- Are Birds Really Dinosaurs? - A DinoBuzz article covering the theory, and objections towards it, of the dinosaurian origin of birds.
- BBC Science and Nature: Gastornis - Provides an illustration and information on this fearsome bird, its description, distribution, behavior and history.
- Genera and Species of Paleocene Birds - Provides details of the bird genera of this epoch that have been classified from their fossil record.
- Phorusrhacos - Partial fossils of this bird have been found in Argentina dating back to 27 million years ago.
