Macroevolutionary patterns in the pelvis, stylopodium and zeugopodium of megalosauroid theropod dinosaurs and their importance for locomotor function

Royal Society Open Science, Journal Year: 2023, Volume and Issue: 10(8)

Published: Aug. 1, 2023

During the Mesozoic, non-avian theropods represented one of most successful clades globally distributed, with a wide diversity forms. An example is clade Megalosauroidea, which included medium- to large-bodied Here, we analyse macroevolution locomotor system in early Theropoda, emphasizing Megalosauroidea. We scored

Language: Английский

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Forelimb muscle activation patterns in American alligators: Insights into the evolution of limb posture and powered flight in archosaurs

Journal of Anatomy, Journal Year: 2024, Volume and Issue: 244(6), P. 943 - 958

Published: Jan. 19, 2024

The evolution of archosaurs provides an important context for understanding the mechanisms behind major functional transformations in vertebrates, such as shifts from sprawling to erect limb posture and acquisition powered flight. While comparative anatomy ichnology extinct have offered insights into musculoskeletal gait changes associated with locomotor transitions, reconstructing motor control requires data extant species. However, scarcity electromyography (EMG) forelimb, especially crocodylians, has hindered neuromuscular archosaurs. Here, we present EMG nine forelimb muscles American alligators during terrestrial locomotion. Our aim was investigate modulation across different postures examine variations phylogeny modes. Among examined, m. pectoralis, largest muscle primary shoulder adductor, exhibited significantly smaller mean amplitudes steps which more adducted (i.e., upright). This suggests that using a helps reduce force work stance. As larger use hip posture, postural transition occurred Triassic could be either cause or consequence body size Comparisons burst phases among tetrapods revealed bird turtle, experienced transformations, displayed distinctive comparison those alligator lizard. These results support notion plan modes sauropsid lineages were significant activation patterns.

Language: Английский

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The evolution of femoral morphology in giant non-avian theropod dinosaurs

Paleobiology, Journal Year: 2024, Volume and Issue: 50(2), P. 308 - 329

Published: May 1, 2024

Abstract Theropods are obligate bipedal dinosaurs that appeared 230 Ma and still extant as birds. Their history is characterized by extreme variations in body mass, with gigantism evolving convergently between many lineages. However, no quantification of hindlimb functional morphology has shown whether these mass increases led to similar specializations distinct Here we studied femoral shape variation across 41 species theropods ( n = 68 specimens) using a high-density 3D geometric morphometric approach. We demonstrated the heaviest evolved wider epiphyses more distally located fourth trochanter, previously early archosaurs, along an upturned head mediodistal crest extended proximally shaft. Phylogenetically informed analyses highlighted traits within six major theropod lineages, regardless their maximum mass. Conversely, most gracile femora were from rest dataset, which interpret specialization “miniaturization” close Avialae (bird lineage). Our results support gradual evolution known “avian” features, such fusion lesser greater trochanters reduction epiphyseal offset, independent variations, may relate type locomotion (more knee than hip driven). The distinction represented decoupling morphology, whose biomechanical nature should be better understand importance its role gigantism, miniaturization, higher parasagittal abilities.

Language: Английский

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Resolving the "Ontogeny Problem" in Vertebrate Paleontology

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 28, 2024

Abstract Ontogenetic change is a major source of phenotypic variation among members species and often greater magnitude than the anatomical differences that distinguish closely related species. Ontogeny has therefore become problematic confounding variable in vertebrate paleontology, especially study systems distant from extant crown clades, rendering taxonomic hypothesis testing (a fundamental process evolutionary biology) rife with difficulty. Paleontologists have adopted quantitative methods to compensate for perception juvenile specimens lack diagnostic apomorphies seen their adult conspecifics. Here, I critically evaluate these assumptions guide interpretation using µCT dataset comprising growth series American Chinese alligator. find several widespread are scientifically unjustifiable, two popular – geometric morphometrics cladistic analysis ontogeny unacceptably high rates type II error present numerous procedural difficulties. However, also identify suite ontogenetically invariant characters differentiate living Alligator throughout ontogeny. These overwhelmingly correspond develop prior (and play signaling role in) development cranial skeleton itself, suggesting ontogenetic invariance consequence widely conserved developmental program. observations suggest architecture cranium fixed early embryonic development, remodeling does not alter topological relationships bones or soft tissue structures they house. propose general model future tests fossil record, which different stages single can be falsified by discovery character cannot attributed plausibly variation.

Language: Английский

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Fibular reduction and the evolution of theropod locomotion

Nature, Journal Year: 2024, Volume and Issue: 637(8044), P. 113 - 117

Published: Nov. 20, 2024

Language: Английский

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