Evolution of the hyoid apparatus in Archosauria: implications for the origin of avian tongue function

Date

2015-08-20

Authors

Li, Zhiheng

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Abstract

While certain aspects of hyolingual function have been intensively studied in extant archosaurs, including both the crocodylian- and bird-lineages, major aspects remain unstudied within their closely related extinct taxa, e.g., basal archosaurs and non-avian dinosaurs. In archosaurs, the hyoid apparatus and the associated larynx control the movement of the tongue and the throat, further affected several essential functions including drinking, food intake and manipulation, sound making, as well as panting and breathing. In addition to feeding, the hyolingual apparatus has also been identified as closely involved in sound production in crocodylians. However, neither the hyoid morphology nor the tongue function has been systematically investigated in extinct archosaurs (e.g., non-avian dinosaurs or other basal birds) because of the assumed limited evidence in the fossil records. So far, little is known about the ability of basal archosaur or non-avian dinosaur to produce sound, what their tongue looked like and how they used it. Therefore, the major goal of the dissertation is to integrate anatomical and functional data on the hyolingual apparatus in Crocodylia and Aves, combined with the most comprehensive assessment of hyoid fossils from extinct archosaurs, finally reconstruct the evolution of hyoid morphology and tongue function in Archosauria. The recoveries of several key specimens from this study filled the morphologic gap in the hyoid evolution from ancestral archosaurs to living birds. New techniques applied as the contrast-enhanced Computed Tomography Imaging combined with a large number of dissections supplement prolific details for inferring the soft-tissues of hyolingual apparatus within archosaurs. The synthesis of data on both bony hyoid and associated muscles illustrate the major pattern of the hyolingual evolution in dinosaur and shed new light into the origin of bird tongue and novel function.

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