Echidna (image) Penn State Share Print E-Mail Caption An echidna is a monotreme. Credit Kateryna Makova, Penn State Usage Restrictions The credit information must be published along with the image. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.