ORIGINAL ARTICLE Gross Morphology of the Intra-Oral rhamphotheca, Oropharynx and Proximal Oesophagus of the Emu (Dromaius novaehollandiae) M. R. Crole* and J. T. Soley Address of authors: Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa Introduction Although aspects of the anatomy of ratites have been the subject of recent in-depth investigations (Aire et al., 2008; Parizzi et al., 2008) and despite numerous studies con- ducted on the intestinal tract (Owen, 1841, 1879; Gadow, 1879; Pycraft, 1900; Mitchell, 1901; Herd, 1985; Bezuidenhout, 1986, 1999; Potter et al., 2006; Porchescu, 2007), very little comprehensive information is available on the structure of the upper digestive tract (oral cavity, tongue, pharynx and oesophagus) of these birds. In con- trast, the upper digestive tract of many other avian spe- cies has been described in some detail (for a review of the earlier literature see Calhoun, 1954; McLelland, 1979). The most comprehensively studied ratite in respect of the upper digestive tract is the ostrich and this region, or parts thereof, have been illustrated and described in a number of publications (Go ¨ppert, 1903; Faraggiana, 1933; Porchescu, 2007; Jackowiak and Ludwig, 2008; Tadjalli et al., 2008; Tivane et al., 2006; Tivane, 2008; Guimara ˜es et al., 2009) with the most detailed description being that of Tivane (2008) who combined gross morphological observations with histology and scanning electron micros- copy of the oropharynx and oesophagus. Descriptions, as well as illustrations of the ratite oropharynx or parts thereof, have also been supplied for the greater rhea (Gadow, 1879; Pycraft, 1900; Faraggiana, 1933; Gussekloo and Bout, 2005), kiwi (Owen, 1879; McCann, 1973) and emu (Faraggiana, 1933; Bonga Tomlinson, 2000; Crole and Soley, 2009a,b). However, no complete description of the emu oropharynx is currently available and the existing information, which essentially records the structure of the tongue and laryngeal mound, is, in part, inaccurate or misleading. Cho et al. (1984), in a brief comparative description of the ratite oropharynx, noted that the shape of the tonsils, as with the tongue, varies between these birds. The description is vague and open to interpretation, giving lit- tle information on the specific location or structure of the tonsils. The authors simply note that ‘The ostrich tonsils and tongue are smooth, blunt and U-shaped. In the Darwin’s rhea both tongue and tonsils have simple, *Correspondence: e-mail: martina.crole@up.ac.za With 5 figures Received August 2009; accepted for publication February 2010 doi: 10.1111/j.1439-0264.2010.00998.x Summary Information on the gross morphology of the upper digestive tract of ratites is sparse. This is an important region considering that it is the first area for food selection and intake which is vital to the nutrition and growth of the animal and therefore its commercial viability. Twenty-three heads from sub-adult (12– 14 months) emus were used to provide a definitive description of the orophar- ynx and proximal oesophagus. Besides supplying baseline morphological data of veterinary importance, this study also underlines the functional importance of this region. The mandibular and maxillary nails, and serrations on the ros- tral mandibular tomia, provide the emu with a formidable combination of gripping, tearing and pecking power. The folded oropharyngeal floor allows distention of the dorso-ventrally flattened cavity during eating and drinking. The laryngeal mound performs both respiratory and digestive functions, whereas the distensible proximal oesophagus supports the particular feeding method employed by ratites. Anatomia Histologia Embryologia ª 2010 Blackwell Verlag GmbH • Anat. Histol. Embryol. 39 (2010) 207–218 207