Assessing ontogenetic maturity in extinct saurian reptiles

Biological reviews/Biological reviews of the Cambridge Philosophical Society, Journal Year: 2020, Volume and Issue: 96(2), P. 470 - 525

Published: Dec. 2, 2020

ABSTRACT Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations morphology that taxa are identified, creating basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity one basic aspects morphological interpretation provides means to study evolution ontogenetic changes, population structure palaeoecology, life‐history strategies, heterochrony along lineages would otherwise be lost time. Saurian reptiles (the least‐inclusive clade containing Lepidosauria Archosauria) have remained an incredibly diverse, numerous, disparate their ~260‐million‐year history. Because great disparity this group, assessing saurian difficult, fraught with methodological terminological ambiguity. We compiled a novel database literature, assembling >900 individual instances assessment, examine critically how has been diagnosed. review often inexact inconsistent terminology used assessment (e.g. ‘juvenile’, ‘mature’) provide routes better clarity cross‐study coherence. describe various methods assess every major integrating from both extant extinct give full account current state field providing method‐specific pitfalls, best practices, fruitful directions future research. recommend new standard subsection, ‘Ontogenetic Assessment’, added Systematic Palaeontology portions descriptive studies explicit diagnoses clear criteria. utility different criteria highly subclade dependent among saurians, even widely neurocentral suture fusion), we phylogenetic context, preferably form bracket, justify use method. Different should conjunction as independent lines evidence when maturity, instead diagnosis resting entirely on single criterion, which common literature. Critically, there need well‐represented growth series integrated fossil record ground assessments well‐constrained, empirically tested methods.

Language: Английский

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Pennaraptoran Theropod Dinosaurs Past Progress and New Frontiers

Bulletin of the American Museum of Natural History, Journal Year: 2020, Volume and Issue: 440(1), P. 1 - 1

Published: Aug. 21, 2020

Language: Английский

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Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures

Nature Communications, Journal Year: 2021, Volume and Issue: 12(1)

Published: June 29, 2021

The question why non-avian dinosaurs went extinct 66 million years ago (Ma) remains unresolved because of the coarseness fossil record. A sudden extinction caused by an asteroid is most accepted hypothesis but it debated whether were in decline or not before impact. We analyse speciation-extinction dynamics for six key dinosaur families, and find a across dinosaurs, where diversification shifted to declining-diversity pattern ~76 Ma. investigate influence ecological physical factors, that was likely driven global climate cooling herbivorous diversity drop. latter due hadrosaurs outcompeting other herbivores. also estimate risk related species age during decline, suggesting lack evolutionary novelty adaptation changing environments. These results support environmentally well

Language: Английский

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Functional constraints on the number and shape of flight feathers

Proceedings of the National Academy of Sciences, Journal Year: 2024, Volume and Issue: 121(8)

Published: Feb. 12, 2024

As a fundamental ecological aspect of most organisms, locomotor function significantly constrains morphology. At the same time, evolution novel abilities has produced dramatic morphological transformations, initiating some significant diversifications in life history. Despite new fossil evidence, it remains unclear whether volant locomotion had single or multiple origins pennaraptoran dinosaurs and individual taxa are controversial. The powered flight modern birds involved exaptation feathered surfaces extending off limbs tail yet studies concerning potential pennaraptorans do not account for structure morphology wing feathers themselves. Analysis number shape remex rectrix across large dataset extant indicates that remiges rectrices degree primary vane asymmetry strongly correlate with ability revealing important functional constraints. Among these traits, phenotypic flexibility varies reflected by different rates at which changes evolve, such traits reflect ancestral condition, whereas others current function. While Mesozoic Microraptor have morphologies consistent birds, anchiornithines deviate providing strong evidence this clade was volant. results analyses support origin dinosaurian indicate early stages sampled currently available record.

Language: Английский

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Morphology and distribution of scales, dermal ossifications, and other non‐feather integumentary structures in non‐avialan theropod dinosaurs

Biological reviews/Biological reviews of the Cambridge Philosophical Society, Journal Year: 2022, Volume and Issue: 97(3), P. 960 - 1004

Published: Jan. 6, 2022

ABSTRACT Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in group theropod dinosaurs (Maniraptoriformes) include crown Aves. Squamous or scaly reptilian‐like skin is, however, considered plesiomorphic condition for theropods and more broadly. Here, we review morphology distribution non‐feathered integumentary structures non‐avialan theropods, covering squamous naked as well dermal ossifications. The record non‐averostran is limited to tracks, which ubiquitously show a tiny reticulate scales on plantar surface pes. This consistent also with younger averostran body fossils, confirm an arthral arrangement digital pads. Among averostrans, confirmed Ceratosauria ( Carnotaurus ), Allosauroidea Allosaurus , Concavenator Lourinhanosaurus Compsognathidae Juravenator Tyrannosauroidea Santanaraptor Albertosaurus Daspletosaurus Gorgosaurus Tarbosaurus Tyrannosaurus whereas ossifications consisting sagittate mosaic osteoderms restricted Ceratosaurus . Naked, non‐scale bearing found contentious tetanuran Sciurumimus ornithomimosaurians Ornithomimus ) possibly tyrannosauroids patagia scansoriopterygids Ambopteryx Yi ). Scales surprisingly conservative among compared some dinosaurian groups (e.g. hadrosaurids); preservation tegument most specimens hinders further interrogation. Scale patterns vary and/or within regions polarised, snake‐like ventral tail latter two genera. Unusual but uniformly distributed patterning occurs feature present only Few currently compelling evidence co‐occurrence feathers Sinornithosaurus although probably retained mani pedes many heavy plumage. Feathers filamentous appear have replaced integuments maniraptorans. Theropod skin, broadly, remains virtually untapped area study appropriation commonly used techniques other palaeontological fields holds great promise future insights into biology, taphonomy relationships these extinct animals.

Language: Английский

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Avialan-like brain morphology in Sinovenator (Troodontidae, Theropoda)

Communications Biology, Journal Year: 2024, Volume and Issue: 7(1)

Published: Feb. 10, 2024

Many modifications to the skull and brain anatomy occurred along lineage encompassing non-avialan theropod dinosaurs modern birds. Anatomical changes endocranium include an enlarged endocranial cavity, relatively larger optic lobes that imply elevated visual acuity, proportionately smaller olfactory bulbs suggest reduced capacity. Here, we use micro-computed tomographic (μCT) imaging reconstruct its neuroanatomical features from exceptionally well-preserved of Sinovenator changii (Troodontidae, Theropoda). While overall morphology resembles typical other troodontids, also exhibits unique are similar paravian taxa non-maniraptoran theropods. Landmark-based geometric morphometric analysis on shape avialan points most closely resembling Archaeopteryx, thus indicating acquisition avialan-grade in troodontids wide existence such architecture Maniraptora.

Language: Английский

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Empirical and Methodological Challenges to the Model-Based Inference of Diversification Rates in Extinct Clades

Systematic Biology, Journal Year: 2021, Volume and Issue: 71(1), P. 153 - 171

Published: June 9, 2021

Changes in speciation and extinction rates are key to the dynamics of clade diversification, but attempts infer them from phylogenies extant species face challenges. Methods capable synthesizing information fossil have yielded novel insights into diversification rate variation through time, little is known about their behavior when analyzing entirely extinct clades. Here, we use empirical simulated data assess how two popular methods, PyRate Fossil BAMM, perform this setting. We inferred first tip-dated trees for ornithischian dinosaurs combined with occurrence test whether underwent an end-Cretaceous decline. then records under constraints determine macroevolutionary preservation can be teased apart paleobiologically realistic conditions. obtained discordant inferences macroevolution including a long-term decline (BAMM), mostly flat steep drop (PyRate) or without one episodes implausibly accelerated (PyRate). Simulations revealed no conflation between preservation, spuriously correlated estimates while time-smearing tree-wide shifts (BAMM) overestimating number Our results indicate that small phylogenetic sets available vertebrate paleontologists assumptions made by current model-based methods combine yield potentially unreliable provide guidelines interpreting existing approaches light limitations suggest latter may mitigated. [BAMM; diversification; fossils; rates; Ornithischia; PyRate.].

Language: Английский

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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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New information on Bonapartenykus (Alvarezsauridae: Theropoda) from the Allen Formation (middle Campanian-lower Maastrichtian) of Río Negro Province, Patagonia, Argentina clarifies the Patagonykinae body plan

PLoS ONE, Journal Year: 2025, Volume and Issue: 20(1), P. e0308366 - e0308366

Published: Jan. 30, 2025

Alvarezsauria is a group of morphologically distinctive, medium- to small-sized later-diverging coelurosaurian theropod dinosaurs, whose record ranges from the Late Jurassic Cretaceous. This clade had widespread distribution in Laurasia what now Europe, Asia, and North America, although there are also several Cretaceous taxa Gondwana Argentina that all belong family Alvarezsauridae. Although alvarezsaurid taxonomic diversity anatomical knowledge has expanded over last decade, internal phylogenetic relationships remain highly debated. In this contribution, we describe new material review previously reported specimens middle Campanian—lower Maastrichtian Allen Formation discovered at Salitral Ojo de Agua locality Río Negro province, Patagonia, Argentina. these were collected different times without precise original provenance information, here gathered X-ray diffraction data associated sediments suggests come same site stratigraphic level as holotype Bonapartenykus ultimus . Based on information morphological similarity considered specimens, tentatively refer them genus These newly referred add shed light body plan Patagonykinae by permitting more complete reconstruction neck, pectoral girdle, hindlimb, tail.

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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