicate the range of changes in RI magnitudes when computed with body widths that were 110% and 90% of the original models.

opencc-zeroAug 2020View details →

An effect size statistical framework for investigating sexual dimorphism in non-avian dinosaurs and other extinct taxa

Despite reports of sexual dimorphism in extinct taxa, such claims in non-avian dinosaurs have been underrepresented recently (~the last decade) and often criticized. Since dimorphism is widespread in sexually reproducing organisms today, underrepresentation might suggest either methodological shortcomings or that this diverse group exhibited highly unusual reproductive biology. Univariate significance testing, especially for bimodality, is ineffective and prone to false negatives. Species recognition and mutual sexual selection hypotheses, therefore, may not be required to explain supposed absence of sexual dimorphism across the grade, likely a type II error. Instead, multiple lines of evidence support sexual selection and variation of structures consistent with secondary sexual characteristics, strongly suggesting sexual dimorphism in non-avian dinosaurs. We propose a framework for studying sexual dimorphism in fossils, focusing on likely secondarily sexual traits and testing against all alternate hypotheses for variation in them using multiple lines of evidence. We use effect size statistics appropriate for low sample sizes, rather than significance testing, to analyze potential divergence of growth curves in traits and constrain estimates for dimorphism magnitude. In many cases, estimates of sexual variation can be reasonably accurate, and further developments in methods to improve sex assignments and account for intrasexual variation (e.g., mixture modelling) will improve accuracy. It is better to compare estimates for the magnitude of and support for dimorphism between datasets than to dichotomously reject or fail to reject monomorphism in a single species, enabling the study of sexual selection across phylogenies and time. We defend our approach with simulated and empirical data, including dinosaur data, showing that even simple approaches can yield fairly accurate estimates of sexual variation in many cases, allowing for comparison of species with high and low support for sexual variation.

opencc-zeroAug 2020View details →

A paraphyletic 'Silesauridae' as an alternative hypothesis for the initial radiation of ornithischian dinosaurs

Whereas ornithischian dinosaurs are well-known from Jurassic and Cretaceous deposits, deciphering the origin and early evolution of the group remains one of the hardest challenges for palaeontologists. So far, there are no unequivocal records of ornithischians from Triassic beds. Here, we present an alternative evolutionary hypothesis that suggests consideration of traditional 'silesaurids' as a group of low-diversity clades representing a stem group leading to core ornithischians (i.e. unambiguous ornithischians, such as Heterodontosaurus tucki). This is particularly interesting because it fills most of the ghost lineages that emerge from the Triassic. Following the present hypothesis, the lineage that encompasses the Jurassic ornithischians evolved from 'silesaurids' during the Middle to early Late Triassic, while typical 'silesaurids' shared the land ecosystems with their relatives until the Late Triassic, when the group completely vanished. Therefore, Ornithischia changes from an obscure to a well-documented clade in the Triassic, and is represented by records from Gondwana and Laurasia. Furthermore, according to the present hypothesis, Ornithischia was the first group of dinosaurs to adopt an omnivorous/herbivorous diet. However, this behavior was achieved as a secondary step instead of an ancestral condition for ornithischians, as the earliest member of the clade is a faunivorous taxon. This pattern was subsequently followed by sauropodomorph dinosaurs. Indeed, the present scenario favors the independent acquisition of an herbivorous diet for ornithischians and sauropodomorphs during the Triassic, whereas the previous hypotheses suggested the independent acquisition for sauropodomorphs, ornithischians, and 'silesaurids'.

opennotspecifiedMar 2016View details →

Figure 2 in Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs

Figure 2 Logistic growth curves for Tyrannosaurus and three related tyrannosaurids.Note that the exponential stages (the regions of maximal slope) are similar in duration but differ in slope (that is, growth rates). Regression equations (mass in kg, age in years) are as follows: T. rex, mass = {5,551/[1 + e‾0.57(age ‾ 16.1)]} + 5, r 2 = 0.953; D. torosus, mass = {1,728/[1 + e‾0.44(age ‾ 12.1)]} + 5, r 2 = 0.992; G. libratus, mass = {1,234/[1 + e‾0.38(age ‾ 12.4)]} + 5, r 2 = 0.950; A. sarcophagus, mass = {1,218/[1 + e‾0.43(age ‾ 14.1)]} + 5; r 2 = 0.985.

opencc-zeroNov 2020View details →

Histological dataset for: Osteohistological analyses reveal diverse strategies of theropod dinosaur body-size macroevolution

The independent evolution of gigantism among dinosaurs has been a topic of longstanding interest, but it remains unclear if gigantic theropods, the largest bipeds in the fossil record, all achieved massive sizes in the same manner, or through different strategies. We perform multi-element histological analyses on a phylogenetically broad dataset sampled from eight theropod families, with a focus on gigantic tyrannosaurids and carcharodontosaurids, to reconstruct the growth strategies of these lineages and test if particular bones consistently preserve the most complete growth record. We find that in skeletally-mature gigantic theropods, weightbearing bones consistently preserve extensive growth records, whereas non-weightbearing bones are remodelled and less useful for growth reconstruction, contrary to the pattern observed in smaller theropods and some other dinosaur clades. We find a heterochronic pattern of growth fitting an acceleration model in tyrannosaurids, with allosauroid carcharodontosaurids better fitting a model of hypermorphosis. These divergent growth patterns appear phylogenetically constrained, representing extreme versions of the growth patterns present in smaller coelurosaurs and allosauroids, respectively. This provides the first evidence of a lack of strong mechanistic or physiological constraints on size evolution in the largest bipeds in the fossil record, and evidence of one of the longest-living individual dinosaurs ever documented.