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The specialized lingual papillae of Tachyglossus aculeatus I. Gross and light microscopic features

The tongue of the echidna, Tachyglossus aculeatus is divided structurally and functionally into two distinct parts; a free rostral portion covered by stratified squamous epithelium bearing filiform papillae and a fixed caudal portion formed by a trapezoidal pad which bears highly specialized keratinized spines. These spines are similar in their morphology to the horny teeth of the living cyclostome Myxine and the hard keratin of rat filiform papillae.