Insight into the growth dynamics and systematic affinities of the Late Cretaceous Gargantuavis from bone microstructure.

Enigmatic avialan remains of Gargantuavis philoinos from the Ibero-Armorican island of the Late Cretaceous European archipelago (Southern France) led to a debate concerning its taxonomic affinities. Here, we show that the bone microstructure of Gargantuavis resembles that of Apteryx, the extinct emeids and Megalapteryx from New Zealand, and indicates that like these slow-growing terrestrial birds, it took several years to attain skeletal maturity. Our findings suggest that the protracted cyclical growth in these ornithurines may have been in response to insular evolution.