Skeletal radiographic anatomy of echidnas: insights into unusual mammals

Long-beaked echidnas (Zaglossus spp.) have received less attention in the literature than Short-beaked echidnas (Tachyglossus aculeatus). Their natural history, anatomy, and physiology are poorly known. To improve our understanding of this unique group, we undertook a radiographic study of the Eastern long-beaked echidna (Zaglossus bartoni), and provide a comparative analysis of its radiographic skeletal anatomy with that of T. aculeatus. We examine conventional radiography and computed tomographic images of Zaglossus and Tachyglossus, describe the anatomical features of Zaglossus, and compare those with Tachyglossus. We provide evidence of epicoracoid overlap in echidnas, a feature not well documented in monotremes. The significance of epicoracoid overlap requires further investigation. Our study is intended as a reference for the radiographic anatomy of Z. bartoni.