Wordnet 3.0
NOUN (1)
1.
sparrow-sized fossil bird of the Cretaceous period having a vestigial tail;
found in Spain;
considered possibly the third most primitive of all birds;
The Collaborative International Dictionary of English v.0.48:
Ibero-mesornis \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]
WordNet (r) 3.0 (2006):
Ibero-mesornis
n 1: sparrow-sized fossil bird of the Cretaceous period having a
vestigial tail; found in Spain; considered possibly the
third most primitive of all birds