MEYERS, J.J.; HERREL, A.; MEAD, J.: Morphology of the feeding apparatus of the Australian thorny devil (Moloch horridus)

The thorny devil (Moloch horridus) is an Australian agamid lizard that has a specialized diet consisting only of ants. As with many species having specialized diets, it has been suggested that M. horridus shows morphological adaptations related to its myrmecophagous diet. We examined the morphology of the feeding apparatus in M. horridus and Pogona vitticeps (a dietary generalist) to understand changes related to an ant diet. In addition to comparisons betweeen M. horridus and a closely related agamid species, we decided to also compare the morphology of M. horridus to North American horned lizards (Phrynosoma), since they are often cited as convergent forms adapted to an ant eating lifestyle. Standard dissection techniques were used to compare hyobranchial musculature of M. horridus, P. vitticeps and Phrynosoma platryhinos. We noted changes in orientation and relative size of several hyobranchial muscles. In M. horridus, we also noticed extreme hypertrophy of the sublingual gland. The gland lies lateral to the middle third of the tongue with a duct extending forward to open near the tongue tip. The gland is bordered by an unusual slip of muscle that may be used as a gland compressor. In addition, scanning electron microscopy was used to compare the tooth structure and tongue surface of both species. M. horridus showed some unusual modifications including medially directed maxillary teeth and interdigitation of the maxillary and dentary teeth.