Forty new specimens of Ichthyornis provide unprecedented insight into the postcranial morphology of crownward stem group birds

PeerJ, Journal Year: 2022, Volume and Issue: 10, P. e13919 - e13919

Published: Dec. 16, 2022

Ichthyornis has long been recognized as a pivotally important fossil taxon for understanding the latest stages of dinosaur–bird transition, but little significant new postcranial material brought to light since initial descriptions partial skeletons in 19 th Century. Here, we present information on morphology from 40 previously undescribed specimens, providing most complete morphological assessment skeleton date. The includes four partially and numerous well-preserved isolated elements, enabling anatomical observations such muscle attachments Mesozoic euornitheans. Among elements that were unknown or poorly represented , specimens include an almost-complete axial series, hypocleideum-bearing furcula, radial carpal bones, fibulae, tarsometatarsus bearing rudimentary hypotarsus, one first-known nearly three-dimensional sterna avialan. Several pedal phalanges are preserved, revealing remarkably enlarged pes presumably related foot-propelled swimming. Although diagnosable exhibit substantial degree variation, some which may relate ontogenetic changes. Phylogenetic analyses incorporating our data employing alternative datasets recover stemward Hesperornithes Iaceornis line with recent hypotheses regarding topology crownward-most portion avian stem group, establish phylogenetically-defined clade names relevant avialan subclades help facilitate consistent discourse future work. provided by these improves evolution among non-neornithine avialans immediately preceding origin crown group birds.

Language: Английский

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Osteohistological analysis of metatarsals reveals new information on pathology and life history of troodontids from the Campanian Dinosaur Park Formation, Alberta, Canada

Journal of Anatomy, Journal Year: 2025, Volume and Issue: unknown

Published: April 19, 2025

Abstract Troodontidae is a family of small‐bodied theropods known predominantly from Asia but are comparatively scarce in North America. In the Dinosaur Park Formation (DPF) Alberta, Canada, they isolated material, precluding taxonomic and ontogenetic precision for this clade. Previously never sampled histologically within DPF, here we attempt to fill gaps our knowledge about life histories clade formation by surveying metatarsals, which among most abundant identifiable troodontid elements DPF. We 11 metatarsals (three metatarsal IIs, three IIIs five IVs) varying sizes included pathological individuals describe microanatomy both healthy determine status each element graph their pattern growth. Osteohistology reveals that grew remodelled asymmetrically cortex, ceasing growth remodelling primarily along articular surfaces entheses. Pathological ranged displaying features response localised stress (chronic callus avulsion/chip fracture) extreme modification trauma inflammation at distal joint. Only latter appeared be related overall growth, suggesting condition either developed early stunted or another underlying cause was responsible resulting observed. Overall, tracking specimens there least two trajectories DPF differentiated timing major spurts plateaus. Whether represents sexual dimorphism, diversity, form variation warrants further investigation.

Language: Английский

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Jaw biomechanics of Troodontidae and their implications for the palaeobiology of this lineage of bird-like theropod dinosaurs

Lethaia, Journal Year: 2025, Volume and Issue: 58(1), P. 1 - 12

Published: Feb. 20, 2025

Language: Английский

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Calibrating geologic strata, dinosaurs, and other fossils at Dinosaur Provincial Park (Alberta, Canada) using a new CA-ID-TIMS U–Pb geochronology

Canadian Journal of Earth Sciences, Journal Year: 2023, Volume and Issue: 60(12), P. 1627 - 1646

Published: July 5, 2023

The 100 m thick stratigraphic section exposed at Dinosaur Provincial Park (DPP; southern Alberta) contains bentonites that have been used for more than 30 years to date DPP’s rocks and fossils using the K–Ar decay scheme. Limited reproducibility among different vintages of 40 Ar/ 39 Ar ages inhibited development a high-resolution chronostratigraphy. Here, we employ further test recently completed U–Pb geochronology associated age-stratigraphy model update temporal constraints on Park’s bentonites, formational contacts, other markers. In turn, document rock accumulation rates calibrate durations informal megaherbivore dinosaur assemblage zones biozones. Weighted mean 206 Pb/ 238 U from five range 76.718 ± 0.020 74.289 0.014 Ma (2σ internal uncertainties) through an interval 88.75 m, indicating duration ∼2.43 Myr overall rate 3.65 0.04 cm/ka. An increase in above Oldman–Dinosaur contact conforms regionally expressed pattern increased accommodation ∼76.3 across Alberta Montana. Palynological biozone data suggest condensed section/hiatus uppermost portion Oldman Formation. exhibit ∼700–600 kyr are significantly shorter those overlying Horseshoe Canyon A decreased turnovers last eight million Mesozoic western Canada may be explained by withdrawal Western Interior Seaway expansion ecologically homogenous lowlands its wake.

Language: Английский

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Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator

Science Advances, Journal Year: 2023, Volume and Issue: 9(49)

Published: Dec. 8, 2023

Tyrannosaurids were large carnivorous dinosaurs that underwent major changes in skull robusticity and body proportions as they grew, suggesting occupied different ecological niches during their life span. Although adults commonly fed on dinosaurian megaherbivores, the diet of juvenile tyrannosaurids is largely unknown. Here, we describe a remarkable specimen Gorgosaurus libratus preserves articulated hindlimbs two yearling caenagnathid inside its abdominal cavity. The prey selectively dismembered consumed separate feeding events. This predator-prey association provides direct evidence an ontogenetic dietary shift tyrannosaurids. Juvenile individuals may have hunted small young until reached size when, to satisfy energy requirements, transitioned megaherbivores. both mesopredator apex predator roles span, factor been key evolutionary success.

Language: Английский

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Early Cretaceous troodontine troodontid (Dinosauria: Theropoda) from the Ohyamashimo Formation of Japan reveals the early evolution of Troodontinae

Scientific Reports, Journal Year: 2024, Volume and Issue: 14(1)

Published: July 25, 2024

A new troodontid dinosaur, Hypnovenator matsubaraetoheorum gen. et sp. nov., is described based on an articulated postcranial skeleton recovered from the fluvial deposits of Albian Ohyamashimo Formation Sasayama Group in Tambasasayama City, Hyogo Prefecture, Japan. distinguished other troodontids by four autapomorphies and a combination additional features. Our phylogenetic analysis positions as oldest one most basal troodontines, forming clade with Gobivenator mongoliensis. The discovery suggests that small-bodied maniraptorans sleeping posture were common not only environments volcanic eolian events or alluvial systems but also systems. Geometric morphometric manual ungual phalanges shows I III exhibit considerable morphological variation are functionally similar, which differs those non-troodontine troodontids, reflecting transition motion within Troodontinae. has mosaic features pes related to cursoriality. This study reveals asymmetrical arctometatarsus occurred Albian, some changes, such shorter digit IV than non-ungual digits roller joints weakly ginglymoid articulation, arose during early Late Cretaceous.

Language: Английский

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Neuroanatomy of the late Cretaceous Thescelosaurus neglectus (Neornithischia: Thescelosauridae) reveals novel ecological specialisations within Dinosauria

Scientific Reports, Journal Year: 2023, Volume and Issue: 13(1)

Published: Nov. 6, 2023

Abstract Ornithischian dinosaurs exhibited a diversity of ecologies, locomotory modes, and social structures, making them an ideal clade in which to study the evolution neuroanatomy behaviour. Here, we present 3D digital reconstruction endocranial spaces latest Cretaceous neornithischian Thescelosaurus neglectus , order interpret paleobiology one last surviving non-avian dinosaurs. Results demonstrate that brain was relatively small compared most other neornithischians, instead suggesting cognitive capabilities within range extant reptiles. Other traits include narrow hearing range, with limited ability distinguish high frequencies, paired unusually well-developed olfactory lobes anterior semicircular canals, indicating acute olfaction vestibular sensitivity. This character combination, conjunction features postcranial anatomy, is consistent specializations for burrowing behaviours clade, as evidenced by trace skeletal fossil evidence earlier-diverging thescelosaurids, although whether they reflect ecological adaptations or phylogenetic inheritance T. itself unclear. Nonetheless, our results provide first neurological identified Ornithischia, more generally, expanding recognized this major clade.

Language: Английский

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The macroecology of Mesozoic dinosaurs

Biology Letters, Journal Year: 2024, Volume and Issue: 20(11)

Published: Nov. 1, 2024

Dinosaurs thrived for over 160 million years in Mesozoic ecosystems, displaying diverse ecological and evolutionary adaptations. Their ecology was shaped by large-scale climatic biogeographic changes, calling a ‘deep-time’ macroecological investigation. These factors include temperature fluctuations the break up of Pangaea, influencing species richness, diversity history. Recent improvements dinosaur fossil record have enabled studies their responses to tectonic, geographic shifts. Trends diversity, body size reproductive traits can now be analysed using quantitative approaches like phylogenetic comparative methods, machine learning Bayesian inference. patterns sometimes align with, but also deviate from, first-order rules (e.g. species–area relationship, latitudinal biodiversity gradient, Bergmann’s rule). Accurate reconstructions palaeobiodiversity niche partitioning require ongoing taxonomic revisions detailed anatomical descriptions. Interdisciplinary research combining sedimentology, geochemistry palaeoclimatology helps uncover environmental conditions driving Fieldwork under-sampled regions, particularly at extremes, is crucial understanding spatial heterogeneity ecosystems across planet. Open science initiatives online databases play key role advancing this field, enriching our deep-time processes, offering new insights into macroecology its broader implications.

Language: Английский

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40 new specimens ofIchthyornisprovide unprecedented insight into the postcranial morphology of crownward stem group birds

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2022, Volume and Issue: unknown

Published: Jan. 12, 2022

ABSTRACT Ichthyornis has long been recognized as a pivotally important fossil taxon for understanding the latest stages of dinosaur–bird transition, but little significant new postcranial material brought to light since initial descriptions partial skeletons in 19 th Century. Here, we present information on morphology from 40 previously undescribed specimens, providing most detailed morphological assessment date. The includes four partially complete and numerous well-preserved isolated elements, enabling anatomical observations such muscle attachments Mesozoic euornitheans. Among elements that were unknown or poorly represented , specimens include an almost-complete axial series, hypocleideum-bearing furcula, radial carpal bones, fibulae, tarsometatarsus bearing rudimentary hypotarsus, one first-known nearly three-dimensional sterna avialan. Several pedal phalanges are preserved, revealing remarkably enlarged pes presumably related foot-propelled swimming. Although diagnosable exhibit substantial degree variation, some which may relate ontogenetic changes. Phylogenetic analyses incorporating our data employing alternative datasets recover stemward Hesperornithes Iaceornis line with recent hypotheses regarding topology crownward-most portion avian stem group, establish phylogenetically-defined clade names relevant avialan subclades help facilitate consistent discourse future work. provided by these improves evolution among non-neornithine avialans immediately preceding origin crown group birds.

Language: Английский

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Insufficient Evidence for Multiple Species of Tyrannosaurus in the Latest Cretaceous of North America: A Comment on “The Tyrant Lizard King, Queen and Emperor: Multiple Lines of Morphological and Stratigraphic Evidence Support Subtle Evolution and Probable Speciation Within the North American Genus Tyrannosaurus”

Evolutionary Biology, Journal Year: 2022, Volume and Issue: 49(3), P. 327 - 341

Published: July 25, 2022

Abstract The Late Cretaceous dinosaur Tyrannosaurus rex was recently split into three species based on the premise that variation in T. hypodigm is exceptional, indicating cryptic and “robust” “gracile” morphs. morphs are proportional ratios throughout skeleton. claimed to be stratigraphically separate, with an early robust followed by gracile descendants. There problems hypothesis: taxon diagnoses two features overlap between species; several skulls cannot identified diagnoses; comparisons other theropods incomparable samples; tooth data problematic; stratigraphic framework divides Hell Creek Formation thirds, without position of each specimen, or independent age control showing subdivisions coeval over entire geographic area; previous work found , but it parsed discrete categories. We tested for analyzing femoral were published multiple study using agglomerative hierarchical clustering. results set explained one cluster, dimorphism not supported. exceptional ratio ; we calculated mean intraspecific robusticity 112 living birds 4 nonavian theropods. showed absolute unexceptional does indicate diversity. conclude “ regina ” imperator subjective junior synonyms .

Language: Английский

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