| genus ibero-mesornis | (n) a genus of fossil bird of the subclass Archaeornithes |
| ibero-mesornis | (n) sparrow-sized fossil bird of the Cretaceous period having a vestigial tail; found in Spain; considered possibly the third most primitive of all birds |
| Ibero-mesornis | n. A sparrow-sized fossil bird of the Lower Cretaceous having a strutlike pectoral bone and vestigial tail; found in Spain; considered possibly the third most primitive of all birds. [ WordNet 1.5 ] |