Mandibles of Crossbills (IMAGE) Proceedings of the National Academy of Sciences Caption These are mandibles of modern Hispaniolan crossbill (A), fossil Hispaniolan crossbill (B), modern White-winged crossbill (C), and modern Mexican crossbill (D). Credit <i>PNAS</i> Usage Restrictions None License Licensed content 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.