The link between vocal anatomy and vocal output has been thoroughly investigated in humans (e.g. Our findings illustrate that strong selection pressures on acoustic signalling not only lead to the specialisation of existing vocal organs but can also result in the evolution of novel vocal structures in both sexes.Įxamining vocal anatomy is an important step towards understanding the proximate factors that shape the vocal signals of a given species. We also confirm that the edges of the intra‐pharyngeal ostium have specialised to form the novel, extra‐laryngeal velar vocal folds, which are much larger than the true intra‐laryngeal vocal folds in both sexes, but more developed and specialised for low frequency sound production in males than in females. We suggest that these features evolved to accommodate the low resting position of the larynx and assist in its retraction during call production. Finally, the digastric, omohyoid and sternohyoid muscles, connected by a common tendinous intersection, form a guiding channel for the dynamic down‐and‐up movements of the ventral hyoid parts and the larynx. Thirdly, the genioglossus and geniohyoid muscles are greatly increased in length. Secondly, three hyoid muscles have lost their connection to the hyoid skeleton. First, the usual retractors of the larynx and the hyoid have their origins deep in the thorax. We also show that koalas can retract the larynx down into the thoracic inlet, facilitated by a dramatic evolutionary transformation of the ventral neck muscles. In addition, the hyoid apparatus has a human‐like configuration in which paired dorsal, resilient ligaments suspend the hyoid apparatus from the skull, while the ventral parts tightly connect to the descended larynx. We show that both males and females have an elongated pharynx and soft palate, resulting in a permanently descended larynx. Here we use advanced imaging techniques, histological data, classical macroscopic dissection and behavioural observations to provide the first detailed description and interpretation of male and female koala vocal anatomy. Koalas are characterised by a highly unusual vocal anatomy, with a descended larynx and velar vocal folds, allowing them to produce calls at disproportionately low frequencies. Vocal tract lengths (mm) in the koala ( Phascolarctos cinereus). Laryngeal vocal fold dimensions (mm), resting and maximally extended, in koalas ( Phascolarctos cinereus). Epiglottis dimensions (mm) in koalas ( Phascolarctos cinereus). Larynx size (mm) in koalas ( Phascolarctos cinereus).
Origin, termination and supposed function of those ventral neck muscles involved in pronounced laryngeal mobility, pharyngeal length changes and adopting the calling posture in the koala ( Phascolarctos cinereus). Thyrohyoid membrane length (mm) in the koala ( Phascolarctos cinereus). Hyoid ligaments in the koala ( Phascolarctos cinereus). Velar vocal fold dimensions (mm), resting and maximally extended, in koalas ( Phascolarctos cinereus). Soft palate dimensions (mm) in the koala ( Phascolarctos cinereus). Cheek pouches in the koala ( Phascolarctos cinereus). Koala specimens ( Phascolarctos cinereus). If Facebook is more your thing, come join us in our FB group.Table S1. It has most of the info you're probably about to ask for, including:Īlso read Answers to pretty much every self-post before making a self-post.Ĭome chat with us on IRC on in #reddit-australia, or via this webchat link.
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