Two exceptionally preserved juvenile specimens of Gorgosaurus libratus (Tyrannosauridae, Albertosaurinae) provide new insight into the timing of ontogenetic changes in tyrannosaurids

Journal of Vertebrate Paleontology, Journal Year: 2021, Volume and Issue: 41(6)

Published: Oct. 1, 2021

Known from dozens of specimens discovered since the early 20th century, Gorgosaurus libratus has arguably contributed more than any other taxon to our understanding life history tyrannosaurids. However, juvenile material for this is rare. Here, we describe two small, articulated (skull lengths ca. 500 mm) that help advance knowledge anatomy and ontogeny tyrannosaurids in general. The new exhibit hallmark tyrannosaurid features, including long, low, narrow skulls, large circular orbits, absent or incipient cranial ornamentation, ziphodont dentition, an overall gracile skull frame. Comparison with various ontogenetic stages allows examination timing morphological changes occurred through relative Of particular note, larger Tyrannosaurus rex are found have experienced similar transformations at percent length known individuals each respective but different absolute body sizes biological ages, occurring a size older age Gorgosaurus. These results suggest dissociation between development Finally, recognition ontogenetically invariant characters makes it possible determine taxonomic identity previously misidentified specimens.

Language: Английский

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The stability of dinosaur communities before the Cretaceous–Paleogene (K–Pg) boundary: A perspective from southern Alberta using calcium isotopes as a dietary proxy

Geological Society of America Bulletin, Journal Year: 2022, Volume and Issue: 134(9-10), P. 2548 - 2560

Published: Feb. 10, 2022

Abstract Reconstructing dinosaur trophic structure prior to the Cretaceous–Paleogene (K–Pg) boundary may provide information about ecosystem organization and evolution. Using calcium isotopes, we investigate preserved biogenic isotope compositions in a set of teeth from three continental formations Alberta, Canada, assess latest Cretaceous food web structure. Tooth enamel δ44/42Ca values are presented for tyrannosaurids (n = 34) potential large herbivorous prey 42) upper Campanian Dinosaur Provincial Park Formation, upper-most Campanian–Maastrichtian Horseshoe Canyon Maastrichtian–lower Paleocene Scollard spanning last ~10 m.y. Cretaceous. The influence diagenesis is assessed subset sample through major trace elemental concentrations ultraviolet (UV) Raman spectra, which provides framework interpreting values. In hadrosaurid systematically heavier than ceratopsid values, difference that interpreted reflect niche partitioning among megaherbivores. Tyrannosaurid scattered but on average, they 44Ca-depleted relative dinosaurs all formations. As data set, have preferentially fed hadrosaurids. These analyses offer possibilities testing whether non-avian ecosystems changed several millions years K–Pg boundary.

Language: Английский

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First application of dental microwear texture analysis to infer theropod feeding ecology

Palaeontology, Journal Year: 2022, Volume and Issue: 65(6)

Published: Nov. 1, 2022

Abstract Theropods were the dominating apex predators in most Jurassic and Cretaceous terrestrial ecosystems. Their feeding ecology has always been of great interest, new computational methods have yielded more detailed reconstructions differences theropod behaviour. Many approaches, however, rely on well‐preserved skulls. Dental microwear texture (DMT) analysis is potentially applicable to isolated teeth, here employed for first time investigate dietary theropods. In particular, we test whether tyrannosaurids show DMT associated with hard‐object than compared Allosaurus ; this would be a sign higher levels osteophagy, as often suggested. We find no significant difference complexity roughness enamel surfaces between tyrannosaurids, which conflicts inferences frequent osteophagic behaviour Tyrannosaurus other Orientation wear features reveals pronounced bi‐directional puncture‐and‐pull mode tyrannosaurids. Our results further indicate ontogenetic niche shift theropods crocodylians, based significantly larger height parameters juvenile might scavenging, resulting bone–tooth contact during feeding. Overall, found very similar extant large, broad‐snouted crocodylians shows similarity throughout Cretaceous.

Language: Английский

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Size-mediated competition and community structure in a Late Cretaceous herbivorous dinosaur assemblage

Historical Biology, Journal Year: 2021, Volume and Issue: 34(11), P. 2230 - 2240

Published: Dec. 8, 2021

It has been argued that, throughout the Mesozoic, immature growth forms of megaherbivorous dinosaurs competitively excluded small herbivorous dinosaur species, leading to left-skewed species richness-body mass distributions their fossil assemblages. By corollary, where large and herbivores coexisted over a geologically significant period time, they must have exhibited niche partitioning. We use multivariate ecomorphological analysis Late Cretaceous ornithischian assemblage North America examine this prediction. Our results indicate good separation most, but not all, at body size, although more work is required demonstrate that these patterns were adaptive. Calculation browse profiles using corrected abundance data bracketed estimates energy requirements suggests megaherbivores – most particularly hadrosaurids outstripped coexisting in control resource base.

Language: Английский

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Mandibular force profiles of Alioramini (Theropoda: Tyrannosauridae) with implications for palaeoecology of this unique lineage of tyrannosaurid dinosaurs

Lethaia, Journal Year: 2024, Volume and Issue: 57(2), P. 1 - 12

Published: June 20, 2024

Language: Английский

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New Carnivoran (Mammalia: Carnivora) specimens from the Siwaliks of Pakistan and India and their faunal and evolutionary implications

Historical Biology, Journal Year: 2022, Volume and Issue: 35(11), P. 2217 - 2252

Published: Nov. 3, 2022

Recently collected carnivoran specimens from the Siwalik Group of Pakistan are described and discussed. These add to our knowledge previously known taxa while also adding biogeographic, stratigraphic, temporal carnivorans Siwaliks. At least eight distinct identified, although most fragmentary, some hyaenid identified further (e.g. Lycyaena Ictitherium). We identify describe first herpestid fossils Chinji Formation, (Lycyaena cf. L. dubia) Tatrot definitive occurrence Ictitherium (Ictitherium I. viverrinum) Dhok Pathan Formation. report occurrences several various sites in Siwaliks Pakistan, including reports any Milan, Kohtehra, Lawa. Individual show a wide range biodiversity, however larger scale trends more discernible when comparing those between formations Several disappear over time fauna Siwaliks, starting with barbourofelines, continuing amphicyonids (and non-carnivoran hyaenodontids). Felids mustelids diverse caniforms become prevalent through time.

Language: Английский

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“Dragons” on the landscape: Modeling the abundance of large carnivorous dinosaurs of the Upper Jurassic Morrison Formation (USA) and the Upper Cretaceous Dinosaur Park Formation (Canada)

The Anatomical Record, Journal Year: 2022, Volume and Issue: 306(7), P. 1669 - 1696

Published: July 11, 2022

Abstract Counts of the number skeletal specimens “adult” megaherbivores and large theropods from Morrison Dinosaur Park formations—if not biased by taphonomic artifacts—suggest that big meat‐eaters were more abundant, relative to plant‐eaters, than one would expect on basis abundance carnivores herbivores in modern mammalian faunas. Models megaherbivore population density (number individuals per square kilometer) attempt take into account ecosystem productivity, size structure populations, individual energy requirements, when combined with values theropod/megaherbivore ratio, suggest may have been abundant landscape estimates extrapolated versus body mass relationship carnivores. meat production populations requirements herbivore productivity insufficient support associated theropods, unless production/biomass ratio was substantially higher, and/or theropod requirement markedly lower, expectations based mammals. Alternatively, or addition both these other factors, likely included dinosaurs as significant components their diet.

Language: Английский

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Bite force estimates in juvenileTyrannosaurus rexbased on simulated puncture marks

PeerJ, Journal Year: 2021, Volume and Issue: 9, P. e11450 - e11450

Published: June 2, 2021

Bite marks attributed to adult Tyrannosaurus rex have been subject numerous studies. However, few bite T. traced juveniles, leaving considerable gaps in understanding ontogenetic changes mechanics and force, the paleoecological role of juvenile tyrannosaurs late Cretaceous. Here we present force estimates for a based on mechanical tests designed replicate previously approximately 13 years old. A maxillary tooth specimen BMR P2002.4.1 was digitized, replicated dental grade cobalt chromium alloy, mounted an electromechanical testing system. The then pressed into bovine long bones various locations with differing cortical bone thicknesses at varying speeds total 17 trials. Forces required punctures were recorded puncture dimensions measured. Our experimentally derived linear models suggest forces up 5,641.19 N from thickness estimated Edmontosaurus Tyrannosaurus. These findings are slightly higher than same size as but fall within expected range when compared rex. results this study offer further insight Cretaceous ecosystems. Furthermore, discuss implications feeding mechanisms, behaviors, niche partitioning.

Language: Английский

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Special Issue in honour of Dale Alan Russell (1937–2019)¹

Canadian Journal of Earth Sciences, Journal Year: 2021, Volume and Issue: 58(9), P. v - vi

Published: Aug. 31, 2021

Language: Английский

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Big boned: How fat storage and other adaptations influenced large theropod foraging ecology

PLoS ONE, Journal Year: 2023, Volume and Issue: 18(11), P. e0290459 - e0290459

Published: Nov. 1, 2023

Dinosaur foraging ecology has been the subject of scientific interest for decades, yet much what we understand about it remains hypothetical. We wrote an agent-based model (ABM) to simulate meat energy sources present in dinosaur environments, including carcasses giant sauropods, along with living, huntable prey. Theropod dinosaurs modeled this environment (specifically allosauroids, and more particularly, Allosaurus Marsh, 1877) were instantiated heritable traits favorable either hunting success or scavenging success. If hunter phenotypes reproductively successful, their propagated into population through offspring, resulting predator specialists. selective pressure favored scavenger phenotypes, would evolve acquire most calories from carrion. Data generated strongly suggest that theropods sauropod-dominated systems evolved detect carcasses, consume store large quantities fat, dominate carcass sites. Broadly speaking, forces did not favor predatory adaptations, because sauropod carrion resource pools, as them, too profitable prey-based pools be significant. This is first research test patterns dinosaurs, estimate theropod mass based on metabolic constraints.

Language: Английский

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