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Article: Shake a Tail Feather: The Evolution of the Theropod Tail into a Stiff Aerodynamic Surface

TitleShake a Tail Feather: The Evolution of the Theropod Tail into a Stiff Aerodynamic Surface
Authors
Issue Date2013
PublisherPublic Library of Science. The Journal's web site is located at http://www.plosone.org/home.action
Citation
PLoS ONE, 2013, v. 8, p. e63115 How to Cite?
AbstractTheropod dinosaurs show striking morphological and functional tail variation; e.g., a long, robust, basal theropod tail used for counterbalance, or a short, modern avian tail used as an aerodynamic surface. We used a quantitative morphological and functional analysis to reconstruct intervertebral joint stiffness in the tail along the theropod lineage to extant birds. This provides new details of the tail’s morphological transformation, and for the first time quantitatively evaluates its biomechanical consequences. We observe that both dorsoventral and lateral joint stiffness decreased along the non-avian theropod lineage (between nodes Theropoda and Paraves). Our results show how the tail structure of non-avian theropods was mechanically appropriate for holding itself up against gravity and maintaining passive balance. However, as dorsoventral and lateral joint stiffness decreased, the tail may have become more effective for dynamically maintaining balance. This supports our hypothesis of a reduction of dorsoventral and lateral joint stiffness in shorter tails. Along the avian theropod lineage (Avialae to crown group birds), dorsoventral and lateral joint stiffness increased overall, which appears to contradict our null expectation. We infer that this departure in joint stiffness is specific to the tail’s aerodynamic role and the functional constraints imposed by it. Increased dorsoventral and lateral joint stiffness may have facilitated a gradually improved capacity to lift, depress, and swing the tail. The associated morphological changes should have resulted in a tail capable of producing larger muscular forces to utilise larger lift forces in flight. Improved joint mobility in neornithine birds potentially permitted an increase in the range of lift force vector orientations, which might have improved flight proficiency and manoeuvrability. The tail morphology of modern birds with tail fanning capabilities originated in early ornithuromorph birds. Hence, these capabilities should have been present in the early Cretaceous, with incipient tail-fanning capacity in the earliest pygostylian birds.
Persistent Identifierhttp://hdl.handle.net/10722/183729
ISSN
2015 Impact Factor: 3.057
2015 SCImago Journal Rankings: 1.395
PubMed Central ID

 

DC FieldValueLanguage
dc.contributor.authorPittman, MD-
dc.contributor.authorGatesy, SM-
dc.contributor.authorUpchurch, P-
dc.contributor.authorGoswami, A-
dc.contributor.authorHutchinson, JR-
dc.date.accessioned2013-06-18T04:10:31Z-
dc.date.available2013-06-18T04:10:31Z-
dc.date.issued2013-
dc.identifier.citationPLoS ONE, 2013, v. 8, p. e63115-
dc.identifier.issn1932-6203-
dc.identifier.urihttp://hdl.handle.net/10722/183729-
dc.description.abstractTheropod dinosaurs show striking morphological and functional tail variation; e.g., a long, robust, basal theropod tail used for counterbalance, or a short, modern avian tail used as an aerodynamic surface. We used a quantitative morphological and functional analysis to reconstruct intervertebral joint stiffness in the tail along the theropod lineage to extant birds. This provides new details of the tail’s morphological transformation, and for the first time quantitatively evaluates its biomechanical consequences. We observe that both dorsoventral and lateral joint stiffness decreased along the non-avian theropod lineage (between nodes Theropoda and Paraves). Our results show how the tail structure of non-avian theropods was mechanically appropriate for holding itself up against gravity and maintaining passive balance. However, as dorsoventral and lateral joint stiffness decreased, the tail may have become more effective for dynamically maintaining balance. This supports our hypothesis of a reduction of dorsoventral and lateral joint stiffness in shorter tails. Along the avian theropod lineage (Avialae to crown group birds), dorsoventral and lateral joint stiffness increased overall, which appears to contradict our null expectation. We infer that this departure in joint stiffness is specific to the tail’s aerodynamic role and the functional constraints imposed by it. Increased dorsoventral and lateral joint stiffness may have facilitated a gradually improved capacity to lift, depress, and swing the tail. The associated morphological changes should have resulted in a tail capable of producing larger muscular forces to utilise larger lift forces in flight. Improved joint mobility in neornithine birds potentially permitted an increase in the range of lift force vector orientations, which might have improved flight proficiency and manoeuvrability. The tail morphology of modern birds with tail fanning capabilities originated in early ornithuromorph birds. Hence, these capabilities should have been present in the early Cretaceous, with incipient tail-fanning capacity in the earliest pygostylian birds.-
dc.languageeng-
dc.publisherPublic Library of Science. The Journal's web site is located at http://www.plosone.org/home.action-
dc.relation.ispartofPLoS ONE-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.titleShake a Tail Feather: The Evolution of the Theropod Tail into a Stiff Aerodynamic Surface-
dc.typeArticle-
dc.identifier.emailPittman, MD: mpittman@hku.hk-
dc.identifier.authorityPittman, MD=rp01622-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1371/journal.pone.0063115-
dc.identifier.pmcidPMC3655181-
dc.identifier.hkuros214613-
dc.identifier.volume8-
dc.identifier.spagee63115-
dc.identifier.epagee63115-
dc.publisher.placeUnited States-

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