Gross anatomical features of the tongue, lingual skeleton and laryngeal mound of Rhea americana (Palaeognathae, Aves): morpho-functional considerations

Abstract

The final publication is available at http://www.springerlink.com/content/6j37487920884049/ Abstract The tongue body of Rhea americana is triangular and partially pigmented with each caudo-lateral margin displaying a round, sub-divided lingual papilla. The tongue root is a smooth, non-pigmented tract of mucosa. The tongue body is supported by the paraglossum and distal half of the rostral projection of the basihyal (RPB), and the tongue root by the proximal half of the RPB, body of the basihyal and proximal ceratobranchials. An urohyal is absent; however, peculiar to R. americana, the caudal margin of the cricoid body displays a median projection, which may represent the remnant of the urohyal incorporated into the cricoid. The laryngeal mound is less elevated, the arytenoid cartilages are smaller than in other ratites, and the caudal margin displays pharyngeal papillae that vary in shape and number. The unique morphology of the lingual skeleton and its positioning within the tongue of R. americana, the rostral insertion of the M. ceratoglossus, the absence of the urohyal (enhanced ventroflexion) and the caudal positioning and mobile attachment of the ensheathed basihyal to the paraglossum would appear to allow independent movement of the tongue body relative to the hyobranchial apparatus. Additionally, the deeply indented base and rostral oval opening in the paraglossum limits the length of cartilage present in the midline of the tongue body. This may allow the tongue the necessary flexibility for the lingual papillae to clean the choana. The cleaning action of the tongue would occur simultaneously Communicated by T. Bartolomaeus.M. Crole ( ) • J. Soley Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa e-mail: martina.crole@up.ac.za with the previously described role of this organ and associated structures during feeding. Thus, the so-called reduced, ancestral tongue of R. americana may be structurally and functionally more complex than previously believed.

A complex hyobranchial apparatus in a Cretaceous dinosaur and the antiquity of avian paraglossalia

“…In the ostrich, the paraglossalia never meet, and instead remain as separate cartilage into adulthood. In other palaeognaths the paraglossalia unite but remain cartilaginous, and may leave an open fenestra in the midline (Crole & Soley, ). In most palaeognaths the paraglossal has a similar arrowhead‐shaped morphology to that described above (Tomlinson, ; Crole & Soley, ); however, in certain tinamous the paraglossal is triangular with scalloped margins (Tomlinson, ).…”

Morphogenesis of the rhea (Rhea americana) respiratory system in different embryonic and foetal stages

“…In the structure of the laryngeal skeleton, besides the arytenoid and cricoide cartilage observed in the rhea foetuses, procricoid cartilage was identified in geese (Onuk et at. 2010), adult ostrich (Abidu-Figueiredo et al 2012) adult quail Coturnix coturnix japonicum (Cevik-Demirkan et al 2007) and rheas (Crole & Soley 2012), and in a later study, was also found in different locations in puppies and adolescent animals. These changes in the anatomical position of procricoid cartilage during the postnatal period and its small size relative to the cricoid and arytenoid cartilage, as shown by these authors, can justify the fact that this structure has not been displayed in rhea embryos or foetuses in the studied phases.…”

Persistence of Meckel's cartilage in sub‐adult Struthio camelus and Dromaius novaehollandiae

“…For example, in lingual feeders, the distal aspect of Meckel's cartilage serves as an attachment for some of the muscles of the tongue ( M. genioglossus ) (Holliday et al, ). However, in the ostrich, emu and greater rhea (Bonga Tomlinson, ; Crole & Soley, ), although Meckel's cartilage was not described, there was no evidence of hyolingual muscles attaching to the latter, or of the distal ends forming part of the mandibular symphysis (Crole & Soley, ). The mandibular rami are completely fused at the symphysis in birds (Bühler, ), a situation also apparent in the ostrich and emu, and Meckel's cartilage would thus not play a role in respect of this joint in these two species as it reportedly does in the lepidosaurs (Holliday et al, ).…”